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Perhydroxyl radical

Perhydroxyl radicals are highly reactive oxygen-containing species that play a key role in various chemical and biological processes.
These radicals are characterized by the presence of a hydroperoxyl group (HO2•), which can participate in oxidation-reduction reactions and contribute to cellular damage or signaling pathways.
Understanding the behavior and impact of perhydroxyl radicals is crucial for fields such as biochemistry, environmental chemistry, and medical research.
This MeSH term provides a concise overview of the perhydroxyl radical, its properties, and its significance in scientific investigations.

Most cited protocols related to «Perhydroxyl radical»

1
Simulating Radiation-Induced Oxygen Interactions
Cited 4 times
The classical version of the TRAX-CHEM code has been modified and is now able to simulate the chemical evolution of ion tracks in water targets under different oxygen pressure conditions. The particle list and the reaction network of the classical version of the TRAX-CHEM code have been, thus, extended (see Table 1 and Table 2) and new species, generated by the interaction of O2 with the radiation-induced water-free radicals, are now included in the track chemical evolution.
In contrast to all other species, which are explicitly included in the code and treated with the step by step approach mentioned above, the molecular oxygen is assumed to be homogeneously distributed in the target and is treated as a continuum. This approximation, proposed by Pimblott et al. [45 (link)], Green et al. [46 (link)], is necessary to limit the computational cost of the simulations and has also been adopted by other authors [13 (link),14 (link),47 (link),48 (link)]. The explicit introduction of the oxygen in the simulation would dramatically increase the computing time, even for very dilute solutions [45 (link)]. As an example, in a chemical simulation of a 10 MeV proton track in a cubic volume of 5 μ m side the number of radiolytic species produced per particle track is about 10 3 . In a fully oxygenated condition (21% pO2 , corresponding to a concentration of 0.27 mmol/litre) the number of oxygen molecule that have to be explicitly introduced (in the same cubic volume of 5 μ m side) and followed at every single step of the simulation is about 2 × 10 7 , increasing the simulation time by more than four orders of magnitude. Considering the relatively low radiation-induced oxygen consumption compared to the total amount of molecular oxygen dissolved in the target, a variation of the global oxygen concentration during the track evolution can be excluded for all the oxygenations and radiation conditions examined. When investigating the possibility of noticeable local oxygen depletion in the track cores, it has to be kept in mind that the interaction of the radiolytic species with the target occurs in a later stage of the expanding chemical track evolution since the reaction dynamic between the induced chemical species is slower. For high LET ions (∼100 keV/ μ m), the highest local density of oxygen removal is reached around 10 ns within 10-20 nm of the track core and stays below 250 μ M, quickly decreasing as the chemical track diffuses and oxygen conversion to superoxide and perhydroxyl becomes important. For even larger LET values, only a slightly delayed onset of the HO2• and O2•− production can, therefore, be expected. Similar conclusions have been reported by Colliaux et al. [15 (link)]. Additionally, the molecular oxygen production through multiple ionizations is not accounted for here, but it has been demonstrated that the contribution of this process to the radical yield is very low [15 (link)].
Under these conditions, given an oxygen concentration cs , the probability for a radiolytic species to interact with an oxygen molecule of the target is determined by the rate equation: dΩ(t)dt=−k(t)csΩ(t),
where Ω(t) is the time-dependent survival probability of the molecule of interest. The time dependent rate coefficient k(t) for the reaction of interest can be calculated according to the Noyes theory [49 ], as: k(t)=4πD′Rreac1+RreacπD′t,
where D′ is the relative diffusion coefficient defined, considering the two species A and B, D′=DA+DB and Rreac is the reaction radius defined according to the Smoluchowski theory, as
Rreac=kAB4π(DA+DB).
The probability for a molecule to react with the dissolved oxygen in a time t will, thus, be: W(t)=1−Ω(t)=1−e−4πD′Rreaccst+2RreactπD′.
Since TRAX-CHEM uses a variable time step, the probability W(t) that a species will interact is calculated for each time step and is sampled through a uniformly distributed random variable x∈[0:1] . When x≤W(t) the reaction is taking place, the reactants are removed from the simulation and replaced by the corresponding reaction products.
Boscolo D., Krämer M., Fuss M.C., Durante M, & Scifoni E. (2020). Impact of Target Oxygenation on the Chemical Track Evolution of Ion and Electron Radiation. International Journal of Molecular Sciences, 21(2), 424.
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Publication 2020
2
Superoxide Radical: Toxicity and Mechanisms
The superoxide radical (O2•) is a highly toxic species that is generated by numerous biological and photochemical reactions via the Haber-Weiss reaction. It can generate the hydroxyl radical, which reacts with DNA bases, amino acids, proteins, and polyunsaturated fatty acids, and produces toxic effects. The toxicity of the superoxide radical could also be due to the perhydroxyl intermediates (HO2•) that react with polyunsaturated fatty acids. Finally, superoxide may react with NO to generate peroxynitrite, which is known to be toxic towards DNA, lipids and proteins.
Boubaker J., Mansour H.B., Ghedira K, & Ghedira L.C. (2012). Polar extracts from (Tunisian) Acacia salicina Lindl. Study of the antimicrobial and antigenotoxic activities. BMC Complementary and Alternative Medicine, 12, 37.
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Publication 2012
Amino Acids Biopharmaceuticals Hydroxyl Radical Lipids Peroxynitrite Polyunsaturated Fatty Acids Proteins Superoxides
3
Radiolytic Transformation of Diuron Using Pulse Radiolysis
Pulse radiolysis was performed using 800 ns pulses of a linear accelerator, and an optical detection system with a cell having 1 cm light path length [12 (link)]. Pulse dosimetry was carried out in air-saturated, 1 × 10−2 mol dm−3 KSCN solutions by monitoring the absorbance of (SCN)2−• at λmax 480 nm. The absorbed doses per pulse were 20 Gy. A 60Co gamma facility with 1.8 PBq activity was used for steady-state gamma irradiation. The dose rate was measured to be ~10 kGy h−1 using ethanol-monochlorobenzene (ECB) dosimetry.
In the radiolysis of water, hydrated electron (eaq−), hydrogen atom (H•) and hydroxyl radical (•OH) form as reactive intermediates as shown in Eq. (1) [13 (link),14 ]. H2Oeaq⇝0.28+H•0.07+•OH0.28 eaq‐+N2O+H2O→OH‐+•OH+N2k=9.1×109mol‐1dm3s‐1 •OH+CH33COH→•CH2CH32COH+H2Ok=6×108mol‐1dm3s‐1 eaq‐+O2→O2‐•k=1.9×1010mol‐1dm3s‐1 H•+O2→HO2•k=2.1×1010mol‐1dm3s‐1 HCO2‐+•OH→CO2‐•+H2Ok=3×109mol‐1dm3s‐1 CO2‐•+O2→O2‐•+CO2k=4.2×109mol‐1dm3s‐1
In Eq. (1) the numbers in parentheses are the radiation chemical yields (G-values) in μmol J−1. Standard radiation chemical techniques were applied in the experiments in order to observe the individual reactions of the intermediates. The •OH reactions were followed in N2O-saturated solutions to convert eaq− to •OH in Reaction (2). Reactions between eaq− and diuron were investigated in N2-saturated solutions containing 5 vol. % tert-butanol to convert •OH to the less reactive •CH2(CH3)2COH in Reaction (3). When the solution was purged with N2 in the absence of tert-butanol, all the three primary species reacted with diuron. In the presence of dissolved O2 (air or O2 saturated solutions), eaq− and H• are converted to superoxide radical anion/perhydroxyl radical pair in Reactions ((4) and (5)). Hence, in these solutions •OH as well as the O2−•/HO2• pair induce the transformations (pKa (O2−•/HO2•) = 4.8). Experiments were also made in O2 saturated solutions containing Na formate (0.05 mol dm−3). In such solutions (in addition to eaq− and H•) •OH is transformed to O2−•/HO2• in Reactions (6) and (7).
In most of the experiments ~1 × 10−4 mol dm−3 diuron solutions were investigated, they were saturated with appropriate gases (N2O, N2, O2 or air) before irradiation.
Kovács K., He S., Mile V., Csay T., Takács E, & Wojnárovits L. (2015). Ionizing radiation induced degradation of diuron in dilute aqueous solution. Chemistry Central Journal, 9, 21.
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Publication 2015
Anions Cells chlorobenzene Diuron Electrons Ethanol formate Gamma Rays Gases Hydrogen Hydroxyl Radical Light Linear Accelerators potassium thiocyanate Pulse Radiolysis Pulse Rate Pulses Radiation Radiometry Radiotherapy Superoxides tert-Butyl Alcohol
4
Ionizing Radiation for Wastewater Micropollutant Degradation
Ionizing radiation such as e-beam accelerators (β-rays) and gamma irradiation (γ-rays, 60Co), originally intended for disinfection, is under research for micropollutant degradation. Table 8 lists the facilities in Europe performing wastewater treatment by ionizing radiation.

Major facilities for wastewater treatment by ionizing radiation (Borrely et al. 1998 (link))

CountryRadiation sourceEnergy (MeV)Power (kW)/activity (kCi)PurposeDose (kGy)
AustriaEBA0.512.5TCE, PCE removal0.2–2.0
Germany60Co1.25135Disinfection of sludge2.0–3.0

EBA electron beam accelerator, TCE trichloroethylene, PCE perchloroethylene

The basic differences between these two sources are the dose rate and penetration. Gamma rays are highly penetrating, enabling the processing of bulk material. Ionizing radiation leads to OH radical formation in water dependent on dose, rate, and irradiation time (Borrely et al. 1998 (link); Pikaev 2000 (link); Getoff 2002 (link)). When wastewater is irradiated, organic molecules are oxidized. Irradiation excites water electronically and some ions, excited molecules, and free radicals are formed. In the presence of oxygen in water, H⋅-atoms and e−aq (solvated electrons) are converted into oxidizing species: Perhydroxyl radicals (HO2) and anions (O2−), (HO2) and (O2−) together with OH-radicals initiate degradation of pollutants.
The gamma irradiation (60Co) dose required for the elimination of estrogen activity below 1 ng L−1 has been found to be about 0.2 kGy (Kimura et al. 2007a (link)). Complete decomposition of DCF (50 mg L−1) in aqueous solutions requires 4.0 kGy (60Co); however, saturation with N2O decreases the dose to 1.0 kGy (Trojanowicz et al. 2012 ). The sterilization dose for DCF sodium salt, as a pharmaceutical raw material, has been found to be 12.4 kGy (60Co) (Ozer et al. 2013 ). Homlok et al. 2011 (link) described complete removal of DCF with 1.0 kGy. When cost is an issue, it is difficult to give a precise price for irradiation systems in advance because of the many factors involved: the kind and amount of pollutants in water, their properties (chemical, biological, etc.), dose-rate to be used, presence of ozone, combined methods of radiation, and conventional techniques. In general, costs decrease with increase of treatment capacity, and it is possible to say that γ-irradiation costs about four times more than e-beam irradiation because of the high cost of 60Co source and the facility (Borrely et al. 1998 (link)).
Schröder P., Helmreich B., Škrbić B., Carballa M., Papa M., Pastore C., Emre Z., Oehmen A., Langenhoff A., Molinos M., Dvarioniene J., Huber C., Tsagarakis K.P., Martinez-Lopez E., Pagano S.M., Vogelsang C, & Mascolo G. (2016). Status of hormones and painkillers in wastewater effluents across several European states—considerations for the EU watch list concerning estradiols and diclofenac. Environmental Science and Pollution Research International, 23, 12835-12866.
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Publication 2016
Anions Biopharmaceuticals Dietary Fiber Disinfection Electromagnetic Radiation Electrons Environmental Pollutants Estrogens Free Radicals Gamma Rays Ions Ozone perhydroxyl radical Pharmaceutical Preparations Radiation Radiation, Ionizing Radiotherapy Sodium Sodium Chloride Sterilization Trichloroethylene
5
PFAS Removal by Oxygenated Persulfate Treatment
Not available on PMC !

Example 5

This experiment was conducted in steam distilled water spiked with PFAS to evaluate the removal, degradation and de-fluorination of PFOS and PFOA during treatment with oxygenated buffered persulfate. The experiment was specifically designed to evaluate the integrated mechanisms of 1) chemical degradation by oxidation and/or reduction of PFAS; and 2) transfer of PFAS from buffered persulfate as an aerosol or foam by sparging pure oxygen gas into phosphate buffered persulfate water containing PFOS and PFOA. The solution pH was approximately pH 9.0.

Procedure

The experiment was conducted in a plastic column reactor with a sparger at the bottom of the reactor that was filled with steam distilled water. Pure oxygen was sparged into the solution at the bottom of the reactor. The off-gas from the column reactor was passed through an off-gas trap to catch any aerosols or foam and ultimately vented to the ambient atmosphere.

The plastic column reactor and the off-gas trap were tested prior to the experiment to confirm that they did not sorb or desorb fluoride, PFOS, or PFOA. The distilled water used in the testing, as in some of the previously described experiments, contained a background concentration of 3-4 ug/l of fluoride.

To create the test solution, PFOS and PFOA were spiked into 2.3 liters of distilled water, followed by phosphate buffer and persulfate addition at the same concentrations as in previous experiments, to produce a test solution with a pH between pH 9 and pH 10.

This test solution was analyzed for PFAS, pH, and fluoride and transferred to the column reactor where pure oxygen was sparged into the solution at various flowrates and pressures. The fluoride concentration was analyzed as explained previously to assess de-fluorination of the PFAS compounds. At various intervals during the 48 hour experiment, samples were collected from the column and off-gas trap for PFAS analysis.

FIG. 3 and Table 5 present the resulting measured concentration of PFAS over time. The PFAS consists of PFOS and PFOA plus small concentrations of six other PFAS believed to be minor contaminants contained within the purchased PFOS and PFOA chemicals. Only one PFAS, perfluoroheptanesulfonate, was detected greater than 1 ug/l.

TABLE 5
PFAS Experimental Data from Column Reactor
0 hours1 hour2 hours48 hours% removal
PFASConcentration of PFAS (micrograms/liter = ppb).
6:2 Fluorotelomer sulfonate0.25<2.1<0.21<0.01696.8%
Perfluorobutane Sulfonate (PFBS)0.32<2.30.300.009197.2%
Perfluorobutanoic acid<20012<2000.1099.9%
Perfluoroheptane sulfonate6.66.33.20.01099.8%
Perfluoroheptanoic Acid (PFHpA)0.55<2.70.51<0.01298.9%
Perfluorohexane Sulfonate (PFHxS)0.781.70.75<0.01099.4%
Perfluorohexanoic Acid (PFHxA)0.41<1.70.420.01696.1%
Perfluoro-n-Octanoic Acid (PFOA)2502802200.1999.9%
Perfluorooctane Sulfonate (PFOS)18072230.1199.9%
Perfluoropentanoic Acid (PFPeA)<0.21<2.1<0.210.11NC
Perfluorotetradecanoic Acid<0.202.2<0.20<0.013NC
Perfluoroundecanoic Acid (PFUnA)0.15<1.4<0.14<0.009399.7%
TOTAL PFAS (ppb)4393742480.5599.9%
NC: Not Calculated (due to no detection in original sample)

As shown in FIG. 3 and Table 5, the concentration of total detected PFAS in the column reactor decreased by 99.9% within 48 hours, from 439 ppb to >0.6 ppb. The two added compounds, PFOS and PFOA, had an initial concentration of 180 and 250 ppb, respectively, which decreased by 99.9% to 0.11 and 0.19 ppb, respectively, during the same time period. These concentrations are less than the 2009 EPA Provisional Health Advisory Guidelines of 0.2 and 0.4 ppb, respectively, for PFOS and PFOA. The rate of PFAS concentration decrease in the reactor was most significant in the beginning of the test.

The initial PFAS mass in the water contained in the column reactor was 1,010 micrograms but after the 48 hours of testing and 99.9% removal, only 1 microgram of PFAS remained.

Approximately 26% of the initial 1,010 micrograms of PFAS in the column reactor (i.e. 260 micrograms) was transferred with the off-gas from the column reactor to the off-gas water trap. Very little PFAS (0.6 micrograms) were transferred in the first hour, 18 micrograms (2% of the total) in the second hour, with the majority (241 micrograms) of the PFAS transferred between 2 to 48 hours.

The fluoride concentration in the column reactor gradually increased from the initial time zero (i.e., before oxygenation) concentration of 17 ug/l to 52 ug/l after 48 hours. The rate of PFAS de-fluorination resulting in the release of fluoride decreased during the 48 hour test, from 16 micrograms during the first hour, 8 micrograms during the second hour, 4 micrograms/hour for the next 7.5 hours and 1.6 micrograms/hour thereafter. This indicates that, in addition to the PFAS that was transferred from the column reactor to the off-gas trap, some of the PFAS in the reactor was de-fluorinated as indicated by an increase in fluoride anion concentration. Over the 48 hour testing period, the total amount of fluoride released in the column reactor water was 73 micrograms, or about 11% of the theoretical fluorine mass contained in the initial PFAS.

During the 48 hour test the fluoride concentration in each of the three off-gas trap samples also increased from the background concentration of 3 ug/l in the distilled water. The rate of fluoride released and/or transferred to the traps was highest at the beginning of the test with 0.3 microgram released during the first hour, 0.8 microgram released in the second hour, and less than 0.1 microgram released per hour from 2 to 48 hours. In total, 4.4 micrograms of fluoride was released into the three sequential off-gas traps. This is about 1% of all the fluoride contained in the PFAS at time zero. So in total, together with the 11% fluoride released in the column, about 12% of the organofluorine contained in the initial PFAS mass was de-fluorinated to fluoride.

Based on these PFAS and fluoride measurements throughout this 48-hour experiment, the following fluoride mass balance shown in FIG. 4 pie chart results shows the disposition of the initial PFAS during the experiment. The integrated PFAS removal mechanisms of chemical degradation and transfer from the liquid phase as shown in the pie chart indicates that:

    • 0.1% of the initial PFAS was still in the column reactor at the end of 48-hours
    • 26% of the initial PFAS was transferred to the off-gas water trap;
    • 10.7% of the fluorine in initial PFAS was de-fluorinated to fluoride anion and measured in the column reactor;
    • 0.6% of fluorine in the initial PFAS was mineralized to fluoride anion and measured in the off-gas trap;
    • After 48 hours, the remaining 63% of the PFAS remained in the column reactor or the off-gas traps as unidentifiable poly- or per-fluorinated PFAS, or as non-fluorinated breakdown products of PFAS.

The following conclusions are drawn from the experimental results:

    • The oxygenated phosphate buffered persulfate de-fluorinates PFAS and releases fluoride anion.
    • 26% of the PFAS was transferred from the water to the off-gas as aerosols or foam such that more than 99% of PFOS and PFOA were removed from the water in the column reactor.
    • A total of 12% of the organofluorine in PFAS was de-fluorinated to fluoride.

Definitions

“Persulfate” includes both monopersulfate and dipersulfate. Typically, persulfate is in the form of aqueous sodium, potassium or ammonium dipersulfate or sodium or potassium monopersulfate or a mixture thereof.

As used herein, “phosphate” includes both inorganic and organic forms. It can be supplied as a simple inorganic phosphate in the form of sodium or potassium dibasic phosphate, or as sodium or potassium monobasic phosphate, or sodium or potassium tribasicphosphate. The simple forms of phosphate are used as pH buffers. Phosphates can also be supplied as complex inorganic phosphate in the form of sodium tripolyphosphate, sodium-potassium tripolyphosphate, tetrasodium polyphosphate, sodium hexametaphosphate, and sodium trimetaphosphate. These phosphates can also be used as a phosphate source. In aqueous solution, the hydrolytic stability of the phosphate depends on the original phosphate compound. For example, linear polyphosphates undergo slow hydrolysis. This process continues as the shorter chain polyphosphates break down further to yield still shorter chain polyphosphates, metaphosphates, and orthophosphates. Generally, lower pH and higher temperature will increase the rate of hydrolysis. Long chain polyphosphates will break down into shorter, but still functional, polyphosphates. Sodium tripolyphosphate is a strong cleaning ingredient used in detergents to aid surfactants and act as a pH buffer.

Phosphate can also be supplied as phosphonate, which is an organic form of phosphate containing C—PO(OH)2 or C—PO(OR)2 groups (where R=alkyl, aryl). Phosphonates are known as effective chelating agents. The introduction of an amine group into the molecule to obtain —NH2-C—PO(OH)2 increases the metal binding abilities of the phosphonate. Examples for such compounds are EDTMP and DTPMP. These common phosphonates are the structure analogues to the well-known aminopolycarboxylates NTA, EDTA, and DTPA. The stability of the metal complexes increases with increasing number of phosphonic acid groups. Phosphonates are highly water-soluble while the phosphonic acids are only sparingly soluble.

In addition, phosphate can also be supplied as a peroxodiphosphate or perphosphate, which is a peroxide form of phosphate. It is known to form radicals when activated and reacted with organic compounds similarly to persulfate. As the perphosphate radical reacts with organic compounds, it decomposes to perphosphate anions. The rate of reaction with organic compounds is usually much slower compared to persulfate.

When a phosphate will be added to any water that can be potentially used for drinking water, there are approved phosphate compounds that can be added. According to the National Sanitation Foundation, phosphate products for supply of phosphate in potable water conditions can be broadly classified as: phosphoric acid, orthophosphates, and condensed phosphates. These are listed here in detail:

1) Phosphoric Acids

2) Orthophosphates: Monosodium Phosphate (MSP), Disodium Phosphate (DSP), Trisodium Phosphate (TSP), Monosodium Phosphate (MKP), Dipotassium Phosphate (DKP), Tricalcium Phosphate (TCP)

3) Condensed Phosphates: Sodium Acid Pyrophosphate (SAPP), Sodium Trimetaphosphate (STMP), Tetrasodium Pyrophosphate (TSPP), Sodium Tripolyphosphate (STP) and Tetrapotassium Pyrophosphate (TKPP), Sodium Heaxametaphosphate (SHMP).

In addition to the use of phosphates for buffering, reaction enhancement, and radical formation in organic chemical reactions, phosphates also play an important role in soluble metal sequestration and they can form metal precipitates. Phosphate sequestration of metals is a chemical combination of a phosphate chelating agent and metal ions in which soluble complexes are formed. Sequestration is dependent upon pH and a given sequestrant typically works best within a certain pH range. Sodium hexmetaphosphates (SHMP) performs well at neutral pH ranges, while pyrophosphates and polyphosphates work best under alkaline conditions. Phosphate can be used to precipitate unwanted metals, such as lead, from aqueous solution. For example, phosphate forms a lead-phosphate precipitate at an optimal pH around pH 6.0. Phosphate can under certain conditions also react with native metals in a soil/water environment to render the metals non-reactive with any reagents introduced into this environment.

The simple phosphates used as pH buffers are added in concentration ranges from 1 gram per liter (g/l) to 15 g/l in a pH range from pH 4 to pH10. The complex phosphates can be supplied at 1 g/l to 15 g/l in a pH range from pH 4 to pH 10. Phosphate compounds can be added simultaneously or sequentially with the other reagents.

Phosphate compounds can be mixed with other liquid oxidants, such as sodium persulfate and hydrogen peroxide, and then injected to remediate contaminated soil and groundwater. Phosphate compounds can also be dissolved in water and injected by themselves, to bolster treatment zone pH, to activate oxidants, to complex and isolate metals found in the soil formation, and to act as a nutrient source for bioremediation purposes.

These phosphate compounds can be mixed with each other or the other oxidants. Phosphate radical (e.g. HPO4r-) is produced from unactivated phosphate species in the presence of ozone through a multi-step process. First, dissolved ozone reacts with hydroxyl anion in solution to form perhydroxyl anion (HO2-). Ozone then reacts with perhydroxyl anion to form superoxide radical and hydroxyl radical. Phosphates scavenge the hydroxyl radical to produce a phosphate radical species. This phosphate radical can then activate persulfate anion to form sulfate radical.

Example Persulfate activation pathway:

O3+OH-−>HO2r-+O2

O3+HO2r-−>O2r-+OHr+O2

HPO4-2+OHr−>HPO4-+OH—

HPO4r-+S2O8-2−>HPO4-2+SO4-2+SO4r

There are known to be other phosphate species such as HPO3r-radical that can react similarly with persulfate anion to produce sulfate radical.

Several phosphate species, such as peroxydiphosphate (P208-4), will decompose to form phosphate radical species (i.e. PO4r-2). Using an oxidizing form of phosphate like this can avoid the initial activation mechanism involving hydroxyl radical scavenging in order to activate persulfate anion, while still providing buffering capacity after persulfate activation has occurred. Additionally, ozone can then be used to reactivate the spent phosphate for further persulfate anion activation.

Possible reaction pathway: P2O8-4−>2PO4r-2

PO4r-2+S2O8-2−>PO4-3+SO4-2+SO4r

Which then continues like the persulfate activation pathway above.

“Oxygen” includes all forms of gaseous, liquid, and solid oxygen such as pure oxygen gas, air, hydrogen peroxide, and all other inorganic peroxides such as calcium or magnesium peroxide or organic peroxides, such as organic peroxides available from Luperox.

“Salt” includes sodium chloride and other species having both cationic or cationizable components and anionic or anionizable components.

“Oxidizing radicals” includes sulfate radical, hydroxyl radical, hydroperoxide, phosphate radical and others.

“Reducing radicals” includes superoxide.

“Saturated zone” refers to the region of the soil profile that is consistently below ground water level.

“Unsaturated zone” refers to the region of the soil profile that is consistently above ground water level.

“Smear zone” refers to the region of the soil profile through which the ground water level fluctuates, typically on a seasonal basis. The smear zone is the region that when the ground water is at its highest would be considered saturated and when the ground water is at its lowest would be considered unsaturated. It is also called the capillary zone.

“Organic contaminant” is an organic compound that is not native to the soil or water in which it is found. Organic compounds may include, for example, poly- and perfluoralkyl compounds (PFAAs), hydrocarbon-based fuels, halogenated and non-halogenated solvents, pesticides, herbicides, PCBs, volatile hydrocarbons, semi-volatile hydrocarbons, chlorinated volatile hydrocarbons, BTEX and MTBE.

“Area or Radius of influence” describes the area around a well or other injection point defining an area throughout which an adequate amount of reactant can be introduced to oxidize at least some of the organic contaminant present.

While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used.

Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the scope of the present invention. All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that 20 are conjunctively present in some cases and disjunctively present in other cases. All references, patents and patent applications and publications that are cited or referred to in this application are incorporated in their entirety herein by reference.

US11148964B2. Soil and water remediation method and apparatus for treatment of recalcitrant halogenated substances (2021-10-19). OXYTEC LLC [US]. Inventors: Raymond G. Ball [US].
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Patent 2021

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Mechanical Refining of Pretreated Oil Palm EFB

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2
PFAS Removal by Oxygenated Persulfate Treatment
Not available on PMC !

Example 5

This experiment was conducted in steam distilled water spiked with PFAS to evaluate the removal, degradation and de-fluorination of PFOS and PFOA during treatment with oxygenated buffered persulfate. The experiment was specifically designed to evaluate the integrated mechanisms of 1) chemical degradation by oxidation and/or reduction of PFAS; and 2) transfer of PFAS from buffered persulfate as an aerosol or foam by sparging pure oxygen gas into phosphate buffered persulfate water containing PFOS and PFOA. The solution pH was approximately pH 9.0.

Procedure

The experiment was conducted in a plastic column reactor with a sparger at the bottom of the reactor that was filled with steam distilled water. Pure oxygen was sparged into the solution at the bottom of the reactor. The off-gas from the column reactor was passed through an off-gas trap to catch any aerosols or foam and ultimately vented to the ambient atmosphere.

The plastic column reactor and the off-gas trap were tested prior to the experiment to confirm that they did not sorb or desorb fluoride, PFOS, or PFOA. The distilled water used in the testing, as in some of the previously described experiments, contained a background concentration of 3-4 ug/l of fluoride.

To create the test solution, PFOS and PFOA were spiked into 2.3 liters of distilled water, followed by phosphate buffer and persulfate addition at the same concentrations as in previous experiments, to produce a test solution with a pH between pH 9 and pH 10.

This test solution was analyzed for PFAS, pH, and fluoride and transferred to the column reactor where pure oxygen was sparged into the solution at various flowrates and pressures. The fluoride concentration was analyzed as explained previously to assess de-fluorination of the PFAS compounds. At various intervals during the 48 hour experiment, samples were collected from the column and off-gas trap for PFAS analysis.

FIG. 3 and Table 5 present the resulting measured concentration of PFAS over time. The PFAS consists of PFOS and PFOA plus small concentrations of six other PFAS believed to be minor contaminants contained within the purchased PFOS and PFOA chemicals. Only one PFAS, perfluoroheptanesulfonate, was detected greater than 1 ug/l.

TABLE 5
PFAS Experimental Data from Column Reactor
0 hours1 hour2 hours48 hours% removal
PFASConcentration of PFAS (micrograms/liter = ppb).
6:2 Fluorotelomer sulfonate0.25<2.1<0.21<0.01696.8%
Perfluorobutane Sulfonate (PFBS)0.32<2.30.300.009197.2%
Perfluorobutanoic acid<20012<2000.1099.9%
Perfluoroheptane sulfonate6.66.33.20.01099.8%
Perfluoroheptanoic Acid (PFHpA)0.55<2.70.51<0.01298.9%
Perfluorohexane Sulfonate (PFHxS)0.781.70.75<0.01099.4%
Perfluorohexanoic Acid (PFHxA)0.41<1.70.420.01696.1%
Perfluoro-n-Octanoic Acid (PFOA)2502802200.1999.9%
Perfluorooctane Sulfonate (PFOS)18072230.1199.9%
Perfluoropentanoic Acid (PFPeA)<0.21<2.1<0.210.11NC
Perfluorotetradecanoic Acid<0.202.2<0.20<0.013NC
Perfluoroundecanoic Acid (PFUnA)0.15<1.4<0.14<0.009399.7%
TOTAL PFAS (ppb)4393742480.5599.9%
NC: Not Calculated (due to no detection in original sample)

As shown in FIG. 3 and Table 5, the concentration of total detected PFAS in the column reactor decreased by 99.9% within 48 hours, from 439 ppb to >0.6 ppb. The two added compounds, PFOS and PFOA, had an initial concentration of 180 and 250 ppb, respectively, which decreased by 99.9% to 0.11 and 0.19 ppb, respectively, during the same time period. These concentrations are less than the 2009 EPA Provisional Health Advisory Guidelines of 0.2 and 0.4 ppb, respectively, for PFOS and PFOA. The rate of PFAS concentration decrease in the reactor was most significant in the beginning of the test.

The initial PFAS mass in the water contained in the column reactor was 1,010 micrograms but after the 48 hours of testing and 99.9% removal, only 1 microgram of PFAS remained.

Approximately 26% of the initial 1,010 micrograms of PFAS in the column reactor (i.e. 260 micrograms) was transferred with the off-gas from the column reactor to the off-gas water trap. Very little PFAS (0.6 micrograms) were transferred in the first hour, 18 micrograms (2% of the total) in the second hour, with the majority (241 micrograms) of the PFAS transferred between 2 to 48 hours.

The fluoride concentration in the column reactor gradually increased from the initial time zero (i.e., before oxygenation) concentration of 17 ug/l to 52 ug/l after 48 hours. The rate of PFAS de-fluorination resulting in the release of fluoride decreased during the 48 hour test, from 16 micrograms during the first hour, 8 micrograms during the second hour, 4 micrograms/hour for the next 7.5 hours and 1.6 micrograms/hour thereafter. This indicates that, in addition to the PFAS that was transferred from the column reactor to the off-gas trap, some of the PFAS in the reactor was de-fluorinated as indicated by an increase in fluoride anion concentration. Over the 48 hour testing period, the total amount of fluoride released in the column reactor water was 73 micrograms, or about 11% of the theoretical fluorine mass contained in the initial PFAS.

During the 48 hour test the fluoride concentration in each of the three off-gas trap samples also increased from the background concentration of 3 ug/l in the distilled water. The rate of fluoride released and/or transferred to the traps was highest at the beginning of the test with 0.3 microgram released during the first hour, 0.8 microgram released in the second hour, and less than 0.1 microgram released per hour from 2 to 48 hours. In total, 4.4 micrograms of fluoride was released into the three sequential off-gas traps. This is about 1% of all the fluoride contained in the PFAS at time zero. So in total, together with the 11% fluoride released in the column, about 12% of the organofluorine contained in the initial PFAS mass was de-fluorinated to fluoride.

Based on these PFAS and fluoride measurements throughout this 48-hour experiment, the following fluoride mass balance shown in FIG. 4 pie chart results shows the disposition of the initial PFAS during the experiment. The integrated PFAS removal mechanisms of chemical degradation and transfer from the liquid phase as shown in the pie chart indicates that:

    • 0.1% of the initial PFAS was still in the column reactor at the end of 48-hours
    • 26% of the initial PFAS was transferred to the off-gas water trap;
    • 10.7% of the fluorine in initial PFAS was de-fluorinated to fluoride anion and measured in the column reactor;
    • 0.6% of fluorine in the initial PFAS was mineralized to fluoride anion and measured in the off-gas trap;
    • After 48 hours, the remaining 63% of the PFAS remained in the column reactor or the off-gas traps as unidentifiable poly- or per-fluorinated PFAS, or as non-fluorinated breakdown products of PFAS.

The following conclusions are drawn from the experimental results:

    • The oxygenated phosphate buffered persulfate de-fluorinates PFAS and releases fluoride anion.
    • 26% of the PFAS was transferred from the water to the off-gas as aerosols or foam such that more than 99% of PFOS and PFOA were removed from the water in the column reactor.
    • A total of 12% of the organofluorine in PFAS was de-fluorinated to fluoride.

Definitions

“Persulfate” includes both monopersulfate and dipersulfate. Typically, persulfate is in the form of aqueous sodium, potassium or ammonium dipersulfate or sodium or potassium monopersulfate or a mixture thereof.

As used herein, “phosphate” includes both inorganic and organic forms. It can be supplied as a simple inorganic phosphate in the form of sodium or potassium dibasic phosphate, or as sodium or potassium monobasic phosphate, or sodium or potassium tribasicphosphate. The simple forms of phosphate are used as pH buffers. Phosphates can also be supplied as complex inorganic phosphate in the form of sodium tripolyphosphate, sodium-potassium tripolyphosphate, tetrasodium polyphosphate, sodium hexametaphosphate, and sodium trimetaphosphate. These phosphates can also be used as a phosphate source. In aqueous solution, the hydrolytic stability of the phosphate depends on the original phosphate compound. For example, linear polyphosphates undergo slow hydrolysis. This process continues as the shorter chain polyphosphates break down further to yield still shorter chain polyphosphates, metaphosphates, and orthophosphates. Generally, lower pH and higher temperature will increase the rate of hydrolysis. Long chain polyphosphates will break down into shorter, but still functional, polyphosphates. Sodium tripolyphosphate is a strong cleaning ingredient used in detergents to aid surfactants and act as a pH buffer.

Phosphate can also be supplied as phosphonate, which is an organic form of phosphate containing C—PO(OH)2 or C—PO(OR)2 groups (where R=alkyl, aryl). Phosphonates are known as effective chelating agents. The introduction of an amine group into the molecule to obtain —NH2-C—PO(OH)2 increases the metal binding abilities of the phosphonate. Examples for such compounds are EDTMP and DTPMP. These common phosphonates are the structure analogues to the well-known aminopolycarboxylates NTA, EDTA, and DTPA. The stability of the metal complexes increases with increasing number of phosphonic acid groups. Phosphonates are highly water-soluble while the phosphonic acids are only sparingly soluble.

In addition, phosphate can also be supplied as a peroxodiphosphate or perphosphate, which is a peroxide form of phosphate. It is known to form radicals when activated and reacted with organic compounds similarly to persulfate. As the perphosphate radical reacts with organic compounds, it decomposes to perphosphate anions. The rate of reaction with organic compounds is usually much slower compared to persulfate.

When a phosphate will be added to any water that can be potentially used for drinking water, there are approved phosphate compounds that can be added. According to the National Sanitation Foundation, phosphate products for supply of phosphate in potable water conditions can be broadly classified as: phosphoric acid, orthophosphates, and condensed phosphates. These are listed here in detail:

1) Phosphoric Acids

2) Orthophosphates: Monosodium Phosphate (MSP), Disodium Phosphate (DSP), Trisodium Phosphate (TSP), Monosodium Phosphate (MKP), Dipotassium Phosphate (DKP), Tricalcium Phosphate (TCP)

3) Condensed Phosphates: Sodium Acid Pyrophosphate (SAPP), Sodium Trimetaphosphate (STMP), Tetrasodium Pyrophosphate (TSPP), Sodium Tripolyphosphate (STP) and Tetrapotassium Pyrophosphate (TKPP), Sodium Heaxametaphosphate (SHMP).

In addition to the use of phosphates for buffering, reaction enhancement, and radical formation in organic chemical reactions, phosphates also play an important role in soluble metal sequestration and they can form metal precipitates. Phosphate sequestration of metals is a chemical combination of a phosphate chelating agent and metal ions in which soluble complexes are formed. Sequestration is dependent upon pH and a given sequestrant typically works best within a certain pH range. Sodium hexmetaphosphates (SHMP) performs well at neutral pH ranges, while pyrophosphates and polyphosphates work best under alkaline conditions. Phosphate can be used to precipitate unwanted metals, such as lead, from aqueous solution. For example, phosphate forms a lead-phosphate precipitate at an optimal pH around pH 6.0. Phosphate can under certain conditions also react with native metals in a soil/water environment to render the metals non-reactive with any reagents introduced into this environment.

The simple phosphates used as pH buffers are added in concentration ranges from 1 gram per liter (g/l) to 15 g/l in a pH range from pH 4 to pH10. The complex phosphates can be supplied at 1 g/l to 15 g/l in a pH range from pH 4 to pH 10. Phosphate compounds can be added simultaneously or sequentially with the other reagents.

Phosphate compounds can be mixed with other liquid oxidants, such as sodium persulfate and hydrogen peroxide, and then injected to remediate contaminated soil and groundwater. Phosphate compounds can also be dissolved in water and injected by themselves, to bolster treatment zone pH, to activate oxidants, to complex and isolate metals found in the soil formation, and to act as a nutrient source for bioremediation purposes.

These phosphate compounds can be mixed with each other or the other oxidants. Phosphate radical (e.g. HPO4r-) is produced from unactivated phosphate species in the presence of ozone through a multi-step process. First, dissolved ozone reacts with hydroxyl anion in solution to form perhydroxyl anion (HO2-). Ozone then reacts with perhydroxyl anion to form superoxide radical and hydroxyl radical. Phosphates scavenge the hydroxyl radical to produce a phosphate radical species. This phosphate radical can then activate persulfate anion to form sulfate radical.

Example Persulfate activation pathway:

O3+OH-−>HO2r-+O2

O3+HO2r-−>O2r-+OHr+O2

HPO4-2+OHr−>HPO4-+OH—

HPO4r-+S2O8-2−>HPO4-2+SO4-2+SO4r

There are known to be other phosphate species such as HPO3r-radical that can react similarly with persulfate anion to produce sulfate radical.

Several phosphate species, such as peroxydiphosphate (P208-4), will decompose to form phosphate radical species (i.e. PO4r-2). Using an oxidizing form of phosphate like this can avoid the initial activation mechanism involving hydroxyl radical scavenging in order to activate persulfate anion, while still providing buffering capacity after persulfate activation has occurred. Additionally, ozone can then be used to reactivate the spent phosphate for further persulfate anion activation.

Possible reaction pathway: P2O8-4−>2PO4r-2

PO4r-2+S2O8-2−>PO4-3+SO4-2+SO4r

Which then continues like the persulfate activation pathway above.

“Oxygen” includes all forms of gaseous, liquid, and solid oxygen such as pure oxygen gas, air, hydrogen peroxide, and all other inorganic peroxides such as calcium or magnesium peroxide or organic peroxides, such as organic peroxides available from Luperox.

“Salt” includes sodium chloride and other species having both cationic or cationizable components and anionic or anionizable components.

“Oxidizing radicals” includes sulfate radical, hydroxyl radical, hydroperoxide, phosphate radical and others.

“Reducing radicals” includes superoxide.

“Saturated zone” refers to the region of the soil profile that is consistently below ground water level.

“Unsaturated zone” refers to the region of the soil profile that is consistently above ground water level.

“Smear zone” refers to the region of the soil profile through which the ground water level fluctuates, typically on a seasonal basis. The smear zone is the region that when the ground water is at its highest would be considered saturated and when the ground water is at its lowest would be considered unsaturated. It is also called the capillary zone.

“Organic contaminant” is an organic compound that is not native to the soil or water in which it is found. Organic compounds may include, for example, poly- and perfluoralkyl compounds (PFAAs), hydrocarbon-based fuels, halogenated and non-halogenated solvents, pesticides, herbicides, PCBs, volatile hydrocarbons, semi-volatile hydrocarbons, chlorinated volatile hydrocarbons, BTEX and MTBE.

“Area or Radius of influence” describes the area around a well or other injection point defining an area throughout which an adequate amount of reactant can be introduced to oxidize at least some of the organic contaminant present.

While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used.

Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the scope of the present invention. All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that 20 are conjunctively present in some cases and disjunctively present in other cases. All references, patents and patent applications and publications that are cited or referred to in this application are incorporated in their entirety herein by reference.

US11148964B2. Soil and water remediation method and apparatus for treatment of recalcitrant halogenated substances (2021-10-19). OXYTEC LLC [US]. Inventors: Raymond G. Ball [US].
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Patent 2021
3
Radiolytic Pathway Modeling for Cellular Oxidation
Not available on PMC !

Protocol full text hidden due to copyright restrictions

Open the protocol to access the free full text link

Publication 2020
4
Simulating Radiation-Induced Oxygen Interactions
Cited 4 times
The classical version of the TRAX-CHEM code has been modified and is now able to simulate the chemical evolution of ion tracks in water targets under different oxygen pressure conditions. The particle list and the reaction network of the classical version of the TRAX-CHEM code have been, thus, extended (see Table 1 and Table 2) and new species, generated by the interaction of O2 with the radiation-induced water-free radicals, are now included in the track chemical evolution.
In contrast to all other species, which are explicitly included in the code and treated with the step by step approach mentioned above, the molecular oxygen is assumed to be homogeneously distributed in the target and is treated as a continuum. This approximation, proposed by Pimblott et al. [45 (link)], Green et al. [46 (link)], is necessary to limit the computational cost of the simulations and has also been adopted by other authors [13 (link),14 (link),47 (link),48 (link)]. The explicit introduction of the oxygen in the simulation would dramatically increase the computing time, even for very dilute solutions [45 (link)]. As an example, in a chemical simulation of a 10 MeV proton track in a cubic volume of 5 μ m side the number of radiolytic species produced per particle track is about 10 3 . In a fully oxygenated condition (21% pO2 , corresponding to a concentration of 0.27 mmol/litre) the number of oxygen molecule that have to be explicitly introduced (in the same cubic volume of 5 μ m side) and followed at every single step of the simulation is about 2 × 10 7 , increasing the simulation time by more than four orders of magnitude. Considering the relatively low radiation-induced oxygen consumption compared to the total amount of molecular oxygen dissolved in the target, a variation of the global oxygen concentration during the track evolution can be excluded for all the oxygenations and radiation conditions examined. When investigating the possibility of noticeable local oxygen depletion in the track cores, it has to be kept in mind that the interaction of the radiolytic species with the target occurs in a later stage of the expanding chemical track evolution since the reaction dynamic between the induced chemical species is slower. For high LET ions (∼100 keV/ μ m), the highest local density of oxygen removal is reached around 10 ns within 10-20 nm of the track core and stays below 250 μ M, quickly decreasing as the chemical track diffuses and oxygen conversion to superoxide and perhydroxyl becomes important. For even larger LET values, only a slightly delayed onset of the HO2• and O2•− production can, therefore, be expected. Similar conclusions have been reported by Colliaux et al. [15 (link)]. Additionally, the molecular oxygen production through multiple ionizations is not accounted for here, but it has been demonstrated that the contribution of this process to the radical yield is very low [15 (link)].
Under these conditions, given an oxygen concentration cs , the probability for a radiolytic species to interact with an oxygen molecule of the target is determined by the rate equation: dΩ(t)dt=−k(t)csΩ(t),
where Ω(t) is the time-dependent survival probability of the molecule of interest. The time dependent rate coefficient k(t) for the reaction of interest can be calculated according to the Noyes theory [49 ], as: k(t)=4πD′Rreac1+RreacπD′t,
where D′ is the relative diffusion coefficient defined, considering the two species A and B, D′=DA+DB and Rreac is the reaction radius defined according to the Smoluchowski theory, as
Rreac=kAB4π(DA+DB).
The probability for a molecule to react with the dissolved oxygen in a time t will, thus, be: W(t)=1−Ω(t)=1−e−4πD′Rreaccst+2RreactπD′.
Since TRAX-CHEM uses a variable time step, the probability W(t) that a species will interact is calculated for each time step and is sampled through a uniformly distributed random variable x∈[0:1] . When x≤W(t) the reaction is taking place, the reactants are removed from the simulation and replaced by the corresponding reaction products.
Boscolo D., Krämer M., Fuss M.C., Durante M, & Scifoni E. (2020). Impact of Target Oxygenation on the Chemical Track Evolution of Ion and Electron Radiation. International Journal of Molecular Sciences, 21(2), 424.
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Publication 2020
5
Oxidative Removal of PFAS by Buffered Persulfate
Not available on PMC !

Example 5

This experiment was conducted in steam distilled water spiked with PFAS to evaluate the removal, degradation and de-fluorination of PFOS and PFOA during treatment with oxygenated buffered persulfate. The experiment was specifically designed to evaluate the integrated mechanisms of 1) chemical degradation by oxidation and/or reduction of PFAS; and 2) transfer of PFAS from buffered persulfate as an aerosol or foam by sparging pure oxygen gas into phosphate buffered persulfate water containing PFOS and PFOA. The solution pH was approximately pH 9.0.

Procedure

The experiment was conducted in a plastic column reactor with a sparger at the bottom of the reactor that was filled with steam distilled water. Pure oxygen was sparged into the solution at the bottom of the reactor. The off-gas from the column reactor was passed through an off-gas trap to catch any aerosols or foam and ultimately vented to the ambient atmosphere.

The plastic column reactor and the off-gas trap were tested prior to the experiment to confirm that they did not sorb or desorb fluoride, PFOS, or PFOA. The distilled water used in the testing, as in some of the previously described experiments, contained a background concentration of 3-4 ug/l of fluoride.

To create the test solution, PFOS and PFOA were spiked into 2.3 liters of distilled water, followed by phosphate buffer and persulfate addition at the same concentrations as in previous experiments, to produce a test solution with a pH between pH 9 and pH 10.

This test solution was analyzed for PFAS, pH, and fluoride and transferred to the column reactor where pure oxygen was sparged into the solution at various flowrates and pressures. The fluoride concentration was analyzed as explained previously to assess de-fluorination of the PFAS compounds. At various intervals during the 48 hour experiment, samples were collected from the column and off-gas trap for PFAS analysis.

FIG. 3 and Table 5 present the resulting measured concentration of PFAS over time. The PFAS consists of PFOS and PFOA plus small concentrations of six other PFAS believed to be minor contaminants contained within the purchased PFOS and PFOA chemicals. Only one PFAS, perfluoroheptanesulfonate, was detected greater than 1 ug/l.

TABLE 5
PFAS Experimental Data from Column Reactor
0 hours1 hour2 hours48 hours% removal
PFASConcentration of PFAS (micrograms/liter = ppb)—
6:2 Fluorotelomer sulfonate0.25<2.1<0.21<0.01696.8%
Perfluorobutane Sulfonate (PFBS)0.32<2.30.300.009197.2%
Perfluorobutanoic acid<20012<2000.1099.9%
Perfluoroheptane sulfonate6.66.33.20.01099.8%
Perfluoroheptanoic Acid (PFHpA)0.55<2.70.51<0.01298.9%
Perfluorohexane Sulfonate (PFHxS)0.781.70.75<0.01099.4%
Perfluorohexanoic Acid (PFHxA)0.41<1.70.420.01696.1%
Perfluoro-n-Octanoic Acid (PFOA)2502802200.1999.9%
Perfluorooctane Sulfonate (PFOS)18072230.1199.9%
Perfluoropentanoic Acid (PFPeA)<0.21<2.1<0.210.11NC
Perfluorotetradecanoic Acid<0.202.2<0.20<0.013NC
Perfluoroundecanoic Acid (PFUnA)0.15<1.4<0.14<0.009399.7%
TOTAL PFAS (ppb)43937424803599.9%
NC: Not Calculated (due to no detection in original sample)

As shown in FIG. 3 and Table 5, the concentration of total detected PFAS in the column reactor decreased by 99.9% within 48 hours, from 439 ppb to >0.6 ppb. The two added compounds, PFOS and PFOA, had an initial concentration of 180 and 250 ppb, respectively, which decreased by 99.9% to 0.11 and 0.19 ppb, respectively, during the same time period. These concentrations are less than the 2009 EPA Provisional Health Advisory Guidelines of 0.2 and 0.4 ppb, respectively, for PFOS and PFOA. The rate of PFAS concentration decrease in the reactor was most significant in the beginning of the test.

The initial PFAS mass in the water contained in the column reactor was 1,010 micrograms but after the 48 hours of testing and 99.9% removal, only 1 microgram of PFAS remained.

Approximately 26% of the initial 1,010 micrograms of PFAS in the column reactor (i.e. 260 micrograms) was transferred with the off-gas from the column reactor to the off-gas water trap. Very little PFAS (0.6 micrograms) were transferred in the first hour, 18 micrograms (2% of the total) in the second hour, with the majority (241 micrograms) of the PFAS transferred between 2 to 48 hours.

The fluoride concentration in the column reactor gradually increased from the initial time zero (i.e., before oxygenation) concentration of 17 ug/l to 52 ug/l after 48 hours. The rate of PFAS de-fluorination resulting in the release of fluoride decreased during the 48 hour test, from 16 micrograms during the first hour, 8 micrograms during the second hour, 4 micrograms/hour for the next 7.5 hours and 1.6 micrograms/hour thereafter. This indicates that, in addition to the PFAS that was transferred from the column reactor to the off-gas trap, some of the PFAS in the reactor was de-fluorinated as indicated by an increase in fluoride anion concentration. Over the 48 hour testing period, the total amount of fluoride released in the column reactor water was 73 micrograms, or about 11% of the theoretical fluorine mass contained in the initial PFAS.

During the 48 hour test the fluoride concentration in each of the three off-gas trap samples also increased from the background concentration of 3 ug/l in the distilled water. The rate of fluoride released and/or transferred to the traps was highest at the beginning of the test with 0.3 microgram released during the first hour, 0.8 microgram released in the second hour, and less than 0.1 microgram released per hour from 2 to 48 hours. In total, 4.4 micrograms of fluoride was released into the three sequential off-gas traps. This is about 1% of all the fluoride contained in the PFAS at time zero. So in total, together with the 11% fluoride released in the column, about 12% of the organofluorine contained in the initial PFAS mass was de-fluorinated to fluoride.

Based on these PFAS and fluoride measurements throughout this 48-hour experiment, the following fluoride mass balance shown in FIG. 4 pie chart results shows the disposition of the initial PFAS during the experiment. The integrated PFAS removal mechanisms of chemical degradation and transfer from the liquid phase as shown in the pie chart indicates that:

    • 1. 0.1% of the initial PFAS was still in the column reactor at the end of 48-hours
    • 2. 26% of the initial PFAS was transferred to the off-gas water trap;
    • 3. 10.7% of the fluorine in initial PFAS was de-fluorinated to fluoride anion and measured in the column reactor;
    • 4. 0.6% of fluorine in the initial PFAS was mineralized to fluoride anion and measured in the off-gas trap;
    • 5. After 48 hours, the remaining 63% of the PFAS remained in the column reactor or the off-gas traps as unidentifiable poly- or per-fluorinated PFAS, or as non-fluorinated breakdown products of PFAS.

The following conclusions are drawn from the experimental results:

    • 1. The oxygenated phosphate buffered persulfate de-fluorinates PFAS and releases fluoride anion.
    • 2. 26% of the PFAS was transferred from the water to the off-gas as aerosols or foam such that more than 99% of PFOS and PFOA were removed from the water in the column reactor.
    • 3. A total of 12% of the organofluorine in PFAS was de-fluorinated to fluoride.
      Definitions

“Persulfate” includes both monopersulfate and dipersulfate. Typically, persulfate is in the form of aqueous sodium, potassium or ammonium dipersulfate or sodium or potassium monopersulfate or a mixture thereof.

As used herein, “phosphate” includes both inorganic and organic forms. It can be supplied as a simple inorganic phosphate in the form of sodium or potassium dibasic phosphate, or as sodium or potassium monobasic phosphate, or sodium or potassium tribasicphosphate. The simple forms of phosphate are used as pH buffers. Phosphates can also be supplied as complex inorganic phosphate in the form of sodium tripolyphosphate, sodium-potassium tripolyphosphate, tetrasodium polyphosphate, sodium hexametaphosphate, and sodium trimetaphosphate. These phosphates can also be used as a phosphate source. In aqueous solution, the hydrolytic stability of the phosphate depends on the original phosphate compound. For example, linear polyphosphates undergo slow hydrolysis. This process continues as the shorter chain polyphosphates break down further to yield still shorter chain polyphosphates, metaphosphates, and orthophosphates. Generally, lower pH and higher temperature will increase the rate of hydrolysis. Long chain polyphosphates will break down into shorter, but still functional, polyphosphates. Sodium tripolyphosphate is a strong cleaning ingredient used in detergents to aid surfactants and act as a pH buffer.

Phosphate can also be supplied as phosphonate, which is an organic form of phosphate containing C—PO(OH)2 or C—PO(OR)2 groups (where R=alkyl, aryl). Phosphonates are known as effective chelating agents. The introduction of an amine group into the molecule to obtain —NH2-C—PO(OH)2 increases the metal binding abilities of the phosphonate. Examples for such compounds are EDTMP and DTPMP. These common phosphonates are the structure analogues to the well-known aminopolycarboxylates NTA, EDTA, and DTPA. The stability of the metal complexes increases with increasing number of phosphonic acid groups. Phosphonates are highly water-soluble while the phosphonic acids are only sparingly soluble.

In addition, phosphate can also be supplied as a peroxodiphosphate or perphosphate, which is a peroxide form of phosphate. It is known to form radicals when activated and reacted with organic compounds similarly to persulfate. As the perphosphate radical reacts with organic compounds, it decomposes to perphosphate anions. The rate of reaction with organic compounds is usually much slower compared to persulfate.

When a phosphate will be added to any water that can be potentially used for drinking water, there are approved phosphate compounds that can be added. According to the National Sanitation Foundation, phosphate products for supply of phosphate in potable water conditions can be broadly classified as: phosphoric acid, orthophosphates, and condensed phosphates. These are listed here in detail:

    • 1. Phosphoric Acids
    • 2. Orthophosphates: Monosodium Phosphate (MSP), Disodium Phosphate (DSP), Trisodium Phosphate (TSP), Monosodium Phosphate (MKP), Dipotassium Phosphate (DKP), Tricalcium Phosphate (TCP)
    • 3. Condensed Phosphates: Sodium Acid Pyrophosphate (SAPP), Sodium Trimetaphosphate (STMP), Tetrasodium Pyrophosphate (TSPP), Sodium Tripolyphosphate (STP) and Tetrapotassium Pyrophosphate (TKPP), Sodium Heaxametaphosphate (SHMP).

In addition to the use of phosphates for buffering, reaction enhancement, and radical formation in organic chemical reactions, phosphates also play an important role in soluble metal sequestration and they can form metal precipitates. Phosphate sequestration of metals is a chemical combination of a phosphate chelating agent and metal ions in which soluble complexes are formed. Sequestration is dependent upon pH and a given sequestrant typically works best within a certain pH range. Sodium hexmetaphosphates (SHMP) performs well at neutral pH ranges, while pyrophosphates and polyphosphates work best under alkaline conditions. Phosphate can be used to precipitate unwanted metals, such as lead, from aqueous solution. For example, phosphate forms a lead-phosphate precipitate at an optimal pH around pH 6.0. Phosphate can under certain conditions also react with native metals in a soil/water environment to render the metals non-reactive with any reagents introduced into this environment.

The simple phosphates used as pH buffers are added in concentration ranges from 1 gram per liter (g/l) to 15 g/l in a pH range from pH 4 to pH10. The complex phosphates can be supplied at 1 g/l to 15 g/l in a pH range from pH 4 to pH 10. Phosphate compounds can be added simultaneously or sequentially with the other reagents.

Phosphate compounds can be mixed with other liquid oxidants, such as sodium persulfate and hydrogen peroxide, and then injected to remediate contaminated soil and groundwater. Phosphate compounds can also be dissolved in water and injected by themselves, to bolster treatment zone pH, to activate oxidants, to complex and isolate metals found in the soil formation, and to act as a nutrient source for bioremediation purposes.

These phosphate compounds can be mixed with each other or the other oxidants. Phosphate radical (e.g. HPO4r-) is produced from unactivated phosphate species in the presence of ozone through a multi-step process. First, dissolved ozone reacts with hydroxyl anion in solution to form perhydroxyl anion (HO2-). Ozone then reacts with perhydroxyl anion to form superoxide radical and hydroxyl radical. Phosphates scavenge the hydroxyl radical to produce a phosphate radical species. This phosphate radical can then activate persulfate anion to form sulfate radical.

Example Persulfate activation pathway:
O3+OH—→HO2r-+O2O3+HO2r-→O2r-+OHr+O2HPO4-2+OHr→HPO4r-+OH—HPO4r-+S2O8-2→HPO4-2+SO4-2+SO4r

There are known to be other phosphate species such as HPO3r- radical that can react similarly with persulfate anion to produce sulfate radical.

Several phosphate species, such as peroxydiphosphate (P2O8-4), will decompose to form phosphate radical species (i.e. PO4r-2). Using an oxidizing form of phosphate like this can avoid the initial activation mechanism involving hydroxyl radical scavenging in order to activate persulfate anion, while still providing buffering capacity after persulfate activation has occurred. Additionally, ozone can then be used to reactivate the spent phosphate for further persulfate anion activation.

Possible reaction pathway:
P2O8-4→2PO4r-2PO4r-2+S2O8-2→PO4-3+SO4-2+SO4r

Which then continues like the persulfate activation pathway above.

“Oxygen” includes all forms of gaseous, liquid, and solid oxygen such as pure oxygen gas, air, hydrogen peroxide, and all other inorganic peroxides such as calcium or magnesium peroxide or organic peroxides, such as organic peroxides available from Luperox.

“Salt” includes sodium chloride and other species having both cationic or cationizable components and anionic or anionizable components.

“Oxidizing radicals” includes sulfate radical, hydroxyl radical, hydroperoxide, phosphate radical and others.

“Reducing radicals” includes superoxide.

“Saturated zone” refers to the region of the soil profile that is consistently below ground water level.

“Unsaturated zone” refers to the region of the soil profile that is consistently above ground water level.

“Smear zone” refers to the region of the soil profile through which the ground water level fluctuates, typically on a seasonal basis. The smear zone is the region that when the ground water is at its highest would be considered saturated and when the ground water is at its lowest would be considered unsaturated. It is also called the capillary zone.

“Organic contaminant” is an organic compound that is not native to the soil or water in which it is found. Organic compounds may include, for example, poly- and perfluoralkyl compounds (PFAAs), hydrocarbon-based fuels, halogenated and non-halogenated solvents, pesticides, herbicides, PCBs, volatile hydrocarbons, semi-volatile hydrocarbons, chlorinated volatile hydrocarbons, BTEX and MTBE.

“Area or Radius of influence” describes the area around a well or other injection point defining an area throughout which an adequate amount of reactant can be introduced to oxidize at least some of the organic contaminant present.

While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used.

Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the scope of the present invention. All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that 20 are conjunctively present in some cases and disjunctively present in other cases. All references, patents and patent applications and publications that are cited or referred to in this application are incorporated in their entirety herein by reference.

US10519052B2. Soil and water remediation method and apparatus for treatment of recalcitrant halogenated substances (2019-12-31). Oxytec LLC [US]. Inventors: Raymond G. Ball [US], Alan T. Moore [US].
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Patent 2019

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More about "Perhydroxyl radical"

Perhydroxyl radical, HO2•, hydroperoxyl radical, reactive oxygen species (ROS), oxidation-reduction reactions, cellular damage, signaling pathways, biochemistry, environmental chemistry, medical research.
Perhydroxyl radicals (also known as hydroperoxyl radicals) are a highly reactive type of oxygen-containing species that play a crucial role in numerous chemical and biological processes.
These radicals are characterized by the presence of a hydroperoxyl group (HO2•), which can participate in a variety of oxidation-reduction reactions.
The reactivity of perhydroxyl radicals allows them to contribute to both beneficial and detrimental cellular functions.
On one hand, they can be involved in signaling pathways that regulate important biological processes.
However, they can also lead to cellular damage through their oxidative effects, potentially contributing to various health conditions.
Understanding the behavior and impact of perhydroxyl radicals is crucial for researchers across a wide range of fields, including biochemistry, environmental chemistry, and medical research.
By studying the properties and interactions of these radicals, scientists can gain valuable insights that inform their work in areas such as oxidative stress, antioxidant mechanisms, and the development of new therapeutic strategies.
Whther you're investigating the role of perhydroxyl radicals in biological systems or exploring their applications in environmental remediation, staying up-to-date with the latest research and protocls is essential.
With the help of AI-driven platforms like PubCompare.ai, you can quickly locate and compare relevant protocols from literature, pre-prints, and patents, ensuring you adopt the most effective and reproducible approaches for your experiments.