Optima 5300 dv

In the case of P, 0.5 mL of the sample was taken and 4 mL of water Type I and 0.5 mL of ammonium molybdovanadate 1% solution were added. The sample was stirred and the absorbance was measured in a UV-Visible spectrophotometer (UV2600, Shimadzu, Tokyo, Japan). Quantification was based on a calibration curve, and the results were expressed in mg 100 g⁻¹ of dry weight sample.
For the analysis of macronutrients, an aliquot of 4.5 mL of sample was taken in a test tube, 0.5 mL of lanthanum 1% solution was added for determination of Ca and Mg. In the case of Na and K, 0.5 mL of lithium 1% solution was added in the same volume of sample and to eliminate interferences.
For the analysis of micronutrients (Zn, Cu, Fe, and Mn), 5 mL of each sample was taken and no solutions were added for interferences. In the prepared samples, the absorbance was measured in an atomic absorption spectrophotometer (AA7000, Shimadzu, Tokyo, Japan). S and B content were measured directly from the solutions of each sample in an inductively coupled plasma spectrophotometer (5300 Optima DV, Perkin Elmer, Bresia, Italy). The quantification was carried out using calibration curves for each element; the results were expressed as mg 100 g⁻¹ of dry weight sample.

As the simulated gastric fluid (SGF, pH = 1.2), an aqueous solution of 0.1 M HCl without enzymes was used [21 (link)]. The deionized water used for all experiments was obtained from a Milli-Q Plus water purification system (Millipore, Bedford, MA, USA). Zeolite samples were exposed to SGF solution under mild shaking conditions at 37 ± 0.5 °C in 1:2, 1:1, 2.5:1, 5:1, and 10:1 zeolite-to-SGF ratios (w:v) for 1, 3, 5, and 7 days. After immersion, the liquid phase was separated by centrifugation at 4000 rpm for 5 min and filtered through a 45 µm cellulose acetate membrane. The concentrations of Si, Al, Fe, Ca, Mg, K, Na, and P released in SGF were measured using a 5300 Optima DV (Perkin Elmer, Waltham, MA, USA) inductively coupled plasma optical emission spectrometer (ICP-OES) after microwave digestion using the method described previously [9 ]. For the ICP-OES, external calibration using calibration solutions in the range of 0–20 mg L⁻¹ were prepared from 1000 mg L⁻¹ multielement (Na, K, Ca, Mg, Fe and Al) and monoelement (P and Si) standard solutions (Merck, Darmstadt, Germany) diluted in 0.5% (v:v) HNO₃ [39 (link)]. The experiments were carried out in triplicate and the average values were reported. The pH changes of SGF before and after exposure of zeolites were monitored using a Seven Excellence multiparameter (Mettler Toledo, Schwerzenbach, Switzerland) [9 ].

The pH and electrical conductivity (EC) of wastewater were determined using a Seven Excellence multiparameter (Mettler Toledo, Switzerland) after 1 h of settling. Specific metal co (Mn, Al, K, Ca, Na, Fe, Mg, Cu, Pb, Zn, Ni, Cd, and Cr) content was determined by the digestion of samples with a mixture of 65% HNO₃ and 37% HCl at a volume ratio of 1:3 in a closed polytetrafluoroethylene (PTFE) vessel, using a microwave digestion system (Speedwave MWS-3+, Berghof, Eningen, Germany). The resulting solutions were measured using inductively coupled plasma—optical emission spectrometry (ICP-OES, 5300 Optima DV, Perkin Elmer, Whaltham, MA, USA) [29 (link)]. Anionic surfactants from wastewater were determined according to EN 903 [30 ]. Anion (NO₂⁻ and NO₃⁻) content was measured by ion chromatography using a 761 IC compact ion chromatograph (Metrohm, Herisau, Switzerland) according to standard ISO 10301-1 [31 ]. The wastewater samples were filtered through 0.45 μm polytetrafluoroethylene membrane filters to eliminate the solid particles [31 ]. Ammonium (NH₄⁺) content was determined with a Lambda UV–Vis Spectrophotometer (Perkin Elmer, Waltham, MA, USA) applying the salicylate–hypochlorite method [32 ]. Biological oxygen demand (BOD) was determined according to ISO 5815 [33 ] and chemical oxygen demand (COD) was determined according to ISO 6060 [34 ].