Halloysite nanoclay

Chemicals and microbial media used in the experiments were of analytical grade. Dimethyl sulfoxide (DMSO) (RCI Labscan Limited, Bangkok, Thailand), Tween-80, potato dextrose agar (PDA), and halloysite nano clay were procured from Sigma-Aldrich (St. Louis, MO, USA). The fungal culture, typically Aspergillus sp., was isolated by the Thailand Bioresource Research Center (TBRC). Sodium hypochlorite (10%) was purchased from KrungthepChemi (Bangkok, Thailand). All the commercial-grade essential oils (EOs) such as lemongrass, spearmint, ginger, bergamot, lemon, peppermint, thyme, cinnamon, and clove were obtained from J.A.G.A.T. Aroma oils distillation, Namsiang Co., Ltd. (Bangkok, Thailand). Polyvinyl alcohol (PVA) and oriented polypropylene (OPP) films were bought from Loba Chemie PVT. Ltd. (Maharashtra, India). Sterile absorbent food-grade pads (25 mL capacity) were purchased from Dry Square Co., Ltd. (Bangkok, Thailand).

Ascorbic acid, AIBN (2,2′-azobis (2-methylpropionitrile)), AAPH ((2,2′-azobis (2-methylpropionamidine) dihydrochloride), PMHC (2,2,5,7,8-pentamethyl-6-chromanol), DPPH• (2,2-diphenyl-1-picrylhydrazyl), Chelex^® 100 sodium form, cumene, styrene, and tetrahydrofuran (unstabilized) were commercially available (Sigma-Aldrich, Milan, Italy). Solvents were HPLC or spectrophotometry grade and were used without further purification. THF was distilled under vacuum and stored under argon at 5 °C; the content in hydroperoxides was < 50 ppm (μg g^–1), as determined spectrophotometrically (262 nm) by detection of Ph₃P=O after titration with triphenylphosphine (Ph₃P) in iso-propanol. cumene and styrene were percolated through silica and through activated alumina to remove traces of peroxides and were stored under nitrogen. AIBN was recrystallized from methanol and stored at −18 °C. Halloysite nanoclay was purchased from Sigma-Aldrich: it had an average tube diameter of 70 nm and inner lumen diameter of 15 nm. Typical specific surface area of this halloysite is 65 m² g⁻¹, pore volume of ~1.25 cm³ g⁻¹, refractive index 1.54, and specific gravity 2.53 g cm⁻³.

Halloysite nanoclay, potassium tetrachloropalladate (K₄PdCl₄), copper nitrate trihydrate (Cu(NO₃)₂·3H₂O), cobalt nitrate hexahydrate (Co(NO₃)₂·6H₂O), nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) and sodium borohydride (NaBH₄) were purchased from Sigma-Aldrich Co. Ltd. All reagents were used without further purification.

Kaolinite, polystyrene foam, and clay minerals were obtained from a domestic market, Thailand. Commercial grade paraquat was purchased from Ag−gro (Thailand) Co., Ltd., (Chiang Mai, Thailand). The active ingredients were 1,1′−dimethyl−4,4′−bipyridinium dichloride at 27.6 percent weight−per−volume, water at 30 to 60 percent, emulsifiers at 10 to 29 percent, and other non−hazardous ingredients at less than 1 percent. The emetic and dye without percentage contribution were also listed as ingredients in the paraquat chemicals. Potassium phosphate dibasic (K₂HPO₄) and magnesium sulfate (MgSO₄∙7H₂O) were analytical reagent (AR) grade and acquired from Loba Chemie Pvt. Ltd., India. Sodium chloride (NaCl), ammonium fluoride (NH₄F), and ammonium phosphate (NH₄PO₄) were AR grade and purchased from EMSURE^®, Germany. Halloysite nanoclay, 25% glutaraldehyde (C₅H₈O₂), 4% osmium tetroxide (OsO₄), ethanol, hexane, and hexamethyldisilazane (HMDS) were obtained from Sigma−Aldrich, USA. The Thailand Institute of Scientific and Technological Research Culture Collection provided P. putida strain TISTR 1522 and B. subtilis strain TISTR 1248, which are the paraquat−degrading microorganisms [13 (link),33 (link)]. Plate Count Agar (PCA) and Luria−Bertani broth (LB broth) were purchased from HiMedia laboratory Pvt. Ltd., India.

Sodium alginate (SA) (alginic acid sodium salt from brown algae), pure anhydrous calcium chloride (CaCl₂), and halloysite nanoclay (kaolin clay) were acquired from Sigma-Aldrich, China. The reagents were used as received without any purification. The oils included corn oil (0.917 g/cm³) (Cornlite, Nashik, India), hexane (0.659 g/cm³) (Sigma-Aldrich, Shanghai, China), and pump oil (0.880 g/cm³) (Mobil, Surrey, UK).

The sodium carboxymethylcellulose (Na-CMC) (Commercial grade, Lahore, Pakistan) was obtained from Panreac Applichem, Darmstadt, Germany. The polyvinyl alcohol (PVA) of MW 30,000–70,000 g/mol, 87–90% hydrolyzed, was purchased from Sigma Aldrich, St. Louis, MI, USA, the halloysite nano clay was purchased from Sigma Aldrich, and the (3-aminopropyl)triethoxysilane (APTS), ethanol, potassium dihydrogen phosphate, sodium dihydrogen phosphate, and potassium chloride were purchased from Merck, Germany. All the chemicals were of analytical grade and used without any further treatment.

Halloysite nanoclay (Sigma-Aldrich™), phenyl phosphonic acid (PPA, 98%, Sigma-Aldrich™), 3-aminopropyl triethoxysilane (APTES, 99%, ACROS Organics™), triethylamine (TEA, 99%, ACROS Organics™), bromo-isobutyryl bromide (BiBB, 98%, Sigma-Aldrich™), two-dimensional Dimethylamino ethyl methacrylate (DMAEMA, 98%, Sigma-Aldrich™), ethyl α-bromoisobutyrate (ETBriB, 98%, Sigma-Aldrich™), copper monochloride (CuCl, 97%, Sigma-Aldrich™), Toluene (anhydrous, 99.8%, Sigma-Aldrich™), Toluene (Certified ACS, Fisher Sci.™), dichloromethane (DCM, anhydrous, ≥99.8%, Sigma-Aldrich™), isopropanol (Certified ACS, Macron Fine Chemicals™), Sudan IV(Fisher Chemical), styrene (≥99.5%, Sigma-Aldrich™), azobisisobutyronitrile (AIBN, Sigma-Aldrich™), octyl triethoxysilane (≥97.5%, Sigma-Aldrich™) were used without further purification.