Sodium arsenate dibasic heptahydrate na2haso4.7h2o

The reagent-grade chemicals including arsenic trioxide (As₂O₃), humic acid (HA), salicylic acid (SA) and sodium arsenate dibasic heptahydrate (Na₂HAsO₄.7H₂O) were purchased from Sigma Aldrich (St. Louis, MO, USA). The other chemicals, including nitric acid (HNO₃), sodium hydroxide (NaOH), hydrochloric acid (HCl), sodium dihydrogen phosphate (NaH₂PO₄.H₂O), magnesium sulfate (MgSO₄.7H₂O) and ferric chloride hexahydrate (FeCl₃.6H₂O), were procured from local suppliers. The pure water from Millipore water purification system (Milli-Q, Millipore Co., Bedford, MA, USA) was used to prepare stock solutions and synthetic test samples. Before use, all glassware was washed with 15% HNO₃ followed by rinsing with pure water to avoid contamination. The stock solutions of As(III) and As(V) at 100 mg/L were prepared separately by dissolving As₂O₃ and Na₂HAsO₄.7H₂O in 1 M NaOH solution and pure water, respectively. The stock solutions of hydrophobic HA and hydrophilic SA were prepared by dissolving 500 mg chemical in 100 mL pure water. The detailed procedure for HA and SA solution preparation can be found elsewhere [58 (link)]. The stock solution of coagulant (100 mM) was prepared using FeCl₃.6H₂O. The working solutions of trivalent and pentavalent As were prepared via sequential dilution from each stock solution for each experimental run.

All chemicals used in the experiments were of reagent grade. Graphite fine powder extra pure (with a mean particle size of <50 μm) was purchased from Merck- Germany. PSF (with average M_w = 22,000 g/mol) was obtained from Sigma-Aldrich Co-Germany. N,N-Dimethylformamide >(DMF) was purchased from Sigma-Aldrich and used without purification as a solvent to prepare cast solution. Analytical grade H₂SO₄ (98 %-Merck), NaNO₃ (99 %, Sigma–Aldrich), KMnO₄ (99 %, Sigma–Aldrich) and H₂O₂ (30 % solution, stabilized-Merck) were used as received. Sodium arsenate dibasic heptahydrate (Na₂HAsO₄-7H₂O) was obtained from Sigma-Aldrich. The deionized (DI) water was used in the sample preparation and for pure water flux measurements.

All chemicals used in the experiments were of reagent grade. Polysulfone (number average molecular weight, Mn ~22,000), N,N-dimethylacetamide (DMAC), acetone, zinc oxide (ZnO) nanoparticles, sodium (meta) arsenite (90%), and sodium arsenate dibasic heptahydrate (Na₂HAsO₄ 7H₂O) were purchased from Sigma-Aldrich (Sydney, Australia). Graphene oxide water dispersion (0.4 wt%) was purchased from Graphenea (Cambridge, MA, USA). Deionized (DI) water was used for sample preparation and pure water flux measurements.