Zirconium/PVA modified flat-sheet PVDF membrane as a cost-effective adsorptive and filtration material: A case study on decontamination of organic arsenic in aqueous solutions

Organic arsenic in waters has been a global concern in drinking water due to its higher toxicity to humans. In this study, a novel zirconium/polyvinyl alcohol (PVA) modified polyvinylidene fluoride (PVDF) membrane was applied to remove organic arsenic from water. The impregnation of zirconium ions within the modified membrane was attributed to the coordination reactions among the zirconium ions, ether and hydroxyl groups. The synthesized membrane worked better at the acidic conditions and achieved the optimal uptake for both monomethylarsonic (MMA) and dimethylarsinic (DMA) at pH 2.0. The adsorption isotherm study demonstrated that the adsorption of both organic arsenic species was controlled by the mono-layer adsorption process; the maximum adsorption capacities for MMA and DMA were 73.04 and 37.53 mg/g at pH 2, and 29.78 and 19.03 mg/g at pH 7.0, respectively. The presence of humic acid had a negligible impact on the uptake of organic arsenic, whereas varying impacts on the arsenic adsorption were observed due to the presence of coexisting anions such as fluoride, phosphate, carbonate and silicate. A single piece of membrane with a surface area of only 12.56 cm² could treat 7.5-L MMA and 4.1-L DMA solution with an influent concentration of about 100 μg/L to meet the WHO and USEPA standard of 10 μg/L. Based on the XPS analyses, the ion exchange reaction between chloride ions on the membrane surface and organic arsenic species was responsible for the removal of both MMA and DMA.