Selective sequestration of p-arsanilic acid from water by using nano-hydrated zirconium oxide encapsulated inside hyper-cross-linked anion exchanger

Aromatic organoarsenic compounds (AOCs) are widely used as animal feed additives worldwide. Their concentration in waters is often much lower than the ubiquitous anions or natural organic matters (NOMs), e.g., below 1 mg.L-1. The efficient removal of AOCs from waters still remains challenging owing to their high stability and mobility. Herein, we employed a recently developed nanocomposite HZO@HCA, i.e., nano-hydrated zirconium oxide (HZO) encapsulated inside hyper-cross-linked anion exchanger (HCA), to decontaminate water from p-arsanilic acid (p-ASA), a representative AOC. Due to the specific interaction between nano-HZO and arsenic moieties, HZO@HCA exhibited preferable p-ASA adsorption (> 23.00 mg.g(-1)) even in presence of massive sulfate, chloride and nitrate (300 mg.L-1). Moreover, the hyper-cross-linked nature of HCA host endowed HZO@HCA with abundant micropores (< 2 nm), which prevented humic acid (HA, a representative NOM) diffusing inside the nanocomposite because of size exclusion. Thereby, the adsorption of HZO@HCA toward p-ASA was almost unaffected by the coexisting HA (2-10 mg.L-1). A successive 5-cyclic adsorption-regeneration assay suggested that the exhausted adsorbent could be fully refreshed by NaOH-NaCl binary solution for repeated use without any loss in adsorption efficiency. Fixed-bed adsorption demonstrated that HZO@HCA column could successively generate similar to 680 bed volume (BV) effluent from a synthetic surface water containing p-ASA to meet surface water quality standards of China ([As] < 50 mu g.L-1), while the HCA column could only generate similar to 80 BV effluent under otherwise identical conditions. This study may provide new opportunity for advanced treatment of AOCs-contaminated water.