Enhanced Arsenite Removal from Silicate-containing Water by Using Redox Polymer-based Fe(III) Oxides Nanocomposite

• Published in: Water research (Oxford) 2021-02, Vol.189, p.116673, Article 116673
• Main Authors: Fang, Zhuoyao, Li, Zhixian, Zhang, Xiaolin, Pan, Siyuan, Wu, Mengfei, Pan, Bingcai
• Format: Article
• Language: English
• Subjects: Active site; Adsorption; Arsenic; Arsenites; Ferric Compounds; Inner-sphere complex; Nanocomposites; Oxidation; Oxidation-Reduction; Oxides; Polymers; Regeneration; Silicate; Silicates; Water; Water Pollutants, Chemical; Water Purification
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2020.116673

•Simultaneous oxidation and adsorption enhance silicate resistance of nano-FeOOH•The protons produced during As(III) oxidation inhibit silicate polymerization•The adsorption-oxidation capability can be fully refreshed by NaOH-NaClO solution The efficient removal of arsenite [As(III)] from groundwater remains a great challenge. Nanoscale oxides of Fe(III), Zr(IV), and Al(III) can selectively remove arsenic from groundwater through inner-sphere complexation. However, owing to polysilicate coatings formation on nanoparticles surface, the ubiquitous silicate exerts remarkably adverse effects on As(III) removal. Herein, we propose a new strategy to enhance silicate resistance of nanoscale oxides by embedding them inside the redox polymer host. As a proof-of-concept, the nanocomposite HFO@PS-Cl was employed to remove As(III) from silicate-containing water. The polymer host (PS-Cl) contains active chlorine to oxidize As(III) into arsenate [As(V)], and the embedded Fe(III) oxides enabling specific adsorption toward arsenic. Silicate exerts negligible effects on As(III) removal by HFO@PS-Cl in pH 3-7, but increasing the residual arsenic concentration from 49 µg/L to 166 µg/L for the solutions treated by HFO@PS-N, i.e., the nanoscale Fe(III) oxides embedded inside the polymer host without active chlorine. During the six cyclic decontamination-regeneration assays, HFO@PS-Cl steadily reduces As(III) below 10 µg/L. As for HFO@PS-N, however, the residual arsenic increases to ~57 µg/L in the sixth run. In column mode, HFO@PS-Cl column generates >3200-bed volume (BV) clean water ([As]