High phosphate removal using La(OH)3 loaded chitosan based composites and mechanistic study

Our present study was to prepare a biomass-supported adsorbents with high adsorptive capacity and high selectivity to prevent the accelerated eutrophication in water body. To this end, different metal hydroxide (La, Zr and Fe) first was successfully loaded on chitosan microspheres. Then the quaternary ammonium group with different content was introduced into the adsorbent by polymerization. By comparison of adsorption properties, chitosanLa(OH) 3-quaternary ammonium-20% (CS-La-N-20%) has strong adsorption to phosphate (160 mg/g) by immobilizing nano-sized La(OH)(3) within a quaternary-aminated chitosan and it maintain high adsorption in the presence of salt ions. The pH results indicated that the CS-La-N-20% would effectively sequestrate phosphate over a wide pH range between 3 and 7 without significant La3+ leaching. What's more, adsorption capacity on the introduce of positively charged quanternary-aminated groups was significantly higher than that of the un-modified adsorbents at alkaline conditions. The column adsorption capacity reached 1300 bed volumes (BV) when phosphate concentration decreased until 0.5 mg/L at 6 BV/hr. The column adsorption/desorption reveals that no significant capacity loss is observed, indicating excellent stability and repeated use property. Characterizations revealed that phosphate adsorption on CS-La-N-20% through ligand exchange (impregnated nano-La(OH)(3)) and electrostatic attraction (positively charged quanternary-aminated groups). All the results sug-gested that CS-La-N-20% can serve as a promising adsorbent for preferable phosphate removal in realistic application. (C) 2021 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

In this study, biomass-supported adsorbents with high adsorptive capacity and selectivity were prepared to prevent accelerated eutrophication in water bodies. By introducing metal hydroxides and quaternary ammonium groups onto chitosan microspheres, the resulting CS-La-N-20% demonstrated strong adsorption to phosphate and maintained high adsorption in the presence of salt ions. The adsorbent showed promising potential for phosphate removal in practical applications, with stable and repeatable performance.