Enhanced phosphate removal using zirconium hydroxide encapsulated in quaternized cellulose

Zirconium-based materials are efficient adsorbent for aqueous phosphate removal.However,current zirconium-based materials still show unsatisfied performance on adsorption capacity and selectivity.Here,we demonstrate a zirconium hydroxide encapsulated in quaternized cellulose(QC-Zr) for the selective phosphate removal.Zirconium hydroxide nanoparticles were simultaneously generated in situ with the QC framework and firmly anchored in the three-dimensional(3D) cross-linked cellulose chains.The maximum P adsorption capacity of QC-Zr was 83.6 mg P/g.Furthermore,the QC-Zr shows high P adsorption performance in a wide pH range,generally due to the electrostatic effects of quaternized cellulose.The enhanced adsorption of P was also achieved in the presence of competing anions(including Cl~-,NO_3~-,SO_4~(2-),SO_4~(4-)) and humic acid(HA) even at a molar ratio up to 20 levels.The column adsorption capacity of QC-Zr reached 4000 bed volumes(BV) at EBCT=0.5 min as the P concentration decreased from 2.5 to 0.5 mg/L.Mechanism study revealed that both-N+(CH_3)_3 groups and zirconium hydroxide were involved in phosphate adsorption via electrostatic interactions between -N+(CH_3)_3 and phosphate,and the formation of zirconium hydrogen phosphate(Zr(HPO_4)x).The 31 P nuclear magnetic resonance(NMR) study implied that P surface-precipitated and inner-sphere complexed with zirconium hydroxide at a ratio of 3:1.