Phosphate Removal and Recovery with Calcined Layered Double Hydroxides as an Adsorbent

Abstract

The adsorption properties of calcined layered double hydroxide (denoted as CLDH) for phosphate and desorption for recovery phosphate were examined. The influences of chemical composition of adsorbents, adsorbent dose, and co-existing anions on the phosphate removal have been investigated. It has been found that the LDHs with Mg/Al molar ratio of 2 represented the highest capacity to remove phosphate from aqueous solution. Phosphate ion removal in presence of other ions decreases in the order CO₃ ²⁻ < SO₄ ²⁻ < F⁻ < Cl⁻. Phosphate adsorbed on the CLDH was effectively desorbed at Na₂CO₃ solution and the CLDH were reconstruction to LDHs at the same time. Phosphate in the exhausted desorption solution was recovered as calcium phosphate by precipitation with Ca²⁺.

Keywords:

• Adsorption
• desorption
• layered double hydroxides
• phosphate
• recovery

Acknowledgments

This work was supported by the Natural Science Foundation of Zhejiang Province (Y406345) and National Natural Science Foundation (No. 9030612), the State Key Laboratory of Chemical Resource Engineering (No. 200706).