A Novel Anion Exchanger Composed of Formate Hydrotalcite for Sorptive Recovery of Phosphorus

Abstract

Feasibility of a renewable sorbent for phosphorus was determined by testing the anion-exchange ability of hydrotalcite, which holds formate ions in its interlayer. The formate hydrotalcite, successfully prepared by reacting raw hydrotalcite with a formic acid/1-propanol solution, exhibited high performance for phosphorus removal and collection based on a stoichiometric anion-exchange principle. It was estimated that the collected orthophosphate ions existed as poly-anion forms of HPO₄^2– and PO₄^3– with a ratio of 67.6:32.4 in the interlayer after the sorption. The formate hydrotalcite is also able to revert to the starting hydrotalcite after the sorption, when treated with Na₂CO₃ aqueous solution, demonstrating that it can be an attractive alternative to the conventional chloride or nitrate hydrotalcite as an anion exchanger.