Removal behaviors and mechanisms of orthophosphate and pyrophosphate by calcined dolomite with ferric chloride assistance

Abstract

Phosphate is one of the main contaminations in water, so an effective method of decreasing or removing phosphate is needed. The main purpose of this paper is to synthesize CaFe-LDHs and MgFe-LDHs from the mixture of calcined dolomite and ferric chloride to remove orthophosphate and pyrophosphate. The study showed that removal of orthophosphate was attributed to the precipitation by Ca²⁺ and adsorption by MgFe-LDHs, where the former played a main role. As for pyrophosphate, it was mainly removed by precipitation at the initial pyrophosphate concentration ranging from 3.228 to 17.04 mmol/L. When the initial concentrations became relatively higher, the removal efficiency of pyrophosphate decreased because the complexation effects by Fe³⁺, Ca²⁺ and Mg²⁺ took place.

Keywords: CaFe-LDHs; Calcined dolomite; MgFe-LDHs; Removal of orthophosphate and pyrophosphate.