Simultaneous Separation and Recovery of Phosphorus from Aqueous Solution by Bipolar Membrane Electrodialysis

Abstract

Recycling phosphorus from phosphorus-containing wastes and byproducts is a promising secondary phosphorus resource. Steelmaking slag is generated in large quantities as a byproduct of the iron and steelmaking industry, and contains phosphorus that could be a possible secondary phosphorus resource. Phosphorus can be extracted from slag into aqueous solution; however, the phosphorus concentration is generally lower than other elements, causing a problem for phosphorus recovery. In this study, bipolar membrane electrodialysis was applied to separate and recover phosphorus from solution. The reaction and performance of phosphorus recovery were investigated. The effect of initial phosphorus concentration, volume ratio, and electric potential on recovery process was determined. Ion adsorption on an anion-exchange membrane during the initial stages and ion competition between H₂PO₄⁻ and OH⁻ in the later stages are the main factors affecting the extraction efficiency. In this study, the maximum concentration ratio achieved was 2.46, and the minimum phosphorus concentration in treated solution was 3.64 mg/L, which is under the Japanese effluent standard. In general, bipolar membrane electrodialysis has good potential for concentrating and recovering phosphorus from aqueous solution.