Efficient extraction of phosphorus from food waste biogas digestate ash through two-compartment electrodialysis cell

Abstract

It is necessary to recover and utilize phosphorus from waste due to the nonrenewable and irreplaceable nature of phosphate rock. The ash of food waste biogas digestate after incineration is enriched with phosphorus resources. In this paper, two-compartment cell electrodialysis experiments with different times and currents were employed to extract phosphorus and separate metals from the food waste biogas digestate ash (FDS). Eventually, the phosphorus was extracted at the anode, and the metal was separated into the cathode. Compared with the method of simple acid leaching (65%), electrodialysis with 10 mA current achieved more than 90% extraction of phosphorus after 7 days, which is in the form of phosphoric acid. Investigation of the extraction mechanism reveals a positive effect between the precipitation-dissolution equilibrium of the Ca-P precipitation and the mechanism. The percentage of phosphorus leakage to the cathode is less than 3%. Almost all of the dissolved metal is separated, except for a very minor amount of Fe (5%) that remains in the anolyte. Our research introduces an efficient phosphorus extraction method from FDS utilizing electrodialysis and creates a new market for the resource utilization of food waste biogas digestate ash.