Abstract
Phosphorus (P) is an essential raw material for many value-added chemicals in modern industry, yet the natural minerals to extract P are depleting. As an alternative, municipal wastewater is a promising secondary source of P. Recovery of P from wastewater by chemically induced precipitation as insoluble metal phosphates is a typical practice. Mg3(PO4)2 is a commonly found phosphate in sewage sludge or incinerated sewage sludge ash. Here we try to extract elemental P from Mg3(PO4)2 by electrochemistry. By using molten CaCl2 as the solvent, PO4 3− in the Mg3(PO4)2 crystal can be quickly leached into the melt as free ions. The presence of Mg2+ in the melt boosts the solubility and dissolution rate of PO4 3− significantly. High-purity elemental P can be isolated from free PO4 3− in the melt by electrolysis. This work demonstrates that Mg3(PO4)2 is a possible precursor to prepare elemental P by electrochemistry, though the negative influence of Mg2+ of forming solid MgO on the electrode surface during electrolysis needs to be addressed.
Published Version
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