Arsenic as a contaminant of struvite when recovering phosphorus from phosphogypsum wastewater

Background: Phosphogypsum is a waste product from production of phosphorus and is stored in a containment pond. Phosphogypsum wastewater still contains a usable amount of phosphorus. In addition to phosphorus, this water contains a small amount of arsenic, which prevents direct use of this water in agriculture. Method: Recycling of phosphorus from phosphogypsum wastewater was performed by struvite (NH4MgPO4 center dot 6H(2)O), precipitation. Arsenostruvite (NH4MgAsO4 center dot 6H(2)O) has always occurred naturally in the presence of struvite. The properties of arsenostruvite in comparison with struvite were monitored. The effect of selected reductants (SnCl2, ascorbic acid, K2S2O5) on the potential of reducing the concentration of As in the struvite crystallized from phosphogypsum wastewater, was monitored. Findings: When recovering phosphorus from phosphogypsum wastewater in the form of struvite the results showed that a ratio of As to P was lower by 50% compared to the original wastewater. K2S2O5 proved to be the most effective reducing agent for reducing the arsenic content of the product, but it was still not sufficient for the product to be used as a fertilizer without any further treatment. (C) 2021 Published by Elsevier B.V. on behalf of Taiwan Institute of Chemical Engineers.

Automated summary

The study focused on recycling phosphorus from phosphogypsum wastewater using struvite precipitation, and monitored the properties of arsenostruvite. Results showed that K2S2O5 was the most effective reducing agent for lowering arsenic content in the product, however additional treatment was still needed for it to be used as fertilizer.