Enhancing the sustainability of phosphogypsum recycling by integrating electrodialysis with bipolar membranes

Phosphogypsum – a by-product of phosphoric acid production – piled near eco-sensitive regions, poses both environmental and health risks. By reacting phosphogypsum with NaOH, Ca(OH)2 is produced, which can be utilized for CO2 sequestration. The cost of NaOH, however, and the low market value of the byproduct, a concentrated Na2SO4 stream, hinder the economic viability of this approach. Here, we propose to increase the cost-efficiency of phosphogypsum processing by converting the Na2SO4 to NaOH and H2SO4 using bipolar membrane electrodialysis (BMED). The result is a cleaner and more circular process, as NaOH can be recycled for dissolving phosphogypsum, while H2SO4 can be reintroduced into the industrial phosphoric-acid production, or used to leach valuable metals out of the phosphogypsum. To assess the feasibility of BMED integration, we used a bench-scale system to probe the trade-off between obtaining high base-product concentration; and obtaining high specific energy consumption. This was done for synt...