Abstract:
Phosphogypsum (CaSO sub(4)) is produced as a waste by-product during phosphoric acid production in the fertilizer industry. Only 15 percent of worldwide phosphogypsum production is recycled, while 85 percent is stored in the vicinity of factories as huge piles resulting in environmental and health hazards. An extensively studied biotransformation of phosphogypsum to calcium carbonate or calcite (CaCO sub(3)) using sulfate reducing bacteria (SRBs) is a prolonged process and results in the formation of extremely hazardous H sub(2) S gas. Here we report for the first time a novel approach for biotransformation of phosphogypsum to CaCO sub(3) using urease producing Lysinibacillus sphaericus strain GUMP2. The strain could effectively transform phosphogypsum to crystalline, bead-shaped CaCO sub(3) precipitates. In a batch reactor with the PG loading rate of 60 g/L, 100 percent biotransformation was observed within seven days. After calcite recovery, the ammonium sulfate formed in the supernatant was recovered by precipitation. Urease-producing L. sphaericus strain GUMP2 could be used to remove the hazardous phosphogypsum from the environment by converting it to the industrially useful CaCO sub(3) and ammonium sulfate, a valuable agricultural fertilizer. This novel and sustainable approach could be a promising solution for the hazardous phosphogypsum in the phosphoric acid industries.
