High-Efficiency Purification and Morphology Regulation of CaSO·2HO Crystals from Phosphogypsum.

Phosphogypsum is a solid waste with great environmental stockpile pressure produced by the wet production of phosphoric acid. Although there are various methods to purify and utilize phosphogypsum, the means for environmentally friendly, low energy consumption, and high value-added utilization still need to be further explored. Here, CaSO·2HO crystal was directly purified and regulated from phosphogypsum by using the anti-solvent method. The antisolvent can be adsorbed in the -axis direction of the crystal and further inhibit the growth rate in this direction, resulting in a change in the morphology of the crystal. By adjusting the polarity and chain length of the anti-solvent, the morphology of CaSO·2HO crystal can change from butterfly-like flake crystals to hexagonal prism-like crystals. When n-propanol with long chain was used as the anti-solvent, the morphology of the CaSO·2HO crystal showed a hexagonal prism with a specific surface area of 19.98 m/g and a Cu loading efficiency of 52.67%. The encouraging results open up new possibilities for the application of phosphogypsum.