Portlandite wet-synthesis process from phosphogypsum waste using hydroxide medium: application in both CO2 capture and brine water salinity reduction.

Portlandite (Ca(OH)₂) preparation from phosphogypsum waste (PGW) was evaluated in numerous works; however, the use of this compound is not applied yet in the brine water salinity reduction. In this work, the purity of Ca(OH)₂ prepared from PGW and soda aqueous solution was tested for different NaOH/PG molar ratios (MR) close to the stochiometric value (1.5 < MR < 3). The obtained Ca(OH)₂ at the optimal conditions was used for both the CO₂ capture and brine water (BW) salinity reduction, resulting in high-quality calcium carbonate synthesizing. The XRD results show that a MR higher than the stochiometric value (MR > 2) is most efficient to obtain high-quality portlandite (P_2.5 and P₃). An estimation of the carbon capture efficiency of the prepared portlandite was made. Based on the results of this work, using 4 g of P_2.5 allows to capture 2.4 L of CO₂ and treat 0.4 L of BW. Overall, our work confirms the technical viability of the proposed route to synergize CO₂ capture, BW and PGW recycling. From an economic and ecological standpoint, our investigated routes were eco-friendly and cost-effective. [ABSTRACT FROM AUTHOR]