Valorization of acid leaching post-consumer gypsum purification wastewater

Industries are required to utilize treatment technologies to reduce contaminants in wastewater prior to discharge and to valorize by-products to increase sustainability and competitiveness. Most acid leaching gypsum purification studies have obviated the treatment of the highly acidic wastewater produced. In this work, acidic wastewater from acid leaching purification of post-consumer gypsum was treated to recover a valuable solid product and reusable water. The main aims of this work were to determine the impact of recirculating acidic and treated wastewaters on the efficiency of the acid leaching purification process and to valorize the impurities in the wastewater. Samples were characterized through X-ray fluorescence and X-ray diffraction. SimaPro 9.5 and the ReCiPe 2016 midpoint method were used for the life cycle assessment of three sustainable wastewater management approaches. The reuse of the acidic wastewater did not improve the chemical purity of gypsum. Soluble impurities were precipitated at pH 10.5 as a magnesium-rich gypsum that could be commercialized as fertilizer or soil ameliorant. The alkaline-treated water was reused for six acid leaching purification cycles without impacting the efficiency of the purification process. An acid leaching–neutralization–filtration–precipitation approach demonstrated superior overall environmental performance. Barriers and enabling measures for the implementation of an in-house wastewater treatment were identified.