Preparing high‐purity calcium carbonate and potassium sulphate at a low cost using industrial by‐product gypsum

Abstract The substantial annual production and low utilization of industrial by‐product gypsum (IBPG) have led to significant ecological, environmental, and safety challenges. To address these issues, a cost‐effective and environmentally friendly approach to convert IBPG and CO 2 ‐sourced raw material into high‐value products, that is, 100% high‐purity of calcium carbonate (CaCO 3 ), ammonium chloride (NH 4 Cl), and potassium sulphate (K 2 SO 4 ), is proposed under ambient conditions by using a developed two‐step method. By employing a recyclable phase transfer catalyst of ammonium acetate and a mixed solution containing saturated terminal products as a simulated mother liquor, efficient leaching of low‐solubility IBPG, impurity separation, and enhanced reaction rates are simultaneously achieved. Some crucial conditions for preparing high‐value target products are optimized, and many traditional by‐products (e.g., syngenite, koktaite, calcium acetate hydrate, K 2 SO 4 · (NH 4 ) 2 SO 4 , and KCl · NH 4 Cl) are successfully suppressed. The favourable recirculation of the mother liquor demonstrated the prominent advantage in production cost reduction and environmental protection, confirming its industrial feasibility. Therefore, a promising, low‐cost, and sustainable solution for IBPG's resource utilization to prepare high‐value products is put forward here, providing some significant theoretical and industrial guidelines for solid waste disposal and carbon fixation.