Conversion, separation, and application of highly active sulfur calcium components in waste gypsum

Abstract

Industrial gypsum residues, including phosphogypsum, flue gas desulfurization gypsum, titanium gypsum, and fluorogypsum, represent a major category of calcium-based solid waste generated by the chemical industry. With rapid industrial growth, the accumulation of such residues has reached unprecedented levels, posing significant environmental risks due to improper disposal and underutilization. This review systematically examines the current status of resource utilization technologies for industrial gypsum, identifies critical limitations in existing approaches, and proposes a novel pathway for high-value added recycling, the preparation of α-calcium sulfate hemihydrate (α-HH) from purified industrial gypsum and its application in rubber and plastic composites. By addressing the challenges of impurity removal (e.g., heavy metals, phosphorus, fluorine) and phase transformation control, this work highlights the feasibility of multi-physics field assisted crystallization and physicochemical synergistic regulation to achieve high-purity α-HH. Furthermore, the integration of α-HH into rubber and plastic matrices is explored as a sustainable strategy to enhance mechanical properties, durability, and environmental compatibility of polymer-based products. This review establishes a “cradle-to-grave” framework for industrial gypsum utilization, emphasizing cross-sectoral collaboration and technological innovation to mitigate environmental burdens while unlocking economic value.