Preparation and characterization of expanded perlite and industrial waste salt composite thermochemical heat storage material

The reuse of industrial waste salts offers significant potential for environmental protection and resource conservation. This study investigates the application of industrial waste salt, primarily composed of magnesium chloride hexahydrate, as a thermochemical heat storage material. Expanded perlite was selected as the porous matrix to prepare composite materials, and comparative analyses were performed to evaluate the water adsorption, dehydration, and cyclic performance of waste salt and pure salt composite materials. Results indicate minimal differences in water adsorption and dehydration behavior between waste and pure salts. The heat storage density of pure salt and waste salt are 541 J·g⁻¹ and 515 J·g⁻¹, respectively. The both composite materials demonstrated a water adsorption capacity of approximately 1.0 g·g⁻¹ within 24 h and complete dehydration within 4 h. Expanded perlite effectively mitigated deliquescence leakage during hydration, maintaining structural integrity. Additionally, the water adsorption rate increased with humidity. This study highlights that the thermochemical energy storage properties of waste salts are comparable to those of pure salts, making waste salts a cost-effective alternative for thermal storage material development. This approach provides a sustainable pathway for industrial waste salt reuse, eliminating the need for costly purification processes and supporting large-scale applications in energy storage systems.