Temperature-Dependent Crystallization Optimization for Upcycling Purified Ash from the Calcium Carbide Industry: A Sustainable Approach for Mg(OH)2/Aragonite Coproduction

This study employs a wet precipitation–carbonation method to recycle and utilize purification slag from the calcium carbide industry, extracting high-value-added magnesium hydroxide (Mg(OH)2) and aragonite nanoparticles. Experimental results demonstrate that the reaction temperature significantly influences the yield, morphology, and crystallinity parameters of the products. The optimal preparation temperatures for Mg(OH)2 and aragonite are 60 °C and 80 °C, respectively. Analysis via X-ray diffraction (XRD) combined with the Williamson–Hall method reveals that within the temperature range of 60–90 °C, the crystallite sizes of Mg(OH)2 and aragonite are 40.07–59.25 nm and 70.03–109.18 nm, respectively. As the temperature increases, the crystallite size, strain, lattice stress, and energy density of Mg(OH)2 exhibit a decreasing trend, whereas the corresponding crystallographic parameters of aragonite gradually increase.