Mechanism of aluminosilicate decomposition and stepwise impurity removal in barite based on a roasting–acid leaching–alkali leaching process

High-purity barium sulfate is essential for reflective coatings, radiation-shielding materials, and high-end fillers, where residual Fe, Al, and Si impurities affect whiteness and service performance. However, deep purification of natural barite is often hindered by quartz, Fe 2 O 3 , and aluminosilicate inclusions closely associated with the BaSO 4 matrix. These limitations are primarily attributable to the structural stability of aluminosilicate impurities and low reactivity of quartz-type SiO 2 during conventional leaching. This study proposes a combined roasting–sulfuric acid leaching–alkaline leaching process to achieve stepwise impurity removal from barite concentrate. The results indicate that, under the optimized conditions, Fe decreased from 400 ppmw to approximately 50 ppmw, Al decreased from 1700 ppmw to approximately 50 ppmw, and Si decreased from 3.11 wt% to 2.78 wt%, while BaSO 4 purity increased from 89.64 wt% to 92.47 wt%. The overall Al removal efficiency reached 97.06 %, and the final Fe content satisfied the impurity-control requirement of GB/T 2899–2017. The results demonstrate that roasting at 1023 K mainly promotes aluminosilicate decomposition through the cleavage of Si–O–Al bonds. During sulfuric acid leaching, Fe 2 O 3 is preferentially dissolved, and part of the Al released from decomposed aluminosilicate enters the liquid phase. This study clarifies the stepwise purification mechanism of complex barite and provides a feasible route for preparing high-quality BaSO 4 raw materials.