Mechanism of Desulfurization Pretreatment of Barium-Containing Waste Slag by Calcium Carbonate Precipitation Method
Barium slag, a solid waste from barium salt production, poses environmental risks due to high sulfur and soluble barium content. This study investigated the desulfurization of barium slag using sodium carbonate (Na2CO3) as a precipitating agent. The effects of reaction temperature, time, and Na2CO3 concentration on desulfurization efficiency were systematically evaluated. X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) were employed to analyze phase transformations and microstructural evolution. Results showed that desulfurization primarily proceeds via the reaction of ettringite (Ca6(Al(OH)6)2(SO4)3·26H2O) with Na2CO3, forming calcium carbonate (CaCO3) precipitates. However, the precipitated CaCO3 accumulates on ettringite surfaces, hindering further reaction. Under optimal conditions (60 °C, 5 h, 2 mol/L Na2CO3), the desulfurization efficiency reached 91.21%, reducing sulfur content in the slag to 0.27%, meeting the HJ 662—2013 standard for cement kiln co-processing. This work provides a mechanistic basis for efficient and environmentally sound treatment of barium slag, supporting its resource utilization in cement production.