Mechanism of Desulfurization Pretreatment of Barium-Containing Waste Slag by Calcium Carbonate Precipitation Method

• • Optimal desulfurization conditions: 60 °C, 5 h, 2 mol/L Na2CO3, achieving 91.21% desulfurization efficiency and reducing sulfur content to 0.27%, meeting HJ 662—2013 for cement kiln co-processing. • • The reaction mechanism involves ettringite reacting with Na2CO3 to form CaCO3 precipitates, which remove sulfur from the slag; however, CaCO3 accumulation on ettringite surfaces limits reaction completion. • • Raw barium slag contains 40.3% Ca, 3.058% S, and 1.36% Ba, with sulfur primarily bound in ettringite; no stable barium sulfate phases were detected, indicating sulfur is readily releasable under alkaline conditions. • • The process addresses the bottleneck of high sulfur content in barium slag that restricts its co-processing ratio in cement kilns, enabling higher substitution rates without compromising cement quality.