Insights into Coproduction of Silica Gel via Desulfurization of Steel Slag and Silica Gel Adsorption Performance

[Image: see text] Steel slag is a calcium-containing alkaline industrial solid waste that can replace limestone for flue gas desulfurization. It can remove SO(2) and coproduce silica gel while avoiding CO(2) emission from limestone in the desulfurization process. In this study, steel slag with a D(50) of 3.15 μm was used to remove SO(2). At room temperature, with a solid–liquid ratio of 1:10, a stirring speed of 800 rpm, and the mixed gas introduced at a flow rate of 0.8 mL/min, 1 ton of steel slag could remove 406.7 kg of SO(2), a SO(2) removal efficiency typical of existing calcium-rich desulfurizers. As limestone desulfurization can release CO(2), when limestone desulfurization was replaced with steel slag of equal desulfurization ratio, CO(2) emissions could be reduced by 279.6 kg and limestone could be reduced by 635.5 kg. The yield of silica gel was 5.1%. Silica gel pore structure parameters were close to those of commercially available B silica gel. Products after desulfurization were mainly CaSO(4)·2H(2)O, CaSO(4)·0.5H(2)O, CaSO(3)·0.5H(2)O, and silica gel. With a silica gel dosage of 30 mg, a temperature of 20 °C, a pH value of 6.00, a stirring time of 0.5 h, and a methylene blue concentration of 0.020 mg/mL, the removal ratio of methylene blue adsorbed by silica gel was 98.4%.