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

Abstract

Steel slag is a calcium-containing alkaline industrial solid waste that can replace limestone for flue gas desulfurization. It can remove SO2 and coproduce silica gel while avoiding CO2 emission from limestone in the desulfurization process. In this study, steel slag with a D50 of 3.15 μm was used to remove SO2. 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 SO2, a SO2 removal efficiency typical of existing calcium-rich desulfurizers. As limestone desulfurization can release CO2, when limestone desulfurization was replaced with steel slag of equal desulfurization ratio, CO2 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 CaSO4·2H2O, CaSO4·0.5H2O, CaSO3·0.5H2O, 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%.