SO2 removing from smelter off-gas by converting to elemental sulfur with application of CaS particles synthesized by solvothermal method

Abstract The sulfur dioxide (SO 2 ) in the smelter off-gas can be treated by converting it to sulfuric acid in the commercial sulfuric acid plants only when its concentration is between 3% and 13%. In this study, both the octahedron-like CaS (Sol-S-CaS) and the broccoli-like CaS (Sol-T-CaS) particles were prepared using the solvothermal synthesis method. The CaS samples were used to convert the SO 2 with the concentration higher than 3% into sulfur particles. The CaS samples were characterized by SEM, N 2 physisorption, XRD, EDS, HRTEM and XPS analysis. As proven by the XRD and EDS results, both Sol-S-CaS and Sol-T-CaS were high-purity CaS materials. These materials displayed a SO 2 removal efficiency above 99% in the initial 60 min of the desulfurization period and were more attractive than the other CaS samples. Additionally, Sol-S-CaS exhibited a stable recyclability while the recyclability of Sol-T-CaS declined sharply. It was discerned from SEM images that the apparent aggregations of Sol-S-CaS particles were not observed after eight cycles and the SO 2 removal efficiency decreased slowly from 99.44% to 98.83%. Sol-S-CaS also proved effective anti-NO poisoning and could act as a promising material to recover sulfur from the smelter off-gas. The Sol-S-CaS particles were divided into four size groups and the particles of the size of 75–150 μm demonstrated the best SO 2 removal performance. The XPS results indicated that the solid products after the desulfurization were predominantly CaSO 4 without any by-products, and it was helpful to obtain a stable SO 2 removal efficiency. In a quantum mechanics investigation into the reaction between CaS and SO 2 , the reaction pathway was evaluated and the optimized geometries of the structures of intermediates and transition states were determined.