Valorization of calcium carbonate-based solid wastes for the treatment of hydrogen sulfide in a semi-continuous reactor

Abstract : The carbonation of residual brines generates large volumes of carbonate-based solid wastes. Physicochemical properties of these solids are adequate for acid-gas removal. This work studies the valorization of calcium carbonated-based solid wastes for efficient H2S removal from air at low concentrations (≤200 ppmv) in a three-phase semi-continuous reactor. Synthetic air polluted with H2S was bubbled into the slurry of two different wastes in a stirred tank to evaluate their effect for H2S removal. The efficiency of H2S removal was kept constant and could reach up to 98% during 8 h of reaction. Adequate physico-chemical characterization of used sorbents allowed understanding the interaction of sulfide species with sorbent particles. Thus, the reaction pathway for H2S removal was determined. It has been demonstrated that the dissolution of H2S gas at the gas-liquid interface was then accelerated by high basicity of calcium carbonate-based wastes, followed by the oxidation of dissolved sulfide species. This last was catalyzed by metals and metals oxides which were initially present in the solid wastes. The results obtained demonstrate the possibility to valorize the carbonates which have been precipitated during the carbonation of industrial brines to develop a low cost H2S removal process.