Novel desulfurization technology by employing coal gangue slurry as an absorbent: Performance and mechanism study

The elimination of SO2 pollutants from coal fired flue gas through using industrial solid waste as absorbent has received widespread attention. Herein, a novel process on SO2 purification by employing coal gangue slurry is proposed for the first time. The effects of different operating variables on SO2 absorption efficiency were studied, indicating that coal gangue slurry has superior desulfurization performance. The desulfurization capacity can reach up to 33.12 g SO2/L coal gangue slurry. In addition, the desulfurization active substances and products are determined based on the analysis of the composition of gas, liquid and solid phase substances during the desulfurization process. It is found that the Fe3+ dissolved from coal gangue have a significant effect on the efficient absorption of SO2. The HSO3− formed by the dissolution of SO2 in water can be rapidly converted into SO3•− radicals under the catalytic action of trace Fe3+, thereby inducing active oxidizing substances, such as SO5•−, SO4•−, HO2• and HO•, to promote the transformation of SO2 towards SO42−. Subsequently, SO2 removal pathways are revealed. This result has important implications for the industrial application of coal gangue slurry desulfurization technology.