Soil utilization analysis of synergistic pyrolysis products of flue gas desulfurization gypsum and biomass

Flue gas desulfurization gypsum (FGDG) is one of the typical bulk solid wastes. With its vast production and considerable storage capacity, it accumulates in substantial quantities, occupies an extensive amount of land, and poses a severe pollutant threat to the ecological environment. To achieve large-scale consumption of FGDG, this study puts forward a method for the soil utilization and ecological reconstruction involving the co-pyrolysis of FGDG and biomass. The main emphasis is placed on exploring the alterations in leaching toxicity and plant-available elements under diverse conditions of temperature, biomass addition, and pyrolysis time. The co-pyrolysis parameters were optimized, and the changes in mineral composition of FGDG and biomass under different pyrolysis circumstances were investigated using XRD and SEM characterization methods. The experimental outcomes demonstrated that the optimal pyrolysis conditions were a temperature of 700 °C, a biomass content of 60 %, and a pyrolysis time of 5 h. The toxic and harmful substances within FGDG were solidified and stabilized, achieving a harmless treatment of FGDG. Simultaneously, the usable elements for plants were released. Through the analysis of mineral composition and microstructure, it was discovered that the pyrolysis products contain a considerable amount of CaSO₄ and C, and the microstructure mainly consists of porous aggregates. The reason for the reduced leaching efficiency of toxic and harmful substances might be attributed to the formation of stable minerals such as heavy metals through crystallization and vitrification mineralization after the removal of crystal water from FGDG. Under the reduction effect of C, the available elements for plants are liberated. This study furnishes a theoretical basis for the industrial application of FGDG and biomass for large-scale soil utilization treatment.