Graded synthesis of high performance adsorbent from coal gasification fine slag and its application in the removal of methyl blue

The resource utilization of coal gasification fine slag (CGFS) and the harmless treatment of printing and dyeing wastewater are of great significance for the construction of zero-emission industrial system and resource circular economy. In this study, residual carbon and slag particles were separated from CGFS by froth flotation, and their pore structure was modified by alkali activation and acid leaching. Then, the two materials were surface functionalized and applied as adsorbents for the removal of methyl blue (MB) from printing and dyeing wastewater. The results show that optimization of flotation process parameters can achieve efficient separation of residual carbon and slag particles. The adsorption performance of both materials for MB was significantly improved after surface functionalization. The maximum adsorption capacities of modified residual carbon and slag particles for MB were 1708.01 mg·g−1 and 1249.46 mg·g−1, which were 1.4 and 64.6 times higher than before the modification, respectively. The pseudo-second-order kinetic model satisfactorily described the adsorption behavior, which was mainly chemisorption. In addition, the adsorption state of MB on the material surface was analyzed by FT-IR and XPS, and possible adsorption mechanisms were proposed. Based on the idea of high value utilization of solid waste, this research has achieved the resourceful transformation of CGFS into high performance adsorbents.