Extraction of Al and preparation of polyaluminum chloride from coal gasification fine slag by high-pressure HCl leaching method

With the widespread promotion of coal gasification technology, the mass-produced solid waste coal gasification slag has caused serious threat to the environment. Coal gasification fine slag (CGFS) is rich in aluminosilicates, which can be used as a source of aluminum (Al). In this study, a hydrothermal method with enhanced mass and heat transfer was used to extract Al from CGFS. The Al3+-rich acid leaching solution was polymerized with calcium aluminate powder to obtain polyaluminum chloride (PAC). Orthogonal test results show that when the extraction rate of Al ions from CGFS reaches 78.9%, the Al2O3 content and basicity of PAC are 30.95% and 58.09%, respectively. When the prepared PAC is added to domestic sewage at 100 mg/L, the turbidity of the sewage drops from 68 to 12 NTU, and the removal rates of chemical oxygen demand and ammonia nitrogen reach 60% and 52.5%, respectively. It is a promising approach for environmental protection and high value-added utilization of CGFS.