Zero-waste strategy for lithium extraction clay slag: Preparation of polyaluminium chloride and silica-enriched cement ingredient

Abstract

With the rapid development of new energy vehicles and renewable energy industries, the demand for lithium resources has increased significantly, and the resulting large amount of solid waste from lithium extraction poses a serious threat to the environment. For zero-waste utilization of lithium extraction clay slag, this study employed an acid leaching-polymerization-aging process to prepare polyaluminium chloride for water treatment and silica-enriched ingredient for cement production. Optimization of preparation conditions yielded liquid polyaluminium chloride (PAC) containing 10.06% Al₂O₃ with 59.16% basicity, which complies with the national standards. Meanwhile, the illite residue derived from the Al leaching process, with a silica modulus of 2.4, satisfies the requirement for clay raw materials in cement production. In coagulation tests using simulated wastewater, the synthesized PAC demonstrated removal efficiencies of 96.92% for turbidity and 97.32% for chemical oxygen demand (COD) in humic acid wastewater, and 99.24% for turbidity and 92.21% for COD in methyl orange wastewater, outperforming a commercially available polyaluminium chloride. These results demonstrate that the proposed strategy facilitates the complete utilization of lithium extraction slag, thereby promoting sustainable development in the lithium industry.

Keywords

lithium extraction slag / polyaluminium chloride / clay raw materials for cement production / high-value utilization / complete consumption

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