A novel approach for extracting lithium from overhaul slag by low temperature roasting – water leaching

Overhaul slag, as one of the hazardous wastes generated in the aluminum industry, which can pollute the environment and waste resources when arbitrarily stockpiled or landfilled. Scientific and standardized recycling of overhaul slag with both valuable and pollutant characteristics can avoid environmental pollution, and greatly alleviate the global resource shortage crisis. In this paper, an innovative process of sulfuric acid roasting and water leaching is proposed, which can efficiently and environmentally recover F, Al and Li from overhaul slag. The effects of roasting parameters including H2SO4 dosage, roasting temperature and time were systematically investigated. The optimal conditions have been established as: m(H2SO4)/m(overhaul slag) of 1.4:1, roasting temperature of 360 ℃, and time of 2.0 h. Under this conditions, the lithium was converted to NaLi(SO4) and the aluminum was converted to NaAl(SO4)2, during which the HF volatilization rate reached 99.4 %. The roasted clinker was then subjected to water leaching for the extraction of lithium and aluminum. About 99.5 % of lithium and 72.57 % of aluminum was extracted by the leaching process under the optimal conditions. After the leaching solution was treated by pH adjustment, roasting and water leaching, lithium and aluminum could be effectively separated, and the leaching rates of lithium and aluminum were 99.34 % and 0.12 %, respectively. The process proposed in this paper is not limited to the treatment of overhaul slag, but can also be applied to the processing of other aluminum industrial wastes and has a wide application potential.