Investigation on froth flotation separation of gypsum from lithium refinery residue with an eco-friendly and efficient surfactant

With the rapid advancement of the new energy industry, the expansion of lithium smelting has resulted in significant discharge and accumulation of lithium refinery residue (LRR), consuming vast land resources and posing a serious threat to the local environment. Aluminosilicate, the primary component of LRR, shares a similar structure with pyrophyllite, making it a viable substitute. The separation of gypsum from LRR is essential for producing qualified aluminosilicate products. In this study, an eco-friendly surfactant, N-SLS, was utilized as a collector to efficiently separate gypsum from LRR via flotation. N-SLS selectively adsorbed to the gypsum surface, likely due to the complexation of carboxylate groups with calcium ions, enhancing its hydrophobicity and facilitating flotation. Meanwhile, aluminosilicate retained its hydrophilicity and remained in the slurry, separating gypsum and aluminosilicate. Using 300 g/t N-SLS as the collector and 3000 g/t sodium silicate as the depressant at natural pulp pH, qualified aluminosilicate products (SO 3 grade <0.6 %, a concentrate yield >70 %) were produced through an open-circuit flotation process, consisting of one roughing and three scavenging steps. The industrial recovery of aluminosilicate products from LRR based on this flotation process offered an economic benefit of 25.27 USD/t. This study provided a cost-effective and environmentally friendly solution for the large-scale, continuous, and stable disposal of lithium slag.