Method and mechanism of reverse flotation for dephosphorization of spodumene concentrate using sodium alginate as a depressant

In industry, the content of P2O5, mainly derived from apatite, must not exceed 0.5% in spodumene concentrate. Strong acid leaching of phosphorus-containing minerals with the disadvantages of seriously harming the environment and high investment in equipment, is the main method for removing phosphorus. Therefore, in this work, sodium alginate (SA) depressant was effectively used to depress spodumene and float apatite. Li2O grade and recovery in the spodumene concentrate were 6.18% and 87.66% obtained by the binary mixed mineral flotation tests with 1.1 × 10-4 mol/L SA and 3 × 10-4 mol/L sodium oleate (NaOL) collector at pH 5. The P2O5 content in the real spodumene concentrate could be reduced from 4.58% to 0.49% using 500 g/t of SA. The contact angle tests showed that the hydrophilicity of spodumene increased after the treatment of SA. Zeta potential and atomic force microscope (AFM) measurements revealed that anionic SA had more adsorption on the spodumene surface and hindered the subsequent adsorption of NaOL. Density functional theory (DFT) calculations further showed that SA could chelate with Cu2+ pre-adsorbed on the spodumene surface to form a 4-membered ring. Therefore, the method of reverse flotation has great application potential in the dephosphorization of high-phosphorus lithium concentrate.