Enhanced leaching process of ion-adsorbed rare earth ores with itaconic acid and magnesium sulfate compound leaching agent

•The addition of itaconic acid (IA) improves leaching efficiency of rare earths.•IA can leach the colloidal sedimentary- and mineral-phase rare earths.•The addition of IA reduces the amount of MgSO4 added during leaching.•IA can improve the environment of the ore area after leaching. A compound leaching agent (CLA) composed of itaconic acid (IA) and MgSO4 was employed in this study, and the effects of the ratio of the two components, in addition to the initial pH, temperature, and liquid–solid ratio on the leaching rate of rare earths were investigated. Under the following conditions: MgSO4 content=1 %, IA concentration = 6.0 g/L, pH = 4.5, liquid–solid ratio = 3:1, and reaction temperature = 25 ℃, the leaching efficiency of rare earths was 95.03 %, which was 9.34 % higher than that observed when using the MgSO4 (85.69 %). Furthermore, the residual Mg content in the tailings was decreased because of the reduction in the amount of MgSO4. Compared with the tailings obtained using pure MgSO4 as the leaching agent, the tailings obtained using CLA had 52.66 % lower Mg in the water-soluble state and 14.77 % lower Mg in the exchangeable state. [Display omitted]