Selective recovery of lanthanum from magnesium-containing solution via phosphoric acid modified kaolin prepared by a simple mechanochemical process

As the world's demand for rare earths soars, the supply of rare earths is in danger of being depleted. The recycling rate of rare earth is only 1 % of all rare earth. Therefore, the recovery of rare earth is crucial and challenging. A phosphoric acid modified kaolin (P-K) was prepared by a simple mechanochemical method, and the selective recovery of rare earth element lanthanum (La) was studied. The P-K was characterized and analyzed by SEM, EDS, and FT-IR. Additionally, the different modification conditions of P-K preparation such as milling speed, time, and mass ratio of H3PO4/kaolin on La adsorption were investigated, and the effects of operating conditions such as solution initial pH, adsorption time, and adsorbent concentration on La adsorption were studied. The adsorption behavior of La by P-K was consistent with the Langmuir isothermal adsorption model with a saturated adsorption capacity of 18.55 mg/g, and the adsorption kinetics accorded with the pseudo-second-order kinetic model. Additionally, La in the mixture of La and magnesium (Mg) can be selectively adsorbed through P-K, while the adsorption rate of Mg is almost 0. P-K load with La could be eluted by 0.03 mol/L HCl, and the elution rate of La can reach 99.9 %. As a result, this study demonstrates a method for the recovery of La from rare earth wastewater.