A novel process for precipitation of rare earths using carboxylic acid compounds

Weathered rare earth ores are an important strategic mineral resource in China, and they are the primary source of medium and heavy rare earths (MHRE). The efficient recovery of MHRE is of great significance from an industrial standpoint. In this study, fulvic acid (FA) is employed as a precipitant to investigate the precipitation of rare earth (RE). The results indicate that the precipitation rates ( w ) of RE range from 89.69 wt% to 99.86 wt% with the pH of 9, the molar ratio of 2, and the temperature of 40 °C, except for Lu 3+ , the w reaches 97.33 wt% with the pH of 9, the molar ratio of 3, and the temperature of 25 °C. The w of RE in the ammonium acetate rare earth leaching solution ranges from 95.99 wt% to 98.54 wt%, with the MH/L of the rare earth distribution after precipitation increasing from 0.77 to 0.80. The use of FA as a precipitant is demonstrated to yield effective precipitation of RE, particularly those of MHRE. FA complexes with RE 3+ , where deprotonation of COO – increases the surface electron density of oxygen atoms, creating additional active sites for electron-deficient RE 3+ . The mechanism provides a theoretical basis for using carboxylic acid compounds as new precipitants. Further, a novel technology for FA complexation precipitation of RE from lignite extract is proposed.