A Novel Approach for Selective Removal of Aluminum Ion from Rare Earth Leaching Solution by Using Hydrotalcite as Solid Base

Abstract Removing Al 3+ from the rare earth leaching solution is a challenging task. The main issues are slow filtration speed and significant rare earths loss in the Al(OH) 3 precipitate. In this study, hydrotalcite was proposed as a solid base for selective removal of Al 3+ and accelerating the filtering speed. A comparison was made between hydrotalcite and ammonia on Al 3+ removal rate, loss rate of rare earth, and filtering speed under different pH values. Results showed that the filtering process can be completed within 20 s using hydrotalcite, compared to several minutes with ammonia precipitation. At pH value of 4.3, the Al 3+ removal rate reached 92% with a rare earth loss rate of only 1.9% for hydrotalcite, whereas ammonia achieved 89.2% and 4.3%, respectively. The mechanism of rare earth loss with alumina hydroxide was also analyzed. Based on the analysis, water washing and organic acids complexing was used to reduce the loss of rare earth by decreasing the Al 3+ surface adsorption and the mixed crystal formation of rare earth in Al(OH) 3 precipitates. Thus, the using of hydrotalcite as a solid base for Al 3+ removal from rare earth leaching solution shows significant progress.