An Investigation of Lanthanum Recovery from an Aqueous Solution by Adsorption

Lanthanum (La(III)) is one of the high-demand rare earth elements with applications in various products. However, La(III) in mining waste streams and electronic waste also poses environmental and health concerns. Therefore, recovery of La(III) in the waste is needed. In the present study, adsorption of La(III) with Dowex 50W-X8, Amberchrom50WX4, Amberlyst 15, and Amberchrom 50WX2 was evaluated, using a shaker water bath. Dowex 50W-X8 was found to be the best adsorbent and used to investigate the effect of the shaker speed (RPM=50-150), adsorbent dosage (1.0-4.0 g), pH (2.0-7.0), and temperature (20-40oC) on adsorption. La(III) adsorption was found to increase with the shaker speed, as expected. On the other hand, adsorption capacity decreased with the adsorbent amount. Also, the highest La(III) adsorption was observed at pH = 6.0. La(III) percentage removal didn’t vary significantly with temperature from 20 oC -40oC. However, the first-order kinetic rate constant decreased moderately with increases in temperature. Adsorption of La(III) by Dowex 50-X8 followed the Freundlich isotherm model better than the Langmuir model. In addition, adsorption kinetics was represented well by the first-order kinetic model. Moreover, enthalpy and Gibbs free energy changes were found to be negative, indicating an exothermic and thermodynamically favourable adsorption process.