Selective recovery of rare earth elements from aqueous solution obtained from coal power plant ash

The biosorption-desorption of multi-components solution obtained from coal power plant ash aqueous solution composed on La, Ce, Er etc. as rare earth ions (REEs) and Li, Fe, Cu, Al as metals were investigated using 450 °C carbonized gingko leaves as low-cost biosorbent. Evaluation of the effect of pH with respect to contact time indicated a dependency of the system with those parameters. pH = 3 was found as optimum one and a rapid uptake of Er ions up to 95% in 900 s is observed. La and Ce despite their low concentration in the solution reached their maximum uptake within 900 s. The effect of counter ions like Li, Fe and Cu indicated that REEs were adsorbed together with metals. The mechanism of the biosorption is explained by the electrostatic interaction between carbonate ions on the surface of the biosorbent and ions in the solution as well as adsorption onto carbonyl functional group. Desorption system was highly dependent on temperature and time and was not favorable for La and Ce ions whereas 99.22% of Er ions were recovered with 0.3 M concentrated HCl pointed out a selective recovery of Er ions.