Simultaneous sorption of rare earth elements (including scandium and yttrium) from aqueous solutions using zeolite clinoptilolite: A column and speciation study

Abstract

Rare earth elements including scandium and yttrium (REY) are valuable elements that are used in different economically valuable applications. Moreover, these elements are in demand especially in electronic products and energy gadgets such as solar panels and wind turbines. Thus, their recovery from industrial wastewaters will be very beneficial to the economy of the world. The current study reports on the simultaneous recovery of REY (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu) from aqueous solutions using column studies. The role of pH (2 – 8), concentration (2 – 10 mg L−1), bed height (3 – 9 cm) and flow rate (2.0 – 5 mL min−1) on the uptake of REY was investigated. The effect of the presence of SO42−, Cl− and PO43− at different conditions was also assessed. Column models were used to describe the column sorption data. The speciation of the elements was determined using PHREEQC geochemical modelling. The highest adsorption capacity was reached with 3 cm bed height and 2 mL min−1 flow rate at pH 5.5, with>98% removal efficiency of all the elements. The REY removal process was ineffective in highly acidic pH. There was no significant difference on the removal of REY in the absence or presence of Cl−. >75 and 90% removal percentage of REY was observed in the presence of SO42− and Cl−, respectively, but the adsorption was low in the presence of PO43−. Natural zeolite proved to be a suitable adsorbent for simultaneous removal of REY from wastewaters.