Modelled and Measured Adsorption of Rare Earth Elements onto Bentonite with Various Geochemical Conditions Using a Generalised Surface Complexation Approach

The demand for rare earth elements (REEs) is likely to outweigh supply. As such, every effort should be taken to salvage REEs from waste streams and other sources of discharge. In this study, PHREEQC geochemical modelling code coupled to parameter estimation software (PEST) was used to simulate the adsorption of REEs onto generalised sorption sites representing natural bentonite. Experimental observations and bentonite characterisation were used to calibrate the model. A total of 83-99.9%, 57-99.5%, 29-99% and 1-85% adsorption efficiencies were observed at 2, 5, 10 and 50 mg L-1 initial concentration, respectively. The adsorption efficiency (> 99%) of REEs at pH 6 was not affected by the presence of anions and cations at different concentrations. Thus, PHREEQC modelling coupled to PEST can be used to simulate the adsorption of elements using limited data. This study indicated that natural bentonite is a suitable and competent adsorbent for the recovery of REEs from wastewater.