Recovery and concentration of Eu(III) from phosphogypsum leachate using ouricuri endocarp

Ouricuri endocarp was utilized as a biosorbent for the recovery of europium (Eu(III)) from aqueous solutions and rare earth elements (REEs) from authentic leachate derived from phosphogypsum, which encompasses various REEs. Various characterization techniques were applied to analyze the physicochemical and adsorptive properties of the biosorbent. The results indicate that the adsorption kinetic data conform well to the pseudo-first-order model, while the Liu model describes the equilibrium data well. Ouricuri endocarp and Eu interactions are favorable and spontaneous. The maximum adsorption capacity for Eu(III) is determined to be 22.9 mg/g according to the Liu model. Based on experimental results and adsorbent characteristics, the proposed adsorption mechanisms between ouricuri endocarp and Eu include ion exchange and electrostatic interactions as the primary mechanisms. The Eu(III) recovery is also feasible as a continuous flow process demonstrating inclined breakthrough curves and lower values of the length of the mass transfer zone. Ouricuri endocarp demonstrates its selectivity for recovering various REEs from authentic phosphogypsum leachate. It achieves a 98% recovery rate for Eu and approximately 60% for Ce, La, and Nd, affirming its efficacy under real-world conditions. Finally, concentration of REE was done by ashing loaded ouricuri endocarp, and a solid with around 34% (in weight) of REE is obtained.