Application of a low-cost material for uranium removal: experimental variables and study of concomitants

Abstract

In the present work, the extent in which the presence of concomitant ions affects the removal capacity of uranyl ion by the natural mineral perlite was studied. By using synthetic solutions of uranyl nitrate in batch systems, the variables affecting the process, namely sorbent dose, contact time, pH and initial UO22+ concentration, were firstly investigated. The zeta potential and the sorption capacity of perlite, as well as relevant kinetics and thermodynamic parameters were measured. Removals up to 90 % were achieved for a dose of 45 g of Pava L-1 and a concentration of U of 100 µg U L-1, of 74 % when the concentration was 1 mg U L-1, 60 % for 10 mg U L-1 and 25 % for a concentration of 50 mg U L-1. The best linear correlations in the adsorption isotherms were achieved by applying the Langmuir and Dubinin-Radushkevich models with adsorption energy of 8.72 kJ mol-1. The thermodynamic variables indicated the feasible, spontaneous and exothermic nature of the sorption of UO22+ by perlite. The influence of concomitant ions, in decreasing order, was: Cs+ > Ba2+ > Mg2+ > K+ ~ Na+ > NH4+ > Ca2 +. The results of these investigations will allow determining the best treatment, weather the solution is an effluent from a nuclear plant or in case of environmental contamination.