Adsorptive removal and recovery of U(VI) by citrus waste biomass

Abstract

Adsorption and recovery of hexavalent uranium from dilute aqueous solutions by low cost citrus waste biomass was investigated by performing adsorption-desorption studies. Different samples of citrus waste biomasses were screened for removal of U(VI) from aqueous solutions. The results indicated that the biosorption capacity was strongly affected by the solution pH, biosorbent dose, contact time, and initial uranium concentration. Uranium binding by the test biomass was rapid, achieving >79% sorption efficiency within 15 min, and the equilibrium was established in 60 min. Optimum biosorption capacity (qe) was observed at pH 4.0, biosorbent dose 0.1 % (w/v), initial uranium concentration of 100 mg/L. The kinetic data fitted well to a pseudo-second-order rate equation (R2=0.980). The adsorption process conformed to a Langmuir adsorption isotherm model. Gibbs free energy (ΔGo) and enthalpy change (ΔHo) indicated that reaction was spontaneous and exothermic in nature at the studied temperatures. FT-IR studies showed the involvement of carbonyl, carboxyl, and amide groups in the biosorption process. Treatment of biomass with different reagents affected its biosorption capacity, and maximum removal (70.63%) was recorded with polyethyleneimine (PEI) treated biomass. EDTA had the best effects as an eluent, showing 94.7% desorption capacity.