Adsorption of uranium from uranium mine contaminated water using phosphate rock apatite (PRA): Isotherm, kinetic and characterization studies

Abstract

Adsorption of uranium (U) from real mine contaminated water (U 1.652mg/L) by phosphate rock apatite (PRA) was investigated in the batch experiment and flow column test system. In batch experiment, the equilibrium adsorption amount is 0.1133mg/g with the highest uranium removal efficiency of 76.89% under the ratio of solid to liquid (1:100) in 15h. And the pH of wastewater became neutral (pH 7.51) from acidic (pH 3.88) after adsorption equilibrium. The saturated adsorption amount (0.2021mg/g) in batch experiment is higher than the maximum accumulative adsorption amount (0.0684mg/g) in column experiment. Langmuir model and pseudo-second order kinetic model are fitted well and, indicating that PRA is a favorable adsorbent with monolayer coverage and a chemisorption for uranium. Moreover, the surface morphology of the adsorbent by SEM confirmed the surface changes after uranium adsorption. XRD spectra showed that two new mineral phase of Metaankoleite [K(UO2)(PO4)·3H2O], Chernikovite [H2(UO2)2(PO4)2·8H2O] have been generated on PRA after uranium adsorption, but which were trace for relatively low uranium concentration in tested polluted water. In addition, the FT-IR spectra results confirmed the uranium in contaminated water was adsorbed onto the PRA in the form of (O=U=O)2+ with the participation of the PO43–in binding of it.