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

Adsorption of uranium (U) from real mine contaminated water (U 1.652   mg/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 0.1133   mg/g with the highest uranium removal efficiency of 76.89% under the ratio of solid to liquid (1:100) in 15   h. And the pH of wastewater became neutral (pH 7.51) from acidic (pH 3.88) after adsorption equilibrium. The saturated adsorption amount (0.2021   mg/g) in batch experiment is higher than the maximum accumulative adsorption amount (0.0684   mg/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(UO 2 )(PO 4 )·3H 2 O], Chernikovite [H 2 (UO 2 ) 2 (PO 4 ) 2 ·8H 2 O] 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 PO 4 3– in binding of it.