Surfactant assisted APTES functionalization of graphene oxide intercalated layered double hydroxide (LDH) for uranium adsorption from alkaline leach liquor

The efficacy of uranium adsorption by modified layered double hydroxide (LDH) has been studied in detail in this work. The effects of initial uranium (U) concentration, solution pH, adsorbent dose, temperature and the presence of other ions were investigated. The removal efficiency varied from 98% to 92% for the initial U concentration 54–216 mg/L. However, the removal efficiency was decreased to 84% when the feed concentration was increased to 432 mg/L. The removal of uranium increased with the solution pH and beyond 8.5 it was invariant indicating the adsorbent is highly suitable for treatment of alkaline leach liquor. The adsorption capacity decreased with temperature and the Langmuir capacity of the adsorbent were found to be 948, 1,026, and 1162 mg/g at 323, 313, and 303 K, at pH 8.5. Evaluation of isotherm in alkaline pH is rare in the literature and the adsorption capacity of U of the LDH based adsorbents are reported in the range of 180 to 1143 mg/g with a pH variation of 3–7 at 298 K. Second order rate equation described the adsorption kinetics adequately. It was shown that switching of pH to 11.5 resulted remarkable desorption of U. Thus, the developed adsorbent has tremendous potential to separate U from alkaline leach liquor. Much research is required to immobilize the nano-sized adsorbents in a suitable media for preparation of the commercial scale filters.