Removal of uranium (U(VI)) ions using NiO NPs/Ag-clinoptilolite zeolite composite adsorbent from drinking water: equilibrium, kinetic and thermodynamic studies

The present research describes the performance of NiO NPs/Ag-clinoptilolite composite adsorbent for the removal of uranium (U(VI)) ions from drinking water of Dezful city-Iran. Prior to the experiment reactions, Na-clinoptilolite was chemically treated with NaCl, Silver ions (Ag+) and subsequently Nickel (NiO) NPs to prepare NiO NPs/Ag-clinoptilolite. The samples were characterized by SEM, AAS, XRD and FTIR techniques. The removal process of U(VI) ions by the NiO NPs/Ag-clinoptilolite adsorbent was exploited under various conditions including pH, adsorbent dose, the contact time and initial concentration at room temperature. The adsorption isotherm models including Langmuir, Freundlich, Temkin and Hasley were applied. Experimental adsorption isotherm is successfully described by Langmuir model with a maximum adsorption capacity 23.5849 mg of U(VI)/g of NiO NPs/Ag-clinoptilolite. The ICP-AES results indicated that U(VI) was adsorbed on the composite surface active after 60 min at room temperature with a yield 94%. The reaction kinetic information was studied by utilizing pseudo first and second orders kinetic models. The adsorption kinetics was found fit the pseudo-second-order models. Further the evaluation of the thermodynamic parameters such as DG0, DH0 and DS0, denoted that adsorption process of U(VI) was spontaneous and illustrates a physical adsorption properties and exothermic nature of the adsorption.