The uptake of uranium by tea wastes investigated by batch, spectroscopic and modeling techniques

Tea wastes have been widely re-cycled in wastewater disposals towards various environmental pollutants. In this study, the uptake of uranium from aqueous solutions by tea wastes was investigated as a function of reaction time, pH, ionic strength, initial concentration and temperature under ambient conditions. The results indicated that the uptake of uranium by tea wastes was strongly dependent on pH and ionic strength. The maximum adsorption capacities of tea wastes calculated from Langmuir models at pH 4.0 and T = 298 K was 29.412 mg/g. The thermodynamic parameters (ΔH0, ΔS0 and ΔG0) calculated from the temperature dependent adsorption isotherms indicated that the adsorption of uranium by tea wastes was an endothermic and spontaneous process. At low pH, the uranium uptake was dominated by ion exchange with Na+/H+ on the surfaces of tea wastes, whereas inner-sphere surface complexation was observed at high pH. The uptake of uranium on tea wastes can be satisfactorily fitted by diffuse double layer model with ion-exchange and surface complexation sites. It is determined that tea wastes may have a good potentiality for the disposal of uranium-bearing wastewaters in environmental cleanup.