Biosorption of uranium and cadmium using sorbents based on Aloe vera wastes

The biosorption of uranium and cadmium using Aloe vera wastes was investigated regarding the effect of pH, sorbent mass, concentration, contact time and temperature. Additionally, modification of the raw material by acidic and alkaline reagents was carried out in order to enhance its sorption ability for the tested metals. Several models as pseudo-first and pseudo-second order equation as well as Elovich and intra-particle diffusion model were satisfactorily applied to reproduce the kinetics data indicating the complexity of the sorption mechanism. The sorption isotherms were simulated by Langmuir and Freundlich models and thermodynamic data were determined in order to assess the uptake behavior. It was found that the biosorbent modified by alkaline reagent, exhibited high sorption capacity with q(max) values, 370.4 and 104.2 mg g(-1) for uranium and cadmium respectively. TCLP tests for the investigation of environmental compatibility of the loaded biosorbents and desorption tests were also performed. Furthermore, SEM/EDS, XRD and FTIR were used for the characterization and elucidation of the sorption mechanism which is complex and involves different mechanisms as physical sorption, ion-exchange, metal binding and surface precipitation.