Adsorption of selenite and selenate ions onto thiourea-formaldehyde resin

In this study, thiourea-formaldehyde (TUF) resin was synthesized and the adsorption of selenite (SeO32-) and selenate (SeO42-) ions onto TUF resin was examined. Firstly, the elemental analysis of the TUF was done to determine the composition. FTIR spectra and SEM/EDS micrographs of TUF resin before and after the adsorption of selenite ions were also recorded.The effect of initial acidity-alkalinity of selenite and selenate solutions on the adsorption was studied and the optimum acidities were found as 3 M HCl concentration for selenite ions and 5 M HCl for selenate ions. Moreover the effect of initial concentration of selenite and selenate ions was also studied and the adsorption data were applied to the Langmuir and Freundlich adsorption isotherm. It was found that the data for the both adsorption fitted more to the Langmuir isotherm. The adsorption capacities of the resin were calculated as 833,3 for selenite ions and 526,3 mg.g?1 for selenate from the Langmuir isotherm. It was seen that elemental selenium (Se0), red-orange color, occurred in the adsorption of both selenite and selenate ions onto the TUF resin. It was found that the adsorption mechanism was controlled by the reduction to elemental selenium in the both adsorption.