Adsorption Of ~(60)co Radionuclides From Aqueous Solution By Raw And Modified Bentonite

摘要

Bentonite and formaldehyde modifled-bentonite (MF-bentonite) were tested for removal of the radioactive isotope ~(60)Co. The two adsorbents were characterized (FTIR spectroscopy and scanning electron microscope) before and after modification. Some enhancement was obtained in the mesopore region due to impregnating the bentonite with 35% of formaldehyde solution and the modified sample had better adsorption performance. Furthermore, the adsorption capacity of MF-bentonite increased by increasing the quantity of formaldehyde deposited on the surface. The adsorption potential of bentonite and MF-bentonite for the removal of ~(60)Co radionuclide from radioactive waste solutions has been investigated. The influence of pH, contact time, adsorbent dosages and temperature is reported. Pseudo first-order and pseudo second-order kinetic models were used to analyze the adsorption rate data. The pseudo second-order model was found to best correlate the kinetic data. Adsorption isotherms were determined to assess the maximum adsorption capacity of bentonite and MF-bentonite. The Langmuir model fitted the data reasonably well in terms of regression coefficients. Adsorption studies were also performed at different temperatures to obtain the thermodynamic parameters. The numerical value of △G~0 decreased with an increase in temperature, indicating that the adsorption is more favorable at higher temperature. The positive values of △H~0 corresponded to the endothermic nature of adsorption processes.