Adsorption Of Uranium(Ⅵ)by Amino-based And Phosphate-based Bentonite

The application of nuclear power in human life and industrial increased as its demand within many countries has rised.However,the uranium contained waste water which was caused by the mining and utilizing of uranium has serious effect on environment due to the high radioactivity and high toxicity of uranium.Bentonite has excellentr cation exchange ability,therefore can be widely used for adsorption of nuclide in waste water.Unfortunately,bentonite has its limits about adsorb uranium,hence it is neccessary to modify bentonite to improve the adsorption ability towards uranium.This study use the natural Gaomiaozi bentonite in Inner Mongolia as raw bentonite.After a series of pretreatment,the raw bentonite was modified respectively by 2-aminoterephthalic acid,trisodium phosphate,potassium hydrogen phosphate hydrate,ammonium dihydrogen phosphate and palmityl sulfobetaine.Varies characterizations were carried out such as X-ray diffraction（XRD）,scanning electron microscope（SEM）and fourier transform infrared spectroscopy（FT-IR）.The change of structure,morphology,interlayer spacing and functional group were discussed and anylasized.Batch experiencement was used to determine the opstimal conditions of adsorption.Isothermal adsorption model,kinetic model and thermodynamic model was applied to discuss the process and mechanism of adsorption by modified bentonite.And the results are as follow:（1）Bentonite modified by 2-aminoterephthalic acid showed the decrease of specific surface area on the surface and the increase of interlayer space,indicated the stripping of bentonite structure.The adsorption ability of modified bentonite is better than raw bentonite.At pH=6,when the dosage of adsorbent was 10 mg and the range of cercentration is between20-400 ppm,at the time of 400 min,the max adsorption ability was 200.7 mg·g^-1.The adsorption process is influenced by chemical action which is also nonuniform adsorption on the surface.The results of thermodynamics study suggested that the adsorption process is endothermic and spontaneous.（2）Bentonite modified by trisodium phosphate,potassium hydrogen phosphate hydrate and ammonium dihydrogen showed the increase of interlayer space.At pH=4,when the dosage of adsorbent was 10 mg and the range of cercentration is between 20-400 ppm,at the time of 400 min,the max adsorption for trisodium phosphate,potassium hydrogen phosphate hydrate and ammonium dihydrogen ability was 130.07 mg·g^-1,163.18 mg·g^-1 and 150.69mg·g^-1.The adsorption process is influenced by chemical action which is also nonuniform adsorption on the surface.The results of thermodynamics study suggested that the adsorption process is endothermic and spontaneous.（3）Bentonite modified by palmityl sulfobetaine increased the interlayer space to 1.835nm.At pH=7,when the dosage of adsorbent was 10 mg and the range of cercentration is between 20-400 ppm,at the time of 200 min,the max adsorption ability was 301.06 mg·g^-1.The adsorption process is influenced by chemical action which is also nonuniform adsorption on the surface.The results of thermodynamics study suggested that the adsorption process is endothermic and spontaneous.