Performance of U(Ⅵ)enrichment by tannic acid sodium and alginate composite microspheres
With the rapid development of nuclear energy,the development of environmentally friendly bio-based ad-sorbents is of great significance for controlling radioactive nuclide pollution.A novel tannic acid and sodium algi-nate(TA/SA)composite microsphere was prepared using a mixed crosslinking method.The effects of TA/SA mass ra-tio,solution pH,initial concentration of U(Ⅵ),contact time,and temperature on the adsorption behavior of U(Ⅵ)by TA/SA microspheres were investigated,and the adsorption kinetics and thermodynamics were studied.The adsorp-tion mechanism of TA/SA microspheres on U(Ⅵ)was also explored.The results showed that the optimal mass ratio of TA to SA was 1∶2,and pH had little effect on the adsorption of U(Ⅵ)by TA/SA microspheres.When the mass concentration of U(Ⅵ)was 50 mg/L,the dosage of TA/SA microspheres was 0.1 g/L,the solution pH was 4,the tem-perature was 323 K,and the contact time was 2 hours,the maximum adsorption capacity of TA/SA microspheres for U(Ⅵ)was 263.42 mg/g.The adsorption behavior conformed to the quasi second order kinetic model and Freundlich isotherm adsorption model.The adsorption of U(Ⅵ)by TA/SA microspheres was a spontaneous endothermic pro-cess,and the reaction could be divided into three stages,including surface adsorption,mesopore diffusion,and mi-cropore diffusion.TA/SA microspheres had an irregular grooved surface and a three-dimensional network structure with numerous openings inside.The reduction reaction played a dominant role in the adsorption of U(Ⅵ)by TA/SA microspheres.
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