甲醛修饰酿酒酵母对铀的吸附研究

采用批次实验方法探究了甲醛修饰酿酒酵母对铀的生物吸附过程.结果显示,甲醛修饰能显著提高酵母对铀的吸附能力,其吸附量是同等实验条件下活酵母的6倍,动力学研究表明,达到吸附平衡仅需90 min,并且能较好地符合准二级动力学吸附模型.实验的最佳吸附pH为5.8.Langmuir和Freundlich模型均能用于拟合实验数据且实验结果与Langmuir模型更加吻合.扫描电镜和傅里叶变换红外光谱分析结果表明,甲醛修饰改变了细胞的表面形貌和蛋白结构,使氨基发生了甲基化,羟基形成配位共价键,在酵母吸附铀后,细胞表面不均匀地附着了一层鳞片状的铀沉淀.铀沉淀与络合物的形式多种多样,且与羧酸盐主要络合物为双齿配体结构,甲醛修饰酿酒酵母与铀酰离子相互作用存在着络合,沉淀以及静电吸附等多种机理.

Biosorption of Uranium by methanal modified Saccharomyces cerevisiae

The biosorption of uranium from aqueous solutions in batch by methanal modified Saccharomyces cerevisiae biomass was investigated. Results show that methanal modification could significantly improve the cells sorption capacity which was six times than that of raw cells under the same condition. Kinetic study suggests that the reaction reached an equilibrium within only 90 min and the pseudo-second-order model was well in great correlation with the adsorption behavior. The optimum uranium uptake pH was determined at 5.8. Langmuir and Freundlich equation were applied to fit the experimental data and the Langmuir model was better fit with the results. Scanning electron microscopy (SEM) images and Fourier transform infrared (FTIR) spectrum show that methanal treatment had changed cell surface morphology and protein structure, alcoholic-hydroxylate of amino groups and dative-linked with alcoholic groups. After exposed in uranium solution, the surface of cells was attached with scale-like uranium precipitation unevenly, the uranyl ion complexes and precipitation are multiplicate, and the type of uranyl-carboxylate complexes is mainly bidentate chelating coordination. The complexation, precipitation and electrostatic interaction were the mechanisms of methanal modified yeast-uranium interaction.