活性污泥吸附铀的性能及机理研究

Adsorptive power of uranium by the activated sludge and its mechanism

通过静态吸附试验考察了溶液pH值、温度、铀的初始质量浓度及活性污泥投加量等因素对活性污泥吸附处理含铀废水的影响,研究了其吸附过程的热力学、动力学及吸附平衡模式,探讨了活性污泥吸附铀的反应机理。结果表明,活性污泥吸附低浓度铀的最佳条件为:pH值3～4,活性污泥投加量8 g/L,温度10～60℃。活性污泥吸附铀的动力学过程可分为3个阶段:初始阶段(t≤30 min)、过渡阶段(30min<t≤40 min)和一级吸附过程阶段。各阶段相对应的吸附动力学方程分别为:lnC_t=-4×10^(-5)t^2-8×10^(-4)t-4.588;lnC_t=-0.0556Int-4.716;lnC_t=-4.333×10^(-4)t+4.531。活性污泥吸附铀的等温线与Freundlich等温式拟合较好,活性污泥吸附铀属多层覆盖吸附,饱和吸附量随温度升高而上升,吸附传质速率由孔隙扩散阶段和内表面吸附共同控制。活性污泥表面的活性功能团对铀的络合作用是活性污泥吸附铀的主要机理,铀主要与细胞表面的—OH、C=O、P-O及-NH_2等活性官能团螯合,形成配合物。

The present paper has done a series of static absorption experiments in measuring the aqua＇ s pH, temperature, uranium＇s initial concentration, the activated-sludge＇s concentration, etc, in hoping to find influence of the activated sludge（AS） on the uranium biosorption in the uranium-containing sewage. For our research purpose, we have studied its thermodynamic, dynamic and the equilibrium mode of the adsorption, inquiring into the AS＇ s reaction mechanism of the uranium biosorption. The experimental results we have gained show that, （1） the optimum condition for the activated sludge to adsorb low-density uranium turned to be pH = 3 - 4, whereas the concentration of AS equals 8 g/L with the temperature being 10-60 ℃ . （2） The adsorption dynamics equation of uranium by AS can be classified into 3 phases： the beginning phase （ t ≤30 min） , the transition phase （30 min 〈 t ≤ 40 min） and the lst-order adsorbing phase. The dynamic equations of the relative adsorption are： InCt = -4× 10^-5st^2 8× 10^-4t-4.588; InCt = -0.0556Int-4.716; InCt = -4.333× 10^-4t ＋ 4.531 respectively. （3） The isotherm of uranium adsorption by AS proves to be in close conformity with Freundlich＇ s, which belongs to the multilevel molecule adsorption： The saturation adsorption capacity tends to rise with the increase of the temperature, with the velocity of uranium biosor-ption being both controlled by the hole＇ s diffusing phase and the inside surface adsorption. （4） The coordination adsorption of uranium by the active functional groups from the AI, proves to be the chief mechanism for the uranium adsorption, mainly chelated with some chemical groups, such as--OH, C = O, P-O and -NH2 etc. in the cells, and form the complexness.