地质特种水泥对模拟含铀废液的静态吸附动力学研究

针对含铀废液这类具有放射性的特殊废液,本实验选用养护28 d、粒径为200-220μm的水泥颗粒作为吸附剂,通过改变吸附时间t以及pH值,获得地质特种水泥对含铀溶液的静态吸附规律。实验结果表明,地质特种水泥对不同浓度含铀溶液(20 mg·L~(-1)、30 mg·L~(-1)、40 mg·L~(-1))的静态吸附均在第1.5 d基本达到吸附平衡,最大吸附量(q_e)分别达到40.257 mg·g~(-1)、60.423 mg·g~(-1)、80.386 mg·g~(-1),最终静态平衡吸附率高达99.95%;保持铀溶液浓度一定(30 mg·L~(-1)),改变吸附体系的pH值(5、7、9),地质特种水泥对U(Ⅵ)的吸附率均可达到99.50%,无显著差异。以上结果表明,在本实验设定的环境条件下,地质特种水泥对U(Ⅵ)有极强的吸附能力,且其吸附效果基本不受含铀溶液浓度和pH值的影响。同时,静态吸附动力学模型研究表明,伪二级动力学模型能很好地描述地质特种水泥静态吸附铀的全过程(t=0-41 d),其相关系数R~2高达99.99%,表明地质特种水泥对U(Ⅵ)的吸附机理为:吸附速率按照与吸附驱动力(q_e-q_t)的平方呈正比关系进行演变。

Study on static adsorption kinetics of simulated uranium-bearing wastewater by geological specialty cement

Background: The cement medium is usually used to solidify the uranium-bearing wastewater, however,little attention was paid to adsorption capacity and mechanism of the cement powder in related search reports. Purpose: This study aims at the static adsorption behavior of geological special cement blank powder for uranium-bearing wastewater. Results: The results show that the adsorption equilibrium of static adsorption of geological special cement for uranium solution at different concentrations (20 mg?L?1, 30 mg?L?1 and 40 mg?L?1) was at 1.5 d. The maximal adsorption capacity (qe) was 40.257 mg?g?1, 60.423 mg?g?1 and 80.386 mg?g?1, respectively, and the final static equilibrium adsorption rate was up to 99.95% when the concentration of uranium solution was kept at 30 mg?L?1, the adsorption rate of geological special cement for U(VI) could reach 99.50% no matter the pH value of adsorption system changes among 5, 7 and 9. Conclusion: The geological special cement has a strong adsorption capacity for U(VI), and its adsorption effect is basically not affected by the concentration of uranium solution and the pH value. The pseudo secondary dynamical model can describe the whole adsorption process (t=0?41 d) well, and its correlation coefficient R2 is up to 99.99%, which demonstrates that the adsorption rate evolves according to the positive correlation relation with the square of the adsorption driving force (qe?qt).