红壤胶体对U(Ⅵ)的吸附性能及机理

Sorption and Mechanism of Aqueous U(Ⅵ)Onto Red Soil-colloid

采用静态法研究了某铀矿山附近土壤中的红壤胶体在不同pH值、离子强度、吸附平衡时间、铀溶液初始浓度、胶体用量、胶体粒径和有机质条件下对U(Ⅵ)的吸附影响,从热力学和动力学方面对吸附过程进行了分析,并通过元素分析、红外光谱(FT-IR)和扫描电镜(SEM)对吸附机理进行了初步探讨。实验结果表明:离子强度越小,胶体粒径越小,胶体对U(Ⅵ)的吸附量越大;单位质量红壤胶体对铀的吸附量随铀初始质量浓度的增大而增大,随红壤胶体用量的增大而减少;在25℃、pH值为3.5、离子强度为0.001mol/L时,粒径小于1μm的红壤胶体的饱和吸附量qmax为76.76μg/mg。红壤胶体吸附铀酰离子前后的红外光谱表明,与吸附相关的主要基团为羟基、羰基、Si—O、Si—O—Fe等。红壤胶体对铀的吸附遵循Langmuir吸附等温线,符合准二级吸附动力学方程。

By static adsorption experiments ,the effects of pH ,ionic strength ,adsorp-tion time ,uranium initial concentration ,adsorbent dosage ,red soil-colloid size ,and organic matters on the biosorption capacity of red soil-colloid extracted from the soil around uranium tailing for uranium were studied .The adsorption process was analyzed by thermodynamics and kinetics ,and the adsorption mechanism was characterized by the element analysis ,infrared spectroscopy and scanning electron microscopy .The results show that the adsorption capacity for U （Ⅵ ） on red soil-colloid increases with the decrease of ionic strength or particle size ,increases with the initial concentration of uranium ,decreases with the increase of the amount of red soil-colloid ;the saturated adsorption capacity qmax can be up to 76.76 μg/mg by red soil-colloid which diameter is less than 1 μm at 25 ℃ and pH=3.5 ,when the ionic strength is 0.001 mol/L .FT-IR micrograph before and after red soil-colloid adsorbed uranyl ions indicates that the red soil-colloid are mainly composed of hydroxyl ,carbonyl ,Si-O ,Si-O-Fe ,etc .The adsorption of U（Ⅵ） on red soil-colloid follows Langmuir adsorption isotherm ,and the pseudo-second-order equation provides the best correlation for the adsorption process .