改性锯末对铀的吸附机理研究

Study of Adsorption Mechanism of Uranium by Modified Sawdust

基于锯末的吸附类型对锯末进行改性,通过静态吸附试验,研究改性锯末对模拟废水中铀的吸附影响因素以及吸附过程中的动力学和热力学行为,并分析改性锯末对铀的吸附机理。结果表明:氯化锌改性的锯末对铀的吸附效果最好;在溶液pH=4.5时,改性锯末对铀的去除率最高;改性锯末对铀的吸附平衡时间约为30min;改性锯末对铀的吸附遵循Langmuir吸附等温线,符合准二级动力学方程;改性锯末对铀的吸附热力学参数△H=-25.792kJ/mol、△G=-16.327^-15.851kJ/mol、△S=-31.760J/(mol·K)均小于零,说明吸附反应是一个放热自发的过程。SEM和FTIR分析表明:改性锯末对铀的吸附主要是表面络合吸附,吸附后改性锯末的表面变得相对平整;参与吸附活动的官能团主要为改性锯末表面的酰胺基、羟基、酮基和芳烃C—H键等基团。

This paper modifies the sawdust based on its adsorption types,and uses it in the static adsorption experiments of uranium to study the influencing factors of modified sawdust on the uranium adsorption and the kinetics and the modynamics behaviors during the adsorption process,and analyzes the adsorption mechanism.The results show that the adsorption of uranium by zinc chloride modified sawdust is the best of the five kinds of modified sawdust,and the maximum adsorption occurs at about pH=4.5,and the adsorption equilibrium time is about 30 min.The adsorption process of uranium on modified sawdust is in accordance with the quasi-second-order kinetics model（R2=0.997 6）.The Langmuir equation could describe better the isothermal adsorption of uranium by modified sawdust,and adsorption thermodynamics parameters are△H=-25.792 kJ/mol,△G=-16.327^-15.851 kJ/mol,△S=-31.760 J/（mol·K）respectively,which suggests the adsorption is an exothermic spontaneous process.The SEM and FTIR analysis indicate that the surface of modified sawdust becomes relatively flat after adsorption,and there are surface complexation adsorption in adsorption process and the functional groups involved in adsorption are mainly amide group,hydroxyl group,ketone group and aromatic C—H bond group on surface of modified sawdust.