磁性多壁碳纳米管吸附水中双氯芬酸的热力学与动力学

研究了磁化多壁碳纳米管(MWCNTs)对于水中非甾体抗炎药双氯芬酸的吸附过程.结果表明,双氯芬酸的吸附量随磁性MWCNTs投加量的增加而增大,而且吸附剂量增加到一定阶段后,双氯芬酸的吸附量达到平衡.在磁性MWCNTs的量为0.7g·L-1时,水溶液中双氯芬酸被磁性MWCNTs吸附的量达到最大,为33.37mg·g-1,对应的双氯芬酸去除率为98.1%.双氯芬酸的去除率随溶液pH的增加先增大后下降,随温度的升高而下降.用准一级、准二级模型进行了动力学分析.回归结果表明,准二级模型更准确地反映了吸附动力学.通过实验确定了Langmuir和Freundlich等温线的线性相关系数与标准偏差,结果揭示出Langmuir等温线与实验数据有很好的拟合度.对热力学参数的计算表明,ΔG00,意味着磁性MWCNTs对双氯芬酸的吸附是自发的;ΔH00,指明吸附是一个放热的物理吸附过程,温度低对吸附有利;ΔS00,代表该吸附是熵增过程.

Thermodynamics and Kinetics of Adsorption of Diclofenac on Magnetic Multiwalled Carbon Nanotubes in an Aqueous Solution

We investigated the adsorption of diclofenac (an anti-inflammatory drug) in aqueous solutions by magnetic multiwalled carbon nanotubes (MWCNTs). The results showed that the amount of adsorbed diclofenac initially increased with magnetic MWCNT dosage and stabilized at a magnetic MWCNT dosage of 0.7 g·L^-1. The amount of diclofenac adsorbed by the magnetic MWCNTs was 33.37 mg·g^-1 and the removal rate of diclofenac was 98.1%. The removal rate for the diclofenac increased and then decreased with the pH value of solution, but it decreased with the temperature of solution. Kinetic analysis was conducted using pseudo first and second order models. Regression results showed that the adsorption kinetics was more accurately represented by a pseudo second order model. The linear correlation coefficients and standard deviations of the Langmuir and Freundlich isotherms were determined and the results revealed that the Langmuir isothermfit the experimental results well. The calculated thermodynamic parameters were: ΔG⁰<0 indicating that the adsorption of diclofenac on magnetic MWCNTs was spontaneous, ΔH⁰<0 indicating that the absorption reaction was exothermic and that low temperatures are favorable for adsorption, and ΔS⁰>0 indicating that the adsorption process was a entropy enhancing process.