活性炭表面负载金属离子对其吸附苯并噻吩的影响

Effects of different metal ions loaded onto activated carbon on adsorption of benzothiophene

主要研究了活性炭表面负载不同的金属离子对其吸附苯并噻吩的影响.通过浸渍法分别将6种不同的过渡金属离子负载在活性炭表面上,用静态吸附法测定了苯并噻吩硫化物在改性活性炭上的吸附等温线,应用软硬酸碱理论分析和讨论了其吸附能力的差异.结果表明,活性炭表面负载Ag+、Ni2+、Cu2+或Zn2+离子,可提高活性炭吸附苯并噻吩硫化物的能力,而活性炭表面负载Fe3+或Co3+离子,反而降低了活性炭吸附苯并噻吩硫化物的能力,这主要是活性炭表面的酸碱性质发生变化.采用密度泛函数理论法计算结果表明,苯并噻吩的电负性χ为2.638,属软碱类物质;由于Ag+为软酸,活性炭负载Ag+离子,增加了其局部表面的软酸,从而增强了对苯并噻吩硫化物的吸附;由于Ni2+、Cu2+和Zn2+离子属交界酸,负载Ni2+、Cu2+、Zn2+离子增加了活性炭表面的交界酸,也在一定程度上提高了其表面对苯并噻吩硫化物的吸附;当活性炭表面负载了硬酸性Fe3+或Co3+离子,其局部表面硬酸增大从而降低了其对苯并噻吩的吸附.

In this work, the effects of different metal ions loaded onto activated carbon on the adsorption of benzothiophene were investigated. Six kinds of transition metal ions were separately loaded on the activated carbon by the impregnation method. Isotherms of benzothiophene on the activated carbon were separately measured at different temperature, and then the variation of the adsorption of benzothiophene on the activated carbon was discussed with the help of the hard and soft acid and base （HSAB） principle. The results showed that loading Ag^＋ , Ni^2＋ , Cu^2＋ or Zn^2＋ ion on the activated carbon obviously improved its adsorption of benzothiophene, while loading Fe^3＋ or Co^3＋ ion on the activated carbon caused a decrease in its adsorption of benzothiophene in comparison with the original unloaded activated carbon, which was due to the variation of the nature of soft and hard acid on the surface of the activated carbon. Absolute hardness calculation using the density functional theory （DFT） indicated that benzothiophene belonged to soft bases. Since Ag^＋ was a soft acid, the loading of Ag^＋ ion on the activated carbon led to an increase in the soft acid on its surface and thus improved its adsorption of benzothiophene, and since Ni^2＋, Cu^2＋ and Zn^2＋ ions belonged to borderline acids, the loading of these ions on the activated carbon led to an increase in the borderline acids on its surface and thus improved its adsorption of benzothiophene to some extent. Since Fe^3＋ and Co^3＋ ions belonged to hard acids, the loading of Fe^3＋ or Co^3＋ ion on the activated carbon led to an increase in the hard acid on its surface and consequently a decrease in its adsorption of benzothiophene.