改性活性炭吸附咪唑类离子液体的效果

Effect of Modified Activated Carbon on Adsorption of Imidazole Ionic

[目的]通过氧化处理提高活性炭吸附量。[方法]活性炭的表面化学性质可以直接影响活性炭对离子液体的吸附,采用过氧化氢、硝酸、过硫酸铵氧化活性炭(F300),改变其表面的官能团含量,合成过氧化氢改性活性炭(HF300)、硝酸改性活性炭(NF300)、过硫酸铵改性活性炭(SF300),研究其对氯化1-丁基-3-甲基咪唑(Bmimcl)和氯化1-辛基-3-甲基咪唑(Omimcl)的吸附影响。[结果]HF300、NF300、SF300表面的含氧官能团显著增加;HF300、NF300、SF300中SF300对含亲水性阳离子的Bmimcl的吸附效果最佳且提升最为显著,吸附容量由TF300的0.19 mmol/g增加到0.29 mmol/g;HF300、NF300、SF300对含疏水性阳离子的Omimcl的吸附无明显变化。SF300对Bmimcl和Omimcl的吸附均符合Freundlich模型;SF300对Bmimcl和Omimcl的吸附符合准二级动力学,Bmimcl在SF300上的准二级动力学速率常数为0.016 3 g/(mg·min),Omimcl在SF300上的准二级动力学速率常数为0.002 2 g/(mg·min)。无机阳离子(Na^+,Ca^(2+))会抑制SF300对Bmimcl和Omimcl的吸附,且Ca^(2+)的抑制效果强于Na^+。SF300对Bmimcl和Omimcl的吸附量随pH的升高呈现出先升高后变低的变化趋势,对Bmimcl和Omimcl的吸附量分别在pH=7和5时达到最大。[结论]氧化处理可以提高活性炭的吸附量。

[Objective]The aim was to improve the activated carbon adsorption. [Method]Surface chemical properties can directly affect the adsorption of imidazole ionic liquid on activated carbon. In order to change the surface functional groups, HF300, NF300, SF300 was synthesized by oxidation of activated carbon using hydrogen peroxide, nitric acid and ammonium persulfate. The adsorption of 1-butyl-3-methylimidazolium chloride （Bmimcl） and 1-octyl-3-methylimidazolium chloride （Omimcl） was studied on HF300, NF300, SF300. [Result]The results showed that modification by surface oxidation led to markedly increased contents of O-containing functional groups in HF300, NF300 and SF300. In comparison with other modified activated carbons, SF300 exhibitedhigher adsorption capacity and more marked promotion in the adsorption of Bmimcl. The adsorption capacity increased from 0.19 mmol/L onTF300 to 0.29 mmol/L on SF300. However, HF300, NF300, SF300 exhibited nearly identical adsorption for Omimcl.The adsorption isotherms of Bmimcl and Omimclon on SF300 could be well describedusing the Freundlich model. The adsorption of Bmimcl and Omimclwell followed pseudo-second order kinetics, with kinetic rate constant of 0.016 3 g/（mg·min） and 0.0022 g/（mg·min）, respectively. Coexisting cation（Na^＋, Ca^2＋） inhibited Bmimcl and Omimcl adsorption, and Ca^2＋ effect was stronger than Na^＋. Bmimcl and Omimcl adsorption on SF300 was highly dependent on pH, and the higher adsorption amounts were observed at pH 7 and 5, respectively. [Conclusion]Oxidation can improve the adsorption capacity of activated carbon.