硝酸镧改性文冠果活性炭对汞离子的吸附

Adsorption of Hg^(2+) on Xanthoceras sorbifolia bunge activated carbon modified by La(NO_(3))_(3)·6H_(2)O

采用硝酸镧对文冠果活性炭进行改性,利用扫描电镜分析、红外光谱分析、X射线衍射分析等手段对改性前后的活性炭进行表征,考察了Hg ^(2+)初始浓度、吸附温度、时间对吸附的影响,并研究了吸附过程的吸附等温线、热力学性质和动力学特性。研究表明,当50 mL Hg ^(2+)溶液初始浓度为250 mg/L,吸附时间为150 min,温度为35℃,改性文冠果活性炭添加量为1.0 g/L时,吸附量最大可达78.9 mg/g。硝酸镧改性文冠果活性炭吸附Hg ^(2+)符合二级动力学方程及Freundlich等温线模型,吉布斯自由能ΔG^(o)<0、焓变ΔH o<0、熵变ΔS^(o)<0,表明该吸附是一个自发的放热过程。

Xanthoceras sorbifolia bunge activated carbon(XSBAC)modified by La(NO 3)3·6H 2O activation was applied for adsorption of Hg ^(2+).The structure of XSBAC before and after modification were characterized by SEM,FTIR and XRD.The adsorption process were carried out including initial concentration Hg ^(2+),adsorption time and temperature.The adsorption isotherm,thermodynamic parameters and kinetics were also investigated.The results showed that the maximum adsorption capacity of Hg ^(2+)reached 78.9 mg/g under initial 50 mL Hg ^(2+)concentration,adsorption temperature,adsorption time and the modified activated carbon dosage of 250 mg/L,35℃,150 min and 1.0 g/L respectively.Modeling of adsorption kinetics indicated good agreement of experimental data with the pseudo-second-order kinetic model.Freundlich equilibrium isotherm fitted the experimental data reasonable well.The calculated values of the Gibbs free energy were as follows:ΔG o<0,enthalpy changeΔH o<0,entropy changeΔS^(o)<0 which revealed the adsorption was a spontaneous and exothermic process.