改性聚乙烯醇吸附镍离子的动力学与热力学研究

研究了自制改性聚乙烯醇对Ni~(2+)的吸附行为,在不同的吸附条件下,探讨相关因素的影响,并对实验数据进行动力学与热力学的拟合。结果表明,室温下,在溶液p H=6.0,NaNO_3的浓度为0.1 mol/L,吸附时间为60 min,液固比为250 m L/g,改性聚乙烯醇对浓度为0.1 mol/L Ni2+的吸附效果好,去除率达到98.05%;当干扰因子设定为0.1 mol/L的Ca(NO_3)_2,对Ni2+的去除率降到59.29%。改性聚乙烯醇对Ni2+的吸附动力学符合准二级动力学方程;Langmuir等温模型的拟合度较高,推测改性聚乙烯醇表面是均一的等质体,计算的最大吸附量为1.35 mmol/g,与实验结果一致;D-R等温模型的拟合度次之,在各温度下,E16 k J/mol,说明改性聚乙烯醇对Ni2+的吸附是以化学吸附为主。通过Van’t Hoff方程的拟合,计算得到的吉布斯自由能以及熵变和焓变表明该吸附过程为吸热化学反应。

2+Kinetics and Thermodynamics of Adsorption of Ni by Modified Polyvinyl Alcohol

2+In this paper, adsorption behavior of Ni by self-made modified polyvinyl alcohol was studied by use of batch technique under different conditions. Fitting of kinetics and thermodynamics of the adsorption process was carried out with regard to the testing data. The results showed that at room temperature, when pH of the solution was 6.0, concentration of NaNO was 0.13 mol/L, adsorption time was 60 min, and liquid/solid ratio was 250 mL/g, adsorption effects of the modified polyvinyl alcohol on Ni were good, with removal efficiency reaching to 98.05%. When the interference factor was Ca (NO ) 0.1 mol/L instead of NaNO , the3 2 3 2+2+removal rate of Ni was reduced to 59.29%. Adsorption of Ni by modified PVA complied with the pseudo-second-order kinetic model well. The fitting level of Langmuir isothermal model was highest and the surface of the modified PVA was regarded as homogeneous plasmid. The calculated maximal adsorption amount was 1.35 mmol/g, consistent with the testing results. The fitting degree of D-R isotherm model was the secondly highest. At different temperature, adsorption energy E was more than 16kJ/mol, 2+indicating that the adsorption of Ni2+ was mainly based on chemisorption process. By fitting of Van’t Hoff equation, thermodynamic parameters such as the calculated Gibbs free energy, entropy and enthalpy indicated that the adsorption process was endothermic chemisorption process.