柠檬酸对膨润土吸附镍离子的影响研究

Effect of Citric Acid on Sorption of Nickel Ion by Bentonite

采用平衡吸附法,研究了柠檬酸对膨润土吸附镍离子的影响。吸附结果表明,当Ni2+初始质量浓度为30 mg/L时,振荡反应90 min,介质pH为5,投加量为5 g/L时,膨润土对Ni2+显示了较好的吸附性能。动力学研究表明该吸附过程符合Lagergren二级动力学模型,等温吸附实验表明其吸附行为符合Freundlich模型。离子强度增大及柠檬酸存在时,会降低其吸附能力。解吸实验发现,通过柠檬酸间接与膨润土结合的Ni2+结合牢固程度较差,更易解吸出来。表明柠檬酸的存在对镍离子的吸附有抑制作用。

The effect of citric acid on nickd ion sorption bentonite is studied by batch method. Sorption experiments are carried out as a function of initial metal concentrations, solution pH, bentonite dose, reaction time and ion strength. Sorption of nickel ion reaches considerable uptake at 5 g/L, pH 5.0 and 90 minutes when the concentration of Ni^2 ＋ is 30 mg/L. The kinetics of the interaction agrees with pseudo second order Lagergen equation fairly well. The absorption data also give good fits with Freundlich isothenn. The absolption is strongly dependent on ion strength and decreases with the increase of the concentration of NaCl. At the presence of citric acid the removal rate of Ni^2 ＋ decreases sharply. Desorption data shows the chelation between nickel ion and the citric acid-bentonite complex is less firm than the ben- tonite - nickel complex and so is easier to desorb from the mineral. All the results show the citric acid weakens the sorption ability of nickel ion by bentonite from aqueous solution.