Department of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China.
J Hazard Mater. 2011 May 30;189(3):732-40. doi: 10.1016/j.jhazmat.2011.03.061. Epub 2011 Mar 23.
The melamine-diethylenetriaminepentaacetic acid/polyvinylidene fluoride (MA-DTPA/PVDF) chelating membrane bearing polyaminecarboxylate groups was prepared for the removal of Ni(II) from wastewater effluents. The membrane was characterized by SEM, (13)C NMR and FTIR techniques. Quantitative adsorption experiments were performed in view of pH, contact time, temperature, the presence of Ca(II) and lactic acid as the controlling parameters. Adsorption kinetics and equilibrium were examined regarding the single Ni(II) system, binary Ni(II) and Ca(II) system and nickel-lactic acid complexes system. The desorption efficiency was also evaluated, and the adsorption mechanism was suggested based on experimental data. The results show that the sorption kinetics fit well to Lagergren second-order equation and the isotherms can be well described by Langmuir model. At 298 K, the second-order rate constant is calculated to be 4.171, 11.39, 6.203 cm(2)/(mg min) and the equilibrium uptake is 0.0264, 0.0211 and 0.0216 mg/cm(2) in the aforementioned three systems. The distribution coefficient of Ni(II) slowly decreases from 4.27 to 2.72, and the separation factor (f(Ni(II)/Ca(II))) increases from 3.10 to 8.46 when the initial Ca(II) concentration varies from 20 to 200mg/L. This reveals the chelating membrane shows more affinity for Ni(II) than Ca(II) ions. In the studied range of lactic acid concentration, Ni(II) uptake decreases with the maximum ratio of 10%. Chemical bonding (chelation) dominates in the adsorption process, and the negative ΔG° and ΔH° indicate the spontaneous and exothermic nature of adsorption.
用于从废水中去除 Ni(II) 的三聚氰胺-二乙三胺五乙酸/聚偏二氟乙烯 (MA-DTPA/PVDF) 螯合膜是通过聚胺羧酸基团制备的。采用 SEM、(13)C NMR 和 FTIR 技术对膜进行了表征。考虑 pH、接触时间、温度、Ca(II)的存在和乳酸作为控制参数，进行了定量吸附实验。针对单 Ni(II) 体系、双 Ni(II) 和 Ca(II) 体系以及镍-乳酸配合物体系，考察了吸附动力学和平衡。还评估了洗脱效率，并根据实验数据提出了吸附机制。结果表明，吸附动力学很好地符合 Lagergren 二级方程，等温线可以很好地用 Langmuir 模型描述。在 298 K 下，计算出二级速率常数分别为 4.171、11.39 和 6.203 cm(2)/(mg min)，在上述三个体系中，平衡吸附量分别为 0.0264、0.0211 和 0.0216 mg/cm(2)。当初始 Ca(II)浓度从 20 到 200mg/L 变化时，Ni(II)的分配系数从 4.27 缓慢下降到 2.72，分离因子 (f(Ni(II)/Ca(II))) 从 3.10 增加到 8.46。这表明螯合膜对 Ni(II)比 Ca(II)离子具有更高的亲和力。在所研究的乳酸浓度范围内，Ni(II)的摄取量随最大比例下降 10%。化学结合（螯合）在吸附过程中起主导作用，负的 ΔG°和 ΔH°表明吸附是自发和放热的。
