HHMHC对Cu2+、Ni2+的萃取性能

以对羟基苯甲酸为原料,通过化学修饰合成得到上沿羧基化的杯6]芳烃羟肟衍生物,即5,11,17,23,29,35-六羧基-37,38,39,40,41,42-六羟肟酸甲氧基杯6]芳烃(HHMHC),采用IR对其结构性能进行表征,并探讨了溶液初始pH值、初始重金属离子(Cu2+、Ni2+)浓度、萃取时间、温度等因素对HHMHC萃取重金属离子的影响.结果表明,在温度为30℃时HHMHC萃取Ni2+和Cu2+的最佳pH值分别为5.0、6.0,萃取平衡时间均为30min.用准二级动力学模型(R2>0.99)和Freundlich等温模型(R2>0.999)均可较好的拟合其萃取过程,通过计算萃取过程的热力学参数,得到Gibbs自由能(ΔG0)和焓变(ΔH0)均小于0,表明萃取反应是一个自发的放热反应.通过红外光谱图分析和考察溶液pH值对萃取分配比的影响,探讨HHMHC萃取Cu2+、Ni2+的机理,结果表明此萃取过程除了存在阳离子交换机理外,还存在与冠醚萃取相同的离子配位萃取,参与配位作用的主要是羟肟基团(–CONHOH).

Extraction of Cu2+ and Ni2+ with HHMHC

5,11,17,23,29,35-hexacarboxy-37,38,39,40,41,42-hexa-methoxy-hydroxamic calyx6]arene (HHMHC) was synthesized by modifying p-hydroxybenzoic acid, and characterized by IR. The effects of pH, Cu2+ and Ni2+ initial concentration, extraction time and temperature on the calixarenes extraction behavior of Cu2+ and Ni2+ were investigated. The results showed that the maximum extraction were observed under the experiment conditions of 30℃ with a contact time of 30min, a pH of 6.0(Cu2+), 5.0(Ni2+), when the initial concentration of Cu2+ and Ni2+ was 5mg/L. The extration of Cu(II) and Ni(II) onto HHMHC had a close agreement with the pseudo-second-order model (R2>0.99) and the Freundlich model (R2>0.999). In the extraction process, the negative values of Gibbs free energy (ΔG0) revealed this extraction was spontaneous. Meanwhile, the value of enthalpy(ΔH0) was negative, indicating that the extraction reaction was exothermic progress. Based on the analysis of IR spectra and the effect of pH on the extraction distribution ratio (D), it was found that the extraction mechanism of Cu2+ and Ni2+ with HHMHC not only followed the ion exchange mechanism, but also included the coordination effect, on which the functional group -CONHOH played an important role.