组合液膜对自配淋洗液中Cd的提取回收效果

淋洗法是解决土壤重金属污染的有效方法之一，其对土壤Cd污染的治理效果较好，但需对Cd污染土壤进行淋洗后的含Cd淋洗废液进行再生和回收利用.为了克服传统液膜分离技术不稳定、膜溶液易流失等缺陷.采用P204（磷酸二异辛酯）为络合剂的组合液膜提取技术对自配土壤淋洗液中Cd2+进行提取，考察水相pH、w（P204）、接受相酸浓度、膜相与接受相体积比、接收相不同酸、水相初始c（Cd2+）对Cd2+提取率的影响，并提出动力学方程，进一步研究Cd2+在多金属离子分离条件.结果表明:①络合剂与Cd2+形成络合物在液膜系统中传输，最佳提取条件为pH 4.2、w（P204）5.0%、接受相酸浓度4.0 mol/L、膜相与接受相体积比1:3，接收相酸种类对提取率影响不明显；②水相c（Cd2+）越低，提取率越高；③基于传质动力学模型，建立了回收系数与水相pH和w（P204）的关系方程，分别为P_c=（3.20×104+2.03×1010H+]2）-1和P_c-1=3.208×104+1.742C0]-2，得到Cd2+通过料液和膜边界层的厚度（d_w）为17.8 μm，络合物通过膜的扩散系数（D_m0）为7.61×10-8 m2/s.研究显示，在最佳提取条件下，初始c（Cd2+）为5.0×10-3 mol/L时，240 min内提取率可达93%，通过调节多金属离子体系中Cd2+的提取条件与参数，或调节每种金属提取条件与参数，进行反复提取，Cd2+可以与其他重金属成功分离. 

Extraction and Recovery of Cadmium from Simulated Soil Leachate by Composite Liquid Membrane

Leaching is an effective method to remove the heavy metals in contaminated soil, and it has a good treatment effect on soil Cd pollution. However, it is necessary to regenerate and recycle the waste liquid containing Cd after leaching the contaminated soil. In order to optimize the extraction conditions to overcome the defect of traditional liquid membrane method, a combination of liquid membranes was studied to improve the extraction recovery rate of Cd2+. The extraction of cadmium (Cd2+) in a simulated soil leachate was studied using a composite liquid membrane with P204 (2 hexyl ethyl phosphonate) as a complexing agent. The extraction rate of Cd2+ was investigated by studying the effects of the pH value of the aqueous phase, mass fraction of the complexing agent, the volume ratio of the receiving phase complexing agent and receiving phase, the type of acid in the receiving phase and the Cd2+ concentration in the aqueous phase. At the same time, the kinetic equation and the separation conditions for Cd2+ ions in polymetallic solutions are also presented. The study showed that the complexing agent and the formed Cd2+ complex transport in the liquid membrane system, and the optimum extraction conditions were:pH value of 4.2, w(P204) 5.0%, concentration of the receiving phase 4.0 mol/L and volume ratio of receiving phase complexing agent to receiving phase 1:3. The type of acid in the receiving phase had no obvious effect on the extraction rate, and the lower the concentration of aqueous-phase Cd2+, the higher the extraction rate. The relationship between the recovery coefficient and aqueous-phase pH and the complexant concentration was established based on the mass transfer kinetic model. These equations were P_c=(3.20×104+2.03×1010H+]2)-1 and P_c-1=3.208×104+1.742C0]-2. The thickness of Cd2+ transport through the liquid-membrane boundary layer (d_w) was 17.8 μm, and the diffusion coefficient of the complex through the membrane (D_m0) was 7.61×10-8 m2/s. The results showed that the extraction rate can reach 93% under the optimum conditions within 240 minutes, when the initial c(Cd2+) of the aqueous phase was 5.0×10-3 mol/L. Cd2+ can be successfully separated from other heavy metals by adjusting the extraction conditions and parameters of Cd2+ in the multi-metal ion system, or by adjusting the extraction conditions and parameters of each metal, and repeated extraction.