Behnajady Bahram, Najafi Matin, Karimi Saeid
Research Centre of Advanced Materials, Faculty of Materials Engineering, Sahand University of Technology, Sahand New Town, Tabriz, Postal Code: 5331817634, Iran.
Department of Metallurgy and Materials Engineering, Hamedan University of Technology, Hamedan, 65169-13733, Iran.
Phys Chem Chem Phys. 2024 Sep 25;26(37):24407-24422. doi: 10.1039/d4cp01464b.
Deep eutectic solvents (DESs) represent a novel class of solvents characterized by their favorable biodegradability and compatibility, which have been used for dissolving various metals. In this study, choline chloride-maleic acid (ChCl-Me) DES was synthesized, and the FTIR technique was used to investigate the formation of DES. Then, ChCl-Me DES was applied to dissolve cold filter cakes (CFCs), and FTIR analysis proved the stability of DES during leaching. Response surface methodology (RSM) was used to investigate the effects of time, temperature, DES to CFC ratio, and stirring speed on the leaching efficiency of Zn, Ni, and Cd. Analysis of variance (ANOVA) showed that the leaching time has a significant effect on all three metals' leaching efficiency. Also, the DES to CFC ratio and the interaction between time and the DES to CFC ratio significantly affect Zn leaching efficiency. Moreover, the second order of the DES to CFC ratio significantly affects Cd leaching efficiency. Optimal conditions were determined as follows: a time of 20 hours, a DES to CFC ratio of 70, a temperature of 60 °C, and a stirring speed of 300 rpm. The UV-vis spectra of the leaching solution showed that metals leached as chlorides in DES. Also, CFC characterization by FESEM-EDS before and after leaching ChCl-Me DES proved almost complete leaching of metals. Therefore, this solvent can be used as a suitable solvent for the cumulative dissolution of Zn, Ni, and Cd metals with a dissolution efficiency of 90%. Molecular dynamics (MD) simulation and density functional theory (DFT) were employed to obtain detailed information about the complexes formed by Zn, Cd, and Ni ions. The surface charge density, obtained from COSMO computations, shows the notable impact of Cl anions and O atoms within ChCl and Me compounds, respectively, on the Zn, Cd, and Ni complexes. The radial distribution function (RDF) result highlights strong attractive interactions between ions and Cl in ChCl, extending to bonded atoms. In addition, RDF results show that oxygen atoms in Me have an impact on CFC dissolution in ChCl-Me DES.
深共熔溶剂（DESs）是一类新型溶剂，其特点是具有良好的生物降解性和兼容性，已被用于溶解各种金属。在本研究中，合成了氯化胆碱-马来酸（ChCl-Me）DES，并使用傅里叶变换红外光谱（FTIR）技术研究了DES的形成。然后，将ChCl-Me DES应用于溶解冷滤饼（CFCs），FTIR分析证明了DES在浸出过程中的稳定性。采用响应面法（RSM）研究了时间、温度、DES与CFC的比例以及搅拌速度对锌、镍和镉浸出效率的影响。方差分析（ANOVA）表明，浸出时间对所有三种金属的浸出效率都有显著影响。此外，DES与CFC的比例以及时间与DES与CFC比例之间的相互作用对锌的浸出效率有显著影响。而且，DES与CFC比例的二次项对镉的浸出效率有显著影响。确定的最佳条件如下：时间为20小时，DES与CFC的比例为70，温度为60°C，搅拌速度为300转/分钟。浸出溶液的紫外可见光谱表明，金属在DES中以氯化物形式浸出。此外，通过场发射扫描电子显微镜-能谱仪（FESEM-EDS）对浸出ChCl-Me DES前后的CFC进行表征，证明金属几乎完全浸出。因此，这种溶剂可作为锌、镍和镉金属累积溶解的合适溶剂，溶解效率为90%。采用分子动力学（MD）模拟和密度泛函理论（DFT）来获取有关锌、镉和镍离子形成的配合物的详细信息。从导体屏蔽连续介质模型（COSMO）计算中获得的表面电荷密度分别显示了ChCl和Me化合物中的Cl阴离子和O原子对锌、镉和镍配合物的显著影响。径向分布函数（RDF）结果突出了离子与ChCl中的Cl之间强烈的吸引相互作用，并延伸到键合原子。此外，RDF结果表明，Me中的氧原子对ChCl-Me DES中CFC的溶解有影响。
