The Dissolution Behavior And Electrochemical Study Of Metal Compounds In Choline-based Eutectic Solvents

In the current situation of shortage of copper,zinc and other non-ferrous mineral resources and serious environmental pollution,the extraction and utilization of valuable metal resources from secondary resources such as metallurgical dust and waste residue has become the focus of attention.As a new type of green solvent,deep eutectic solvent?DES?has excellent ionic conductivity,wider electrochemical window,select solubility,alternative toxicity and low product price,etc.The use of DES as solvents to deal with secondary resources with complex components,which are expected to solve the problems of leaching selectivity and complex impurity separation in the traditional acid leaching process.In this paper,choline chloride?ChCl?-urea?urea?deep eutectic solvent is used as a research system,the dissolution and electrochemical behavior of metal compounds contained in metallurgical dust in ChCl-urea deep eutectic solvent were systematically studied.By measuring the solubility of some metal compounds,this paper analyzed the selective characteristics of zinc in some common zinc fume and dust extracted by deep eutectic solvent,and probes into the thermodynamic behavior of metal compounds dissolved by deep eutectic solvent.At the same time,the dissolution behavior and electrochemical behavior of different compounds of the same metal in deep eutectic solvent were further studied,and the influence mechanism of the crystal water of the complex was discussed.The main research contents and conclusions are as follows:?1?The solubility of metal compounds in ChCl-urea was measured in the temperature range of 323k-363k,and the results showed that the solubility of all metal compounds increased with the increase of temperature,and the solubility of the various metal compounds obtained was as follows:Chloride>Nitrate>Sulfate>Oxide>Chloride.Studies on the forms of different metal compounds dissolved in deep eutectic solvents showed that different metal compounds were dissolved in ChCl-urea to form different compound ions:the coordination mode of Cu Cl is[Cu Cl₂]^-;The complexes formed by Zn SO₄were[Zn Cl₄]^2-;In addition,after the dissolution of the compound with crystalline water,part of the distribution body water will be gradually replaced by chloride ion ligands.?2?The activity coefficient of ZnO in ChCl-urea deep eutectic solvent is much smaller than that of other transition metal oxides,indicating that the interaction force between ChCl-urea and ZnO is greater than that of other transition metal oxides.?3?The electrochemical behaviors of different copper compounds?Cu₂O,Cu Cl,Cu₂S?and zinc compounds?Zn Cl₂,ZnO,Zn SO₄?dissolved in ChCl-urea deep eutectic solvent at the same metal ion concentration were studied.Results show that different compounds of the same metal as the precursor dissolved in deep eutectic solvent,and the electrochemical reduction behavior of different metal ions such as the initial reduction potential,exchange current density,the nucleation and growth mechanism are different,resulting in The preferential growth of deposited metal and the difference in morphology can be obtained by electrochemical analysis of the same compound with crystal water.The introduction of crystal water changes the viscosity and conductivity of the system and promotes the electrochemical reduction process of the metal.