Study On The Production Technology Of The Cathodic Electrodeposition Andanodic Dissolution Of Chromium In Deep Eutectic Solvents

In this thesis, the cathodic deposition, anodic dissolution and simultaneous electrolysis of chromium was optimized in a novel ionic liquid which named deep eutectic solvents. The nature of the deep eutectic solvents and electrochemical reaction mechanism of chromium were studied.At first, the electrochemical properties of deep eutectic solvents were analyzed, and their natures such as melting point, conductivity, viscosity, and potential window were determined. It was found that the conductivity and viscosity of deep eutectic solvents had something to do with the nature of hydrogen bond donor. And conductivity σ of choline chloride/ethylene glycol was highest, which reaches to 17.72 m S/cm, and the value of potential window was 3.36 V. So this deep eutectic solvent was most suitable for electrolysis.In the process of the electrodeposition, it was found that the additives of oxalic acid and ammonium chloride were not as effect as singly using when they were both used in the electrolyte. In single factor experiments, the temperature had significant effects on the electrodeposition, mainly reason was that the conductivity was strongly influenced by temperature. The optimum condition of electrodeposition was operated at a current density 450 A/m2 at 353 K and 1 h, with the agitation rate of 300 rpm. The best value of cathode current efficiency was 14.01%.In the anodic dissolution of chromium, the anode current efficiency of acid additives was higher than alkaline additives’. The effect of temperature on the anodic dissolution was also remarkable, just as the influence of agitation rate on cell voltage and current efficiency. The highest anode current efficiency of this process was 73.94%. Only the influence of temperature and cathodic current density are significant in simultaneous electrolysis, and the anode and cathode current efficiency were 16.94% and 70.23%, respectively. In this test we made a exploratory research on the process of simultaneous electrolytic chromium in deep eutectic solvents, the most results of anode current efficiency were higher than 70%.It was determined that reduction of chromium was a irreversible reaction without the front reaction by using the cyclic voltammetry, and the activation energy, reaction order and transfer coefficient was calculated used the steady-state polarization curves of different temperature. Their activation energy was 14.446 k J/mol, and the reaction was controlled by diffusion. The anode and cathode polarization curves were determinated respectively, through the analysis of anodic polarization curve, it was found that the increasing of temperatures could weaken anode passivation, namely to promote the dissolution of anode.