Experimental Study On The Elimination Of Chlorine Using Electrode And Membrane Integrated Equipment In The Cobalt Electrowinning Process

At present, the cobalt electrowinning industry often uses cobalt chloride electrolysis system for the recovery of cobalt. However the chlorine gas generated problem during electrowinning process has been one of the factors that plagued the industry further development. On the one hand, the produced of chlorine will inevitably bring about the high cost of alkali, the frequently replacement of the diaphragm bag also can produce some unfavorable factors; on the other hand, the collection and absorption efficiency of chlorine can not reach 100%, often, the concentration of chlorine in cobalt electrolytic workshop is beyond the national standard, which brought a great hidden danger for workers health working in the workshop.This topic starting from the improvement of the electrodeposition process of cobalt, with two membrane three room process as a starting point, using the electrode and membrane integrated equipment to study the eliminate of chlorine during cobalt electrolytic. This research is mainly consist of two parts: the laboratory stage and field test stage. The test studied various parameters(cobalt ion concentration in cobalt electrowinning electrolyte,electrolyte pH, temperature of electrolyte, current density, the mass fraction of hydrochloric acid solution and sulfuric acid solution) through single factor experiment that influence the cobalt electrowinning process during laboratory stage, then obtain the best electric product parameters under laboratory conditions after analysised the test results. In addition, the situation of the enrichment of hydrochloric in middle compartment and the generation of chlorine during every electrowinning were analyzed and detected.The ion concentration of cobalt was measured by flame atomic absorption spectrophotometry, the chloride ion concentration was determinaed by potentiometric titration,the pH was measured using a portable pH meter measurement, the sulfate concentration using barium chromate spectrophotometry.The field test stage was based on the results of the laboratory stage, considering the enlargement scale of the electrode and membrane integrated equipment in the field test stage,to perfect the support materials and design of the equipment, strengthen the support and protection of the outerside of the anion exchange membrane, considering the deformation effect of electrolyte environment on the electrode and membrane integrated equipment in a greater extent. The field test is consist of four stages, after each stage, the problems which appeared in last stage would be solved. Through field test for a period of four stages, the most imporment things of the situation of the enrichment of hydrochloric in middle compartment and the generation of chlorine were studied. After four stages of the field test, we can sum that, through one cycle(120 hours) of cobalt electrowinning, the average current efficiency ofcobalt electrowinning reached 91.3%, average power consumption of cobalt electrowinning reached 5000 kW h/t, average amount of mass fraction of 6% hydrochloric acid recovered reached 691.25 L, average reduction of chlorine reached 96.83%, and the direct savings of cobalt electrowinning cost reached 5942.49 yuan/ton. Movever, the pH value, the concentration of cobalt ion, the concentration of chloride ion, the concentration of sulfate ion which in the electrolyte solution, hydrochloric acid solution, sulfuric acid solution that versus with time were determined after the field test, and analyzed with that.At the end of the article the factors affecting electrode electrowinning process were analyzed, it can be drawn through the analysis that:(1) The relative positions of the cathode and anode change will influence the edge of the cathode effect;(2) The relative size of the electrode area will also affect the edge around and the cathode quality;(3) The electrode gap of slight change will not cause severe change of cathodic deposition form;(4) The cathode surface smoothness or not is directly related to the cathode deposition cobalt good cohesiveness, and will cause the cathodic deposition cobalt surface blowhole formation;(5)It's good to keep the purity of effusion to avoid various ions in the process of electrical product discharge effect on the cobalt deposit.Through the study in elimination of chlorine by the electrode and membrane integrated equipment, we can concluded: the using of this equipment greatly reduces the production of chlorine during cobalt electrowinning, cancelled the use of diaphragm bag during cobalt electrowinning, reduces the cost of the absorption of chlorine, improves the working environment of workers in the workshop. At the same time, it save the production cost of electricity product cobalt industry, cobalt for electricity industry benign development laid a certain foundation. Through the study of test in laboratory and field test, it is certain that:the electrode and membrane integrated equipment using in the field test stage is successful and the starting point of this process is novle.