Electroanalysis Pure Cr Using Two Membrane Three Room Electroplate

The chromium produced by the way of electrowinning is ductile and can be used to manufacture components.The reduce potential of chromium is so negative that the reaction of hydrolysis is violent during the process of chromium electrowinning,which lead to a rather low current efficiency.A system of chrome-alum electrolyte was studied with three-compartment cell using an ion exchange membrane and an perfluoro-ion exchange membrane.Ru-Ti electrode consumedly reduces quality of Cr(â…¥)in three-cell for electrolyzation,the produce of Cr⁶⁺ which is adverse to the environment was well controlled,the problem of Cr⁶⁺pollution is drastically resolved.Electrowinning for 15 minute,with three-compartment cell,pH values only changed 0.01,with one-compartment cell pH values changes 0.21,with two-compartment cell pH values changed 0.19,the problem of electrolyte stability was resolved. Different pH values were investigated in the chromium electrowinning,it was found that the current efficiency get the peak at the pH 2.2～2.4.The efficiency was high when current density equaled 12.5A/dm²,and the deposit had good crystal status.28～35℃was the best temperature for a highest current efficiency.Quadrature experiment was studied for temperature,current density,duty ratio and frequency.Current efficiency rised distinctly,when temperature above 25℃and under 45℃.Duty ratio had best about 80%. Current efficiency increased when frequency was in the range of high and low frequency.Current density'influence was little.Electrowinning with intermission square wave and plus-minus square wave,intermission square wave' influence was little for increasing current efficiency.Current efficiency increased 8.30%with plus-minus square wave.The experiments of chromium electrowinning in the OP-10-free electrolyte and the electrolyte with 40mg/L OP-10 were separately conducted under the same condition of pH 2.3,30℃and current density 12.5A/dm².The current efficiency of the former was 20.30%and which of the latter was 28.60%, the current efficiency was promoted 8.30%.It showed that OP-10 could hamper the process of hydrolysis in the course of chromium electrowinning.With plus-minus square wave electrowinning,the current efficiency was 38.98%,which was higher 10.38%than only with plus-minus square wave.The polarization curves of hydrolysis in the KCl solution of different concentration on chromium electrode were scanned by the Potentiodynamic Scan Method under the condition of 30℃and pH 2.0.It was found that theη-lgi curves of lower overvoltage were linear and accord with the Tafel relation.The Tafel parameters were fitted,the slope b =0.06547 and intercept a=0.3107 in the 1.0mol/L1KCl,the slope b= 0.2663 and intercept a=0.3590 in the 0.1mol/L^-1KCl showing that Chromium is of low hydrolysis overvoltage,and the slope b= 0.2034 and intercept a=0.2461 in the 0.01mol/L^-1KCl showing that Chromium is of low hydrolysis overvoltage.The effects of OP-10 additves on the polarization curves of the electrowinning system were researched.The experiment results indicated that the addition of OP-10 caused the polarization curves moved towards positive,prevented the hydrolysis effectively.