THE ANODIC-OXIDATION OF CR(III) TO CR(VI) IN A LABORATORY-SCALE CHROMIUM ELECTROWINNING CELL

The factors affecting the anodic processes in the electrowinning of ch romium were investigated by carrying out electrolysis experiments with a chromium ammonium sulfate solution in a laboratory-scale cell of ap proximately 90 mi equipped with a diaphragm. The current density (838- 1077 A m(-2)), temperature (50-70 degrees C), and rate of electrolyte flow (5-18 ml/h) from catholyte to anolyte were varied to determine th eir effects on the anodic oxidation of Cr(m) to Cr(VI). There was no a ttempt to optimize the cathodic deposition process. The behavior of th e traditional lead-silver anode with an effective surface area of 10 c m(2) was compared with that of two commercially available dimensionall y stable anodes. The current efficiency for the anodic oxidation of th e chromic ion varied from about 75 to 100% with the lead-silver anode while it was only about 10 to 20% with the dimensionally stable anodes . The other variables had a much less significant effect. (C) 1997 Els evier Science B.V.