Effect of tubes bundle electrode on removal of cadmium from simulated wastewaters by electrodeposition

BACKGROUND: The performance of a novel pilot scale, fixed bed flow‐through cell, consisting of a cathode formed by a bundle of stainless steel tubes having two tube arrangements (920 tubes of 0.6 cm outer diameter and 360 tubes of 1.0 cm outer diameter) was investigated for the removal of cadmium in a batch re‐circulation mode. The electrochemical reaction studied was the cathodic reduction of Cd⁺² using 0.5 mol L^?1 sodium sulphate as supporting electrolyte. The parameters analyzed were initial Cd⁺² concentrations and electrolyte flow rates. RESULTS: Experimental results for the two different tube arrangements showed that the mass transfer coefficients were higher for the 0.6 cm diameter tubes than for the 1.0 cm diameter tubes. The former gave a fractional conversion of 80.4% with a current efficiency of 70.75% compared with a fractional conversion of 58.5% with a current efficiency of 45.7%, for the 1.0 cm diameter tubes, for a Cd⁺² concentration of 200 ppm and flow rate of 250 L h^?1. These results were correlated to: for 5 < Re < 28 and Sc = 649, where Sh is the Sherwood number, Re the Reynolds number and Sc the Schmidt number. CONCLUSION: Experimental results, analysis, correlations and figures of merit showed better performance of the cell for the removal of Cd⁺² with 0.6 cm diameter tubes than with 1.0 cm diameter tubes. Copyright © 2010 Society of Chemical Industry