Endeavor toward competitive electrochlorination by comparing the performance of easily affordable carbon electrodes with platinum

ABSTRACT

Kinetics of chloride ion oxidation was studied on graphite, glassy carbon (GC), and platinum electrodes. The performance of the electrodes was monitored using the cumulative productivity and current efficiency of the cell as indicators. It was seen that the performance of the working electrode improved with repeated uses, the current efficiency increased from 22% in the third use to about 46% in the tenth use. The study also revealed that the role of diffusion to the total anodic current was insignificant and chloride ions were transported at the electrode surface only by conduction. The hypochlorite production in case of platinum was about 3.66 times than that of graphite and GC with the current efficiency of 75% in contrast to 46% found in graphite and GC. But platinum undergoes passivation to a significant extent unlike the graphite and GC electrodes. Chronopotentiometry experiments confirmed the passivation process in platinum electrodes, showed a steep rise in potential from 1.2 to 2 V while the electrode potential was uniformly maintained at 1.7 V in carbon electrodes. The highest i_o, exchange current density value was observed at 0.45 mA/cm² in 0.5 M electrolyte, which is an indication of improved electrocatalytic activity with increased molar concentration. After continuous uses the corrosion rate studies revealed that platinum and GC electrodes were corrosion resistant whereas graphite underwent corrosion at the rate of 0.006 mm/h. The study dictated that carbon electrodes has great potential to be used as an alternatives to platinum electrodes, however, further investigations are required to assess its practical applicability in the public water supply system.

KEYWORDS:

• Carbon
• disinfection
• drinking water
• electro chlorination
• electrosynthesis
• kinetics
• platinum
• sodium hypochlorite

Acknowledgments

We would like to thank Organic Process laboratory, Chemical Engineering Department, IIT Bombay and Waste Water Engineering lab, Department of Environmental Science & Engineering, Indian Institute of Technology (Indian School of Mines), Dhanbad for providing in kind assistance for performing the research work.