Electrochemical Oxidation of Rokaphenol N-6 in a Flow Electrolyzer

Abstract

Abstract Rokaphenol N–6 is the name commonly used in Poland for 18-p-nonylphenyl–3,6,9,12,15,18-hexa-oxaoctadecan–1-ol. This compound belongs to the group of non-ionic surface active substances (NSAS). Detergents containing NSAS of this type are toxic in the aqueous environment and their biodegrada-tion is very slow. The lack of effective methods for treatment of waste waters containing NSAS at higher concentrations has led us to investigate this subject. For electrooxidation platinum and oxide electrodes (RuO 2 40% and TiO 2 60%) have been used. It was found in batch experiments that electric charge is most effectively used for oxidation of Rokaphenol N–6 in the range of substrate concentrations 160 to 500 mg/dm 3 . The flow of an electric charge greater than 0.025 Ah through the electro-lyzer produces, in fact, a constant degree of oxidation about 90% in the batch experiments. Similar results were obtained by oxidizing Rokaphenols N–8, N–14 and detergent Roksol IT. Parameters for oxidation in the flow electrolyzer were the optimum parameters determined in the batch experiments. The flow rate of electrolyte in the 100 cm 3 electrolyzer varied from 0,35 to 5 cm 3 /min. A current density of 0.025 A/cm2, a temperature of 313 K and a NaCl concentration of 10 g/dm 3 were used. These parameters allow obtaining of about 80% degree of conversion in the flow electrolyzer. The products of Rokaphenol N–6 electrolysis show much lower toxicity to aquatic organisms and do not inhibit the growth of algae.