Photoelectrochemical treatment of 1-amino-8-hydroxynaphthalene-3,6-disulphonic acid at electrode covered with TiO2/RuO2

Results of electrochemical oxidation of 1-amino-8-hydroxynaphthalene-3,6-disulphonic acid (H acid) show that the substrate is easily oxidised at titanium electrode covered with TiO2/RuO2 than at platinum. The process should be carried out at potentials lower than the potential at which oxygen evolution starts. The reaction rate does not depend on pH in the range from 3.5 to 10. H acid is destroyed by 25% during electrochemical oxidation. Anion radical is one of the products of one-electron oxidation of the substrate. It quickly undergoes deprotonation. The final products of H acid oxidation are as follows: CO2, H2O, NH3, SO42− and at least 7 other organic compounds – naphthalene derivatives. Electrochemical oxidation combined with photochemical reaction causes an increase in the conversion (calculated as a change in TOC) to about 50%. At the same time, COD value decreases by about 70%. Addition of TiO2 catalyst in dispersed form to the solution causes further decrease in TOC and COD to 55 and 75%, respectively.