Ultrasound assisted electrochemical oxidation of synthetic dye wastewater

This study reports the treatment of synthetic dye wastewater in a sono-electrochemical reactor. The influence of three different supporting electrolytes (Na2SO4, NaCl, and Na2NO3) on % decolorisation was studied and higher decolorisation was observed with NaCl. The increase in applied current density (0.25, 0.5, 0.75, 1, 1.25 A/dm(2)) enhanced the color removal and the optimum current density arrived was 1.25 A/dm(2). The % decolorisation was studied at three different pH (3, 7 & 11), and about 95.7% decolorisation was observed at pH 3. The inter electrode distance of 1 cm gave highest decolorisation. The addition of Na2SO4 and Na2NO3 in the sonolyzer bath did not influence the % decolorisation significantly. The sono-electrochemical process gave 99.16% decolorisation and 91.15% COD reduction while the electrochemical process gave 94.79% decolorisation and 76.82% COD reduction. The optimum electrolyte concentration, current density, pH and electrode distance of 0.5 g/L, 1.25 A/dm(2), 3, and 1 cm, respectively gave highest decolorisation. The reaction kinetics of the sono-electrochemical oxidation treatment was also investigated. The higher mineralisation rate at a lower residence time indicates that the combined treatment is promising for degrading recalcitrant compounds present in wastewater.

Automated summary

This study investigated the treatment of synthetic dye wastewater using a sono-electrochemical reactor. The results showed that the addition of NaCl as a supporting electrolyte resulted in higher decolorization. Increasing the applied current density and decreasing the pH also improved the color removal. The sono-electrochemical process demonstrated better decolorization and COD reduction compared to the electrochemical process. The combined treatment under optimum conditions showed promising results in degrading recalcitrant compounds in wastewater.