Simultaneous removal of metal ions and linear alkylbenzene sulfonate by combined electrochemical and photocatalytic process

Combined electrochemical removal of Zn++ and Ni++ and photo-oxidation of linear alkylbenzene sulfonate (LAS) by suspended TiO2 particles was investigated. The effect of different process variables such as current density, pH and liquid flow rate on the sole electrochemical reduction of metal ions was also evaluated. At pH of 5.0, the removal of Zn++ increased by 28% with increases in the liquid flux from 0.0021 to 0.0172 m3 m−2 s−1 while the removal of Ni++ was only enhanced marginally. Under optimum operating conditions used in the present study (liquid flux = 0.0172 m3 m−2 s−1, current density = 0.166 mA cm−2, pH 5.0 and in the presence of LAS), Zn++ and Ni++ were reduced by 86 and 56%, respectively, over 7 h of the sole electrochemical treatment. For the sole photocatalytic treatment of LAS at pH of 5.0, a 60% LAS degradation was obtained. However, the liquid flow rate did not have any considerable effect on the LAS oxidation. Finally, in the combined photocatalytic-electrolytic process, the LAS degradation increased to 76%. Nonetheless, in the combined system the Zn++ and Ni++ removal remained at comparable levels to those obtained in the sole electrochemical system.