Treatment of naphtalene sulphonic acids used as dye assisting chemicals in the textile industry by electrocoagulation

In the present study, the treatability of a commercial naphthalene sulphonic acid formulation frequently used as a dyebath auxiliary in the textile dyeing operation by electrocoagulation with stainless steel electrodes was studied and its organic matter removal performance was compared with that of plain coagulation process using iron salts and alum. Electrocoagulation was operated with 750 and 1500 mg/L NaCl serving as the electrolyte at applied current densities of 11 and 22 mA/cm² and an initial pH of 3.9. An increase in the applied current density accelerated the rate of organic matter removal significantly. Over 80 % COD and TOC removals were obtained within a reasonable reaction time of 60 min under all conditions tested in the present study. Hence electrocoagulation of naphthalene sulphonic acid formulation proved to be an effective method in removing organic matter even at the lowest current density applied in the present study. Plain coagulation also worked well yielding 60 % COD removal. However, the advantage of electrocoagulation over plain coagulation was the high degree of mineralization achieved.