Removal of chloride from simulated zinc sulfate electrolyte by ozone oxidation

• A novel method for removal of chloride from zinc sulfate electrolyte was proposed.
• The effects of various process factors were studied and the mechanism was discussed.
• Under optimum conditions, the concentration of Cl− was reduced from 300 to 5 mg·L− 1.

The removal of chloride from simulated zinc sulfate electrolyte by ozone oxidation was investigated. The effects of various process factors including the O2 flow, bubbling time, reaction temperature, H2SO4 and ZnSO4 concentration, and existence of Mn2 + were systematically studied. The results showed that with increasing O2 flow, the chloride removal increased first and then decreased. Increasing both the bubbling time and reaction temperature was beneficial to dechlorination while an increase in the ZnSO4 concentration had an adverse effect. With increasing sulfuric acid concentration, the dechlorination rapidly rose due to the increasing hydrogen ion concentration in electrolyte. Optimum dechlorination process conditions in the absence of Mn2 + were obtained as follows: O2 flow 0.4 L·min− 1, H2SO4 concentration 160 g·L− 1, Zn2 + concentration 40 g·L− 1, reaction temperature 70 °C, and reaction time 120 min. Under these conditions, the concentration of Cl− was reduced from 300 to 5 mg·L− 1. The existence of Mn2 + can further accelerate the reaction of ozone with chloride, which was probably through charge-transfer and coordination catalysis mechanism.