Systematic study on sulfate removal from mining waters by electrocoagulation

The mining industry is known to be a major producer of sulfate-rich waters that are harmful to aquatic systems, accelerate acid mine drainage formation and hinder the reuse and recycling of process water. In recent years, many treatment techniques have been studied and developed to treat sulfate-rich streams. One such technique, electrocoagulation (EC), was proposed as a possible alternative to conventional treatment technologies. Electrocoagulation has been used for the removal of nitrate, cyanide and toxic metals from mining waters, but the information about sulfate removal is scarce. In this paper, the results from a systematic study on sulfate removal by EC with iron electrodes applying a 3³-full factorial design are discussed. The results show the leading role of applied current on sulfate removal. In addition, the study concludes that the utilisation of iron electrodes was more efficient in terms of sulfate removal comparing to aluminium electrodes. The removal of sulfate was as high as 54% and 10% using iron and aluminium electrodes respectively. Under the studied experimental conditions, sulfate was proposed to be removed because of particle charge neutralisation and enmeshment of the studied anion in iron oxides and hydroxides.