Arsenic removal from drinking waters by electrocoagulation and filtration

Arsenic removal from drinking waters was investigated using Electrocoagulation (EC) process followed by filtration process in this study. Batch electrocoagulation experiments were performed in the laboratory scale using iron electrodes, which were placed horizontal in the electrocoagulation reactor and connected to a power supply in monopolar, parallel arrangement.Non-toxic and readily available iron plate was used as electrode material because of its strong adsorption affinity for arsenic. Moreover, when iron electrodes are used in EC process, depending on range of pH, it can generate by-products such as iron hydroxides, hematite, maghemite, magnetite, goethite, lepidocrocite, rust, which are widely used in arsenic removal from drinking waters.The experiments were carried out to investigate the effects of initial arsenic concentration, residence time, current, presence of salt, surface area of electrodes and oxidation states of arsenic (As(V) and As(III)) at pH 6-8.The sand filter was used to remove flocs, which were generated in EC. During the filtration process air was injected with the aquarium pump through air diffuser (air stone) to remove excessive iron species (ferric, ferrous) occurred in EC depending on pH changing and other factors.The initial arsenic concentration and the electrode surface area had no significant effect on arsenic removal. It was observed that the changing of current and residence time are significant for optimizing and controlling of EC performance. When natural contaminated groundwater (As(III) ) in Sasali-Izmir was investigated and compared with arsenate (As(V) ) contaminated solutions, slower removal then arsenate removal was observed due to oxidation As(III) to As(V).As well, with addition of salt, bigger and dense flocs (green rust) formation was obtained. The residual arsenic and iron concentrations were determined by ICP-OES. The ninety nine percentage of arsenic removal was achieved in the EC experiments.