Defluoridation of groundwater in central Mexico by electrocoagulation

Electrocoagulation (EC) was used to treat groundwater contaminated with the fluoride ion (F^-). The groundwater was drawn from wells in the states of San Luis Potosi and Aguascalientes in central Mexico. Batch tests were performed using aluminium electrodes in an EC reactor. The EC response variables were the energy consumption, the electrode consumption, and the required processing time for removing F^- to the maximum permissible limit (1.5 mg L^-1) in water for human consumption that has been established by the World Health Organization (WHO). The sludge generated in the process was characterised using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The results showed that EC is an effective technique for groundwater defluoridation. A reduction in the F^- concentration from 5.17 to 1.5 mg L^-1 was achieved in 4 minutes. The energy and electrode consumption were 0.99 kW h m^-3 and 37.36 g m^-3, respectively. The reflections in the XRD pattern indicated that the sludge formed consists in gibbsite Al(OH)₃ and calcite (CaCO₃).