An empirical model for defluoridation by batch monopolar electrocoagulation/flotation (ECF) process.

Excessive presence of fluoride concentration in community water supplies can cause fluorosis that affects the teeth and bones. Batch experiments with monopolar aluminium electrodes for fluoride removal were conducted and an empirical model is developed using critical parameters such as current concentration, electrode distance, and initial fluoride concentration. Fluoride ions were removed electrochemically from solution by electrocoagulation/flotation (ECF) process. The electrolytic dissolution of aluminium anodes in water produced aqueous Al3+ species and hydrogen bubbles at the aluminium cathodes. The fluoride removal efficiency increases steadily with increasing current values from 1 to 2.5 A. In the batch monopolar ECF process, the optimal detention time (dto) was found to be 55 min when the operational parameters including initial F- concentration, current value, and inter electrode distance were respectively kept at 10 mg/l, 1.5 A, and 5 mm. The experimental results showed that the rate constant (K) for defluoridation by monopolar ECF process depends on the current concentration (I/V), electrode distance (d) and initial fluoride concentration (C0). The Al3+/F- mass ratio is found to be not significantly different between monopolar and bipolar ECF systems. Overall, the results showed that the electrocoagulation technology is an effective process for defluoridation of water.