Defluoridization of drinking water by electrocoagulation (EC): process optimization and kinetic study

In this work, removal of fluoride ions from drinking water using electrocoagulation (EC) was carried out using combination of different electrode materials in both monopolar and bipolar connections. The most effective pair of electrode for fluoride removal was found to be Al/Al in bipolar connection. Experiments were conducted to optimize the various operating parameters of EC such as pH, salt dose, stirring speed, inter electrode distance (IED) and current density for efficient removal of fluoride from water. Initial pH of 7.0, current density of 129.31 A/m², IED of 1 cm, salt dose of 0.33 g/L, stirring speed of 500 and EC time of 40 minutes were found to be optimum conditions to reduce 10 mg/L fluoride ions from water below 1.5 mg/L, which is maximum contaminant level in drinking water as declared by WHO and Indian standard of drinking water. Efficacy of EC process on TDS and turbidity removal of the solution at different operating conditions had also been studied. First order kinetic model was found to fit for fluoride removal. Rate constant (k) increased from 0.02566 to 0.117 min⁻¹ with increase in CD from 17.29 to 258.62 A/m² due to availability of more aluminum hydroxide flocs in the solution.