Removal of fluoride from water using coagulation-flocculation process: a comparative study

The use of safe and easily available coagulants for removing pollutants from water has been recommended. The aluminum sulfate, polyaluminum chloride and ferric chloride extensively have been used for quantitative elimination of fluoride from water. One factorial method has been used for design of experiments and the main variables such as pH of solution, initial fluoride concentration, coagulants dosage and turbidity were optimized. Results showed that the maximum removal of fluoride was 57%, 50% and 53% using alum (pH 4), PACl (pH 4), and Fe3+ (pH 8), respectively. The coagulant dosage showed a significant effect on the process using Al3+. The highest removal efficiency (83%) obtained at 30 mg/L of aluminum sulfate. The effect of turbidity on the process using alum was insignificant. Furthermore, the results showed the insignificant effect of initial concentration of fluoride on the process.