Fluoride removal from drinking water using the combination of electro and chemical coagulation processes

Fluoride is a toxic chemical for human. The present study was aimed to investigate fluoride removal from urban drinking water by the combination of batch electrochemical reactor، using copper-copper electrodes، and poly aluminum chloride (PAC) as chemical coagulant. Fluoride contaminated drinking water samples were prepared and thence the effect of different variables including pH (4. 2-9)، initial fluoride concentration (3-9 mg/L)، contact time (10-40 min)، PAC concentration (10-50 mg/L)، distance between electrodes (1. 5 cm)، and current density (1. 5-4. 5 mW/cm2) on fluoride removal efficiency was studied. The experimental results have shown that the maximum removal efficiency of 87. 0% was obtained in the electrochemical reactor for 9 mg F-/L at 1. 5 cm distance between electrodes، current density of 4. 5 mA/cm2، electrolysis time of 40 min and pH 7. 5. Similarly، the maximum fluoride removal (100%) was obtained when the operating conditions were set as electrode distance 1. 5 cm، current density 3 mA/cm2، electrolysis time 40 min and pH 7. 5. Incorporating PAC in electrochemical reactor resulted in a very high fluoride removal (over 99%) from high-fluoride water (9 mg/L) when distance between electrodes، current density، contact time، and pH were 1. 5 cm، 4. 5 mA/cm2، 10 min and 7. 5، respectively. At a contact time of 10 min، pH 7. 5 and 10 mg PAC/L، the enhanced coagulation achieved a complete fluoride removal (100%) when the distance between electrodes and current density were respectively 1. 5 cm and 4. 5 mA/cm2. It has been found that fluoride removal from high-fluoride contaminated water in an electrochemical batch reactor is practicable. The enhanced coagulation process with copper-copper electrodes and PAC was more effective for fluoride removal as compared with the use of batch electrochemical reactor solely.