Capacity of regenerated bone char in removal of fluoride in treatment of drinking water

Abstract

Re use of fluoride saturated bone char as a way of reducing fluoride in domestic water was investigated. The study was aimed at determining the most effective solution (NaOH, Na2CO3, NaHCO3 or Na3PO4) to use in the regeneration of fluoride saturated bone char. Effect of temperature on regeneration and removal capacity of regenerated bone char is also reported. Samples of 40 grams of bone char per 50 mL solution were used in determination of effectiveness of different sodium solutions. Samples were taken at contact times of 0.5-24 hours for fluoride analysis. Determination of temperature effect was carried out using 40 grams bone char/ 50 mL 1% NaOH solution, one-hour contact time and temperature of 20- 60 . Removal capacity was determined using 40 grams bone char/ 50 mL natural water containing 5.96-ppm fluoride at contact time of 20 minutes. Fluoride and pH of unknown samples was analysed using fluoride and pH meter respectively. The data was analysed using Two Way Analysis of Variance to compare the efficiency of different concentrations of different solutions. NaOH solution was the most effective with 130.55-186.14 ppm and lowest was NaHCO3 with 4.35-6.03 ppm of fluoride released from fluoride saturated bone char. The efficiency of the four solutions was found to follow the order NaHCO3 < Na2CO3<Na3PO4 < NaOH. Increasing regeneration temperature increased amount of fluoride released from bone char. Regenerated bone char was able to treat about 6.85 litres of water before breakthrough of 1.5 ppm as compared to fresh bone char that treated 7.56 litres. Removal capacities were found to be 0.880 and 0.988 mg/g for regenerated and fresh bone char respectively. The study confirmed that sodium hydroxide solution is the most effective solution for regeneration. Regenerated bone char was found to be effective as fresh bone char. In conclusion, regenerated bone char is a viable option for reducing excess fluoride in drinking water. However, further investigation will be required to determine the most effective and economical method for regeneration that is either bucket or continuous. The findings from this research have potential of increasing the levels of renewable defluoridation materials available to communities with challenges of excessive fluoride in drinking water.