Abstract:
Fluorides are one of the many pollutants found in water. At low concentration, fluorides are essential for improving
the density and hardness of bones and teeth enamel during their growth. A concentration greater than 1.5 mg/L in drinking water
has several detrimental effects on human health, including dental and skeletal fluorosis. There are several methods employed to
rid water of fluorides. These include, reverse osmosis, adsorption, ion exchange, coagulation and flocculation. This study
focuses on removal of fluorides from aqueous solutions by coagulation using quaternary ammonium functionalized waste paper
bio-coagulant. Quaternary ammonium compounds were synthesized from waste paper by first nitrating cellulose present in
waste paper. The attached nitro groups, were reduced to amine groups and quaternization was done using methyl iodide. The
prepared bio-coagulant was characterized using FTIR and TGA. The coagulant was used to remove fluorides from model
solutions and real water samples from Gilgil area in Nakuru county, Kenya. A fluoride ISE was used to determine fluoride ion
concentration in each model solution and in the real water samples. Optimized parameters included pH, initial fluoride ion
concentration, contact time and bio-coagulant dosage. Characterization data confirmed successful quaternization was achieved.
Thermal stability of the material was up to a temperature of 563.15 K. The optimum pH value was 4.0 while the contact time
was 15 minutes. Fluoride removal increased with increase in initial concentration up to an optimum 20 mg/L. Fluoride removal
was also observed to increase with increase in coagulant dosage. Obtained data fitted well on Langmuir adsorption isotherm
with R
2
value of 0.9707, confirming chemisorption as the predominant intermediate process. An adsorption capacity of 3.6311
mg/g was obtained. Fluoride ion removal percentage in the model solution was 81% and 66.25% in the real water sample.
