Effect of preparation temperature on the ability of bone char to remove fluoride ion and organic contaminants

The excessive intake of fluoride ion (F^-) from drinking water causes dental and skeletal disorders and thus methods for the removal of F^- from water are desired. A method for removing organic contaminants from water is also desired. Bone char is a composite material composed of char and hydroxyapatite (HA). Bone char can remove F^- because of the HA in the bone char. It is expected that bone char containing small grain size HA will remove F^- effectively because of its high surface area. Additionally, the char in bone char can remove organic matter from contaminated water, and controlling the amount of char in bone char is also important. Bone char is fabricated by heating porcine bone at 200-600°C for 1 h under a limited oxygen supply. The grain size of HA in these samples increases with an increase in heating temperature. The amount of organic matter and char in these samples decreases with an increase in heating temperature. Bone char with a controlled HA grain size and the amount of char was fabricated by changing the heating temperature. Their ability to remove F^- and methylene blue (MB), as a model organic contaminant, was evaluated by immersing the samples in F^--containing and MB-containing solutions. The sample prepared at 400°C was able to remove most of the F^- and less than 1.5 mg·dm^-3 F^- remained, which is within the World Health Organization recommended level for drinking water. Additionally, the sample prepared at 400° C was also able to remove most of the MB. Bone char can thus be used to remove F^- and organic contaminants.