Fluoride contamination

S. Tripathy, M.K. Panigrahi, N. Kundu, Geochemistry of soil around a fluoride contaminated area in Nayagarh District, Orissa, India Factor analytical appraisal. Environ. Geochem. Health 27 (2005) 205-216. 

J.G. Stannard, Y.S. Shim, M. Kritsineli, P. Labropoulou, A. Tsamtsouris, Fluoride levels and fluoride contamination of fruit juices, J. Clin. Pediatr. Dent. 16 (1991) 38-40. 

The usual method of preparing boron trifluoride from calcium fluoride, boric oxide, and sulfuric acid is unsatisfactory, since yields are low, much silicon fluoride contaminates the product, and a solid residue which is difficult to remove remains in the generator. 

Fluoride-related health hazards are associated with the use of fluoride-contaminated water for drinking and cooking. This corresponds only to 2-4 L per capita per day. Fluoride removal in rural areas in LDCs, where centralized water treatment and distribution facilities are unavailable, should consequently be carried out at a household level and the system applied should be simple and affordable. In this regard, tea bag POU system becomes handy. Although this kind of system has not been specifically reported for water defluoridation, it has been tested for arsenic [37,107], It is therefore a short-term potential technique worth considering. In this technique, adsorption medium is placed in a tea bag-like packet, which is subsequently placed in a bucket of water to be treated. To ensure faster defluoridation kinetics, the bag should be swirled inside the water. It therefore operates like a batch reactor and hence requires a relatively longer adsorption time to achieve the permissible levels. Since the swirling motion is supposed to be human-powered, the technique would require a material with very fast kinetics or very fine adsorption media. 

The Nalgonda technique has been introduced in many countries, e.g. India, Kenya, Senegal and Tanzania. However, the method has a number of disadvantages. These include the treatment efficiency is about 70%, which means the process cannot be used in cases of high fluoride contamination a large amount of aluminium sulphate, up to 700-1200 mg L 1 may be needed the adverse health effects of dissolved aluminium species in the treated water. 

Given the implications involved in fluoride contamination in the environment, the development of... 

Susheela AK (1998) Scientific evidence on adverse effects of fluoride on human tissues due to fluoride contaminated drinking water, due to fluoridated dental products, due to fluoride therapy. Document presented to Members of Parliament, House of Lords and House of Commons, Westminster, London. 

There are also problems dealing with fluoride-contaminated discharge water from wet scrubbers, and the drainage of precipitation from areas where spent pot linings are discarded, since fluoride constituents of electrolyte leach from these. Careful disposal of spent pot linings can minimize this problem. The problem may be eliminated by fluoride recovery followed by recycle of the carbon content. 

Goodman, J. Andrews, S. Fluoride contamination from fluoropolymers in semiconducfor manufacture. Solid State Technol., June 1990. 

Zhu, M., Xie, M., and Jiang, X., Interaction of fluoride with hydroxyaluminum-montmorillonite complexes and implications for fluoride-contaminated acidic soils, Appl. Geochem., 21, 675, 2006. 

The reaction starts without warming. Phosphorus (V) fluoride contaminated with AsFg accumulates as a white solid in the trap. After completion of the conversion the crude PFg is purified fractionation. 

Cavalchi and Fomaciari [88] affirmed that the bee matrix was difficult to interpret due to the complexity of the factors influencing the assimilation of pollutants, but that honey and propolis appeared to be good biological markers of fluoride contamination. 

Goodman, J., and Andrews, S., Fluoride Contamination from Fluoropolymers in Semiconductor Manufacture, Solid State Technology, Jun. 1990. 

---