This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Larsen, M.J. Articles by Jensen, S.J. Search for Related Content PubMed PubMed Citation Articles by Larsen, M.J. Articles by Jensen, S.J. Social Bookmarking                         What's this?

Defluoridation of Water at High pH with Use of Brushite, Calcium Hydroxide, and Bone Char

Royal Dental College, Vennelyst Blud., DK-8000 Aarhus C, Denmark

E.I.F. Pearce

Dental Research Unit, Health Research Council of New Zealand, P.O. Box 27007, Wellington, New Zealand

S.J. Jensen

Royal Dental College, Vennelyst Blud., DK-8000 Aarhus C, Denmark

The aim of this study was to improve the efficiency of the bone-char method of water defluoridation by pre-treating the water with brushite and calcium hydroxide. Various amounts of brushite, calcium hydroxide, and bone char were suspended batchwise in 100 mL of distilled water containing 0.53 mmol/L fluoride for 24 h under gentle agitation. At suitable intervals, pH and the concentrations of fluoride, calcium, and phosphate in the water were determined and, when possible, the degrees of saturation with respect to brushite, hydroxyapatite, and fluorapatite calculated. Bone char used alone took up fluoride slowly and inefficiently. The addition of brushite and calcium hydroxide resulted in high concentrations of calcium and phosphate, making the solutions highly supersaturated with respect to fluorapatite, and led to a 20-fold increase in fluoride removal from the water. The combined use of all three salts left low concentrations of phosphate in solution and optimized the fluoride uptake capacity. Repeated use of the same bone char for 18 consecutive runs demonstrated that uptake of fluoride by the bone char was improved by repeated use, provided that brushite and calcium hydroxide were added. Therefore, addition of the two salts to the water may prolong the life of the bone char indefinitely, ensure the removal of fluoride, and thus avoid the problem of determining when the bone char is exhausted. In conclusion, we show that the bone-char defluoridation technique can be improved by addition of brushite and calcium hydroxide to the water. The problem of high terminal pH remains, however, and further work is required to improve potability.

Journal of Dental Research, Vol. 72, No. 11, 1519-1525 (1993)
DOI: 10.1177/00220345930720111001


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?