The efficiency in water treatment by granulated complexes formed from the clay bentonite with (i) micelles of the cations of octadecyltrimethyl-ammonium (ODTMA) or (ii) liposomes of didodecyldimethyl-ammonium (DDAB) was investigated. The bentonite–ODTMA complexes were synthesized in three variations: I. mass ratio of 68/32, which resulted in an excess of positive charge of half of the clay cation exchange capacity and is denoted “ordinary”; II. complexes having higher loads of ODTMA, denoted “enriched”; and III. “neutral”. These variations were designed to optimize the efficiency and reduce the costs of water treatment. “Ordinary” and “neutral” complexes of DDAB were also synthesized. The “ordinary” complex of ODTMA was shown to be efficient in the removal of anionic/hydrophobic molecules and bacteria. The “enriched” complexes were more active in removal of bacteria from water by filtration due to the higher release of free ODTMA cations, which causes biostatic/biocidal effects. The corresponding “ordinary” and “neutral” complexes of ODTMA and DDAB yielded the same efficiency in removal from water of the neutral and hydrophobic herbicides, S-metolachlor (i) and alachlor (ii), respectively. Model calculations, which considered sorption/desorption and convection yielded simulations and predictions of filtration results of the herbicides. The neutral complexes are advantageous since their production saves about 1/3 of the amount of ODTMA or DDAB, which constitutes the expensive component in the respective composite.

Fluoride uptake by the surface enamel of teeth treated with fluoride solutions in vitro and fluoride release into saliva after topical applications in vivo were determined. The fluoride uptake after NaF + Na2HPO4 treatment was higher than that after NaF treatment. The fluoride release into saliva was less after NaF + NaHPO4 than after NaF application, pointing to a greater permanent fluoride fixation. Topical fluoride applications are widely used for the prevention of dental caries. The effectiveness of topical agents is dependent on their ability to deposit fluoride as fluorapatite on the surface enamel. In vitro and in vivo evidence has shown that fluoride deposits acquired in this way may not be of a completely permanent nature.1 2 Fluoride acquired during topical treatment is lost into the oral environment unless allowed to react with the surface enamel for several hours after exposure.2-4The purpose of the present investigation was to study the rate of fluoride release into saliva after topical fluoride application in vivo. Fluoride uptake by surface enamel of extracted teeth treated with fluoride solutions in vitro was also examined.Materials and Methods Fluoride treatments were carried out in vitro and in vivo with solutions containing 2% NaF of pH 7.7 and 2% NaF + 0.1 M Na.,HPO, of pH 7.95. In order to eliminate the influence of an acid pH, Na2HPO4 was used instead of the common H2P04.Topical fluoride applications were made in 17 human beings 25-28 years of age.Plaque and calculus were removed carefully from the tooth surfaces before the treatment. Paraffin-stimulated saliva samples were collected from each person for ten minutes, commencing six hours after treatment and subsequently every morning before breakfast and toothbrushing for nine days. Control saliva samples were taken from each subject before the beginning of the experiment. The saliva samples were made slightly alkaline with fluoride-free calcium hydroxide, which served as a fluoride fixative and were then evaporated to dryness and ashed at about 400C. The ashed samples were transferred to fluoride stills. The chlorides were precipitated with silver sulfate. Fluoride was steam-distilled at 135C to 137C in the presence of sulfuric acid as described by Gedalia and Kalderon5 and determined calorimetrically according to Singer and Armstrong.6 Fluoride uptake by surface enamel in vitro was studied in the teeth of nine children aged 12-14 years, from each of whom three homologous intact premolars were extracted for orthodontic reasons. The teeth were thoroughly cleaned after extraction. One tooth from each child was kept as an untreated control, assuming that fluoride values of the homologous teeth are similar;5 the remainder were dipped into one of the fluoride solutions for four minutes, rinsed with water for a few seconds, and dried. Samples of surface enamel for fluoride analysis were ground off with a rotating diamond wheel, as described in a previous publication,5 to a uniform depth of approximately 50 /ut. Fluoride was steam-distilled from...