Interaction of inositol phosphate with calcite

The interaction of myo-inositol hexaphosphate with calcite was studied to e valuate the adsorption mechanisms and the electrochemical modifications ind uced by interaction of a molecule at such a high-charge density. In additio n to quantitative information through the construction of adsorption isothe rms, FT-IR and Laser Doppler Velocimetry - Photon Correlation Spectroscopy (LDV-PCS) were employed to investigate the nature of the adsorbent-adsorbat e bonds and to determine the electrophoretic mobility and size of the parti cles before and after sorption. The experiments were also run with orthopho sphate (Pi) for comparison. The amount of sorbed P increased to reach a pla teau at 17.8 mu mol m(-2) for inositol hexaphosphate (IHP) while for Pi ros e 1.4 mu mol m(-2) but at C-e > 6.10(-4) M it had a sharp increase reaching 155 mu mol m(-)2. As expected, for Pi, adsorption predominated up Ce 6.10( -4)M by covering about 20% of total surface. The adsorption occurred at sit es that behaved as nucleus of formation of the clustering of Ca- and PO4-io ns with the ending formation of calcium phosphate precipitates at C-e highe r than 6.10(-4)M. The reaction of inositol hexaphosphate with calcite invol ves, besides adsorption, precipitation of Ca salts and hence calcite dissol ution also at the lowest added IHP concentrations, accounting for the large amount retained by calcite. Sorption of IHP on calcite caused aggregation of particles at low concentrations followed by an increase of their negativ e charge and hence re-dispersion at higher concentrations. These results in dicate a great IHP-fixing capacity of calcite that can affect its accumulat ion in soils and P bioavailability, and a considerable change of calcite el ectrochemical properties and particle size distribution that can modify agg regate stability.