Equilibrium studies in natural fluids:: interactions of -PO43-, -P2O74- and -P3O105- with the major constituents of sea water

The interaction of PiO(3i+1)((i+2)-) (i = 1,2,3) with the major components of seawater has been studied potentiometrically, at 25 degrees C, in an artificial seawater (Na+, K+, Ca2+, Mg2+, Cl- and SO42-) at different salinities (5-45 parts per thousand). Apparent protonation constants have been calculated, from potentiometric data, and estimated, using an appropriate complex formation model. Formation constants of complexes formed by phosphates and the cation of seawater (the inorganic content of seawater being considered as a single 1:1 salt) have been determined. The comparison between experimental and estimated results showed that a suitable complexation model can be used with a fairly good accuracy in predicting acid-base properties of polyphosphates in seawater. The single salt approximation for the inorganic major components of seawater, which is a good tool in estimating the mean strength of polyanion interaction in seawater, has been applied.