4 research outputs found
Comprehensive Study of the Chelation and Coacervation of Alkaline Earth Metals in the Presence of Sodium Polyphosphate Solution
The effect of chelation of three
alkaline earth metals (Ca, Sr,
and Ba) by polyphosphates on the pH and viscosity of the solution
is examined and correlated to the phosphate glass properties. Also,
the impact of the polyphosphate average degree of polymerization (<i>D</i><sub>p</sub>) as well as the type and
amount of chelated divalent cation on the degradation rate of the
chains is studied. Subsequently, the number of divalent cations required
for polyphosphate chain agglomeration to form a coacervate, and the
resulting composition of these coacervates, was investigated. A decrease
in polyphosphate solution pH during chelation was routinely obtained,
with a sudden shift in the rate of pH drop occurring around a divalent
cation/phosphorus molar ratio of 0.18. Longer chains or cations with
a smaller ionic radius accelerated the rate of <i>D</i><sub>p</sub> reduction. The number of divalent cations
required for coacervation depends on different variables such as the
polyphosphate concentration, the <i>D</i><sub>p</sub>, and the type of divalent cation. The formed coacervate
retains the <i>D</i><sub>p</sub> of
polyphosphate originally used for coacervation, and the resulting
Ca/P molar ratio depends largely on the amount of calcium being used
during coacervation. Overall, this article helps one to understand
the coacervation of polyphosphates in order to exploit their potential
as a biomaterial