Precipitation of calcium oxalates from high ionic strength solutions IV. Testing of kinetic models

Abstract

The following parameters characterizing the kinetics of precipitation from unseeded solutions are defined: the induction period ( t i), the maximum precipitation rate ( R max), the number of particles per cm 3 ( N), the order ( p) and rate constants ( K α , K s) of the crystal growth process, the critical time ( t aggr ∗), the critical supersaturation ( S aggr ∗) and the rate constant of aggregation ( k j) as well as the relative changes in the surface area ( ΔP/ P) and the degree of the reaction (Δα/α) due to aggregation. The information which these parameters yield on nucleation, crystal growth and aggregation is evaluated. The model is applied to the precipitation of calcium oxalate trihydrate (COT) from 0.3 molar sodium chloride solutions, with and without the presence of tryptophan or ornithine. At the given concentrations both aminoacids inhibit crystal growth and change the mode of aggregation of COT.