Kinetic Characterization of Precipitation Reactions: Possible Link between a Phenomenological Equation and Reaction Pathway

Abstract

The characteristic time scale of reactive crystallization is traditionally investigated as a function of supersaturation in the deterministic regime, but no chemical meaning is assigned to the empirical power law. Applying chemical model systems in which various oxalate complexes form beside the precipitate, we show that the exponent provides information about the reaction pathways. The speciation of the reactant solution is revealed by combining equilibrium calculations and conductance measurements; the precipitate is identified with powder X-ray diffraction. A link between microstructure and kinetics is illustrated by scanning electron microscopy. The functionality of complex-shaped particles is examined by utilizing them as filler material to modify the wetting properties of a fluoropolymer-based thin film. Finally, it is shown that investigating the characteristic time scale as a function of the analytical concentration instead of supersaturation may also provide valuable information.

Synthesis and composition modification of precipitate tubes in a confined flow reactor

“…The added salts are not only significant because they increase the supersaturation, but they are characterized by faster precipitate formation compared to the magnesium–carbonate system. 20 Because of this, the nucleation process of magnesium containing precipitate could be accelerated by heterogeneous nucleation, for example, by the formation of magnesium precipitates on tiny calcium carbonate crystals. In the concentrated magnesium chloride solution (1.5 M) we could dissolve the strontium chloride up to 1 M, while the barium chloride up to 0.5 M. Fig.…”

Population Mass Balance Model for Precipitation with Turbidity Measurements

“…In many studies concerning DPB modeling, the measured PSD is used to fit the parameters appearing in the density function. , In this work, we present a method to predict PSDs using temporal precipitate concentration curves. The evolution of product concentration in the case of precipitation can be followed with various experimental techniques, for example, by measuring conductance, dynamic light scattering, or turbidity. The latter can be conveniently monitored utilizing a photometer − or a high-speed camera .…”

“…The latter can be conveniently monitored utilizing a photometer − or a high-speed camera . As a case study, a previously investigated calcium oxalate formation is selected, from which the temporal evolution of turbidity for various initial reactant concentrations and the scanning electron microscopy (SEM) images of the products are available. By utilizing our new method, we can predict the PSD to provide information on the precipitate size domain.…”

Nucleation kinetics of lithium phosphate precipitation

“…25,27 For small supersaturation classical nucleation theory is used to describe nucleation, 28,4 whereas the kinetic approach is more often applied for barely soluble electrolytes at high supersaturation 29,30 as well as for nanoparticle formation. 31 In this work we go beyond binary electrolytes, where several kinetic studies have been performed, 29,32 and investigate the nucleation of lithium phosphate in a well-stirred system.…”