A Classic Azo–Dye Agglomeration System: Evidence for Slow, Continuous Nucleation, Autocatalytic Agglomerative Growth, Plus the Effects of Dust Removal by Microfiltration on the Kinetics

Abstract

An important but virtually ignored 1978 paper by Reeves and co-workers, which examined a dye-OAc hydrolysis and then agglomeration system, is reanalyzed in light of current state of knowledge of nucleation and growth/agglomeration phenomena. The Finke-Watzky two-step mechanism is used to account quantitatively for the kinetics data, in turn providing deconvolution of dye hydrolysis and nucleation of agglomerative growth, from the agglomerative growth step, including their separate rate constants. Significantly, the effects of microfiltration of the removable dust on the two steps and their rate constants are uncovered and quantitated for the first time, including the finding that the presence of dust accelerates both steps by ca. 10-fold or more. A postulated minimum mechanism able to account for all the observed results is provided. The results allow the excellently designed and executed, now nearly 40-years old, classic studies of Reeves and co-workers to be placed in its proper position in history, while at the same time providing six insights and conclusions detailed in the Discussion and Conclusions sections of the paper.

Dust Effects on Ir(0)n Nanoparticle Formation Nucleation and Growth Kinetics and Particle Size-Distributions: Analysis by and Insights from Mechanism-Enabled Population Balance Modeling

“…Our results teach that if one has created a PBM that has more than 3–4 total parameters, that is also a PBModel based on nonexperimental input (e.g., such as Classical Nucleation Theory), then the resulting simulations need to be treated with great caution and could be misleading as in a recent example The literature cited in the Introduction, demonstrating that microfiltration sharpens the PSDs of Au(0) n and S n particle formation as well as azo-dye aggregation, provides highly suggestive evidence for the broader application of the kinetics and mechanistic findings uncovered herein of the effects of dust on particle formation reactions and especially on their associated nucleation rate constants. However, much remains to be understood about the effects of dust on nucleation and growth, especially a more detailed physical picture of precisely how the presence of dust has the effects observed both here and in the prior literature. − Some discussion and a working hypothesis based on the concept of Prenucleation Clusters − are provided in the Supporting Information about how dust z– might possibly be functioning in systems with cationic precatalyst components such as Ir I (1,5-COD) + . That said, the work herein is just a start on the needed additional studies, of the effects of common, omnipresent dust and the analysis of its effects by methods that include ME-PBM, for a range of nucleating systems across nature. …”

“…However, much remains to be understood about the effects of dust on nucleation and growth, especially a more detailed physical picture of precisely how the presence of dust has the effects observed both here and in the prior literature. − Some discussion and a working hypothesis based on the concept of Prenucleation Clusters − are provided in the Supporting Information about how dust z– might possibly be functioning in systems with cationic precatalyst components such as Ir I (1,5-COD) + . That said, the work herein is just a start on the needed additional studies, of the effects of common, omnipresent dust and the analysis of its effects by methods that include ME-PBM, for a range of nucleating systems across nature.…”

“…There, filtration of dust narrowed the final size distribution 2-fold, a result remarkably close to the effect of removing dust in the present Ir(0) n nanoparticle formation system, vide infra. Then, another 15 years later, Reeves et al reported in a 1978 paper , the effects of microfiltration on the hydrolysis of an azo-dye followed by agglomeration of the resultant alcohol. Reeves et al found that the filtration of the reactant solution through a 0.2 μm nucleopore microfiltration membrane slowed the rate of colloidal product formation by a factor of ca.…”

“…Reeves et al found that the filtration of the reactant solution through a 0.2 μm nucleopore microfiltration membrane slowed the rate of colloidal product formation by a factor of ca. 21 . Another 35 years later, Kulkarni et al showed in a state-of-the-art 2013 paper that the simple filtration of isonicotinamide reactant solution through a 0.45 μm membrane filter caused the crystallization rate to drop by 2.7-fold.…”

LaMer's 1950 model of particle formation: a review and critical analysis of its classical nucleation and fluctuation theory basis, of competing models and mechanisms for phase-changes and particle formation, and then of its application to silver halide, semiconductor, metal, and metal-oxide nanoparticles

“…Worth mentioning here is that precedent has existed since 2005 [56][57][58] that the pseudo-elementary steps of B + B -C (rate constant k 3 ) [55][56][57][58] then B + C -1.5C (rate constant k 4 ) [56][57][58] can quantitatively describe the kinetics of a number of aggregating systems, [56][57][58]188,[213][214][215][216][217] basically a sequence of bimolecular nucleation of aggregation (B + B -C) followed by smallerlarger size-focusing aggregation (B + C -1.5C) that has often been found to be faster, k 4 c k 3 . [56][57][58]188,[213][214][215][216][217] Hence, further efforts are once again needed to understand what is a historically very important particle-formation system: namely how massive, nearly uniform size silica particles are formed.…”