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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

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journal contribution
posted on 20.09.2017 by Saim Özkar, Richard G. Finke
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.

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