MICROPHASE-ASSISTED AUTOCATALYSIS IN A SOLID-LIQUID REACTION WITH A PRECIPITATING PRODUCT - I - THEORY

There are a number of industrially important reactions in which a spar ingly soluble solid reacts with a liquid-phase reactant with one of th e products precipitating out as a solid. If the particles of the preci pitate are in microphase dimensions, i.e. less than the diffusion leng th of the system, the solubility of the solute is increased by the mic rophase action of the product in the vicinity of the solid phase. The principal objective of the present work is to describe such 'autocatal ytic' microphase action by developing a model which simultaneously con siders reaction, crystallization, and microphase processes. The chief conclusion is that the growth kinetics and initial crystal size distri bution of the precipitating solids have a profound influence on the re action rate. Earlier models were deficient in that only microphase act ion was considered with limited effects of nucleation. The theoretical conclusions reported here are sought to be experimentally validated i n Part II of this study. (C) 1998 Elsevier Science Ltd. All rights res erved.