New modelling approach to liquid-solid reaction kinetics: From ideal particles to real particles

Typical features of liquid-solid reactions were reviewed: reaction kinetics, mass transfer effects and particle morphology. It was concluded that classical liquid-solid models based on ideal, non-porous geometries (sphere, infinite cylinder, slab) cannot satisfactorily describe real reactive solid particles with various surface defects, such as cracks, craters and limited porosity. 'Typically a too low reaction order for the reactive solid is predicted by the classical models. The surface morphology can be revealed by electron microscopy, which gives inspiration to develop new mathematical models for reactive solids. Generalized product layer and shrinking particle models were developed for arbitrary geometries deviating dramatically from ideal geometries. The approach is based on the use of a shape factor (a), which can obtain high values for particles with surface defects. The modelling approach was illustrated with numerical simulations and an experimental case, leaching of zinc sulphide with ferric ions: A general methodology for investigation of fluid-solid reactions was proposed. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.