Malachite Crystallisation in a Diffusing-Reacting System

Abstract

The crystallisation of malachite has been studied in a system involving the counter diffusion of Cu2+ and CO3 through a silica gel column at 25 ºC. In such a system supersaturation is a function of time and position along gel column. Under these conditions kinetic variables are required in order to justify nucleation behaviour. Supersaturation rate has revealed as the most important parameter controlling nucleation features (waiting time, position of the precipitate, and metastability levels). The results presented here confirm the general nucleation behaviour reported by Prieto et al., (1989, 1991, 1994) for other carbonates. On the other hand, supersaturation changes during crystallisation process control the morphological evolution of malachite crystals.