MORPHOLOGY AND CRYSTALLINITY: INSIGHTS INTO THE MECHANISM OF GROWTH OF DSP

The impact of different silica sources on the precipitation of desilication product (DSP) from synthetic spent Bayer liquors at 95°C has been examined. Experiments were conducted to examine DSP formation from three morphologically different kaolins as well as a soluble silica source. All sources produced a woolball DSP morphology, and an additional spherulite-like morphology was present in the samples produced from a soluble silica source. DSP was formed indirectly from the soluble silica source via a zeolite A phase, unlike the kaolin sources, which produced DSP directly. We did not observe selective dissolution of the kaolin, or growth of the DSP on any particular face. The DSP woolballs did not appear to contain any partially dissolved kaolin, and TEM imaging suggests that during early formation, these structures are comprised of small platy particles that may be mostly amorphous in nature.