Additives effects on crystallization and morphology in a novel caustic aluminate solution decomposition process

Abstract

A novel process of caustic aluminate solution decomposition by alcohol medium was developed by the Institute of Process Engineering, Chinese Academy of Sciences in order to solve the problem of low decomposition ratio in the traditional Bayer seeded hydrolysis process. In this research, effects of additives on the crystallization ratio, secondary particle size and morphology of aluminum hydroxide in the new process were studied to obtain high-quality products. On the basis of primary selection of additives, an orthogonal design L9(3⁴) was used as a chemometric method to investigate the effects of additives. The studied parameters include the reaction style, quantity of additives, caustic soda concentration, as well as the combination manner. The crystallization ratios of sodium aluminate solution and crystal size of aluminum hydroxide, determined by ICP-OES, SEM and MLPSA (Malvern Laser Particle Size Analyzer), were used to evaluate the effects of the additives. The results showed that different combination manners could promote agglomeration or dispersion. An additive composed by Tween 80 and PEG 200 could promote agglomeration, while a spot of PEG species had a relatively strong dispersion effect. However, the additives had little effects on the crystallization ratios. According to the Raman spectra result, the added alcohol medium might serve as a kind of solvent.

Keywords

additive / crystallization / morphology / caustic aluminate solution / aluminium hydroxide

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Acknowledgements

The financial support of the National Natural Science Foundation of China (Grant No. 50874099), the National High Technology Research and Development Program of China (Grant No. 2006AA06Z129), Chinese Academy of Sciences Knowledge Innovation Program (Grant No. KGCX2-YW-321-2) and the Major State Basic Research Development Program of China (Grant No. 2007CB613500) are gratefully acknowledged.

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2014 Higher Education Press and Springer-Verlag Berlin Heidelberg