THE EFFECT OF 3,4 DIHYDROXY BENZOIC ACID (3,4 DHBA) ON THE PRECIPITATION AND ATTRITION OF ALUMINA TRIYDRATE

Tran, T., Kim, M.J., Emanuel, H.J., Wong, P.L.M.

The detrimental effects of organic impurities during the precipitation of alumina trihydrate have been well known in commercial practices. The presence of organics in Bayer liquors has caused decrease in yield and precipitation rate, as well as the incorporation of soda into the alumina product.

Using scanning election microscopes, this study was conducted to investigate the effect of a model compound (3,4 DHBA) on the deposit morphology during the three stages of precipitation (nucleation, agglomeration and crystal growth) of alumina trihydrate from synthetic liquors. In the presence of 3,4 DHBA, the crystallinity of the precipitate becomes irregular with uncontrolled growth on the 001 plane, compared with the denser hexagonal structures, commonly observed in the absence of organic contaminants. The study also attempted to evaluate the impact of organic contamination on the attrition of alumina trihydrate.