IDENTIFICATION OF HYDRATE ACTIVE ORGANICS (HAO) PRESENT IN SPENT BAYER LIQUORS BY STATE-OF-THE-ART ANALYTICAL METHODS

Picard, F., Audet, D., Boily, H. and Larocque, J.

Considerable progress has been made over the last decade to identify organic compounds that hinder hydrate precipitation and certain polyfunctional entities, including mannitol, gluconate and tartrate have received particular attention. Using mass spectrometry detection liquid chromatography (LC/MS) and ion chromatography (IC/MS), we have undertaken an extensive identification of organic compounds present in Bayer liquor or adsorbed on aluminium trihydrate. These analytical techniques allow the identification of more than one hundred different compounds of low (300 a.m.u.) molecular weights. Using these and other newly developed analytical methods, we have compared the concentration of specific organic compounds present in Bayer liquors with those found on washed hydrate. We found that compounds with adjacent chemical functions such as phthalate and salycilate had the highest affinity for hydrate surfaces. However, alditols, suspected earlier as HAO, were not detected in the liquors nor adsorbed on hydrate samples. Based on the analysis of samples from different alumina refineries, we are able to predict which thermally stable HAO’s are likely to be present in high and low temperature Bayer liquors.