Study on the effect of humate and its removal on the precipitation of aluminium trihydroxide from the Bayer process

摘要: Abstract A process to remove humate from Bayer spent liquor using polymers of diallyldimethyl ammonium chloride (polyDADMAC) has been developed. Using a UV–visible spectrometric technique, the concentration in liquors obtained an alumina refinery was found be 5 ± 1 g/l. The removal is based on its selective reaction with polyDADMAC, which can added at 1:1 weight ratio (with respect content) effectively liquors. involves, first between polyDADMAC and humate. Next, acidification convert humic acid carried out, follows by esterification step tertiary butanol. ester formed then causticized pH 9 recovered Results precipitation test showed that increase does not adversely affect yield precipitated aluminium trihydroxide (Al2O3 · 3H2O) product. However presence during causes decrease average particle size final precipitate range most affected 20–80 μm, after 48 h seeds 73.6 μm. By removing liquors, whiteness for specialty could also improved.