Study on the various factors affecting the quality of precipitated non-metallurgical alumina trihydrate particles

Processes for production of superfine white alumina trihydroxide (ATH) powd ers from actual plant Bayer liquor have been developed for use in non-metal lurgical applications. The specialty grade hydroxides suitable for non-meta llurgical application should conform to certain qualities such as fineness, purity, brightness, etc. The effect of a number of parameters such as prec ipitation temperature, amount of seed, seed surface area, precipitation tim e, soda content of pregnant liquor, modifier/additives, etc, on the precipi tation of ATH were studied to achieve the required fineness. At higher temp eratures, a purer product (with respect to soda) is obtained and particle s ize is increased, whereas at lower temperatures particle size is reduced an d the soda quantity in the product is increased. The effect of seed surface area and seed quantity are found to have marked effects on the productivit y and particle size of precipitated ATH. Higher seed specific surface area and higher seed quantity favoured productivity and finer particle size. Inc reased soda content in the pregnant liquor also enhanced productivity and f iner size particles. The single most important parameter that influenced th e precipitation process with respect to productivity, particle size and pur ity is the effect of a modifier, namely aluminium sulfate. ATH productivity is doubled when a modifier is added and the particle size is also reduced to similar to 1 mum An improvement in yield and finer size is also observed when organic additives are used. (C) 2001 Elsevier Science B.V. All rights reserved.