Intensifying gibbsite precipitation from sodium aluminate solution by adding a mixed seed

Abstract

Gibbsite precipitation from sodium aluminate solution was intensified by adding mixed industrial and self-prepared active seeds, and its mechanism was researched preliminarily. The interfacial properties of seed/aluminate solution were determined for separate industrial and active seed. Contact angles of seed/aluminate solution and the specific surface area of seeds were respectively measured by sessile drop and BET method, and the morphology and particle size of precipitates were recorded by SEM and laser diffraction. The results show that, compared with the industrial seed, the active seed has a better wettability, lower interfacial tension, and larger specific surface area, being conducive to enhancing gibbsite precipitation from sodium aluminate solution. SEM analysis of the precipitates indicates that the embedment and accumulation/agglomeration of extremely fine particles on the surface of coarse industrial seed can effectively control the content of fine particles in the precipitation product. With extra 3.1–4.6 g/L active seed, the gibbsite precipitation ratio was increased by 3.23%–3.92%. Moreover, the mass percentage of particles <45 μm in precipitation product has even a slight decrease compared with that for the traditional precipitation product or of the industrial seed itself. The result presented is favorable to developing an intensified gibbsite precipitation process for commercial alumina manufacture.