The interaction of water and the alumina surface is comprehensively reviewed. Water can be incorporated in the alumina crystal structure resulting in the formation of aluminum hydroxides such as gibbsite. Alumina dissolves into water to an extent that depends primarily upon the solution pH and temperature. The soluble Al (III)aq species (hydrolysis products) likewise depend upon the solution pH, temperature, aluminum, and other salt concentrations. The development of charge on the surface of alumina is controlled by amphoteric surface ionization reactions. The charging behavior of both alumina powders and single crystal faces is compared. The differences can be explained by the reactivities of different types of surface hydroxyl groups. The substantial difference in surface charging behavior of single crystal sapphire and alumina powders indicates that experiments and modeling conducted on single crystals is of limited use in predicting suspension behavior. The atomic scale structure of the hydroxylated sapphire (0001) basal plane is nearly identical to the gibbsite (001) basal plane. The observed surface structures are consistent with the charging behavior of the surfaces. The role of surface charge on the adsorption of processing additives is briefly discussed. How surface charge and processing additives at the alumina aqueous solution interface influence surface forces between particles is reviewed. The influence of these forces on suspension properties such as rheological behavior is outlined. The importance of controlling these behaviors to improve colloidal ceramic powder processing is stressed.

Charging Behavior at the Alumina–Water Interface and Implications for Ceramic Processing

A review of the literature over the past 30 years on the processing of nickel laterites by high temperature acid leaching has been carried out to provide a better understanding of the mineralogy, leaching process chemistry and effect of operating conditions on nickel recovery, residue properties and scaling. Particular attention is paid to the leaching experience of the commercial Moa Bay plant and to the recently reported testwork and flowsheets associated with the three Western Australia lalerite plants that will be operating in 1999. It is shown that laterites can vary significantly in their mineralogy according to location, climate and depth, and that the main host minerals for nickel and cobalt can be either goethite (iron oxide) or nontronite (clay) or manganese oxides. The mechanism of leaching involves acid dissolution of the host mineral lattice followed by hydrolysis and precipitation (transformation) of a variety of insoluble oxides and sulphates of iron, aluminium and silica under the...

Pressure Acid Leaching of Nickel Laterites: A Review

Leaching and separation of Co and Mn from electrode materials of spent lithium-ion batteries using hydrochloric acid: Laboratory and pilot scale study

Aluminium salt slag characterization and utilization - A review

Research and industrialization progress of recovering alumina from fly ash: A concise review

Production of η-alumina from waste aluminium dross

Acid dissolution of alumina from waste aluminium dross

A pyro-hydrometallurgical process for the recovery of alumina from waste aluminium dross

Rheological behaviour of nickel laterite suspensions

Precipitation of boehmite in sodium aluminate liquor

I.N. Bhattacharya

Papers

Production of η-alumina from waste aluminium dross

Acid dissolution of alumina from waste aluminium dross

A pyro-hydrometallurgical process for the recovery of alumina from waste aluminium dross

Rheological behaviour of nickel laterite suspensions

Precipitation of boehmite in sodium aluminate liquor