Thermally Activated Al(OH)₃: Part I—Morphology and Porosity Evaluation

Abstract

Aluminum hydroxide is an essential material for the industrial production of ceramics (especially insulators and refractories), desiccants, absorbents, flame retardants, filers for plastics and rubbers, catalysts, and various construction materials. The calcination process of Al(OH)3 first induces dehydration and, finally, results in α-Al2O3 formation. Nevertheless, this process contains various intermediary steps and has been proven to be complicated due to the development of numerous transitional alumina. Each step of the investigation is vital for the entire process because the final properties of materials based on aluminum trihydroxide are determined by their phase composition, morphology, porosity, etc. In this paper, five dried, milled, and size-classified aluminum hydroxide specimens were thermally treated at 260, 300, and 400 °C; then, they were studied in order to identify the effects of temperature on their properties, such as particle morphology, specific surface area, pore size, and pore distribution. The major oxide compounds identified in all samples were characteristic of bauxite—namely, Al2O3 * 3H2O, SiO2, Fe2O3, Na2O, and CaO. Particles with smaller sizes (2/g and their small pore width (3–3.5 nm).

Keywords

• alumina
• gibbsite
• thermal treatment
• morphology
• absorbent