Preparation and Properties of Pseudo-boehmite Obtained from High-Alumina Fly Ash by a Sintering–CO2 Decomposition Process

Abstract

A sintering–CO2 decomposition process for preparation of pseudo-boehmite is proposed for clean valorization of high-alumina fly ash. The effects of different synthesis conditions on the crystal structure and textual properties of the pseudo-boehmite were studied systematically. The results showed that the main product was NaAlCO3(OH)2 when the decomposition terminal pH was below 9.5, and the optimal terminal pH for the pseudo-boehmite (PB) product was 10.5. The optimal aging time was 4 h, and the peptization ratio of PB reached 97.5% when the aging temperature was 90°C. Under decomposition conditions of 30 g/L initial alumina concentration in liquid phase and temperature of 40°C, followed by 4 h of aging treatment, the specific surface area of PB was 425 m2/g. The pore volume of PB product reached 0.6920 cm3/g at decomposition conditions of 40 g/L and 30°C.