Hazardous characteristics and transformation mechanism in hydrometallurgical disposing strategy of secondary aluminum dross

Abstract

To further understand the transformation behavior of active phase during hydrometallurgical disposal, and then provide theoretical guidance for the recovery and utilization of secondary aluminum dross (SAD) valuable resource, factors affecting the harmlessness efficiency, transformation behavior of active phase and kinetics of the leaching process investigated. The results indicate that harmless residues can be achieved when treated at the conditions of liquid-solid ratio of 5, leaching temperature of 80 ℃, extracting time of 4 h and SAD particle size less than 2000 μm. The capacity of emissing gas, which is composed of small amount of ammonia, methane and dominant proportion of hydrogen, increases with the enlargement of particle size. The small particles with relative high proportion of aluminum carbide and aluminum nitride tend to release more methane and ammonia. During hydrometallurgical process, the active substances generate intermediate phase of aluminum hydroxide spontaneously, cover on the interface of SAD particles, and then react with acidic or alkaline medium. The hydrolysis of active phases and the dissolution of fluoride follow the Avrami-Erofeyev Model and internal diffusion model, respectively, while the rate both of them are all controlled by diffusion. This work is hopeful for providing a deep insight into disposal and comprehensive utilization of SAD.