Gas and liquid state ammonia boosted in the hydrolysis of secondary aluminum dross

Abstract

This study elucidates the behavior of gas and liquid state ammonia generation in both short-term and long-term hydrolysis of secondary aluminum dross (SAD) powders, with detailed characterizations of the chemical structure and surface chemical state change of SAD particles during the hydrolysis reaction. Altered aluminum hydroxides, boehmite, bayerite, and gibbsite, were formed selectively on the surface of SAD in prolonged hydrolysis, which play principal roles in the progress of the hydrolysis reaction and generation of gas and liquid state ammonia. The influence of the reaction temperature on the hydrolysis of SAD is also clarified in advance, which demonstrates a distinguished reaction dynamics and mechanism. It was found that the gasification of dissolved liquid state ammonia is a predominant process, instead of a promoted hydrolysis of SAD for enhanced gas state ammonia production. Moreover, a novel and facile approach is introduced for boosting both gas and liquid state ammonia via beads mill-assisted hydrolysis of SAD powders. During beads mill process, the coverage of aluminum hydroxides on SAD was hindered via the mechanical breaking of particle surface. Continuous hydrolysis was then achieved through the further promoted reaction between water and the exposed new surface of SAD, which significantly enhances ammonia generation.