Removal Process and Kinetics of Nitrogen and Chlorine Removal from Black Aluminum Dross

Black aluminum dross (BAD) is a hazardous solid waste generated during the recycling process of aluminum scrap. The mixture of phases in BAD is complex, and the effective removal of harmful elements such as nitrogen and chlorine is the critical factor for enabling its utilization. In this paper, two processes for removing nitrogen and chlorine from BAD are proposed: 'washing dechlorination–roasting denitrification' and 'alkali-catalyzed denitrification and dechlorination.' A single-factor experimental method was used to optimize the influencing factors of the two processes, and the methods were compared to obtain the best denitrification and dechlorination process conditions. The results show that the alkali-catalyzed denitrification and dechlorination method for treating BAD has a higher nitrogen and chlorine removal rate and a lower cost. The optimal denitrification and dechlorination conditions are a temperature of 90 °C, a reaction time of 300 min, a 6:1 liquid–solid ratio (mL:g), a stirring speed of 300 r/min, and a particle size smaller than 150 mesh. Under optimal leaching conditions, the nitrogen and chlorine removal rates are 93.48% and 99.84%, respectively. In addition, the kinetic behavior of aluminum nitride in BAD under uncatalyzed and catalyzed conditions was studied. Under uncatalyzed conditions, the leaching process of aluminum nitride conforms to the unreacted nucleus model of mixed control of the chemical reaction and diffusion, with an apparent activation energy of Ea = 40.51 kJ/mol. Under alkali-catalyzed conditions, the leaching process of aluminum nitride is diffusion-controlled, and its apparent activation energy is Ea = 27.66 kJ/mol.