Mechanism study of synergistic aluminum extraction and purification by ammonium for high-value conversion of secondary aluminum dross

Secondary aluminum dross (SAD) constitutes a significant volume of hazardous solid waste with huge productions. Balancing extraction efficiency and purity within the current resourcing recovery process proves challenging and impedes high-value conversion. Consequently, the NH4HSO4-H2SO4 system was employed in this study to convert SAD into high-purity alumina nanoparticles, and the effect of ammonium was investigated. The results indicated that the leaching rate reached 85.98 % under the optimum conditions (170 degrees C, [Htot]= 12 mol/L, 16/1,6 h); the interaction of NH4+ and H+ with the oxygen atoms on the surface of Al2O3 was demonstrated to enhance the reactivity of the aluminum atoms by DFT calculations. The incorporation of NH4+ also facilitated the separation of aluminum by leveraging the temperature-dependent solubility characteristic of NH4Al(SO4)2. Molecular dynamics simulation revealed that NH4+ inhibits the diffusion rate of Al3+, thereby regulating the doping impurities such as Mg and Ca, and improving the purity of Al2O3 (95.29-99.64 %). Additionally, Nanoscale regulation was executed through the conversion of the NH4AlO(OH)HCO3 precursor and control. The sintering and agglomeration problems brought about by pyrolysis in atmospheres such as H2O and SO3 were avoided. This research provides reference for the high-value utilization of aluminum-containing solid waste.