Recycling secondary aluminum dross to make building materials: A review

Secondary aluminum dross (SAD) is consisted of alumina, aluminum nitride (AlN), salts and heavy metal oxides. Over 6.5 million tons of SAD is discharged in the world annually. Currently, recycling SAD to make building materials is a promising way of waste recovery. Building materials made from SAD can be divided into structure materials and insulation materials. Structure materials inherits the high strength, fire resistance and chemical stability of alumina in SAD. The products include cement, bricks, ceramics and glass ceramics. Insulation materials are manufactured by utilizing reactivity of AlN in SAD. AlN can hydrolyze or be oxidized to release gas. Insulation materials include porous bricks, porous ceramics and porous glass ceramics. Environmental and economic benefits analysis was conducted on structure materials and insulation materials made from SAD. Ceramics and porous ceramics were taken as evaluation objects. Manufacturing a ton of ceramics and porous ceramics from SAD attained profits of 370.2 and 388.2 dollars, and reduced carbon emissions of 746.2 and 261.5 kg. Therefore, recycling SAD to make ceramics possessed a better carbon reduction. In order to further reduce carbon emission and utilize AlN in SAD, we proposed a novel idea of manufacturing metal/alumina composite ceramics from SAD and metallurgical solid waste. AlN in SAD reduced the metal oxides into alloy, which can strengthen the alumina ceramics. We should clarify the thermodynamics and kinetics of AlN reducing metal oxides and strengthening mechanisms of metal/alumina composite ceramics.