Aluminium dross, a byproduct of the

aluminium smelting Aluminium smelting is the process of extracting aluminium from its oxide, alumina, generally by the Hall-Héroult process. Alumina is extracted from the ore bauxite by means of the Bayer process at an List of alumina refineries, alumina refinery. ...

process, can be mechanically recycled to separate the residual

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

metal from the aluminium oxide.

Thermo-mechanical metal extraction

The mechanical process of

recycling Recycling is the process of converting waste materials into new materials and objects. The recovery of energy from waste materials is often included in this concept. The recyclability of a material depends on its ability to reacquire the p ...

does not use any toxic chemicals previously used in the process of extracting the valuable aluminium in the dross.

Hot dross processing Hot or the acronym HOT may refer to: Food and drink *Pungency, in food, a spicy or hot quality *Hot, a wine tasting descriptor Places *Hot district, a district of Chiang Mai province, Thailand ** Hot subdistrict, a sub-district of Hot Distric ...

is a system whereby the majority of metal is recovered without chemically reducing the aluminium oxides. The

dross Dross is a mass of solid impurities floating on a molten metal or dispersed in the metal, such as in wrought iron. It forms on the surface of low- melting-point metals such as tin, lead, zinc or aluminium or alloys by oxidation of the metal. For ...

is first crushed then separated into aluminium metal rich particles and aluminium oxide rich particles based on density. The metal rich particles are then melted in a furnace to remove the remaining oxide particles.

Mechanical extraction vs chemical

The recovery of aluminium metal from dross has traditionally caused severe environmental issue with highly alkaline waste waters, a waste product that is rich in waste flux and that evolves ammonia gas on contact with water and can spontaneously combust if allowed to get wet A novel method developed in New Zealand claims to be an environmentally sensitive method, and is not toxic and different from previous methods which resulted in a concentrated highly toxic

salt cake Sodium sulfate (also known as sodium sulphate or sulfate of soda) is the inorganic compound with formula Na2SO4 as well as several related hydrates. All forms are white solids that are highly soluble in water. With an annual production of 6 milli ...

residue.

An example of a recycling facility

An operating aluminium dross recycling plant (news coverage) https://www.youtube.com/watch?v=t_z8jlDgdCU

Products that can be made with the residual

A variety of products can be made from the residual aluminium dross after it is recycled into aluminium oxide. See more information on aluminium oxide. Aluminium oxide Aluminium oxide has a variety of industrial uses which includes being used in

paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...

dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...

explosives An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An expl ...

, and

fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...

Dross recycling is different

Aluminium dross recycling is a completely different process to strictly

aluminium recycling Aluminium recycling is the process by which scrap aluminium can be reused in products after its initial production. The process involves simply re-melting the metal, which is far less expensive and energy-intensive than creating new aluminium thr ...

. Aluminium recycling is where pure aluminium metal products (previously used in another form) are re-melted into aluminium

ingot An ingot is a piece of relatively pure material, usually metal, that is cast into a shape suitable for further processing. In steelmaking, it is the first step among semi-finished casting products. Ingots usually require a second procedure of sh ...

s and then re-used to new aluminium products. While aluminium dross recycling is where the dross, a byproduct of the smelting process in the creation of aluminium from

bauxite Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO(O ...

, can be mechanically recycled thus separating the residual aluminium metal from the aluminium oxide.

References

{{reflist Aluminium Recycling