Summary: Metal sensing processes fall into three types, each of which is being used or explored to improve recovery. Pyrometallurgy, hydrometallurgy, and biotechnology are three of them.
Metal recycling has a long and illustrious history. Metals were saved and reprocessed in large quantities to serve the war effort as early as WWII. The simplicity with which steel may be magnetically sorted is one of the reasons for this interest. Modern recycling machinery can identify many metals, while non-ferrous metal separation requires more advanced technology.
Separating ferrous and non-ferrous metals is the most basic type of metal sorting. Magnets are attracted to ferrous metals because they contain iron, and this makes it simple to extract iron and steel from a waste stream. Cranes equipped with electromagnets can move large chunks of scrap. Auto salvage yards are the most common place to get this type of rusted machinery.
Municipal waste streams contain easily identifiable ferrous metals and aluminum portions, primarily from abandoned food and beverage containers, in mixed or partially sorted waste streams. Paper is usually removed first from mixed streams, leaving metals and plastics. Metals are affected when electric currents are induced across the remaining components, while polymers are unaffected. Eddy current separation is the term for this phenomenon. The majority of materials recovery facilities now use this type of metal recycling technology. Even though metal is not magnetic, eddy currents can lift it, allowing the plastics to be removed and the aluminum to be removed.
Because of the worth of copper, lead, gold, silver, platinum, and palladium, recovering precious metals from electronic waste becomes economically viable if enough scrap can be collected. This procedure necessitates the use of more technologically advanced metal recycling machinery. In large facilities, the use of sensors to identify metals via x-ray and infrared scanning is becoming more common.
Pre-shredding the objects to minimize the size of the fragments is the best way to achieve large-scale metal recycling of mixed materials. This increases the surface area and aids in the separation of smaller fractions. Metal sensing processes fall into three types, each of which is being used or explored to improve recovery. Pyrometallurgy, hydrometallurgy, and biotechnology are three of them.
Pyrometallurgical methods are used to heat combined metals and separate the fractions while they are still molten. The melting points of metals differ, allowing for this separation. Various chemicals to mixed waste, usually in a water solution, are known as hydrometallurgy. The metals will be removed from the slurry individually due to the numerous regulated interactions with them. Biotechnology is another exciting option, as it realizes that some microorganisms will seek out and eat specific metals, which can then be extracted.