BRAZIL – Metals play an essential role in technology: cars, cell phones, buildings, surgical materials, and many other products, all are made of metal.  However, while there is a continuing demand increase for metal materials, there is depletion of the rich ores metals sources such as Cassiterite (tin ore) and Chalcopyrite (copper ore). Thus, there is a growing concern about the impact of metal production on the environment.

In the last two decades, the world production of strategic metals (eg, copper, tin, gold and nickel) has been undergoing major changes in their processes. One of such changes is the replacement of pyrometallurgical processes – where the raw material is crafted in a high temperature furnace; has polluting problem.  Among the new metal production technology there is the hydrometallurgy, a process in which the ore containing the desired metal is dissolved in acid. Therefore, the metal of interest is sequestered with the use of a specific molecule, separated from the solution by extracting with organic solvents and ultimately recovered chemically with the help of the application of an electric current.

Currently, over 20% of world copper production is made in this way.  However, hydrometallurgy has its limitations. The main one is that organic solvents and sequestering agents cause damage to the environment.  Furthermore, the process of extraction of metals is complex and requires several steps.

A process developed by Brazilian scientists in 2012, has been further developed for an automation process called magnetic nanohidrometalurgia (NHM) which aims to improve the hydrometallurgy and solve those two limitations. The key is magnetite nanoparticles, tiny magnets whose surface may be prepared for capturing metals in aqueous medium.  So, just put a sample of these nanoparticles in a solution containing the metal of interest, shake and use a magnet to direct the nanoparticles to the surface of an electrode, where the metal is produced by passing an electric current.

After use, the same magnetic nanoparticles can be reused to capture more metal in an indefinite number of cycles, which makes the process more economical.

In addition to serving the production of metal alloys, the NHM technique can be employed in radiography recovery of silver and copper from old computer boards, among other utilities. The technique is yet to be applied in mining industries until it is patented and improved in the laboratory in order to enable the use of the technique in larger scales. Such attempt is currently ongoing.

Source: UOL