Recycling 2.0, molecular sorting to scavenge raw materials from wastes

Electronic wastes consist of material matrices that are difficult to recycle; molecular sorting could be the solution.derek Gavey/CC BY 2.0

Even if design for disassembly made all the strides for which one could hope, the fact remains that high-tech requires more components consisting of composite materials. Glued, melted, laminated, or otherwise mixed together to give properties the old-fashioned nuts, bolts, and solder approach could never offer, these matrices of different materials make recycling hard.

Take, for example, a modern circuit board. Many of the precious materials, and toxic metals, live sandwiched tightly into layers of resin. Resources like the metal tantalum have already been identified as critical to meet increasing demand. And with an estimated 24 mg of gold per mobile device, over 100,000 ounces of gold could be recovered from the 129 million disposed in 2009 according to US EPA statistics (only 8% of which were recycled anyhow!) Even the resins could become scarce as we run out of the oil which serves as a raw material for many modern plastics.

Molecular sorting project

ink molecule separationnudomarinero/CC BY-SA 2.0 Simple ink molecule separation experiment

Recycling methods that can separate these complex materials down to their individual molecular constituents -- without destructive techniques such as burning -- are needed to recover the valuable resources in our wastes. The quest for such technology drives the Fraunhofer Beyond Tomorrow project "Molecular Sorting for Resource Efficiency."

Molecular sorting can be relatively simple, as the experiment shown in the image above demonstrates. These strips of color were created by touching a common felt-tip marker into a solution of solvent on chromatography paper. The different colors visible demonstrate that the ink in the marker consists of several different colors, effectively different dye molecules that have traveled along the paper at different speeds, resulting in separation of the original color into its component colors.

molecular separation for chemical BY 2.0
Separation for chemical analysis

Separation methods perfected to enable identification of chemicals support many a modern Sherlock Holmes. Identification of DNA patterns and quality control of industrial processes are just a few modern technologies that rely on separation techniques.

But efficient recycling increases the challenges, presenting various chemicals in complex hybrid components, and requiring that their separation should not require destructive methods.

Brighter glass and smarter wood

Two of the initial areas of focus include glass and wood recycling. The glass used in solar energy applications must have high purity, especially low iron contamination, to optimize light transmission. As low-iron raw materials dwindle, scientists are working on ways of separating iron molecules out of the melted glass.

Treated woods hinder wood recycling opportunities, because wood treatment for preservation or fire resistance contaminates the wood with toxic chemicals. The project uses automated chemical identification processes to separate wood into various treatment options, such as supercritical fluid dissolution of the contaminants. When combustion or pyrolysis techniques must be used, the process still recovers the materials such as copper that were used to treat the wood originally.

According to the Fraunhofer Institute:

Plastics, adhesives, cellulose, basic chemicals and other products can also be obtained from the cleaned wood. In about three years’ time the researchers aim to produce a demonstrator sorting unit for scrap wood which will use a cascading process to recover a large part of the wood that is wasted today .

Obviously, achieving automated and cost effective processes to get precious resources out of wastes in as good or better condition than when they went in will require a lot of development -- and may not even be possible until raw materials become even more scarce (and hence expensive) than they are today. But it is nice to know someone is thinking now about how we can do it when we run out of the stuff our world runs on.

See also: Fukushima radiation reveals migratory habits of Pacific bluefin tuna

Tags: E-Waste | Recycling | Reusability


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