New technique uses steam to make smelly plastics recyclable
Although chemicals, foods and other odorous substances are often sold in recyclable plastic containers, sometimes the smells absorbed by the plastic make it unsuitable for recycling. A new process, however, is claimed to get the stink out.
Developed by Prof. Andrés Fullana and researcher Andrea Cabanes, from Spain's University of Alicante, the technique reportedly removes volatile organic compounds (VOCs) that are emitted by a plastic container's contents and absorbed by its polymer matrix. According to the researchers, such a deodorizing process is currently impossible via conventional washing and recycling methods.
The procedure begins with used plastic containers being sorted, separated and pre-conditioned, after which they're crushed into small particles, chemically-washed with a special soap, rinsed and then dried. It's in the final "steam distillation" step that the actual odor-removal takes place.
Also known as "steam stripping," steam distillation basically involves passing steam through a material, within a column. As that steam rises, it carries VOCs that were in the material with it. When the steam subsequently condenses within a collector flask, the resulting VOC-laden liquid water can be separated and disposed of. That said, the process can also be used to obtain useful products, such as essential oils that are distilled from plant leaves.
The U Alicante technique has recently been patented, with five companies now expressing interest in commercializing the technology.
"There is a need to recycle in an efficient and environmentally-friendly way [this] plastic waste for later use as raw material, as well as to reduce its presence in landfills, reduce production costs in the industries of the sector, and to increase the added value of the product," says Cabanes.
Source: University of Alicante