20 May 2009
Sorting out recycling: new separation method for plastics
A new method for separating different types of waste plastic has been developed by Turkish
researchers. The ‘flotation’ method recovers PVC and PET, among the most difficult plastics to
separate from each other. It could help increase the amount of plastic waste that can be
recycled and ease pressure on bulging landfill sites.
Globally, 100 million tonnes of plastic are produced each year and much ends up as waste. Burning is not an
option as it releases toxic gases that can be hazardous to human health and the environment. Even landfilling may
release some hazardous chemicals, since the long-term products of degraded plastic are somewhat uncertain. In a
separate research project commissioned by the European Commission1, landfill was found to be an acceptable
intermediate means of disposing PVC products, but its use must be reduced in favour of more efficient waste
recovery strategies.
With space available for landfill continually shrinking, recycling is, theoretically, one of the most attractive
alternatives. Practically, however, plastic waste poses a problem because it needs to be sorted before recycling.
The polymers polyvinylchloride (PVC) and polyethylene terephthalate (PET) must be separated because crosscontamination can make the reprocessed plastic unusable.
The new separation method, so far only tested at laboratory-scale, recovers over 98 per cent of PVC from a
mixture of finely shredded PVC and PET. Importantly, the recovered material is 100 per cent pure PVC. Rather
lower recovery rates are shown for PET at 57 per cent, but the recovered product is still pure enough to be
recycled. The researchers found the ideal conditions for the process by changing factors such as temperature, size
of shredded particles and amount of sodium hydroxide added.
Flotation separation takes advantage of PET’s behaviour in water, which changes after being treated with a
strongly alkaline chemical such as sodium hydroxide. The behaviour of PVC, on the other hand, does not change.
Whilst PET sinks in water after treatment, PVC floats. On this basis, the researchers were able to recover the PVC
from a mixture in water by collecting the floating material. To demonstrate that their method worked, they used
different coloured plastics and weighed the amount of each colour they collected.
An estimated 20.4 per cent of plastics are recycled in Europe2; globally this figure is less than 3 per cent. The new
flotation method provides a means for PVC – one of the most widely used plastics – to be sorted and recycled like
other forms of waste, providing that an efficient and economically viable process can be developed at an industrial
scale.
1. Baitz et al. (2004). Life Cycle Assessment of PVC and of Principal Competing Materials. EUROPA. Available online:
http://ec.europa.eu/environment/waste/studies/pvc/lca_study.htm
2. See: http://www.plasticseurope.org/Content/Default.asp?PageName=openfile&DocRef=20081022-001
Source: Burat, F., Güney, A. and Olgaç Kangal, M. (2009). Selective separation of virgin and post-consumer polymers (PET and PVC) by
flotation method. Waste Management. 29(6):1807-1813.
Contact: [email protected]
Theme(s): Waste
Opinions expressed in this News Alert do not necessarily reflect those of the European Commission
To cite this article/service: "Science for Environment Policy": European Commission DG Environment News Alert Service, edited by
SCU, The University of the West of England, Bristol.
European Commission DG ENV
News Alert Issue 152
May 2009
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