High-density polyethylene is one of the most frequently used plastics in the manufacture of containers for the storage of hazardous substances. After their use, these containers are classed as hazardous waste. In order to recycle them, any remaining hazardous residues must first be eliminated.
In Europe, traditional cleaning systems involve a three-step cleaning and rinsing process that is applied to the ground plastic waste, known as triple washing and rinsing procedure. The process uses large quantities of water, a large amount of energy, chemical cleaning products. This procedure thereby generates a large volume of wastewater that requires subsequent treatment. At the end of this process, the ground plastic material is free of hazardous substances and ready for use, yet the aggressive nature of this cleaning procedure usually undermines the quality of the plastic itself. This is why this treated plastic is often used in applications of low added value.
LIFE EXTRUCLEAN: Project was launched in order to mitigate the drawbacks of this conventional recycling process, improve the final quality of the plastic and enable the material to be used in its original application.
LIFE EXTRUCLEAN: is a European project involving five Spanish companies, which have joined forces to develop a more efficient decontamination and recycling process for polyethylene plastic packages that have contained hazardous substances.
This technology is based on the use of supercritical carbon dioxide; supercritical fluids have been successfully used by the food, wood and leather industries in extraction processes. Supercritical carbon dioxide is inert, inexpensive, highly-available and is not harmful to the environment. It has also been shown to be highly efficient in the removal of hazardous substances, arising from organic solvents and pesticides. This makes this technology perfect for the removal of contaminating substances.
In the LIFE EXTRUCLEAN process, two of the three washing and drying stages, used on the traditional decontamination methods have been eliminated, employing supercritical carbon dioxide at the extrusion stage during the polyethylene recycling process.
This new process reduces water consumption, the use of cleaning agents and energy use. It results in less wastewater and its associated sludge. After being used, the CO2 is purified and reused in the cleaning process, preventing further emissions into the atmosphere. Because carbon dioxide is an inert gas, most of the mechanical properties of the decontaminated plastic are conserved. This means that it can be reused in applications calling for better quality plastic, such as in manufacture of new containers for hazardous materials.
These helps to close the life cycle of these plastic materials. At the pilot plant scale, this new technology was found to be nearly 70 % more effective than other traditional decontamination procedures.
These results will be corroborated at the last phase of the project, where the process will be applied at the industrial scale.
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Toronto Newsroom
