As today is World Environment Day, we take a look at some innovations in the recycling of plastic waste, a major threat to our environment. The Technical University Delft in the Netherlands is working on separating types of plastic better, while the Dutch company Ioniqa developed a way to chemically clean plastics and recycle coloured PET.

Plastic recycling can reduce the amount of waste, as well as reduce the demand for oil, but there are still many hurdles to take. The process be complicated, considering that there are so many variations. There are some 250 types of plastic used, each with their own characteristics and function, which with the current recycling facilities can only be separated into four of five broad categories of polymers. Melting down mixed plastic degrades the material. If separation is too expensive, plastic materials are often burned.

Separating plastic waste
The aim of the TU Delft is to separate plastic waste into as many as fifty to a hundred different raw materials. They developed Magnetic Density Separation (MDS) method, which separates waste according to density by means of a sink-float method. The electronic and plastic waste is shredded into small particles which are put in a bath of ferromagnetic fluid. Specially designed magnets are then used to change the density in the fluid, so the particles will start to float at different levels according to their density.

MDS was developed 10 years ago, but is still being refined. Working together with TU Twente, TU Eindhoven, Radboud University and Utrecht University, the researchers are now concentrating on increasing the laminarity of flow, superconducting magnets, nanofluids, and magnetic fields, all to make the process better.

Aside from the type of plastic, the plastic also needs to be separated by colour. Cameras detect plastics with a certain colour, but the problem is to mechanically remove this flake of plastic from the pile. Currently, this is done using air drafts with a diameter of 5mm, but because of the thickness of this draft, other flakes of plastic might be taken along. Rather than using air, researchers at the TU Delft use ultra thin water beams, with which they can separate the flakes much more accurately, leaving pure plastics that can easily be recycled.

Recycled PET plastic
We use PET plastic for a whole range of products, from food to detergents. These plastics have to be separated, because a bottle that contained for instance ammonia is not safe to be reuse as food packaging. The company Ioniqa created a process to chemically clean the material, leaving a pure resource that is safe for food packaging.

They also claim to be able to remove colour from for instance soda bottles. The recycled material is supposed to be of the same quality as virgin plastic.

Ioniqa has recently opened a testing facility in collaboration with food giant Unilever.

Photos: TU Delft