To the left paint from virgin material, to the right paint from recycled titanium dioxide.
Titanium dioxide is one of the more common substances used to produce white paint. But titanium dioxide is an expensive material that is extracted by refraction. In today's chemical processes for paint production, much titanium dioxide is wasted. In collaboration with AkzoNobel and Stena Recycling, Mikael Karlsson, at Chalmers Department of Chemistry and Chemical Engineering, has developed a method of recovering titanium dioxide through pyrolysis, a type of separation process that occurs through heating.
The method involves separating organic from inorganic material. Mikael Karlsson has primarily looked at titanium-based white paint because it does not contain as many other types of inorganic material as coloured paints.
"By my method, we can recycle titanium dioxide of sufficient quality to be used as a matte wall paint, which is one of the biggest uses for white paint," says Mikael Karlsson.
The PhD student project is linked to AkzoNobel's strategic work to reduce its carbon footprint by recycling white paint in their processes. But much titanium dioxide is also wasted today in colour cans that come from private individuals and companies to recycling centres. Manufacturers may be required to be responsible for recycling for the products they sell, which makes the method interesting even with regard to this type of waste.
The research has been done with the help of CCR and Mikael Karlsson sees the advantages with having the centre close at hand.
- I have been helped with different points of view during the course of work. Recycling is so wide that it is good to keep knowledge of others close. I am basically a paint technician and my work here has been very interdisciplinary with access to both industry and different research disciplines, "says Mikael Karlsson.
One possible next step in process development is to investigate paint that contains more inorganic materials than just titanium dioxide so that these may be separated to create as efficient value chain as possible.
On May 4, Mikael Karlsson defends his thesis Recycling of TiO2 pigment from waste paint: process development, surface analysis and characterization.
Text and photo: Mats Tiborn