25.1.2018
White as a colour creates an impression of freshness and cleanness. Therefore optical whiteners, or brighteners, as they are also called, are used in a range of products. If you are reading this text in a printed version rather than on the web, the paper most probably contains some kind of brightener that makes the paper appear whiter and the contrast with the print colour greater.
Whiteners are not the same thing as bleaching agents, although they are often used simultaneously with them. Bleaching agents break down dirt through chemical reactions, while whiteners spread onto the surface of the material, giving it a shine. When your white shirt gives off a bluish glow at the nightclub, it is the effect of the whitener that you are seeing.
“Optical brighteners are chemical substances which collect UV radiation and turn it into a visible blue light. As a result, things look cleaner,” says Pedro Fardim, professor of biomass chemical engineering at Åbo Akademi University.
Optical brighteners are also included in washing detergents, cosmetics and medical technology. Their use is very widespread, but far from unproblematic. In the worst case, they may change the human hormone cycle and cause diseases such as ADHD or cancer, but, on the other hand the molecules are unstable, so their impact is relatively short-lived. Furthermore, whiteners are usually transported in liquid form, which is both expensive and a waste of water.
However, the greatest environmental problem is probably that whiteners decompose slowly and do not fasten very well.
“Traditional whiteners consist of a negatively-charged sulphonic acid, and textile fibres, for example, usually also have a negatively-charged surface. This means that the whitener must be chemically linked to the fibres, which is usually done with the application of salts containing calcium or magnesium ions,” Fardim explains.
“They are added to a solution and some of the whitener fastens onto the textiles. The rest enters into the water cycle along with the rinsing water, and this is a big problem, as the whitener is not biologically degradable.”
New technology
It is possible to substitute the optical brighteners with natural products that are less harmful to humans and the environment. Fardim’s research group at Åbo Akademi University has been granted 800,000 euros by Tekes, the Finnish Funding Agency for Innovation, for setting up commercial activities over the next two years. In other words, their research is at a relatively advanced stage.
The research group has developed a new technology; a natural product based on polysaccharides deriving from trees. It uses a component with a charge that can be adapted according to the purpose, and a dye is added which makes it possible to adjust the degree and hue of the whitener’s brightness.
“We can manipulate the component to be positive or negative, and we can regulate the number of photoactive groups. In this way we can get it to fasten better and adjust the brightness,” says Fardim.
“The component is biologically degradable and powder-based, which makes it easy to use, transport and store. One of the big motivators is that we can refine various forms of wood and plant waste – for example industrial by-products – as raw materials by extracting and modifying polysaccharides from the waste.”
Further analyses
In addition to creating the basis for an enterprise during the two years to come, the research group will conduct further analyses of how the product decomposes, whether it has toxic effects in cells, and how it acts in the human body. The fact that it is a natural product does not automatically mean that it is environmentally friendly and healthy.
“I come from Brazil where we have many snakes with a venom which is natural, but it can still kill you. Everything natural is not automatically good. Therefore we must approach this systematically, with a life-cycle analysis, to ascertain its cytotoxicity and biocompatibility. Yes, our component is a natural polymer, but we’re adding a functionality which is synthetic and does not originate in nature,” Fardim says.
“But most polysaccharides do have a good biocompatibility, and they’re non-toxic and biologically degradable. There is an abundance of polysaccharides in nature and we have a large machinery of microorganisms that digest them, so in that sense we’re starting from a very safe platform. Nevertheless, we must work through it systematically.”
The aim is to have a series of products in 2020 which are safe enough to be tested for consumer use before being launched on the market.
“Our most important contribution here is what we can do to protect the water cycle. We don’t expect all material to come from Finnish forests, but the concept is to be Finnish and it should motivate larger global companies to look at the potential in natural products and waste for their chemical solutions. Because there are plenty of possibilities for improving their safety.”
