Cigarette filters that dissolve themselves – completely
Cigarette filters are the product which is most often improperly disposed, by just throwing it away in the open instead of the ashtray. As a consequence, large amounts of cigarette butts now float in our oceans. To counteract this environmental pollution scientists are conducting research on self-degrading cigarette filters.
Between 340 and 680 million tons of cigarettes end up in the oceans, according to the World Health Organization. Max-Fabian Volhard, together with his supervisor, Prof. Dr. Thomas Jüstel, from FH Münster, are investing a chemical that should enable self-degradation of cigarette filters.
“The largest part of cigarette filters is cellulose acetate. This polymer conists of the basic molecule cellulose, modified with acetic acid. It is only poorly degradable because of the acetate-groups in the polymer”, Volhard explains. Now, an additional substance in the filters is supposed to change this. Specifically, titanium dioxide reacts to sunlight and acts as a catalyst. This material is won from the mineral anatase, which occurs naturally in the earth’s crust. When titanium dioxide is activated by the sunlight’s UV-A-rays, it forms radicals, which attack the polymeric structure of the cigarette filter, eventually completely dissolving it. The PhD student estimates a duration of five years until only water and carbon dioxide remain.
This sounds wonderful – in theory. The 32-year old Volhard is now researching how to actually implement titanium dioxide in cigarette filters. The main challenge is to modify the catalyst so that cellulose acetate is effectively degraded, all the while not being affected by the more than 4000 poisonous substance that form during smoking. He’s testing the reaction of the radicals in self-built photoreactor that produced the UV-spectrum of the sun.
“It fits well with my PhD thesis where I concern myself with microplastics from different perspectives”, Volhard says. He has previously shown in lab experiments that the concept of plastic degradation in contact with seawater works, which is why the idea of using a catalyst to dissolve chemical structures is nothing new for him. Several enterprises were very interested in this idea of his, but the high costs were seen as a major hurdle. For only one plastic bottle, some hundred milligrams of the catalysts are needed. This would result in a price increase that is too high in the plastic industry. For cigarettes however, that weigh between 5 and 6 grams, only a couple of milligrams of titanium dioxide would be required to fully degrade the butt. The use of the catalyst would only increase the price by about one cent. “And that was a conservative calculation, it is likely to be cheaper”, Jüstel adds. A cigarette in Germany costs 30 cents on average, a price slightly higher in Switzerland.
The work of the PhD student and his professor are right in line with the Fridays for future movement. They intend to increase awareness for their ideas and show with them that chemistry can contribute to environmental protection. Jüstel adds: “We are of course aware, that nothing will happen without political support.”
Source (German only): https://www.chemie.de/news/1162837/zigarettenfilter-die-sich-selbst-aufloesen.html