The Indian Institute of Technology (IIT) Mandi researchers have developed a method that can transform plastic into hydrogen when exposed to light.
Plastics, most of which are derived from petroleum, are not biodegradable, that is, they cannot be easily broken down into harmless products. It is said that most of the 4.9 billion tonnes of plastics ever produced would end up in landfills, threatening human health and the environment.
“The ideal path to effective annihilation of plastics is to degrade them into useful chemicals. The generation of hydrogen from plastics is particularly useful because the gas is considered the most practical non-polluting fuel of the future, said Dr Prem Fexil Siril, Professor, School of Basic Sciences, IIT Mandi.
The team developed a photocatalyst that can efficiently convert plastics into hydrogen and other useful chemicals when exposed to light.
The photocatalyst combines iron oxide in the form of nanoparticles, with a conducting polymer-polypyrrole.
The team found that mixing iron oxide nanoparticles with pyrrole resulted in strong visible-light-induced photocatalytic activity. Photocatalysts usually need ultraviolet light for activation and therefore require special bulbs. But the new catalyst can function simply with sunlight.
The findings, published in the Journal of Environmental Chemical Engineering, showed that there was 100 per cent degradation within four hours when they used a catalyst in which about 4 per cent weight iron oxide was present in the polypyrrole matrix.
The team then tested this catalyst on polylactic acid (PLA) – a plastic that is extensively used in food packaging, textiles, medical articles and cosmetics. They found that hydrogen evolved during the breakdown of PLA when the catalyst was exposed to visible light.
“While the generation of hydrogen is good in itself, we are even more excited about the absence of carbon dioxide,” Siril said.
While most other photocatalysts that have been developed for hydrogen generation from plastics release the greenhouse gas as a by-product, the IIT Mandi catalyst did not but instead co-produced useful chemicals such as lactic acid, formic acid and acetic acid.
The use of the photocatalyst does not stop with plastic treatment. It can also be used for photoreforming of food waste and other biomass and also for breaking down pollutants in water.