Graphene, a nanomaterial consisting of a one-atom-thick carbon layer, is widely used in the energy sector, including in the production of batteries and capacitors. It is also used in the creation of nanofluids, which can be useful for purifying wastewater. To do this, nanofluids containing graphene nanoparticles are heated under the influence of light, and the heat they accumulate is used for evaporation and later for the condensation of water.
Until recently, scientists did not have a complete understanding of how light with different wavelengths affects the heating of graphene and its derivatives. The scientists from MPEI have attempted to explore the mechanics of this process. The authors created an experimental installation to compare the evaporation of graphene nanofluid (distilled water with graphene nanoflakes) and ordinary distilled water under the influence of blue, green, red, near and far infrared light.
The experiment showed that far infrared light is absorbed mainly by water, which is why the graphene nanofluid and distilled water heated up to the same extent during the 1.5-hour experiment. In the case of irradiation with green and near infrared light, the water barely absorbed the rays and thus did not heat up, whereas the temperature of the graphene liquid rose from 15.5 degrees Celsius to 18.5 degrees Celsius. Finally, irradiation with blue light did not change the temperature of any of the samples, while red light did not affect graphene but cooled the water.
The authors also found that under exposure to sunlight the evaporation rate from the surface of the graphene nanofluid was 68–95% higher than in the case of pure water. Therefore, graphene materials can be used to quickly obtain drinking water.
“A combination of water and graphite flakes can serve as a good working fluid that can absorb a wide range of wavelengths for the direct conversion of solar radiation into thermal energy. The data we have obtained will help solve many applied problems in such areas as solar energy and conventional heating systems. However, to do this, we need to successfully resolve issues related to maintaining the stability of nanofluids,” Inna Mikhailova, candidate of technical sciences, is quoted as saying by the Russian Science Foundation.
