An international consortium are using the world’s most popular soft drink to produce a host of carbon-based storage materials
With 1.9 billion servings sold per day worldwide, Coca Cola® is the most popular soft drink on the planet. But a consortium, led by scientists at Curtin University in Australia, haven’t been using their stockpile to quench their thirst. They see this fizzy drink a potential source of high-quality carbon materials that could help us battle climate change and the energy crisis.
Writing in a recent issue of Carbon [DOI: 10.1016/ j.carbon.2017.02.030], they report on the synthesis of heteroatoms-doped, high surface area, microporous activated carbon (AC) materials from waste Coca Cola®. ACs have been in widespread industrial use since World War II, and today, can be found in everything from air filtering and water treatment, to the processing of metals. As part of a wider question on energy and the environment, ACs extracted from waste biomass have also been proposed for use in CO2 capture, and as supercapacitor electrodes.
The Curtin team chose Coca Cola® as their waste product because, with 11 g of sugar in every 100 ml, it is a rich source of carbon. Thanks to the addition of flavours and colours, it also contains plenty of nitrogen, sulphur and phosphorous; and unlike other biomass, its composition doesn’t vary. The researchers processed their expired Coca Cola® in two stages: (1) it was hydrothermally carbonised to produce porous, non-active carbon spheres – referred to as NACS, and (2) the spheres were either collected, or went on to be activated (via calcination) by either potassium hydroxide (KOH) or zinc chloride (ZnCl2), at various mass ratios.
One sample (AC activated with KOH/HC 4:1) showed a CO2 adsorption capacity of 5.22 mmol g-1 at ambient conditions, which compares favourably to conventional carbon capture processes (~ 3 mmol g-1). The same sample also displayed an impressive adsorption capacity at the pressures displayed by flue gases in coal-fired power plants. Further results suggest that the AC could be reused multiple times, without impacting its capacity. The electrical storage properties of another sample (AC activated with ZnCl2/HC 3:1) were very impressive – its capacitance of 352.7 F g-1 was attributed to its high surface area. The same material was shown to be a robust capacitor too – after 2000 cycles, it retained 91% of this initial capacitance.
So, this paper suggests that while Coca Cola® might be bad for your teeth, it might be really, really good for anyone interested in storing CO2 or electrical energy!
Y. Boyjoo, Y. Cheng, H. Zhong, H. Tian, J. Pan, V.K. Pareek, S. P. Jiang, J.F. Lamonier, M. Jaroniec, J. Liu, “From waste Coca Cola® to activated carbons with impressive capabilities for CO2 adsorption and supercapacitors.” Carbon 116 (2017) 490-499. DOI: 10.1016/j.carbon.2017.02.030