Graphene aerogels as efficient adsorbers of water pollutants and their effect of drying methods.

Environmental accidents highlight the need for the development of efficient materials that can be employed to eliminate pollutants including crude oil and its derivatives, as well as toxic organic solvents. In recent years, a wide variety of advanced materials has been investigated to assist in the purification process of environmentally compromised regions, with the principal contestants being graphene-based structures. This study describes the synthesis of graphene aerogels with two methods and determines their efficiency as adsorbents of several water pollutants. The main difference between the two synthesis routes is the use of freeze-drying in the first case, and ambient pressure drying in the latter. Raman spectroscopy, Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and contact angle measurements are employed here for the characterisation of the samples. The as-prepared aerogels have been found to act as photocatalysts of aqueous dye solutions like methylene blue and Orange G, while they were also evaluated as adsorbents of organic solvents (acetone, ethanol and methanol), and, oils like pump oil, castor oil, silicone oil, as well. The results presented here show that the freeze-drying approach provides materials with better adsorption efficiency for the most of the examined pollutants, however, the energy and cost-saving advantages of ambient-pressure-drying could offset the adsorption advantages of the former case.