Synthesis of three dimensional graphene for sorption of oils and organic solvents

Abstract

Oil spill accidents release large amount of oil and organic liquids in the sea every year. This not only results in huge economic loss but also causes environmental pollution and ecological problems. Conventional mechanical methods of oil recovery need large amount of labor and equipment making the process very costly. Therefore, new oil remediation ways need to be developed. One such method which is attractive due to its low cost is the use of porous materials that can adsorb the oil. Many porous adsorbents are there in the market that include natural and synthetic inorganic and organic materials such as cotton, wool, zeolites, graphite, activated carbon and conjugated microporous polymers but these conventional material have various issues such as low adsorption capacity, high cost and complex synthesis methods. Graphene which is discovered recently in 2004 has been used in various applications such as composites, supercapacitors, electronics and sensors. However 2D graphene cannot be used for oil adsorption on large scale as its only one atomic layer thin. Graphene based three dimensional structures can be used for this purpose due to their high surface area and hydrophobic surface. In this work, 3D graphene is synthesized in two steps. First, graphene oxide solution is synthesized by oxidation of graphite precursor using modified hummers method. Afterwards, graphene hydrogel is formed by hydrothermal treatement of graphene oxide and freeze drying is done to obtain final dry graphene aerogel. Synthesized material is characterized using various morphological and chemical characterization techniques. SEM and nitrogen adsorption desorption tests shows that material has pores of various sizes and shapes made of interconnected graphene sheets. Oil adsorption experiments revealed that this materials can adsorb (40-70 g/g) of various oils and organic solvents which is higher than commercial sorbents. Adsorption rate is studied as most oil spreading occurs within first few hours of oil spill. This kinetic study shows very fast uptake of oils and organic solvents. Adsorbate can be removed from graphene aerogel by heating for several cycles without much change in adsorption capacity of material. These results of high adsorption capacity, fast rate of adsorption and reusability suggest that graphene based 3D material can be promising material for oil spill cleanup than commercial sorbents.

Date of Award	2015
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology