Design And Synthesis Of Carbon Aerogels For Recyclable Oil Adsoption And Recovery

Oil pollution has become one of the most urgent global environment problems due to the frequent accidents during offshore oil production or marine transportation and discharge of industrial oily wastewater.Therefore,porous carbon materials which can efficiently collect and separate oils from water are attracting worldwide attention in recent years.Among them,carbon aerogels are considered to be the most promising adsorbent materials because of their three-dimensional porous structure,high porosity and environmental protection.However,the conventional carbon aerogels still have disadvantages such as low adsorption capacity,low recovery,poor recycleability,and inability to respond to the environment.In this work,the high elasticity graphene aerogels and carbon foams were chosen as two carbon aerogels in order to prepare oil/water separation materials with great adsorption and recovery performance.In addition,the mechanism of smart adsorption and desorption was studied.The main work and results of the thesis are as follows:1.Developing a synthetic method to obtain low-density and high-elasticity carbon aerogel.Ultralight graphene aerogels were prepared via hydrothermal reduction method by using graphene oxide as precursor and cyclohexane as the pore former,with the density of ca.9.4 mg cm-3.The structure and density of graphene aerogels were adjusted by changing the ratio of cyclohexane and graphene oxide.In order to enhance the elasticity of graphene aerogels,carbon nanotubes(CNT)were added into graphene oxide to prepare CNT-coated graphene aerogels.Moreover,a highly elastic carbon foam was prepared from a melamine sponge by a one-step pyrolysis method.The as-prepared carbon foam showed an adsorption capacity of 72-140 g g-1 and the adsorbed oil can be recovered by extrusion.The first recovery ratio is about 67%,and the amount of desorption is the same as adsorption in the subsequent 9 cycles,showing good desorption efficiency and cycle performance.2.Developing a pH-responsive carbon foam.By grafting poly(4-vinylpyridine)(P4VP)onto the surface of carbon foam using atom transfer radical polymerization,the obtained smart foam presented a pH responsiveness,changing superhydrophilic and superhydrophobic surface according to the pH value.Thus,the smart responsive carbon foam could fast adsorb the oil in neutral solution(pH=7)with high oil-absorption capacity of 62-120 g g-1 and desorb mostly all the adsorbed oil in acidic solution(pH=1).In addition,only 3%loss was observed for oil(chloroform)adsorption and recovery after successive reuses of up to 15 cycles,which demonstrated great recyclability of the materials.