Preparation Of Functional Reduced Graphene Oxide Hydrogels And Their Application In Wastewater Treatment

Nanoparticles?NPs?display overwhelming superiority in catalysis towards the corresponding bulk-phase materials,and exhibit potential application for treating environmental pollution and solving energy dilemma.However,NPs tend to aggregate together in catalytic reaction to reduce their surface areas,which leads to an apparent decrease of catalytic performance.Loading NPs on a suitable support is the most commonly used strategy to solve this issue.Therefore,selection and optimization of catalyst supports has become very important issues.Graphene is an ideal catalyst support owing to its extraordinary electron mobility,high surface area,good mechanical property and special adsorption character.Graphene oxide nanosheets?GS?are always choosen to be the precursors of graphene.However,graphenene nanosheets always tend to restack,leading to an obvious reduction of their superior intrinsic property.In addition,the organic pollutants can't be degraded completely only by traditional chemical oxidation.On the basis of the above statements,we have introduced a simple preparation procedure to assemble two-dimensional?2D?GS into three-dimensional?3D?r GS hydrogels,not only increasing the surface area of the catalysts,but also improving the dispersity and decreasing the size of NPs,eventually improve the catalyst activity.It is the strong adsorption effect of the porous structure of hydrogels that can accelerate the reacton solution's mass transport and diffusion,eventually increase the degradation speed.Furthermore,the introduction of magenetic NPs and protection by two supports could reduce the loss of catalysts and improve the hydrogels' reusability.The research details are as follows:First,rGS/Fe₂O₃/polypyrrole?PPy?ternary hydrogels were synthetized in one-step.The formation mechanism of hydrogels was studied through morphology comparison between different samples.In order to evaluate catalytic performance,the r GS/Fe₂O₃/PPy ternary hydrogel were applied to degrade the methyl blue?MB?by Fenton reactions.With the catalysts and H₂O₂ dosage increased in a certain range,and the initial MB concentration decreased,the MB degradation rate speeded up.Because of paramagnetism,the catalysts could be easily seprated from the reaction solution.After repeating the degradation reaction 4 times,the catalysts did not exhibit significant loss of catalytic activity.Second,r GS/Fe₂O₃-Pd Pt/PPy quinary hydrogels were prepared by loading Pd Pt alloys onto graphene hydrogels in one-step.After freeze-drying,qunary hydrogels exhibited hierarchical porous structure,its adsorption on organic dyes was better than the heat-dried.Besides,the Pd Pt alloy NPs dispersed highly with small size.The r GS/Fe₂O₃-Pd Pt/PPy quinary hydrogels showed excellent catalytic performance in catalyzed reduction of 4-nitrophenol?4-NP?.Third,rGS/Fe₂O₃/N-doped carbon nanosheets?NCS?ternary hydrogels were prepared by two-step.The morphology structure and component of hydrogels were characterized.The hydrogels were used to catalyze the photo-Fenton reacton on Rhodamine B?Rh B?degradation.Due to the synergistic effect between the enhanced adsorption of hydrogels and the high catalytic activity of Fe₂O₃ NPs,the hydrogels exihibited superior removal ability.Owing to the incorporation of magenetic Fe₂O₃ NPs,the catalysts could be quickly recycled by using external magnet;and they exhibited good reusability in cycle catalytic test.