Research On Controllable Reduction Of Graphene Oxide And Its Adsorption Properties

Graphene oxide?GO?and reduced graphene oxide?rGO?are two-dimensional?2D?materials derived from graphite oxide.The oxygen content on GO surfaces directly affects their physical and chemical properties,such as conductivity,hydrophilicity,suspension stability,adsorption performance and ion sieving ability.All these properties are influenced by the type and content of oxygen groups in GO surface.The reduction of GO is an effective means to regulate the number and type of surface oxygen functional groups.Many researchers also try to adjust the reduction degree of GO.However,most of them use chemical reductants and other methods to reduce GO.Their results show that the reduction process is difficult to precise control because of the harsh reduction conditions,and inefficiency and large-scale preparation has been not achieved,especially for the oxygen content is still relatively high reduction control.These defects greatly affect the need for rGO for exact applications.For example,graphene oxide?GO?,as a two-dimensional derivative of graphene,exhibits excellent adsorption properties for most heavy metals in water due to its rich oxygen-containing functional groups and electronic structure.However,it is because of the rich oxygen-containing groups of GO that it has strong hydrophilic characteristics,which will lead to the swelling of GO in solution and greatly hinder its application.rGO can solve the swelling problem,so it will be the main research direction to find a suitable degree of reduction for the adsorption application of GO.In this paper,electron beam irradiation and vacuum thermal reduction were used to reduce GO,and the adsorption properties of rGO were studied.The results are as follows:?1?The precise reduction of GO was achieved by simple and efficient green electron beam irradiation?EBI?reduction method.Under the condition of controlling irradiation dose,a series of rGOs with a C/O ratio from 1.6to 4.5 were obtained..In addition,a single oxygen group,i.e.epoxy group or carbonyl group,could be mainly retained in rGO.By controlling the oxygen content,the interlayer spacing of rGO can be changed from 9.6 to 7.4?.The prepared rGO has excellent adsorption effect on Pb?II?ions.The maximum adsorption amount of rGO reaches 194.76 mg g^-1 at the irradiation dose of 5 kGy,which indicates that the proportion of oxygen groups is important for improving the adsorption of rGO in aqueous solution.?2?Controllable reduction of rGO was also achieved by thermal reduction of GO at 120-210?,and the C/O ratio from2.62 to 5.1,which was higher than that of electron beam reduction,indicating that thermal reduction had a better effect on oxygen removal.At this temperature gradient,the reduced rGO can retain a single C=O,and the interlayer spacing of GO decreases from 8 to 3.5?.When the temperature is higher than 180?,GO can be completely reduced.The results are closer to graphite.The adsorption effect of rGO on Pb?II?decreases with the increase of temperature,and is less than that of GO(173.8 mg g^-1).?3?In a word,electron beam reduction is feasible for obtaining rGO with low reduction degree,while thermal reduction is feasible for obtaining rGO with high reduction degree,and both methods can solve the problem of GO swelling in water.