Research On Extraction And Purification Technology Of Graphene Oxide

Graphene oxide(GO)has a planar structure similar to graphene,and the surface contains abundant oxygen-containing functional groups,mainly hydroxyl,carboxyl and epoxy groups.The special structure makes GO possess unique physical and chemical properties,which makes GO widely used in many fields.However,in the preparation process of GO,the purification step is a bottleneck problem.GO is usually purified by washing with water or dialysis,but washing with water takes a long time.And the formation of a very stable and large amount of colloidal solution during the washing process,makes it difficult to separate GO by centrifugation,adds difficulty to the purification process,and makes industrial production costs high.Simultaneous dialysis may take more time than multiple washing-centrifugation cycles.This article proposes a new idea for GO purification to reduce energy consumption,improve purification efficiency and economic benefits.In this study,the improved Hummers method was used to prepare graphite oxide containing impurities,and then the graphite oxide was purified by centrifugal water washing and extraction methods.The purified materials were subjected to vacuum distillation or washing with acetone to remove water and extractant from graphene oxide.The products purified by the centrifugal method were named WGO60 and WGO90,and the products obtained by the extraction method were named MGO200 and W3AT4.By observing the phase separation in the purification process,analyzing the metal ion content and acidity changes in the water phase,the suitable extractant for the extraction method is selected and the purification process conditions are selected.Para-Methoxyacetophenone(p-MOAP)was selected as the extractant,because it can make the phase separation speed in the purification process faster and relatively stable;in the extraction stage,the purification speed is dominant,and the contents of potassium ion and manganese ion were 21.86 mg and 38.38 mg,respectively in the water phase,which were higher than the water phase results obtained by centrifugation,19.26 mg and 34.20 mg;the pH of the water phase changed rapidly during the purification process.After five washings,the pH was5.87 and was greater than the centrifugation result 4.03,and the content of metal ions in all water phases after purification is higher than the result of centrifugal method.After a similar analysis process,the final selection of extraction and purification process conditions are: the ratio of the amount of extractant to the volume of the raw material is 1:1,the ratio of water consumption to the volume of the raw material in the washing process is 1:1,the oscillation temperature is 40 ℃,and the oscillation time is 5 min,the vacuum distillation temperature is 200 ℃.Using Fourier infrared spectroscopy to study the mode of action between GO and p-MOAP,it is found that the two may interact through hydrogen bonds.Using scanning electron microscopy,transmission electron microscopy,X-ray diffraction,Raman spectroscopy and other analytical methods to characterize WGO60,MGO200 and W3AT4,the graphene oxide lamellar structure with wrinkles and undulations can be seen.Analysis of X-ray diffraction and Raman spectroscopy results can show that MGO200 has been reduced to a certain extent,and the degree of graphitization is relatively high.Although W3AT4 has also been partially reduced,the degree of oxidation is still relatively high.The dispersibility of WGO60 and MGO200 in organic solvents is found to be more stable in dispersion in N,N-dimethylformamide,ethylene glycol,and N-methylpyrrolidone.