Mechanism Analysis And Adsorption Properties Of GOs Prepared By Improved Hummers Method

Graphene oxide(GOs)is an important derivative of graphene,which contains a large number of oxygen-containing functional groups on its surface and edge.It is easy to be surface modified and further functionalized,which greatly expands its application field.Hummers method is the most commonly used method to prepare GOs at present.The composition of oxidant and reaction conditions used in the preparation process affect the chemical structure and the number of functional groups of the final product of GOs.The purpose of this study was to analyze the formation mechanism of GOs prepared by Hummers method,so as to realize the regulation of GOs oxidation degree,study the adsorption characteristics and adsorption mechanism of GOs.The research results can provide data and theoretical support for further modification and application of GOs.The main research contents and conclusions are as follows:Based on the traditional Hummer method,the modified group with no sodium nitrate and increased potassium permanganate dosage was used for comparison experiment,the experimental products of graphite oxide(GO)prepared by Hummers method were taken out at different stages,and the effects of oxidant composition,oxidant concentration and reaction time and temperature on graphite oxidation process were studied.The phased evolution of graphite structure during oxidation process was analyzed.On the basis of the formation mechanism of GOs,GOs was prepared by Hummers method.The effects of oxidizing agent concentration and oxidation reaction time at intermediate temperature on the oxidation degree of GOs products were studied.Methylene blue(MB)was used to verify the adsorption capacity of GOs with different oxidation degrees,and the optimal group was selected to study the adsorption mechanism of GOs to MB.The study of graphite oxidation mechanism shows that the graphite intercalation reaction mainly occurs in the low temperature stage,and sodium nitrate only plays an obvious auxiliary role in the intercalation stage,but its effect on the whole oxidation process of GO is weak.The further oxidation of graphite mainly occurs at the intermediate temperature stage,in which potassium permanganate plays a leading role.At this stage,the hydroxyl content of graphite oxide samples increases greatly from19% to 35%.At the high temperature stage,water molecules and the remaining potassium permanganate react together to initiate deep oxidation of the graphite sample and begin to destroy the carbon layer structure of the graphite.The surface of different GOs samples were rich in oxygen-containing functional groups.Increasing the amount of oxidant and the reaction time at medium temperature would increase the oxidation degree of GOs samples,and the oxygen content of GOs samples could be controlled between 33% and 43%.The increase of oxidation degree is accompanied by the increase of defect density.The weight loss of GOs is obviously dependent on the composition of elements.GOc-3 has the maximum weight loss due to the increase of oxygen content,while GOa-1 has high thermal stability.In the study on the adsorption performance of GOs,it is found that the higher the oxidation degree of GOS,the better the adsorption effect on MB,the maximum adsorption capacity of GOb-3 is 0.1988 mg/mg.The isothermal adsorption process of GOs for MB was consistent with Langmuir isothermal adsorption model and quasi-second-order kinetic model,indicating that GOs isothermal adsorption process for MB was monomolecular chemisorption.