Preparation Of Three-dimensional Graphene Material And Its Application In Waste Water Treatment Adsorption Properties

Printing and dyeing industry,petroleum industry,catering industry,machinery manufacturing industry and other industries produced more wastewater into the water body.These wastewater containing dyes and oil pollution will pollute the ecological environment.Pollutants enter the body through the food chain,endanger human health,even inducing carcinogenic and teratogenic effect.Therefore,it is extremely important to purify the wastewater effectively,so that the quality of discharged water can meet the national standard of sewage discharge.In this paper,the modified Hummers method was used to control the structure and surface active groups of graphite oxide?GO?by controlling the dosage of oxidizing agent and the reaction time of medium and low temperature.The reaction conditions of the GO with rich surface active groups were obtained.GO obtained from different amounts of oxidants was used as precursor.Three dimensional reduced graphene oxide?3D r GOs?was obtained by hydrothermal method.The influence of the oxidation degree of precursor GO on the microstructure,structure and adsorption properties of 3D r GOs was investigated.The degree of oxidation of the GO with the best adsorption properties of 3D r GOs was obtained.The graphene oxide?GOs?was prepared by stripping the GO with the oxidation degree as precursor.GOs was modified by L-Cysteine?L-Cys?by atmospheric pressure water bath,the functional three-dimensional graphene oxide aerogel?3D GOL?adsorption material was obtained.3D GOL was applied to the purification and treatment of printing and dyeing wastewater and oily wastewater.The study shows that the effect of oxidant dosage on GO structure and surface group is the most significant,followed by middle temperature time and low temperature time.When the amount of oxidizing agent is three times of graphite and the reaction time of medium and low temperature is 60 and 90 min,the oxygen containing functional group of GO is dominated by hydroxyl group.And the content is 42%,which is about 75.21%of the total oxygen functional group,which is far higher than other oxygen functional groups.At this time,the cation exchange capacity is 473.3 mmo L·?100 g?^-1.The precursor with different oxidation degree has great influence on the morphology,structure and adsorption properties of 3D r GOs adsorbent prepared by hydrothermal method.GO with low oxidation degree can not form stable three-dimensional structure after hydrothermal reaction,and the graphene formed on the microcosmic layer is multi-layered and massive.Fully oxidized GO can form stable porous network three-dimensional structure by hydrothermal reaction.However,the 3D r GOs formed by GO with peroxidation after hydrothermal reaction presents a network structure of fragmentation fragments and crosslinking.The adsorption capacity of3D r GOs increases first and then decreases with the increase of the oxidation degree of GO precursor.And the adsorption capacity is best when the mass ratio of KMn O₄ and graphite is 3,and the maximum adsorption capacity for rhodamine B?Rh B?,methylene blue?MB?and methyl violet?MV?can be up to 90.9,145.4 and 237.4 mg·g^-1respectively.The adsorption force mainly depends on the?bond of the six membered ring in the 3D rGOs structure and the?bond in the dye aromatic ring to form the?-?conjugation.Under normal atmospheric water bath,functional modification of GOs with L-Cys can promote GOs cross-linking to form 3D GOL with porous network structure.3D GOL has good mechanical properties and good thermal stability.The reactions between L-Cys and GOs,such as oxidation-reduction reaction of sulfhydryl with hydroxyl groups,dehydration of sulfhydryl with carboxyl groups,and amidation reaction of amino with carboxyl groups promoted the crosslinking of GOs nanosheets,and induced the GOs nanosheets to assemble into a 3D porous framework.The adsorption capacity of 3D GOL on cationic dye MB(226.5mg·g^-1)is greater than that of orange G(54.6 mg·g^-1)with anionic dye,which is suitable for the purification treatment of cationic dye wastewater.The adsorption of MB and OG on the surface of 3D GOL is a single layer reversible adsorption,which is the reaction of entropy increasing and spontaneous endothermic absorption.The adsorption process is in accordance with the pseudo-first-order kinetic model and the Langmuir isothermal model.3D GOL rich porous network structure can provide a large number of adsorption sites for oil pollution,and the adsorption capacity for oil pollution is up to 45 mg·g^-1.After 8 cycles of regeneration,the adsorption of 3D and GOL can reach more than 90%of the initial adsorption capacity and has good reproducible performance.