Preparation Of Grapheme-based Composites And Their Adsorption Efficiency For Environmental Contaminants

Graphene oxide?GO?has a large specific surface area,abundant?electrons,edge oxygen-containing functional groups and easy modification,making it become a highly efficient adsorbent and widely used in the removal of environmental pollutants.In this paper,two graphene-based composites were prepared using GO as the base material and applied to adsorb environmental pollutants,the corresponding mechanism of adsorption was investigated.The obtained results have important application value and theoretical significance for the synthesis of macrocyclic polyamine and polymeric ionic liquid as well as the removal of environmental pollutants.The main contents are as follows:5,7,7,12,14,14-Hexamethyl-1,4,8,11-tetraazacyclotetradecane?Me₆[14]aneN₄?and5,12-dimethyl-7,14-Diphenyl-1,4,8,11-tetraazacyclotetradecane?Me₂Ph₂[14]aneN₄?were prepared and bonded to the GO surface to obtain two grapheme composites including GO@Me₆[14]aneN₄ and G@Me₂Ph₂[14]aneN₄.The composites were characterized by FT-IR,SEM,TEM and EDX analysis.The adsorption properties of two composite materials as adsorbents towards environmental pollutants were investigated.The results showed that the adsorption performance of GO@Me₆[14]aneN₄ is higher than G@Me₂Ph₂[14]aneN₄.p-Nitroaniline?PNA?was chosen as analytes to investigate the adsorption kinetics and isotherms of GO@Me₆[14]aneN₄.The adsorption behavior of GO@Me₆[14]aneN₄ for PNA accorded with the second-order kinetic adsorption model.The adsorption process conformed to the Langmuir adsorption model and belonged to monolayer adsorption with a maximum adsorption capacity of 150.15 mg/g.The adsorption mechanism is mainly attributed to the?-?interaction and hydrogen bonding interaction.In order to explore the adsorption mechanism of GO@Me₆[14]aneN₄ further and expand its wide applicability as an adsorbent other,organic pollutants such as nitrophenols and inorganic metal ions were selected as analytes.The results showed that the adsorption performance of GO@Me₆[14]aneN₄ for nitrophenols and inorganic metal ions was excellent and there is no competitive adsorption.The adsorption mechanism involved in electrostatic interaction and complexation besides?-?interaction and hydrogen bonding interaction.Magnetic grapheme?G-Fe₃O₄?and polymeric ionic liquid-magnetic mesoporous silica nanoparticles graphene?G-Fe₃O₄@SiO₂-PIL?were prepared and characterized by SEM,TEM,XRD,VSM and BET analysis.G-Fe₃O₄ was used as an adsorbent for adsorption of dyes in environmental pollutants.The results showed that the adsorption efficiencies of G-Fe₃O₄ towards cationic dyes methylene blue,rhodamine B,ketidine,malachite green and neutral red were 100.0%,99.5%,99.6%,97.4%and 97.9%,respectively.The adsorption efficiencies towards anionic dye carmine and amaranth were only 54.6%and 36.4%,respectively.Due to the?-?interaction between graphene and dyes,and the electrostatic interaction between the negatively charged carboxyl groups at the edge of graphene and the anionic/cationic dyes,G-Fe₃O₄ have a higher adsorption efficiency towards cationic dyes than anionic dyes.The adsorption efficiencies of G-Fe₃O₄@SiO₂-PIL as adsorbent towards environmental pollutants were also investigated.The adsorption efficiencies of G-Fe₃O₄@SiO₂-PIL towards cationic dyes Rhodamine B,methylene blue and anionic dyes Carmine,Amaranth were 100.0%,97.1%,100.0%and 100.0%,respectively.Compared with G-Fe₃O₄,G-Fe₃O₄@SiO₂-PIL has a higher adsorption efficiency towards anionic dyes because a large number of imidazole groups in the introduced PIL are rich in positive charge and have electrostatic interaction with anionic dyes.In order to further study the adsorption properties of G-Fe₃O₄@SiO₂-PIL,the adsorption efficiencies towards plasticizer,antibacterial agent,antibiotic and humic acid were also discussed.Above all,the adsorption of G-Fe₃O₄@SiO₂-PIL towards analytes was ascribed to the?-?interaction between graphene and dyes,the hydrophobicity and hydrogen bonding between G-Fe₃O₄@SiO₂-PIL and analytes,the electrostatic attraction interaction between the negatively charged carboxyl group at the graphene edge and cationic dyes and the electrostatic repulsion interaction between the positive charge imidazole group of polymeric ionic liquid in the mesoporous inner wall and the anionic dyes.