Study On Removal Of Hexavalent Chromium And Orange G From Aqueous Solutions By Aminosilane-functionalized Graphene Oxide

In recent years,the problems of heavy metals and dyes pollution have become more and more serious.And the hexavalent chromium and orange G,as the representative of the two kind of pollutants,have caused serious harm to the ecological environment and human health.Graphene oxide(GO)has been used as adsorbent in the field of water treatment due to its large specific surface area and abundant oxygen-containing functional groups.However,its practical application has been limited by the aggregation and separation problem during utilization.Thus,the functionalization of GO is the key to realize the efficient utilization of GO materials.In this study,aminosilane-functionalized graphene oxide(AS-GO)was successfully synthesized by simple one-step refluxing of graphene oxide(GO)with 3-aminopropyltriethoxysilane(AS).The structure and morphology of the obtained materials were explored by various characterization methods.The adsorption behavior of Cr(VI)and OG onto AS-GO was studied under various conditions,including solution pH,initial concentration,contact time,temperature and so on.The adsorption kinetics,thermodynamics and adsorption isotherm model were used to fit the adsorption process,and the possible removal mechanism was studied through the adsorption data and the characterization analysis.In addition,the regeneration performance of AS-GO was also evaluated.The results showed that AS successfully modified GO and produced the corresponding functional materials,namely AS-GO.The recombination between AS and GO not only prevented the aggregation of GO and introduced a large number of amino functional groups,but also made it easy to separate from aqueous solution.And it also had a good removal effect for Cr(VI)and OG in aqueous solutions.When AS-GO was used to remove Cr(VI),it was found that the initial pH of the solution had a great influence on the adsorption behavior of AS-GO.The Langmuir isotherm model and the pseudo-second-order kinetic model could better describe the adsorption process of Cr(VI)on AS-GO,and the data were fitted to obtain the maximum adsorption amount corresponding to 215.2 mg/g.Adsorption thermodynamics suggested that the adsorption onto AS-GO was a spontaneous and endothermic process.The presence of anions(Cl–,NO3– and PO43–)had no significant influence on the adsorption of Cr(VI)except SO42–.The possible mechanisms for Cr(VI)removal consisted of the adsorption and reduction of Cr(VI).In addition,regeneration experiments showed that AS-GO could be reused for the treatment of Cr(VI)in wastewater.When AS-GO was used to remove OG,it was found that the OG adsorption onto AS-GO was highly pH dependent.The process of OG adsorption onto AS-GO,a spontaneous endothermic reaction,could be better described by Langmuir isotherm model and pseudo-second-order kinetic model,and the data were fitted to obtain the maximum adsorption amount corresponding to the 435.8 mg/g(283 K),512.9 mg/g(298 K),576.6 mg/g(313 K).The increase of ionic strength in the solution could inhibit the adsorption process.The possible mechanism for OG removal was the combined action of electrostatic interaction,?-? interaction and hydrogen bond.Among these interactions,electrostatic interaction is the main adsorption mechanism.In addition,it also showed that AS-GO had a good regeneration performance.