Investigation On The Adsorption Of Organic Dyes And Metal Ions On The Photoreduced Graphene Oxide

Today the shortage of fresh water and serious water pollution have become one of the most important challenges around the world.As the main pollutants in water,organic dyes and heavy metal ions lead great harm to human health.The application of graphene and its derivatives in desalination and sewage treatment has drawn increasing attention because of their unique two-dimensional one-atom thickness and excellent physicochemical properties.Firstly,graphene-related materials could be used as an effective separation membrane due to their chemical and mechanical stability,flexibility and most importantly,their one-atom thickness.Secondly,because of the high specific surface area,graphene and its derivatives also can be used as a kind of excellent adsorbent for organic pollutants,which can adsorpt contaminants by hydrogen bonding,hydrophobic interaction,van der Waals interaction,electrostatic interaction,?-?stacking interaction,complexation and so on.What's more,adsorption is the most commonly used in sewage treatment because of its versatility,wide applicability and economic feasibility.Graphene and its derivatives,Graphene Oxide?GO?and Reduced Graphene Oxide?RGO?,have different surface properties because of the hybrid structure of carbon atoms,thus the adsorption effect of graphene materials for different pollutants is quite different.Investigations and comparisons of the adsorption capacities of graphene and its dericatives have great significance on the improvement of pollutants treatment,and thus we can translate them into practical applications.Our main works are as follows:1?Here photoreduced GO?PRGO?was prepared by solar light irradiation,the obtained GO and PRGO were characterized by UV-visible absorption,Raman spectra,Fourier transform infrared spectroscopy?FTIR?,X-ray photoelectron spectroscopy?XPS?,atomic force microscope?AFM?,scanning electron microscope?SEM?and transmission electron microscope?TEM?,respectively.2?The adsorption kinetics of GO and PRGO for cationic dye methylene blue?MB?and anionic dye acid orange?OII?were analyzed.To get insight into the adsorption processes and determine the kinetic parameters,the experimental data are fitted by three different kinetic models:the pseudo-first order model,pseudo-second order model and intraparticle diffusion model,respectively.The adsorption isotherm models of MB,OII and Pb²⁺were also analyzed and fitted by Langmuir,Freundlich and Temkin models.The results show that with the increase of the reduction degree for PRGO,the maximum adsorption capacity of OII was improved by 4 folds for PRGO with solar light irradiation duration time of 72 h.The initial adsorption rate of PRGO is even enhanced by 33 folds.However,the maximum adsorption capacity and the initial adsorption rate of PRGO for MB were a little decreased.The adsorption of OII,MB and Pb²⁺for GO and PRGO was a monolayer exothermic process.As a good adsorbent material,the adsorption capacities of other anionic dyes were also significantly enhanced by PRGO.And the PRGO has the good recycling and regenerating ability.3?The effects of GO and PRGO on the co-adsorption for anionic dye OII-cationic dye MB mixed system and anionic dye OII-Pb²⁺mixed system were studied.In the mixed system of OII-MB,the total adsorption capacities of GO and PRGO for the two kinds of dyes were larger than the sum of the adsorption capacity for single adsorption system.In addition,the adsorption capacities of GO and PRGO have little change for Pb²⁺in OII-Pb²⁺mixed systems,however,the adsorption capacities of OII have greatly increased.