Preparation Of Graphene Oxide/polymer Composite Films For Removal Of Organic Pollutants From Aqueous Solutions

With industrial development,clean and safe water resources become less that is one of the most pervasive worldwide problems.The efficient removal of organic pollutants by graphene oxide（GO）has attracted much attention.However,it is difficult to separate GO adsorbents from the pollutant solution after adsorption,and only cationic organic pollutants can be removed from the aqueous solution using GO.These problems lead to great limitations in the application of GO.In order to solve the above problems,in this work,a simple and inexpensive layer-by-layer assembly technique was employed to deposit multilayer films of polymeric microgels and GO on solid substrates for removal of organic pollutants.The sduty contents of the work are summaried as the two parts:First,the poly（allylamine hydrochloride）（PAH）was cross-linked with borax to prepare the PAH-B,then（PAH-B/GO）*5 films were fabricated by layer-by-layer deposition of PAH-B and GO on solid substrates.The obtained（PAH-B/GO）*5 films were employed to remove doxycycline hydrochloride（DH）from aqueous solutions.The results showed that the saturated adsorption capacity of（PAH-B/GO）*5 films was 466.4 mg·g^-1 for doxycycline hydrochloride at c _DH=12 mg·L^-1 and 298 K.In addition,the adsorption capacity increased with the increase of temperature.The presence of cationic ions inhibited the adsorption of the（PAH-B/GO）*5 films for DH.The detailed studies have shown that adsorption kinetics and isotherms can be described by the pseudo-second-order model and the Temkin isotherm model,respectively.Futhermore,the thermodynamics of adsorption showed that the adsorption of the doxycycline hydrochloride on the（PAH-B/GO）*5 films was a physisorption process and driven by entropy.The regeneration analysis demonstrated that after ten successive cycles of adsorption-desorption experiments,the removal efficiency of（PAH-B/GO）*5 films for DH could be retained about original 65%.Hence,the composite films of PAH-B/GO are satisfied with the requirements of practical application.2.Layer-by-Layer assembly of PAHD-B/GO composite films for removal of cationic,anionic and nonionic dyes from aqueous solutionsPolymer microgels of chemically cross-linked poly（allylamine hydrochloride）（PAH）and dextran（named PAHD）were firt fabricated according to previous report.In order to increase the amount of PAHD deposited during film preparation,PAHD microgels were further crosslinked with borax to prepare PAHD-borax（PAHD-B）microgels.After that,（PAHD-B/GO）*5 films were fabricated by layer-by-layer deposition of PAHD-B and GO on solid substrates.The obtained（PAHD-B/GO）*5 films were used as the adsorbent for removal of cationic,anionic and nonionic dyes from aqueous solutions.The results showed that the saturated adsorption capacity of（PAHD-B/GO）*5 films for carmine,mulberry red and monascus colours are 337.4,376.3 and 488.5 mg·g^-1,respectively at 298 K and 1.0 mg·m L^-1 of the initial dye concentration.In addition,the adsorption capacity increased with the increase of temperature.The detailed studies revealed that the adsorption kinetics and isotherms can be well-described by pseudo-second-order model and Langmuir isotherm model,respectively.In addition,adsorption thermodynamics indicated that the adsorption of carmine and mulberry red onto the（PAHD-B/GO）*5 films was a physisorption process and driven by entropy.Moreover,the PAHD-B/GO multilayer films could be well regenerated in 0.9%Na Cl solution.The mechanism of adsorption of three dyes on（PAHD-B/GO）*5 films was explained at the molecular level.