Study On The Adsorption Properties And Mechanism Of Azacrown Ether-functionalized Graphene Oxide For Thallium

Thallium(Tl)is a non-essential and toxic metal to animals and plants.The frequent water pollutions with Tl from the mineral minining and smelting activities have been highly concerned.Thus,developments for new materials and technologies to remove Tl in water environment has been a research hot.Graphene is the most ideal two-dimensional nano-material at present,and its discovery enriches the types of carbon materials,then rapidly promotes the research on various forms of graphene.Functionalization is the most important means to realize the dispersion,dissolution and molding of graphene.Graphene can also be endowed with new properties by introducing specific functional groups,thus further expanding its application fields and providing new opportunities for the fields of chemistry and materials.Therefore,we functionalized GO with aza-crown ethers,and got functionalized graphene oxide(FGO).This paper aimed at the removal efficiency of Tl in solution by FGO and the material combined with sodium hypochlorite oxidant,and the associated influence factors.Furtherfore,the adsorption mechanism wasstudied by various characterization methods.Firstly,the adsorption efficiency of Tl in solution by GO and FGO was studied,and the effects of pH value,reaction temperature and adsorption dose on the removal efficiency of Tl were discussed.Through the adsorption kinetics and isothermal adsorption model,the adsorption mechanism was explored by the model before and after adsorption by Gaussian09W software combined with the characterization of practical instruments.The results showed that under the condition of room temperature,the best adsorption effect can be achieved when the pH was 9 and the adsorption dose was 0.08 g/L,the removal rate of Tl(I)with concentration of 10 mg/L can reach to 85.88%.FGO removal of Tl from solution was more suitable to use pseudo-second-order kinetic model(R²=988)in adsorption kinetics,and Langmuir model(R²=0.991)was more suitable in isothermal adsorption model.The characterization of FT-IR and XPS showed that Tl(I)mainly neutralizes oxygen in FGO and belongs to chemical adsorption.The rationality and authenticity of the experimental results can be verified by combining the theoretical calculation and analysis of the electrostatic potential,the average local ionization energy and the adsorption energy from Gaussian09W.Secondly,the change of adsorption efficiency of Tl(I)removal by FGO combined with Na Cl O oxidant was studied.It was found that the effect of Tl(I)removal by Na Cl O alone was very poor,and the adsorption efficiency was only 29%.However,after the combination of FGO material,the adsorption efficiency was greatly improved.Under the same experimental conditions,the adsorption efficiency of Tl(I)removal by sodium hypochlorite oxidant added with 20m M can reach to 98.9%,and the coexisting ions Ca²⁺,Mg²⁺and Na⁺had little effect on the adsorption reaction.The removal of Tl(I)by FGO combined with oxidant was more consistent with the pseudo-first-order kinetic model(R²=0.952)in adsorption kinetics and Langmuir(R²=0.997)model in isothermal adsorption.The results showed that the reaction principlewas the joint action of chemical adsorption and oxidative precipitation.FGO is simple to make,and less dosage can achieve good results as an adsorbent to remove Tl(I),which is economical and effective.The present study provides a new technical approach for emergency detection or treatment of actual Tl-containing wastewater.