Preparation And Adsorption Performance Of MnO₂/Graphene-based Materials For Removal Of Dye And Heavy Metal From Aqueous Solution

Dyes and heavy metal ions are the main pollutants in polluted water and pose a long-term adverse threat to human health and natural ecosystems.The adsorption technique has received considerable interest due to its easy handling,comparably low cost,and no secondary pollution among the treatment of sewage.The traditional absorbent materials,such as activated carbon,molecular sieve,and polymer,suffer from low adsorption capacity and low efficiency,which limite the research and application of adsorption method.It is very important to solve the problem of water pollution for the research of adsorbent with high adsorption capacity.Graphene materials has attracted enormous attention because of its outstanding physical,special2D structure and increased external surface area.Unfortunately,there are difficulties separating the graphene from water as the favorable dispersibility and contacting with polar pollutants due to the hydrophobicity of graphene,which greatly limit its application in the field of adsorption.Graphene oxide equipped with lots of oxygen-containing functional groups,making it easy to contact with the polar and charged contaminants.But disadvantages,such as difficulties of separating the GO from water and the high cost also exist at the same time limit its application.This paper attempts to solve the above problems by means of combining functionalization of graphene oxide with manganese dioxide:?1?Graphene oxide?GO?,reduction of graphene oxide?rGO?,sulfonated graphene?SGO?and reduction of sulfonated graphene?rSGO?are prepared via diazotization reaction,and the adsorption experiments of dyes and heavy metal ions in water are carried out.The results showed that the maximum adsorption capacity of SGO to MB was 2530 mg/g,while the adsorption capacity of Pb²⁺was 415 mg/g,which was higher than the maximum adsorption capacity of GO,rGO,rSGO adsorption MB and Pb²⁺.Four types of graphene samples of isotherm and dynamic adsorption process were examined systematically,the results thought that the SGO to MB and Pb²⁺have higher adsorption efficiency and high adsorption capacity,which mainly due to the good dispersion and adsorption of SGO.?2?MnO₂ adsorbent was synthesized by hydrothermal reaction.Three MnO₂samples with different morphologies,such as nano rod,hollow prism,were prepared by regulating the pH value of hydrothermal solution.The effect of the pH,concentration and time on the adsorption of Pb²⁺was studied.The fitted adsorption kinetics model of Pb²⁺showed that the adsorption conforms to the quasi-secondary model,and the adsorption isotherm conforms to L model?Langmiur isothermal adsorption model?,which belongs to the single layer adsorption.The maximum adsorption capacity of Pb²⁺in the synthesized samples was 95.5mg g^-1,and the adsorption capacity of Pb²⁺was still maintained after 6 adsorption cycles.?3?The MnO₂@SGO was synthesized with the aforementioned sulfonated graphene and MnO₂ by water bath.The maximum adsorption capacity of Pb²⁺is the standard,and the optimum compound condition is determined by adjusting the raw ratio.The optimized 20-MnO₂@SGO was used to the adsorption of Pb²⁺,Cd²⁺and Cu²⁺in water,and the effect of concentration and time on adsorption performance was studied.The results showed that the adsorption kinetics of 20-MnO₂@SGO relatived to Pb²⁺,Cd²⁺and Cu²⁺in water were all in accordance with the quasi-secondary model,and the adsorption isotherm conforms to L model?Langmiur isothermal adsorption model?.The maximum adsorption capacity of Pb²⁺,Cd²⁺and Cu²⁺was:754.25 mg g^-1,124.87 mg g^-1 and 305.5mg g^-1,presenting a good comprehensive adsorption performance,which made them own the prospect and potential of practical application.