Construction Of Molybdenum Disulfide-Based Nanohybrid Materials And Study The Adsorption Performance For Ag(Ⅰ)

Due to the excellent ductility,electrical and thermal conductivity,corrosion resistance and dazzling metallic luster as well as stable chemical property,silver（Ag）has been widely used in modern industries such as electronics and electrical appliances,jewelry,medicine and catalysis.However,the wide application of Ag and the compounds has accelerated the excessive consumption of Ag resources and also produced a large amount of industrial wastewater containing Ag（Ⅰ）,which poses a serious threat to the ecosystem and human health.Therefore,it’s urgent need to design an adsorbent with excellent performance and stable structure for the removal and recovery of Ag（Ⅰ）from wastewater.Molybdenum disulfide（MoS₂）,a typical layered transition metal sulfide,has a sandwich structure of S-Mo-S.MoS₂ has rich sulfur groups and sulfur vacancies on the surface and edges,which has a strong affinity for metal ions.However,the poor dispersion of the pure MoS₂ in aqueous solution easily affects adsorption performance by stacking.The construction of MoS₂-based nanohybrid material and the adsorption performance for Ag（Ⅰ）in aqueous solution were studied in the dissertation.（1）Based on the structural and performance characteristics of MoS₂ and carboxylated multi-walled carbon nanotubes（MWCNTs-COOH）,multi-walled carbon nanotubes（MWCNTs）loaded with MoS₂ nanoflowers（MoS₂/MWCNTs）were synthesized by a one-step solvothermal method and used as adsorbent for the adsorption of Ag（Ⅰ）in aqueous solution.MoS₂ nanoflowers were loaded on the MWCNTs by in situ growth,avoiding the agglomeration of MoS₂ and MWCNTs,resulting in the MoS₂/MWCNTs nanohybrid material with a larger specific surface area,and exposing more active sites for the adsorption of Ag（Ⅰ）to improve the adsorption performance.The morphology,structure and composition of the prepared samples were characterized and analyzed by relevant characterization methods,the adsorption property of MoS₂/MWCNTs nanohybrid material under different adsorption conditions were investigated by batch adsorption experiments,and the adsorption process of Ag（Ⅰ）was also studied using adsorption isotherms,kinetic models and thermodynamic parameters.The results showed that the maximum adsorption of MoS₂/MWCNTs nanohybrid material for Ag（Ⅰ）could reach 601.97 mg/g.The adsorption of MoS₂/MWCNTs nanohybrid material on Ag（Ⅰ）was mainly achieved by electrostatic interaction and chemisorption,and a new substance Ag₂S was generated during the adsorption process.The adsorption process was a spontaneous,endothermic and homogeneous monolayer adsorption.In addition,the MoS₂/MWCNTs nanohybrid material exhibited excellent adsorption selectivity for Ag（Ⅰ）in the coexistence of multiple ions.（2）The problem for MoS₂ is difficult separation during water treatment,limiting the further application.Inspired by the excellent adsorption property of MoS₂,self-assembly property of graphed oxide（GO）,good templating property of melamine foam（MF）and easy cross-linking of biomass sodium alginate（SA）,MoS₂/r GO/MF nanohybrid material was constructed by immobilizing MoS₂ in a three-dimensional reduced graphene oxide（r GO）system while forming three-dimensional r GO,which were loaded within the MF system with a three-dimensional network structure by a one-step method.Then a novel and easily separable flexible nanohybrid material（SA@MoS₂/r GO/MF）was prepared by constructing an SA network cross-linked by Ca²⁺on MoS₂/r GO/MF and used for the removal of Ag（Ⅰ）from aqueous solution.In addition,the introduction of the biomass SA cross-linked network could enhance the hydrophilicity and stability of SA@MoS₂/r GO/MF nanohybrid material,which could effectively solve the problem of difficult separation of MoS₂ and r GO in water treatment.The effects of p H of Ag（Ⅰ）aqueous solution,initial concentration of Ag（Ⅰ）,adsorption temperature,contact time,different water environments and coexistence of multiple ions on the adsorption performance of SA@MoS₂/r GO/MF nanohybrid material for Ag（Ⅰ）and the adsorption-desorption recycling performance of SA@MoS₂/r GO/MF nanohybrid material was investigated by batch adsorption experiments.The adsorption process of Ag（Ⅰ）adsorption by SA@MoS₂/r GO/MF nanohybrid material was also investigated by using isothermal adsorption model,thermodynamic model and adsorption kinetic model.The results showed that a novel,stable and easily separable three-dimensional hierarchical network structured SA@MoS₂/r GO/MF nanohybrid material was successfully prepared.In addition,it is possible to prepare SA@MoS₂/r GO/MF in arbitrary shapes by changing the shapes of MF,which could be beneficial for large-scale production.The SA@MoS₂/r GO/MF nanohybrid material had excellent adsorption property for Ag（Ⅰ）,and the maximum adsorption capacity of 1012.51 mg/g.The adsorption process was mainly based on homogeneous monolayer chemisorption.The adsorption of Ag（Ⅰ）by SA@MoS₂/r GO/MF nanohybrid materials was an endothermic,disordered and spontaneous process.During the adsorption process,Ag₂S and elemental silver were produced,could be applied in other fields.Furthermore,the SA@MoS₂/r GO/MF nanohybrid material exhibited excellent adsorption performance on Ag（Ⅰ）under different aqueous environments and multiple ions coexistence conditions.