| It was found previously that neither monomer Mo S2 nor WO3 is an ideal material for the adsorption of organic dyes,while Mo S2/WO3 composites synthesized by a two-step hydrothermal method have outstanding adsorption effects.The effects of different precursor solution concentration on the morphology of Mo S2/WO3 were studied at the beginning of this work.The structure and morphology of the product were characterized by XRD,SEM and TEM.As a result,the concentration of precursor solution affects not only the degree of WO3 coated with Mo S2,but also the formation of flake-like Mo S2 and the development of their layered structure.When the mass of the molybdenum source added to the current flooding solution is 0.018 g,a composite material with a uniform coating structure which has a porous and loose surface is formed.Through the adsorption experiments,it was found that the difference of the structure also leads to the difference of the adsorption performance of the heterostructure.Therefore,it is of great importance to select an appropriate concentration of precursor solution for hydrothermal synthesis of Mo S2/WO3composites with excellent adsorption properties.At the same time,the X-ray photoelectron spectroscopy was used to study the changes in the chemical state of each element before and after recombination and to explore its formation mechanism.The results show that Mo S2 and WO3 generated electronic interaction and then formed a new chemical bond,rather than pure physical doping.This unique ternary structure of shared electron pairs made the composite material have a large number of adsorption active sites in the surface,resulting in the great improvement of the material's adsorption capacity.Secondly,the effects of the initial concentration of the adsorbate solution,the temperature of the adsorption reaction,and the type and ion concentration of the electrolyte of the adsorbate solution on the adsorption equilibrium capacity and the reaction rate were systematically studied.The adsorption test of methylene blue on Mo S2/WO3 composites was carried out under different initial concentrations and a series of temperatures,showing that the prepared composites also had appreciable adsorption capacity and higher adsorption efficiency at lower temperatures.Besides,the experiment of adding a certain amount inorganic salt in the solution showed obvious promotion to the adsorption process,which greatly increased the degradation rate of the material in a certain time.It is noteworthy that Na Cl has the most significant promotion to the adsorption process when the concentration was 0.16mol/L.The adsorption process could be well described by the Freundlich isothermal model and the pseudo-second order model.In addition,the particle-internal diffusion model simulation reveals that the internal diffusion of the particles played an important role in the whole adsorption process.In addition to methylene blue,the composite materials were also applied to the adsorption and removal of methyl violet in aqueous solutions,and the effects of temperature and electrolyte on the adsorption process were studied.Similarly,the composite material has exhibited a satisfactory ability to remove methyl violet.Obviously,Mo S2/WO3 composites with effective adsorption properties are expected to be applied to remove organic dye pollution in water at low temperature. |
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