| In the past decade,the water pollutions caused by anthropogenic activities exert a serious threat on human's production and living,currently how to control and repair the aquatic environment effectively has become an urgent problem to solve.Adsorption has been recongnized as one of the most effective and promising candidates for water remediation,in which the key is to find the new adsorbents with high efficiency and low cost.As a typical layer transition metal dichalcogenide,the molybdenum disulfide(MoS2)has received increasing attention and been widely applied in catalysis,electrochemistry and energy-related fields due to their unique layer structure and excellent performance.Moreover,abundant sulfur groups on surfaces and edges,special sheet-like structure,excellent chemical and thermodynamic stability as well as high dispersibility provide great opportunity for applicatuion of MoS2 in the field of water treatment.In this study,MoS2 ultrathin nanosheets and Fe3O4/MoS2 nanocomposites were synthesized via the simple hydrothermal methods and used as adsorbents to explore their removel ability of heavy metal pollutants in water.The main research contents and results are as follows:Firstly,the molybdenum disulfide ultrathin nanosheets were synthesized via a one-step hydrothermal method without addition of templates or surfactants.The obtained MoS2 product was characterized via various techniques including FESEM,HRTEM,XRD,BET and XPS analyses.Their application in capturing Cr(VI)ions in water was investigated.The results showed that the MoS2 nanosheets was ultrathin with a thickness of 5-10 nm and had a uniform lateral size of 100-200 nm.In addition,these MoS2 nanosheets possessed the enlarged interlayer spacing and had multiple defects on the basal planes,which were proved to be crucial in the removal of Cr(VI).The kinetics of the chromium adsorption were found to follow the pseudo-second-order rate equation and the adsorption isotherm data was well fitted to the Langmuir model with a chromium in-take capacity of about 84.03 mg g-1.This structure-enhanced removal was likely related to the synergism of adsorption and reduction,in which the anionic Cr(VI)was adsorbed on the surface of D-MoS2 via electrostatic interaction and some fraction of adsorbed Cr(VI)were reduced to low toxic Cr(III)at the same time.Secondly,the MoS2 ultrathin nanosheets metioned above with a widened interlayer spacing and defects also exhibited a good removel of Pb(II)in aqueous solution such as fast kinetics,high removel efficiency and a relative pH scope.The adsorption process of lead was found to follow the pseudo-second-order kinetic model and well fitted to Langmuir model with a high lead uptake capacity of about 235.67 mg g-1.These enhanced adsorption abilities were attributed to co-existence of several factors,for instance,the inherent sulfur-rich property of D-MoS2,the ultrathin characteristics of nanosheets,unique layer structure with enlarged spacing and basel defects which provided channels for mass transfer.Furthermore,the D-MoS2 also had ability to remove the different anionic/cationic dyes and presented the synergistic enhanced adsorption in the mixed aqueous solution of methylene blue and lead,indicating that the adsorbents had great application prospects in removal of Pb(II)and dyes pollutants in aqueous system.Thirdly,the novel magnetic micro/nanocomposites(Fe3O4/MoS2)was prepared by the load of magnetic Fe3O4 nanoparticles to the MoS2 nanosheets through a facile solvent thermal method and applied for the removal of heavy metal Cu(II)from aqueous solution.Effects of different experimental conditions like initial solution pH values,contact time,and initial solution concentration on the adsorption of Cu(II)were investigated.The results showed that the adsorption process followed the Freundlich isotherm equation and the pseudo-second-order kinetic model.Moreover,the nanocomposites as adsorbents could be easily separated with assistance of external magnetic field,and the reusability of Fe3O4/MoS2 was studied under the treatment of the hydrochloric acid solution and the results displayed good recycle ability. |
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