Preparation Of MoS₂ Composites For The Removal Of Cr（Ⅵ） And Organic Pollutants

With the rapid development of modern industry,water pollution was becoming increasingly serious,which mainly contains heavy metal pollution represented by hexavalent chromium（Cr（Ⅵ））and organic pollutants represented by phenolic pollutants.Therefore,efficient removal of Cr（Ⅵ）and organic pollutants from water bodies has become an urgent problem.At present,there were many methods are available for removing Cr（Ⅵ）and organic pollutants,such as adsorption,chemical redox,etc.The adsorption has the advantage of being low cost and simple to operate,but it cannot completely eliminate Cr（Ⅵ）toxicity and degrade organic pollutants.The chemical redox is a more comprehensive method of water treatment as it is capable of converting highly toxic Cr（Ⅵ）to less toxic Cr（III）and degrading organic pollutants to small molecule products.However,this method suffers from a slow removal process with low efficiency.Hence,developing a bifunctional material that can efficiently remove hexavalent chromium by adsorption and reduction while degrading organic pollutants from wastewater is crucial.As a typical two-dimensional graphene-like material,MoS₂ not only has excellent lubrication,photocatalytic and electrochemical properties,but also has a large surface area,a large number of active sites and good adsorption properties for both heavy metal ions and organic pollutants in its nano size,which makes it an ideal modified material.Therefore,in this paper,the introduction of cationic polyacrylamide aerogel（CPAMA）in the process of hydrothermal preparation of MoS₂ to prepare MoS₂ nanocomposite（MoS₂@CPAMA）;In addition,ferric chloride was introduced into the precursor of MoS₂ synthesis,and CPAMA supported Fe-doped MoS₂ nanocomposite MoS₂-Fe@CPAMA was prepared by the same method above.The goal is achieve efficient removal of Cr（Ⅵ）and organic pollutants in the solution.The main research contents are as follows:Cationic polyacrylamide was crosslinked and freeze-dried to prepare aerogel（CPAMA）,and was then combined with MoS₂ through a hydrothermal method to obtain MoS₂ nanocomposites（MoS₂@CPAMA）.Taking Cr（Ⅵ）and p-chlorophenol（4-CP）as target pollutants,the removal performance of MoS₂@CPAMA on Cr（Ⅵ）and its ability to degrade of organic pollutants by co-catalyzing PMS were investigated.The main research results were as follows:（1）MoS₂@CPAMA was characterized by SEM,TEM,XRD,Raman and XPS.The results show that the size of MoS₂ nanoflowers structure was significantly reduced and the dispersion is improved.The specific surface area and pore volume were also increased,and the introduction of-N⁺（CH₃）₃ increased surface potential and charge density.Thus,the adsorption effect and reduction performance of Cr（Ⅵ）were enhanced.（2）Removal performance of Cr（Ⅵ）:MoS₂@CPAMA has a removal rate of more than 95%of 50 mg/L Cr（Ⅵ）in 40 m L within 50 min.And the maximum removal capacity of Cr（Ⅵ）is up to 800.0mg/g,which was better than that of almost all MoS₂-based materials previously reported.Mechanism analysis showed that the main removal of Cr（Ⅵ）is reduction.（3）The co-catalytic performance of Fe²⁺/PMS system for 4-CP degradation:MoS₂@CPAMA,as the co-catalyst of Fe²⁺/PMS system,the degradation rate of 4-CP exceeded 94%after 6 min reaction,which was significantly higher than that of MoS₂/Fe²⁺/PMS system（67%）and Fe²⁺/PMS system（44%）.The mechanism analysis showed that MoS₂@CPAMA greatly accelerated the Fe³⁺to Fe²⁺transformation in Fe²⁺/PMS system,resulting in more·OH,SO₄^·-and O₂^·-production.In order to achieve efficient removal of Cr（Ⅵ）and avoid secondary pollution caused by Fe²⁺in the process of solution removal of pollutants.In this paper,CPAMA supported Fe-doped MoS₂ nanocomposites（MoS₂-Fe@CPAMA）with high Cr（Ⅵ）removal efficiency and excellent catalytic performance were prepared by directly introducing ferric chloride into the same hydrothermal method of MoS₂ synthesis as above.Cr（Ⅵ）and p-chlorophenol（4-CP）were used as target pollutants to explore the ability of MoS₂-Fe@CPAMA to remove Cr（Ⅵ）and the degradation of organic pollutants by catalyzing PMS.The main research results are as follows:（1）Performance of catalytic activated PMS to degrade organic pollutants:The degradation rate of 4-CP can reach more than 99%after 10 min reaction in MoS₂-Fe@CPAMA/PMS system.Meanwhile,it has high catalytic degradation ability for most organic pollutants,and has excellent thermal activity and p H adaptability.Mechanism analysis showed that Fe²⁺in MoS₂-Fe@CPAMA reacted with PMS to produce Fe³⁺,and produced·OH,SO₄^·-,O₂^·-and ¹O₂ to degrade 4-CP.（2）Removal performance of Cr（Ⅵ）:Cr（Ⅵ）was removed by MoS₂-Fe@CPAMA.After 30 min reaction,the removal rate of 50 mg/L Cr（Ⅵ）in 40 m L was more than 90%,and the maximum removal capacity of Cr（Ⅵ）was 405.4 mg/g.Reduction to Cr（Ⅲ）was the main means of Cr（Ⅵ）removal.