MoS₂ Composites Based On PPy,CA:Preparation,Properties For Removal Of Hexavalent Chromium

Chromium compounds are widely used in metallurgy,electroplating,wood,leather,textile and other industries,resulting in a large amount of chromium-containing wastewater,and the ecological and environmental problems caused by it have attracted great attention in recent years.Chromium in the water mainly exists in the form of hexavalent chromium（Cr（Ⅵ））and trivalent chromium（Cr（III））.Cr（Ⅵ）has high toxicity and mutagenicity,while the toxicity of Cr（III）is 1/100 of Cr（Ⅵ）,and the mutagenicity is only 1/1000 of Cr（Ⅵ）.Therefore,the research and development of efficient absorption and reduction of Cr（Ⅵ）into Cr（III）in water is of great significance for the treatment of chromium containing wastewater.Molybdenum disulfide（MoS₂）,as a two-dimensional layered material,has excellent structural design and high specific surface area,and has certain reducibility to Cr（Ⅵ）.However,MoS₂ has the disadvantages of low reaction rate and low removal performance in removing Cr（Ⅵ）from water.Based on the mentioned above,polypyrrole and carbon aerogel with excellent adsorption performance were selected to be combined with MoS₂,respectively,and PPy/MoS₂ and CA/MoS₂ were used to improve the removal performance of Cr（Ⅵ）in water.The main research contents of this paper are as follows:PPy/MoS₂ was synthesized by one-step hydrothermal method.SEM,XRD,FTIR and other techniques were used to characterize PPy/MoS₂.In this paper,PPy/MoS₂ was used as an adsorbent to investigate the removal performance of Cr（Ⅵ）by the intermittent adsorption experiment,and the influence factors such as initial p H value and compound dosage on the removal of Cr（Ⅵ）was discussed.Meanwhile,the removal mechanism of Cr（Ⅵ）was preliminarily studied by XPS analysis.The experimental results showed that the removal capacity of PPy/MoS₂ for Cr（Ⅵ）was230.97 mg/g,and the removal rate of Cr（Ⅵ）by the 20 mg composites in 200 min was as high as 99.9%at p H 2.The pseudo-second-order model and Langmuir isotherm model are more suitable for the removal process of Cr（Ⅵ）by PPy/MoS₂.In addition,it was found that PPy/MoS₂ can also be used as a catalyst to degrade organic pollutants,and the removal rate of PPy/MoS₂ to the dye was more than 97%within 20 min.After12 cycles,the removal rate of PPy/MoS₂ to reactive brilliant red 3BF（3BF）was still as above 90%.In order to further enhance the removal efficiency and repeatability of the MoS₂composites on Cr（Ⅵ）in water,carbon aerogel with larger specific surface area was selected to prepare a new MoS₂ composites.Carbon aerogel（CA）was synthesized by D-glucose and aniline,and then CA/MoS₂ was prepared by MoS₂ supported onto the CA by simple hydrothermal method.CA/MoS₂ were characterized by SEM,Raman,XPS and other analytical techniques.In this paper,the removal performance and reusability of Cr（Ⅵ）in water by CA/MoS₂ were studied,and the influence of temperature,initial p H value and other factors on the removal of Cr（Ⅵ）in the water by CA/MoS₂ was investigated.The results showed that the removal capacity of Cr（Ⅵ）by CA/MoS₂ was up to 460.2 mg/g,and the removal performance of Cr（Ⅵ）was the best in the p H range of 1.0-3.0.CA/MoS₂ could almost completely remove Cr（Ⅵ）from the solution within 50 min when the temperature was 25°C,and the removal rate of Cr（Ⅵ）could still maintain 87.5%after 5 times.Compared with PPy/MoS₂,CA/MoS₂ had better removal performance and reusability.In addition,XPS was used to analyze CA/MoS₂ before and after the use,and the process for removing Cr（Ⅵ）from water was discussed.