Research On Preparation And Properties Of 2D Nanocomposite Films Of Tungsten Disulfide

In recent years,two-dimensional materials have been widely studied because of their excellent properties,while two-dimensional films have been widely used in water purification because of their good separation properties.In this paper,tungsten disulfide?WS₂?nanocrystals in transition metal sulfide were used as the base material to prepare different tungsten disulfide nanocrystals and their nanocomposite membranes by dead-end filtration,and the applications of composite membranes in dye desalination,dye separation and catalytic reduction of p-nitrophenol were investigated.This paper mainly studies from the following three aspects:Firstly,tungsten disulfide nanocrystals are rigid.Based on this characteristic,we filtered the prepared tungsten disulfide nanocrystals on the anodic aluminum oxide?AAO?and polyamide?PA?membranes by dead-end extraction from the substrate,and desalted the dyes.Through the experiment,we found that different substrates had a great influence on the stacking regularity of tungsten disulfide nanocrystal sheets,which then affected the surface roughness and water channel of the film,and had a direct influence on the permeability and separation performance of the film.Compared with the tungsten disulfide film based on AAO?WS₂/AAO?,the tungsten disulfide film based on PA?WS₂/PA?has similar dye rejection but higher water flux and lower salt interception.The 250nm thick WS₂/PA film can achieve the water flux of 597 L/m² h bar,the interception of 98.5%Bangladesh rose red?RosB?and 0.3%sodium chloride?NaCl?.This is a great improvement for the two-dimensional film of dye desalination application.Secondly,silver ions are widely used in membrane composite modification because of their positive charge,good anti-pollution and antibacterial properties.When applied to the modification of membrane materials,positively charged silver ions will react with negatively charged materials to change the structure of the materials.At present,many researchers use silver ions to modify the membrane,most of which have achieved good results.However,the modification of two-dimensional transition metal sulfide films by silver ions has not been reported.AgNO₃ solution was mixed with tungsten disulfide nanocrystals to investigate the influence of silver nitrate?0%,5%,10%,15%?of different mass fractions on the two-dimensional tungsten disulfide membrane structure of PA substrates.It was found that the water flux of tungsten disulfide/silver nitrate composite film increased with the increase of silver nitrate content.The pure water flux of WS₂/Ag composite membrane with 10%wt-AgNO₃ as up to 850 L/m² h bar,the interception of cytochrome C?cyt.c?was up to 99.9%,and that of ivens blue?EB?was up to 90%.Finally,based on the studies of the above two parts,we found that the tungsten disulfide film based on PA had good separation performance,and the tungsten disulfide composite film with mixed metal ions was helpful in improving the flux.In order to further broaden the application of tungsten disulfide composite membrane,we mixed the hydrochloric acid solution of palladium chloride?PdCl₂?with the dispersion of tungsten disulfide nanosheet,then reduced the divalent palladium in situ to the nanometer palladium atom by adding sodium borohydride,and then prepared the tungsten disulfide/palladium?WS₂/Pd?nanocomposite membrane by filtration.The Pd modified tungsten disulfide film has many catalytic sites,and the unique layered structure of the two-dimensional film provides a long time for the contact between the catalyzed substance and the catalyst,so it shows good catalytic performance when applied to the catalytic reduction of p-nitrophenol?4np?to p-nitroaniline?4ap?.The experimental results showed that the highest catalytic conversion rate reached 98%and the catalytic performance remained high after several cycles.The results show that the two-dimensional composite membrane has a good application prospect in membrane catalysis.