Study On The Preparation Of Submerged Dual Lyophobic Materials And Their Oil-water Separation Performance

With the frequent occurrence of oil spills and the increasing industrial wastewater,the environment has serious problems,and oil-water separation has always been a hot spot for researchers.Particularly,the separation of oil-water emulsions remains a thorny problem.In recent years,inspired by the wetting behavior of the lotus,researchers have developed a variety of materials of biologically inspired super-wetting surfaces and interfaces.Of course,the super-wetting surface is considered a promising candidate for oil-water separation.However,most of the super-wetting surface materials can only separate oil-in-water emulsions or water-in-oil emulsions.For this reason,most of the stimuli-responsive and Janus membrane materials have recently appeared.Such materials can simultaneously separate oil-in-water emulsions and water-in-oil emulsions,but achieving such effects requires external energy stimulation for stimuli-responsive,such as light,ammonia,and heat,etc.Similarly,Janus membrane requires careful design of the two-sided symmetry of membrane material.Therefore,that super-wetting surface materials of simultaneously separating oil-in-water emulsions and water-in-oil emulsions without external energy stimulation and careful design is a more ideal material.Then,in recent years,the dual superlyophobic material which can achieve such magical function have appeared.Thence,the surface of modified membrane which used a simple method and low-cost raw material realizes the dual superlyophobic to simultaneously separate the oil-in-water emulsions and water-in-oil emulsions in our work.Firstly,the polypyrrole,which contains the hydrophilic nitrogen component and the olephilic hydrophobic conjugated structure,became our research object.Here we used a simple gas-phase polymerization method to prepare a polypyrrole modified cellulose membrane in situ,where FeCl3·6H2O was used as an oxidizing agent for pyrrole polymerization,where filter paper and mixed cellulose filter with different pore size were selected as base materials for oil-water mixture and oil-water emulsions separation.Thus,with oil(methylene chloride)contact angle of 151.8° under water and water contact angle of 155.9° under diesel oil,the polypyrrole-modified filter paper showed the special wettability of dual superlyophobic.At the same time,the polypyrrole modified filter paper membrane can simultaneously separate the light oil-water mixture and the heavy oil-water mixture.Its flux is more than 3000 L·m-2 ·h-1 and the separation efficiency is 99%.Similarly,the polypyrrole modified mixed cellulose filter can simultaneously separate the oil-in-water emulsions and water-in-oil emulsions with 98%retention ratio.In addition,the prepared polypyrrole modified mixed cellulose filter has good cycle separation efficiency,and also has a certain degree of salt tolerance and acid and alkali resistance.The wastewater system is complex,which contains not only oil but also organic dyes.Organic dyes,having complex and stable structure,large molecular weight,and low biodegradability,could threaten the ecological balance and human health.So,it is imperative to deal with organic dyes.Polydopamine,as a high-efficiency adsorbent,it having the ability to remove organic dyes from sewage systems,and having a similar structure to polypyrrole,has become our research object.In our work,using the cotton fabric as the substrate,the nickel ferrite micro-nanoparticles were loaded onto the cotton fabric by polydopamine in a one-step process.We prepared the NiFe2O4/PDA-modified cotton fabric composite material.SEM,EDX,XRD,FT-IR tests and surface wettability test were carried out.The contact angle of the surface of amphiphilic material shows that oil contact angle under water was 153°,water contact angle under oil was 145°.In addition,we have evaluated the oil-water separation performance,cycle performance and adsorption performance of methylene blue dyes,and all of them have shown good oil-water separation performance,cycle performance and adsorption performance.Although the adsorbent has good effect on dye removal,it still has some the disadvantages,such as secondary pollution,cost issues in post-processing.Therefore,the method of catalytic degradation is expected to solve such a problem.In this work,ZnO,with properties of both catalytic and dual superlyophobic wettability,became our research object.On the one hand,ZnO,it can completely remove pollutants as a catalyst to avoid secondary pollution.On the other hand,as a inorganic oxide,it could achieve dual superlyophobic,due to its surface easy to spread various droplets with high surface energy,and its own texture structure could catch the liquid and block another immiscible liquid phase.So,in our work,ZnO nanoparticles grew onto polydopamine-modified kapok fibers,and the obtained PDA/SC/KFs@ZnO fibers were filtered into a membrane(PDA/SC/KFs@ZnO membrane)for further testing.The opposite of such a self-supporting membrane shows oil contact angle of 152.8±0.6° underwater,the water contact angle of 155.3±0.2° under oil,the front of the membrane shows oil contact angle of 158.5°±0.2° under water,and the water contact angle of 155±0.9° under oil.Finally,the special wettability of the dual superlyophobic materials not only shows good oil-water separation performance,but also shows a certain ability to dye adsorption performance.In addition,it has certain visible light catalytic degradation dyes performance.