Preparation Of Stimulus-responsive Super-wetting Material And Its Application In Oil-water Separation

Oil/water separation is a hot research due to the increasing serious oil spill accidents and industrial discharge of oily wastewaters.Recently,there are more and more reports about oil/water separation materials with superwetting property,including superhydrophobic/superoleophilic,superhydrophilic/underwater superoleophobic and stimuli-responsive superwetting materials.Stimuli-responsive materials can achieve wettability transition between superhydrophobicity/superoleophilicity and superhydrophilicity/underwater superoleophobicity,which offers a great flexibility and controllability for practical oil/water separation.Therefore,this work focuses on preparing different stimuli-responsive oil/water separation materials via facial methods and investigating their oil/water separation performance.Firstly,we prepared copper mesh coated by silver tree and constructed a rough surface by extremely simple replacement reaction.After heating treatment,this metallic mesh showed superhydrophobicity-superoleophilicity.Interestingly,the heated mesh had ammonia-responsive wettability transition from superhydrophobicity-superoleophilicity to superhydrophilicity-underwater superoleophobicity under ultraviolet(UV)radiation.Surface morphology,chemical composition and wettability of sample were characterized by X-ray diffractometer(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and contact angle meter(CA).The results showed that this UV-responsive materials can achieve both "oil-removing" separation that can allow oil infiltration but prevent water penetration and "water-removing" separation that can allow water infiltration but blocks oil penetration.Moreover,the as-prepared mesh can maintain its superwettability under the corrosive environment,which exhibits excellent chemical stability.And then,the low surface energy nickel stearic was coated on the porous nickel foam via a facial one-step electrodeposition and the superhydrophobic-superoleophilic surface was obtained.We investigated its micro-nano construction by SEM,analyzed its chemical composition by FTIR and XPS and measured its wettability by CA.We also investigated the effects of electrodeposition parameters on wettability.Interestingly,we found that the superhydrophobic-superoleophilic surface can gradually switch to superhydrophilic-underwater superoleophobic surface upon exposure to ammonia vapor.We evaluated oil/water separation and stability of this ammonia-responsive superwetting material,and it turned out that the as-prepared not only efficiently and controllably separated oil/water mixture and also showed favorable anti-abrasion performance.Finally,we prepared hydrophobic nickel stearate particles by chemical precipitation reaction and this hydrophobic particles were coated on cotton fabric with small pore size by dip-coating method,and thus the superhydrophobic-superoleophilic cotton fabric was obtained.Similarly,surface morphology,chemical composition and wettability of sample were characterized by SEM,FTIR,XPS and CA.The as-prepared fabric can also achieve the wettability transition from superhydrophobicity-superoleophilicity to superhydrophilicity-underwater superoleophobicity upon exposure to ammonia vapor.More importantly,this ammonia-responsive fabric can separate water-in-oil emulsion at the state of superhydrophobicity-superoleophilicity and separate oil-in-water emulsion at the state of superhydrophilicity-underwater superoleophobicity.Therefore,the as-prepared cotton fabric had the ability to separate different types of oil/water emulsion.