Study On Wettability Regulation Of Metal Meshes And Their Application In Oil/Water Separation

The abundant discharges of industrial and domestic wastewater as well as the frequent occurrence of oil leakage accidents have caused great impact on the ecological environment and human health,therefore,making the efficient and reasonable treatment of oily wastewater becomes one of the focused topics of environmental field.With the development of bionics,many porous materials with special wettabilities have been successfully used for oil/water separation.However,the existing materials have the disadvantages of poor corrosion resistance,easy to be polluted by oil,unable to realize on-demand oil/water separation,and operating by discontinuous separation process,etc.In this work,based on the interface science and bionics,we fabricated several kinds of metal meshes with special wettabilities by controlling their surface morphology and chemical composition.The stability of the meshes was assessed,meanwhile,the extra properties of the meshes such as photocatalysis,photo-induced self-cleaning,intelligent wetting conversion,magnetic properties and so on,were extended to make the filters multifunctional.In order to overcome the shortcoming of superhydrophobic/superoleophilic filters,which could easily be blocked by oil.A superhydrophilic and underwater superoleophobic TiO₂nanowires film were fabricated on Ti substrates via a facile low temperature and short time-consuming route.The hierarchical one-dimension nanowires morphology with considerable roughness led to the water permeation in air and oil repellency in water.Not only in pure water,the as-prepared film also exhibited excellent underwater superoleophobicity in corrosive aqueous media,including highly saline,acidic and alkaline solutions.Importantly,the wetting properties and morphologies of the film changed little after immersed into the corrosive solutions even for 168 h,indicating good environmental stability.The Ti mesh with this TiO₂ nanowire film showed good oil/water separation ability with separation efficiency high up to 99.7%.During the oil/water separation process,water passed through the mesh rapidly by gravity,while oils stayed above due to its superoleophobicity.The hydrophilic mesh is easily contaminated by oil in dry condition due to its oleophilicity in air.Aiming at this problem,a W,N co-doped TiO₂ nanobelts film was prepared on Ti mesh.After calcined in air,the film contained of anatase and rutile with W and N co-doped simultaneously,making it possess good light-induced photocatalytic activity.The as-prepared superhydrophilic/underwater superoleophobic mesh can be used for efficient oil/water separation and photodegradation of soluble dye such as Methylene Blue in the water phase.Moreover,the mesh possessed good self-cleaning property on the removal of aqueous insoluble oil on its surface in the presence of ultraviolet and visible light irradiation.A CuWO₄@Cu₂O film was prepared on copper mesh by a one-step electrochemical anodization method.The as-prepared mesh displayed superhydrophilicity and good underwater superoleophobicity due to the hierarchical structure,causing high separation efficiency up to 99.3%for oil/water separation.Moreover,the mesh can separate the mixture of oil and different concentration of salty water.Furthermore,the composite composed of CuWO₄ and Cu₂O can promote the separation of photogenerated electrons and holes,making the film have photocatalytic ability.In the presence of Na₂S₂O₈ that acts as electron trapping agent and visible light irradiation,90.2%of Methylene Blue and 96.4%of Rhodamine B in aqueous solution could be degraded in 120 min,showing good photocatalytic activity.Therefore,the CuWO₄@Cu₂O copper mesh can be used to treat two key pollutants,insoluble oil and soluble organic dyes,which is of great significance to the treatment of wastewater.By using Cu（OH）₂ nanowire array as a template,we fabricated a Cu₂S@Cu_xO nanowire arrays film on copper mesh after a sulfurization process.Compared to the traditional CuO and Cu（OH）₂ based superhydrophilic/underwater superoleophobic copper mesh,the Cu₂S@Cu_xO film possessed better acid-resistance.The surface morphology changed little after being immersed in 1 M of HCl solution even for 48 h.When the mesh been stored in air for about two weeks,the wettability varied from superhydrophilic state to superhydrophobic state,due to the change of surface chemical composition and the increasing of air pockets in the structure.The switching between superhydrophobicity and superhydrophilicity of the mesh can be realized by cyclic storage and plasma treatment,so we can use the two kinds of meshes with opposite wettabilities for intelligent on-demand oil/water separation.In order to further realize on-demand and continuous oil/water separation,a hierarchical FeNiO_x（OH）_y structure on nickel mesh was fabricated via simple and green redox-etching and chemical precipitation reaction.The as-prepared mesh was superhydrophilic and underwater superoleophobic state,but it turned to superhydrophobic and superoleophilic state after PDMS modification.Continuous oil/water separation was realized without considering the density of oils by integrating the opposite meshes into an inverted T-shaped three-limbed tube.Moreover,By virtue of superhydrophobicity/superoleophilicity of the PDMS modified mesh,continuous oil removal on water surface was also achieved.Owing to the special magnetic property of Ni based material,the mesh can be easily taken out by a magnet,which facilitates remote control after the oil is retrieved.