| At present,the security of water sources on which human beings depend for survival has become increasingly prominent.Particularly,the existence of oily sewage not only causes serious environmental pollution,but also generates huge economic losses.Superwetting materials show widespread potential in oil-water separation because they exhibit diametrically opposite affinities for water and oil.However,the current preparation methods of the superwetting materials have many drawbacks,such as complex process,high cost,harmful reagents,and poor stability.The exploration of novel strategy with environmental friendliness for producing superwetting materials is of great significance.In this thesis,benefiting from of the biomimetic technology,hierarchical micro/nanostructured minerals were generated on the surfaces of the stainless steel meshes(SSMs)based on the biomineralization process,leading to the formation of the superhydrophobic/superoleophilic and superhydrophilic/underwater superoleophobic meshes.Then,the superhydrophilic/underwater superoleophobic meshes were prepared via combined techniques of picosecond laser processing and biomineralization process using the stainless steel sheets(SSSs)as the raw materials.Finally,the functional sponge with hydrophobicity were prepared with the melamine sponge(MS)as the matrix,which was integrated with the mineralized SSMs to improve the applicability of the SSMs under complex oil-water separation environments.The main research results of this thesis are as follows:(1)Using the bacterium of B.subtilis as the mineralizing bacterium,a continuous and dense micro-structured CaCO3 mineralization layer was formed on the SSM surface.After surface modification by the stearic acid(SA)with low surface tension,a superhydrophobic/superoleophilic SA/CaCO3-SSM with a water contact angle(WCA)of 152°and an oil contact angle(OCA)of 0° was obtained.The SA/CaCO3-SSM showed excellent oilwater separation performance with a separation efficiency higher than 94.8%and oil flux of up to 9.12×104 L·m-2·h-1.After 10 cycles of use,the separation efficiency was still higher than 94%,and the flux remained stable,showing its good reusability.Furthermore,the SA/CaCO3-SSM demonstrated ideal wear resistance,outstanding anti-pollution performance,and promising antiicing characteristic,endowing it with the capability to work under harsh environments.This work provides an inexpensive,environmental-friendly,and pollution-free method to construct superhydrophilic or superhydrophobic surfaces and opens a new avenue for the fabrication of oil-water separation meshes with multifunctionality.(2)Using the bacterium of S.algae as the mineralizing strain,a CaCO3 mineralized layer with rough hierarchical micro-nano structure was deposited on the SSM surface via microbial mineralization,a superhydrophilic/underwater superoleophobic CaCO3-SSM with a water contact angle of nearly 0° and underwater oil contact angle of up to 161° was obtained.The CaCO3-SSMs showed excellent oil-water separation performance with ultrahigh permeation flux(1.55×105 L·m-2·h-1)and high separation efficiency(≥98.5%),while concurrently demonstrating high chemical and mechanical stability.Furthermore,the CaCO3-SSMs possessed ultralow oiladhesion force in water(≥1.4 μN),endowing them with outstanding anti-oil fouling property.The microbial mineralization of the minerals with hierarchical micro-nano structures could help for the development of next generation superwetting materials.(3)In order to overcome the shortcomings of the commercial metal meshes such as poor mechanical properties,easy deformation and single hole structure,the SSSs with micro-scale annular hole array were prepared using the picosecond laser processing technology.After subsequent biomineralization process,the holes of the SSSs were coated with the calcium carbonate layers,making them superhydrophilic/underwater superoleophobic.When the scanning rate of the laser beam was 1000 mm/s,the power of the laser beam was 1.65-1.85 W,and the number of scans were 200 times,an array of annular holes with a hole diameter of about 50 μm and a hole center spacing of about 150 μm could be obtained.The WCAs on both sides of the SSSs were 0°,while the UOCAs on the front and back sides were 165° and 165.7°,respectively.Furthermore,there was no significant difference in the water flux between the front and back sides.The oil-water separation efficiencies on both sides were higher than 97.4%,and the maximum water flux could reach 87780 L·m-2·h-1.(4)In order to overcome the limitations of the mesh material due to the difference in oil density,melamine sponge(MS)was used as the matrix.The hydrophobic reduced graphene oxide(RGO)and silver nanoparticles(Ag NPs)were loaded on the surface of MS by chemical reduction and immersion methods.A highly hydrophobic RGO-MS and Ag/RGO-MS with WCAs of 140° and 145° were obtained.Due to the unique surface micromorphology and high porosity,the RGO-MS exhibited remarkable absorption capacity of 41-91 times its own weight for a wide range of oils and organic solvents.Both the RGO-MS and Ag/RGO-MS showed excellent oil-water separation efficiencies.The Ag/RGO-MS not only exhibited outstanding absorption capacity and recyclability,but also possessed ideal antibacterial performance towards Gram-positive and Gram-negative bacteria.The hydrophobic and bacteriostatic Ag/RGO-MS provides a solution for aseptic treatment of oily sewages.In addition,the integration of functional sponges and mineralized steel meshes can separate all kinds of light/heavy oil and water mixtures at the same time with a separation efficiency higher than 99.1%.This method well avoided the practical limitations of the mineralized steel mesh due to oil density,and additionally endowed it with new functionality,providing a feasible solution for the optimization of superwetting mesh materials. |
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