Fabrication Of Special Wettability Materials And Their Application In Oil-water Separation Based On Hierarchical CuO

Special wetting behavior attracted a great deal of attention due to its extensive applications.Based on the opposite wettability toward oil and water,the superwetting mesh could separate oil/water mixtures,which is of great significance to the increasing oily sewage and serious resource waste and pollution caused by oil leakage.The multifunctional and smart materials are a hot topic of research especially the materials with reversible switchable superwettability over the decade.Some metal oxides are popularly employed to fabricate special wettability surfaces due to their micro/nanostructures and special properties.CuO arrays have been proved to be an ideal choice for their diverse morphologies along with structural stability.In this dissertation,hierarchical CuO was prepared by a simple heating method,and the superwetting surfaces were prepared based on the CuO micro/nanostructure.When it was applied to different substrates,the as-prepared membranes could separate a series of immiscible oil/water mixtures and emulsions.The separation performance and stability were also estimated.The main contents are shown as follows:(1)Preparation of surfaces with reversible superwetting transition: A simple solutionimmersion method at 85°C was used to fabricate hierarchical CuO on many substrates.By rapid modification with tetradecanoic acid for only 15 s,superhydrophobicity was imparted to the asprepared surface,which was kept well under the salt immersion,oil pollution and corrosion of acid and alkali.The superhydrophobic surface converted back into superhydrophilic by annealing at 300°C for 5 min.A rapid reversible superwetting transition cycle was finished by modification with tetradecanoic acid and annealing treatment.And we had analyzed the mechanism of the reversible superwetting transition.(2)Separation of immiscible oil-water mixtures by superwetting meshes: When the stainless steel mesh coated with CuO,the reversible superwetting transition between superhydrophobic and superdrophilic was realized by modification and annealing.The CuOcoated stainless steel mesh without any treatment showed superamphilic.And the mesh could be reversibly switched between underoil superhydrophobicity and underwater superoleophobicity simply by drying,washing and prewetting alternately.Thus,the two meshes all could realize both “oil-removing” mode and “water-removing” mode.They both realized the efficient and controllable oil/water separation.(3)Separation of emulsions by superwetting membranes: When the CuO coatings was applied to the filter papers and PVDF membranes,the resulting membranes were switchable between underoil superhydrophobicity and underwater superoleophobicity by drying,washing and prewetting alternately.Thus,the membrane could be used for the switchable separation of emulsions.Inspired by the Janus-featured heterogeneous wettability,we introduced a pristine superhydrophilic filter paper on the as-prepared membranes to form the surface energy gradient.The effect of surface energy gradient on separation performance was investigated.