Fabrication And Properties Study Of Super-wetting Materials Based On Complex Oil-water Separation Systems

The increasing discharge of industrial oily wastewater and frequent occurrence of oil-spill accidents not only cause serious damage to the ecological environment,but also lead to huge waste of valuable resources of oil and purified water.Therefore,achieving effective separation of oil/water mixtures is extremely imperative to the sustainable development of humanity and nature.In the actual oil-water separation system,the types of oily wastewater are very diverse,which may not only contain random combinations of various types of oil-water mixtures,but also contain many impurities and other pollutants,greatly increasing the difficulty of separation.Therefore,this paper is aimed at the complex system of oil and water,the preparation of superwetting materials,the use of absorption or filtration to achieve the effective separation of different types of oil/water mixtures.Based on the construction principle of superwetting interface,suitable substrate materials were selected,the surface of which were coated with micro/nanoscale coatings by means of in-situ construction.Through the regulation and modification of the coatings,surfaces with different wettability selectivity to oil and water were obtained,so as to achieve on-demand separation of different types of oil/water systems.The composition,structure,wettability and other physical and chemical properties of these materials were characterized and analyzed.The main research contents are as follows:?1?Porous melamine sponge?MS?with low cost,good elasticity and stable chemical properties was chosen as the substrate material,the surface of which was in-situ grown rough copper nanoparticles?Cu-NPs?coating by one-step redox reaction in aqueous phase at room temperature.The hydrophobic surface was obtained directly without any hydrophobic modification.The Cu-NPs/MS has a stable high-opening network structure and high hydrophobicity?water contact angle is up to 145.8°?,showing high absorption capacity for different oils or organic solvents,with an absorption capacity up to 60-145 g/g.Moreover,Cu-NPs/MS shows excellent mechanical stability,elastic performance and reusability.The recycling of Cu-NPs/MS is realized by dissolving the polluted and damaged Cu-NPs coating and redeposition ones without damaging the skeleton structure of MS itself,making its application in complex oil-water separation environment more feasible.?2?Using green,cheap sisal as raw material and cellulose fiber extracted from it as substrate material,the same one-step functionalization method was used to in-situ construct rough Cu-NPs coating on the fiber surface to obtain the hydrophobic functionalized surface,and finally the functionalized cellulose based aerogel?Cu/CEA?was obtained by freeze-drying technology.The resulting aerogel materials have high porosity and extremely low density,and exhibit high absorption capacity?absorption capacity is up to 164.5 g/g?and absorption rate in oil/water separation experiments.Moreover,the structure of aerogel material can be adjusted effectively by controlling the content of cellulose,thus affecting the performance of oil-water separation.Through comprehensive evaluation,the best performance of Cu/CEA was determined when the cellulose content was 0.8 wt%.Cu/CEA can be also used as a thick aerogel film for continuous and rapid separation of various oil/water mixtures including emulsions,with high separation efficiency?97%?and flux.?3?SiO₂ fiber membrane with stable chemical properties and good mechanical properties was used as the substrate membrane material,the surface of which was in-situ grown Al₂O₃ nanosheet coating by hydrothermal method and calcining process to obtain the Al₂O₃/SiO₂ fiber membrane with rough hierarchical structure.The directly obtained fiber membrane is superhydrophilic/underwater hydrophobic?underwater oil contact angle is 155.1°?,and the surface is hydrophobic?water contact angle is up to158.6°?after modification with sodium laurate.Moreover,Through,the reversible transition of superhydrophobicity and underwater superoleophobicity is realized by the modification and annealing treatment of sodium laurate,alternately,so that it can be used for separating heavy-oil/water and light-oil/water mixtures under oil-removing model and water-removing model,respectively,showing high separation efficiency and separation flux.The Al₂O₃/SiO₂ fiber membrane shows a significant chemical stability and super-wettability even after 5 annealing and surface modification cycles,indicating its excellent durability.Moreover,the obtained fiber membrane still shows excellent chemical stability,corrosion resistance and reuse performance under harsh environment.?4?A waste-to-resource strategy of waste brick was presented,which was as raw material to obtain zinc oxide?ZnO?nanopillars structurized waste brick grains?ZnO/WBG?through physical process and chemical method of in-situ growth.The directly prepared ZnO/WBG show underwater superoleophobicity?contact angle is close to 153°?,while the hydrophobically-modified ZnO/WBG has hydrophobicity?contact angle is about 147°?.Therefore,the particles with opposite wettability can be accumulated with each other to obtain a filter layer for oil/water separation.The transition from immiscible oil/water mixtures to emulsified oil/water mixtures can be realized by adjusting the thickness of filter layer.The obtained filter layer has relatively high separation efficiency and higher separation flux than traditional membrane materials.At the same time,it still shows excellent wettability stability in some harsh treatment environment?such as temperature,pH,salt solution,etc.?.Therefore,this novel and cost-effective ZnO/WBG layer has great application prospects for large-scale and versatile oil-water separation.