Preparation Of Metal And Cellulose Based Materials With Special Wettability And Application In Oil/water Separation

The oil spill accident and the discharge of oily wastewater led to oil pollution problems,which caused serious harm to the environment,economy and human health.The traditional treatment methods could not meet the actual needs.Oil/water separation is controlled by the interfacial phenomenon,thus the use of special wetting materials is considered as an efficient solution.In this paper,the special wettable surfaces were constructed on various substrates and used to realize oil/water separation.The main research contents are as follows:?1?Superhydrophobic surfaces coated with copper stearate?CS?or CS@Fe₃O₄nanoparticles were prepared on stainless steel mesh?SSM?by dip-coating method.The influences of dip-coating times on the wettability of CS@SSM and CS@Fe₃O₄@SSM were analyzed.The superhydrophobicity of CS@Fe₃O₄@SSM was found to be superior to that of SSM coated with bare CS because of the enhanced surface roughness by Fe₃O₄ nanoparticles.The CS@SSM and CS@Fe₃O₄@SSM both show good performance in water repellency,self-cleaning property,long-term storage and chemical stability.?2?Superhydrophobic filter paper and cotton fabric were prepared on by adsorption and solution immersion process.Copper ions were adsorbed on the substrates surface when they were immersed into Cu?NO₃?₂ solution.Then the Cu?OH?₂ nanostructures were generated on the surfaces by immersing into NaOH solution.After modification with stearic acid,superhydrophobic surface was prepared on filter paper and cotton fabric.After the superhydrophobic filter paper and cotton fabric were exposed to air for 6 months,superhydrophobic properties were maintained.Water droplets can carry away contaminants covered on the superhydrophobic filter paper and cotton fabric,so filter paper and cotton fabric possess self-cleaning properties and can avoid pollution.?3?After being immersed into oxalic acid solution,underwater superoleophobic CuC₂O₄nanostructures were fabricated on the filter paper and cotton fabric with Cu?OH?₂nanostructure.A series of characterization of Cu?OH?₂ and CuC₂O₄ micro/nanostructures revealed that the structure of the CuC₂O₄ is more rough after the reaction in oxalic acid,which led to a more significant underwater superoleophobic property.More importantly,after immersing the CuC₂O₄ filter paper and cotton fabric into the corrosive solutions for a certain time,respectively,the underwater superoleophobic properties were still maintained,showing the corrosion resistance.?4?By simple acid etching and replacement reaction,a composite film comprised of copper and silver?denoted as Cu@Ag?with underwater superoleophobic property was prepared.The etching process did not change the chemical composition of the substrate,but the deposition process changed the chemical composition of the substrate and evidently influenced its microstructure.The influences of different concentration of AgNO₃ solution and deposition time on the pore size of copper mesh with 180 mesh was analyzed by scanning electron microscope and contact angle measurement.In addition,the copper meshes with 60mesh,120 mesh and 200 mesh were selected to analyze and compare the influence of mesh number on the underwater superoleophobic properties.?5?The Cu@Ag@DDT film with superhydrophobic and superoleophilic properties was prepared on the copper mesh and copper foam by modifying the Cu@Ag film with n-dodecanethiol?DDT?.The copper mesh with 60 mesh,120 mesh,180 mesh and 200 mesh were selected to analyze and compare the influence of mesh number on the superhydrophobic property.The mechanical and chemical stability of superhydrophobic Cu@Ag@DDT film were studied by a friction test and immersion process in acid,alkali and salt solutions.?6?The separation capacities of the prepared materials for oil/water separation were evaluated.The results showed that these fabricated materials with special wettability all could separate immiscible oil/water mixtures.But for the emulsified oil/water mixtures,especially emulsions stabilized by surfactants,not all prepared materials were effective.The CS@Fe₃O₄@SSM,Cu?OH?₂ filter paper and Cu@Ag@DDT copper foam separated the water-in-oil emulsions,and underwater superoleophobic CuC₂O₄ filter paper and Cu@Ag copper foam separated the oil-in-water emulsions.The oil/water separation mechanisms were systematically discussed.Simple,low-cost and environmentally-friendly preparation approaches make these special wettable materials suitable for practical oil/water separation.