The Preparation And Properties Of Oil/Water Separation Materials With Special Wettability

With the rapid development of the chemical industry and the oil industry,the growing number of industrial oil and oil spills in the world has caused serious environmental and ecological problems.However,almost all of traditional oil/water separation methods have problems in separation efficiency and energy consumption,and will bring environmental concerns.Therefore,oily wastewater and its corresponding oil/water separation technologies have attracted extensive attention from governments and researchers.With the study of the phenomenon of superwetting of creature in nature and the development of solid surface interface theory,the surface interface of materials with superhydrophobic and superlipophilic prepared by imitating the superwetting phenomenon in nature show broad application prospects,such as oil/water separation.From the current research point of view,superhydrophobic oil/water separation materials are mainly divided into two-dimensional(2D)filter material and three-dimensional(3D)absorption materials.The mechanical properties of the 2D mesh substrate and the reusability of the 3D porous substrate are limited,and the roughness of the substrate surface is more fragile and easily damaged,making it difficult to maintain superhydrophobicity.These defects greatly limit the application of superhydrophobic oil/water separation materials.In view of these problems,a series of superhydrophobic or high hydrophobic surfaces were designed and prepared by different surface modification methods based on metal copper(copper mesh and copper foam)substrate with good mechanical properties.The chemical composition,morphology and wettability of the modified substrate surface were analyzed by field emission scanning electron microscopy(FE-SEM),X-ray photoelectron spectroscopy(XPS)and contact angle measuring instrument,and the oil/water separation performance was evaluated by self-designed oil/water separation device.The results provide a solid theoretical and experimental basis for the design and preparation of oil/water separation materials with special wettability.The main contents and results of the study are as follows:(1)The rough structure was constructed on the copper mesh(CM)substrate by nitric acid(HNO3)etching method,and then the etched CM was hydrophobized by n-dodecyl mercaptan(NDM)and FAS to prepare a series of superhydrophobic copper mesh.The effects of HNO3 etching time,copper mesh number and low surface energy on the wettability of modified CM were investigated.The oil/water separation performance of modified copper mesh was also studied.The study indicated that the increase of etching time and the mesh of CM can effectively improve the hydrophobicity of the modified CM;FAS and NDM can effectively improve the surface hydrophobicity,and FAS hydrophobic modification effect is better than that of NDM.When the concentration of HNO3 is 4 mol/L,the etching time is 4 min and the low surface energy modifier is FAS,the surface WCA of the modified CM can reach 154 °,the oil/water separation efficiency can reach more than 95% with up to 558.6 Pa immersion pressure.(2)A simple dip-coating method was explored to construct hierarchical structures on a 3D copper foam(CF)surface by combining the intrinsic properties of mussel-inspired polydopamine(PDA)and a 3D metal structure.The CF substrate was sequentially modified with PDA and Ag nanoparticles(NPs)and then coupled with NDM to create a durable superhydrophobic CF for oil/water separation.The morphology,chemical composition and wettability of the fabricated modified CF surface were characterized.The modified CF surface possesses an increased roughness and exhibits superhydrophobicity,with water contact angle values greater than 150°.The PDA coating on the CF surface can reduce silver ions and anchor the formed NPs onto the surface to construct the hierarchical structure of the superhydrophobic CF.Furthermore,the oil/water separation properties were also investigated.The modified CF can separate a series of oil/water mixtures with a high efficiency and relatively high intrusion pressure.More importantly,the modified CF retains its high efficiency after 30 repeated uses(more than 98% for a dodecane/water mixture),exhibiting excellent durability.(3)A series of thermosetting fluorine-containing acrylate copolymers were prepared by free radical polymerization of methyl methacrylate(MMA),butyl acrylate(BA),hydroxyethyl methacrylate(HEMA)and dodecafluoroheptyl methacrylate(DHFMA),which is initiated with AIBN.Then,a corresponding polymer coating based on CF was prepared by crosslinking and curing the copolymer with hexamethylene diisocyanate(HDI).The effects of MMA and BA ratio on the Tg of the copolymer and the hardness,adhesion,solvent resistance and heat resistance of the coating were investigated.Additional,the effects of DHFMA content and polymerization process on the surface wettability of modified CF were investigated,and the oil /water separation performance of modified CF was studied.The study indicated that with the increase of the ratio of MMA and BA,the Tg of the copolymer increased,the hardness of the coating increased,the coating adhesion decreased,the coating solvent resistance was enhanced,and the coating heat resistance did not change significantly.When the ratio of MMA to BA is 6:4,the copolymer Tg is 25.8? and the coating hardness is 2B,the adhesion grade is 1,80 times MEK wiping and does not change at 200? for 24 h.The wettability of CF surface is changed from hydrophilicity to hydrophobicity after modification with fluorocopolymer,and its hydrophobicity increases with the content of fluorine functional monomer DHFMA.When the content of DHFMA is only about 10%,the WCA of fluorine-containing polymer modified CF prepared with post-polymerization process can reach 137°.The polymer coating modified CF can effectively separate a series of oil/water mixture,and the separation efficiency is more than 95.0% with up to 637 ± 35 Pa immersion pressure.