Fabrication Of Micro-and Nano-scale Interfacial Materials With Special Wettability And Their Applications In Oil/Water Separation

Oil spills and industrial organic pollutants have induced severe water pollutions and threaten every species in ecological system. To handle with the oily water, special wettability stimulated materials was developed in the past decade to separate the oil-and-water mixtures. This article comprehensively reviewed the nano-scale interfacial materials with special wettabilities to water and oils under given circumstances and their applications in the field of oil/water separation. Inspired by the natural superhydrophobic surfaces, scientists extened the superhydrophobicity to the artificial engineering materials and developed the materials with practical applications such as self-cleaning surfaces, micro-fluid devices and oil/water separation films. Herein, we commonly fabricated the special wettability stimulated oil/water separation materials based on a lot of porous substrates, such as fabrics, sponges and copper meshes. Our main research content is mainly focused on two aspects:controlling the surface morphology and altering the surface chemical composition.First, as is known, most of the transition metal elements show strong coordination effect with the thiols. Therefore, the superhydrophobic fabrics and sponges were fabricated from in situ growth of Group VIII and IB metals and oxide nanoparticles (e.g., Fe, Co, Ni, Cu, and Ag) on fabrics and followed by surface modification with thiol. Also, the advantages and disadvantages of in situ growth of metal simple substances and metal oxides were compared. It was obvious that in situ growth of metal simple substances is superior compared with that of metal oxides since the in situ growth of metal simple substances is more controllable for its reaction process. With Ag, for example, the wettability and morphology of the Ag nanoparticles coated fabric can be well controlled by altering the precursor concentration. Accordingly, as-prepared fabrics and sponges can be used to separate water-and-oil mixtures, for both the oils possess densities larger than water and oils possess densities smaller than water.Then, the superhydrophobic and superoleophilic copper mesh films were also developed by a facile electrochemical deposition process and followed by surface modification with thiol. The surface morphology of the as-prepared superhydrophobic copper mesh film is affected by various experimental parameters such as electroplating time, current, electrolyte temperature and electrolyte concentration. The optimal experimental parameters were obtained by investigating the wettability variation with these parameters. The mechanical stability was specifically studded by compression, thermal, and ultrasonic tests to illustrate the good stability of as-prepared copper mesh films. Accordingly, as-prepared copper mesh films can be applied for oil/water separation efficiently and rapidly.As the former methods illustrated the significant role of surface morphology to the surface wettability, the controllable wettability induced by the changing of the surface chemical composition was also conducted by simultaneously grafting the methyl-terminated thiol and carboxyl-terminated thiol on the rough structured fabrics and copper mesh films. In air, the resultant fabric/copper mesh films shows superhydrophobic property to neutral and acidic water and superhydrophilic property to basic water. In aqueous environment, the fabric/copper mesh films shows superoleophilic property in acidic/neutral aqueous environment and superoleophobic property in basic aqueous environment. Based on this property, as-prepared samples were successfully used for the controllable oil/water separation that can both remove oils from water and remove water from oils.In addition, it is found that, compared to other transition metal elements, the as-prepared textiles with Fe nanoparticles grown cannot be modified by thiols unless accompanying by certain post-treatment. On the basis of this property, superhydrophobic-superhydrophilic hybrid textiles were prepared by combining the in situ growth of Fe and Co nanoparticles with the following immersion in ethanol solution of thiol. The ratio of superhydrophobic component to superhydrophilic component on the surface of the as-coated textile could be changed by altering the concentrations and the proportion of Fe(â…¡) and Co(â…¡) ions in the precursor solution, thus realizing the tunable transformation of the whole wettability of textiles from superhydrophobicity to superhydrophilicity. This study would inspire researchers to develop the novel materials with the water harvesting property.