Zhengxin Gao

Fabrication of superhydrophobic/superoleophilic cotton for application in the field of water/oil separation

Cotton with superhydrophobic and superoleophilic properties had been successfully fabricated for application in the field of oil/water separation by the combination of SiO2 nanoparticles on cotton fiber surface and subsequent octadecyltrichlorosilane modification. The as-prepared cotton could be used to selectively absorb various common oils and organic solvents up to above 50 times of its own weight while repelling water completely. The absorbed oils were easily collected by a simple vacuum filtration, and the recovered cotton could be reused for several cycles while still keeping high absorption capacity. Moreover, the as-prepared cotton was simply spun into cloth, which not only could be tailored to the water-repellent clothing but also could be used in the oil/water separation filter system. The results presented in this work might provide a simple, low-cost and environment friendly approach for application in the field of water/oil separation.

Fabrication of TiO2/EP super-hydrophobic thin film on filter paper surface.

A composite filter paper with super-hydrophobicity was obtained by adhering micro/nano structure of amorphous titanium dioxide on the filter paper surface with modifying low surface energy material. By virtue of the coupling agent, which plays an important part in bonding amorphous titanium dioxide and epoxy resin, the structure of super-hydrophobic thin film on the filter paper surface is extremely stable. The microstructure of super-hydrophobic filter paper was characterized by scanning electron microscopy (SEM), the images showed that the as-prepared filter paper was covered with uniform amorphous titanium dioxide particles, generating a roughness structure on the filter paper surface. The super-hydrophobic performance of the filter paper was characterized by water contact angle measurements. The observations showed that the wettability of filter paper samples transformed from super-hydrophilicity to super-hydrophobicity with the water contact angle of 153 ± 1°. Some experiments were also designed to test the effect of water-oil separation and UV-resistant by the super-hydrophobic filter paper. The prepared super-hydrophobic filter paper worked efficiently and simply in water-oil separation as well as enduringly in anti-UV property after the experiments. This method offers an opportunity to the practical applications of the super-hydrophobic filter paper.

Improvement of chemical stability and durability of superhydrophobic wood surface via a film of TiO2 coated CaCO3 micro-/nano-composite particles

A superhydrophobic wood surface with a water contact angle of 155° and a sliding angle of 4° was made by attaching stearic acid modified micro-/nano-composite particles made of titanium dioxide coated calcium carbonate. According to tests, the as-prepared wood surface had an outstanding chemical stability and durability.

Mechanical stability of superhydrophobic epoxy/silica coating for better water resistance of wood

Abstract A three-step procedure has been developed for superhydrophobic coating on wood based on epoxy/silica materials in combination with hydrophobization. First, the epoxy resin is adhered to wood by immersing the samples into an epoxy resin acetone solution, then amino-functionalized silica particles are anchored by the epoxide groups, and finally, the created surface is modified by octadecyltrichlorosilane (OTS). The superhydrophobic surface not only is water repellent, as shown by the contact angle (CA) tests, but also decreases essentially the wood’s water absorption as determined by a 120-day water immersion test. The good mechanical stability of the coating was confirmed by a sand collision method.

Superhydrophobic melamine sponge with excellent surface selectivity and fire retardancy for oil absorption

Flexible porous materials have been widely used as precursors for preparing superhydrophobic oil absorbents due to their high capacity and extraordinary recyclability. A final product with multiple characteristics such as superhydrophobicity, fire retardancy, good elasticity, low cost, and environmental friendliness is highly needed for practical applications. In this study, superhydrophobic melamine sponges (SMSs) with the above characteristics were prepared by modifying melamine sponges with polymethylsilsesquioxane via an immersion method. A villiform layer of organosilane was coated on the surface of the melamine fibers and disclosed by scanning electron microscopy. The superhydrophobicity of the sponge with a water contact angle of 156° is due to the increased surface roughness and methyl terminal groups exposed at the interface. Polycondensation reaction between the secondary amine groups on the raw sponge surface and silanol is identified by ATR-FTIR and EDX spectra. The SMS effectively absorbs various organic solvents and oils from water with excellent absorption rate. In addition, it maintains stable superhydrophobicity in extreme environments, including strong acid/alkali conditions, high/low temperatures, and prolonged immersion in organic solvents. Importantly, the SMS retains the intrinsic fire retardancy of the raw melamine sponge. In simulating oil spill environments, the SMS shows good performance in blocking spread of crude oil spill and separating surfactant-free water-in-oil emulsions. These advantages make it a promising material for oily wastewater treatment and oil spill clean-ups.

Preparation and characterization of cotton fabric with potential use in UV resistance and oil reclaim.

Here we report a simple, facile and low-cost approach to the cotton textile with significant properties. After treatment, the cotton textiles exhibit not only an excellent superhydrophobicity with the water contact angle (WCA) of 151.5(o), but also an efficient shielding property against UV with the transmittance under 2.0%. More importantly, this cotton displays an outstanding potency in oil reclaim, which can recycle oil from the waste water with oil stain efficiently. Apparently, our results suggest an innovative material that should find practical and diversified applications, particularly in the field of oil spill cleanup.