Tianhui Ren

A cellulose sponge with robust superhydrophilicity and under-water superoleophobicity for highly effective oil/water separation

We fabricate a cellulose sponge with stable superoleophobicity (θoil > 150°) under water and superhydrophilic wettability (θwater ≈ 0°) under oil without any further chemical modification for oil–water emulsion separation. The cellulose sponge shows superoleophobicity to various oils under water and possesses stable superoleophobicity in corrosive liquids like strong acid, alkali and salt solution. The sponge is made from the dissolution and regeneration of cellulose powder which is green, low cost, simple and easy to scale up. The natural hydrophilicity of the cellulose ensures its excellent under-water superoleophobicity and antifouling properties. The double layer construction of different pore sizes, which contains a top-layer with a pore size lower than 1 μm and a sub-layer with a pore size larger than 3 μm, ensures that the oil phase is resisted and the water phase easily and quickly permeates the sponge. Our cellulose sponge can separate oil–water mixtures, with >99.94% separation efficiency, solely using gravity and has excellent antifouling properties.

Low Drag Porous Ship with Superhydrophobic and Superoleophilic Surface for Oil Spills Cleanup

To efficiently remove and recycle oil spills, we construct aligned ZnO nanorod arrays on the surface of the porous stainless steel wire mesh to fabricate a porous unmanned ship (PUS) with properties of superhydrophobicity, superoleophilicity, and low drag by imitating the structure of nonwetting leg of water strider. The superhydrophobicity of the PUS is stable, which can support 16.5 cm water column with pore size of 100 μm. Water droplet can rebound without adhesion. In the process of oil/water separation, when the PUS contacts with oil, the oil is quickly pulled toward and penetrates into the PUS automatically. The superhydrophobicity and low water adhesion force of the PUS surface endow the PUS with high oil recovery capacity (above 94%) and drag-reducing property (31% at flowing velocity of 0.38m/s). In addition, the PUS has good corrosion resistance and reusability. We further investigate the wetting behavior of water and oil, oil recovery capacity, drag-reducing property, and corrosion resistance of the PUS after oil absorbed. The PUS surface changes significantly from superhydrophobic to hydrophobic after absorbing oil. However, the oil absorbed PUS possesses better drag-reducing property and corrosion resistance due to the changes of the motion state of the water droplets.

Three-dimensional structured sponge with high oil wettability for the clean-up of oil contaminations and separation of oil–water mixtures

Oil spills not only result in extensive economic losses but also damage marine ecological environments. A series of materials with special wettability are investigated for the separation of oil–water mixtures. However, few studies have investigated the adsorption behaviors of sponges to crude oil (high viscosity). To solve the restrictions of high viscosity oil absorption, low oil absorption rate and oil–water emulsion separation of oil absorption materials, a superhydrophobic and superoleophilic polyurethane (PU) sponge was synthesized via an environmentally friendly surface grafting of a polymer molecular brush. This grafted sponge exhibited high oil absorption rate because of the expansion in oil and collapse in water of the polymer molecular brushes. The grafted PU sponge also possessed high absorption capacity (23 times of the self weight), high oil retention (93%), high mechanical strength and good recyclability (more than 400 times). We anticipate that the grafted sponge will have numerous applications and will show outstanding performance on a larger scale. A quick clean-up of marine spilled oil/organic solvents and the separation/recycling of an oil–water mixture/emulsion can also be achieved.

Ultra low water adhesive metal surface for enhanced corrosion protection

A superhydrophobic surface with ultra low water adhesive force is fabricated on various metals for enhanced corrosion protection. The superhydrophobic surface is constructed by passivated zinc oxide (ZnO) and low surface energy poly(dimethylsiloxane) (PDMS). The process of wettability transformation and corrosion are evaluated by a salt spray test and electrochemical measurement. The superhydrophobic surface is separated layer-by-layer to reveal the function of each layer in corrosion protection. The surface adhesive force is applied as a novel metric for precisely determining the wettability state on the substrate surface. The results reveal that the ultra low water adhesive force of the superhydrophobic surface can effectively suppress water condensation on the metal surface which can suppress the transformation from the Cassie to Wenzel state. The superhydrophobic surface can effectively inhibit corrosion because of the synergistic effect of the triple layered protection system of air, PDMS and ZnO.

The tribological behaviour and tribochemical study of B–N type borate esters in rapeseed oil—compound versus salt

Two novel borate ester additives, (2-(2-(bis(2-hydroxyethyl)amino)ethoxy)-1,3,2-dioxaborolan-4-yl)methyl oleate and a tris(2-hydroxyethyl)amine salt of (2-hydroxy-1,3,2-dioxaborolan-4-yl)methyl oleate were prepared and used as anti-wear and extreme pressure agents in rapeseed oil. The tribological performance was evaluated using a four-ball machine. The results show that the additives possess high anti-wear and extreme pressure properties. XANES, XPS and AFM were used to analyse the composition and structure of boundary films at the worn surfaces. The results for the compound and salt of borate esters are compared, and it is shown that the boundary films formed by compound or salt are similar and mainly composed of B2O3.

Study of synergistic effect of cellulose on the enhancement of photocatalytic activity of ZnO

Semiconductor photocatalysts play a major role in photocatalytic process. Zinc oxide (ZnO) is supposed to be a preferred photocatalyst due to its high photosensitivity, mechanical–thermal stability, tunable morphology and non-toxicity. To enhance the photocatalytic activity of ZnO, cellulose/ZnO composite films (CZ films) with snowflake-like ZnO micro/nanoparticles immobilized in cellulose matrix were prepared by a simple dissolution and regeneration of cellulose and subsequently one-step hydrothermal synthesis of ZnO. The immobilization of ZnO was conducive to overcoming the shortcomings of aggregation easily and reclamation difficulty of scattered nanopowders. The obtained CZ films exhibited excellent photocatalytic efficiency (85.3%) to degrade methylene blue with minor amount of ZnO photocatalyst (<6xa0mg). The experimental results show that a photocatalytic process involving absorption–degradation–desorption was proposed. Notably, the synergistic effects between cellulose film and the supported ZnO via absorption and desorption processes were important to enhance the photocatalytic efficiency. This work provided an effective method to support ZnO photocatalyst and improve the photocatalytic efficiency via a functional substrate.