Zhenxing Wang

Mussel-Inspired Hybrid Coatings that Transform Membrane Hydrophobicity into High Hydrophilicity and Underwater Superoleophobicity for Oil-in-Water Emulsion Separation

We first report here mussel-inspired, hybrid coatings formed in a facile manner via simultaneous polymerization of mussel-inspired dopamine and hydrolysis of commercial tetraethoxysilane in a single-step process. The hybrid coatings can firmly adhered on hydrophobic polyvinylidene fluoride (PVDF) substrate, and the hydrophilicity of the coating can be tuned by adjusting silane concentration. The reason for the changed hydrophilicity of the coating is disclosed by a series of characterization, and was applied to rationally design optimized hybrid coatings that transform commercial PVDF microfiltration (MF) membrane hydrophobicity into high hydrophilicity with excellent water permeability and underwater superoleophobicity for oil-in-water emulsion separation. The PVDF MF membrane decorated with optimized coatings has ultrahigh water flux (8606 L m(-2) h(-1) only under 0.9 bar, which is 34 times higher than that of pristine membrane), highly efficient oil-in-water emulsion separation ability at atmospheric pressure (filtrate flux of 140 L m(-2) h(-1)) and excellent antifouling performance. More importantly, these membranes are extremely stable as underwater superoleophobicity are maintained, even after rigorous washings or cryogenic bending, disclosing outstanding stability. The simplicity and versatility of this novel mussel-inspired one-step strategy may bridge the material-induced technology gap between academia and industry, which makes it promising for eco-friendly applications.

Mussel-inspired tailoring of membrane wettability for harsh water treatment

Novel hybrid coatings with excellent wettability are architecturally constructed on the surfaces of different types of separation membranes via simultaneous polymerization of mussel-inspired dopamine and hydrolysis of commercially available and low-cost silane through a highly efficient one-step approach. After coating with the designed hybrid coatings, the ultrafiltration (UF) membranes possess high hydrophilicity and excellent dry storage ability while the microfiltration (MF) membranes are endorsed with superhydrophilicity and underwater superoleophobicity. Such unique UF and MF membranes can be deployed for treating protein-rich water with drastically enhanced functions and separating oily water (oil-in-water emulsion) under atmospheric conditions with ultrahigh water flux and superior antifouling abilities. This versatile strategy to tailor membrane surface wettability paves the way for separation membranes to be used in harsh water environmental remediation and greatly stimulates the rapid development of mussel-inspired pDA based hybrid materials for advanced applications.

A novel mussel-inspired strategy toward superhydrophobic surfaces for self-driven crude oil spill cleanup

The current available superhydrophobic modification techniques that utilize mussel-inspired polydopamine (pDA) to construct hierarchical structures require the addition of nanoparticles or the usage of a high concentration of dopamine. These requirements are expensive and therefore lower the application efficiency. Herein, for the first time, a superhydrophobic fabric was prepared by a novel and simple mussel-inspired strategy with a much lower concentration of dopamine without any additional nanoparticles. Folic acid (FA) was first applied to a surface to induce the formation of rough pDA coatings with hierarchical structures. These hierarchical structures can be readily controlled by adjusting FA concentration or coating duration. After octadecylamine (ODA) chemical manipulation, the obtained fabric exhibited water contact and rolling off angles of about 162° and 7°, respectively, indicating that it was endowed with superhydrophobicity. Importantly, the superhydrophobic fabric can withstand continuous and drastic 3.5 wt% NaCl solution rinses and repeated tearing with an adhesive tape more than 30 times, suggesting that it has excellent durability. This novel mussel-inspired strategy can facilely and cost-effectively realize superhydrophobic manipulation and tailoring of materials. Moreover, an energy-saving and highly-efficient mini boat fabricated from our novel superhydrophobic fabric was utilized for self-driven oil spill cleanup. The boat can automatically recycle crude oil spills while floating freely on water with a cleanup rate of crude oil spill up to 97.1%, demonstrating great potential in environmental remediation. The novel strategy designed in this study will inspire the fast development of mussel-inspired superhydrophobic materials for applications in various fields.

Highly regenerable alkali-resistant magnetic nanoparticles inspired by mussels for rapid selective dye removal offer high-efficiency environmental remediation

Most recently, polydopamine (PDA) and its hybrid nanomaterials have been developed as promising adsorbents to remove organic dyes. However, PDA-based adsorbents are typically limited by a poor alkali resistance, lack of selective adsorption capacity and unsatisfactory recyclability. Herein, novel PDA-based magnetic nanoparticles are fabricated for the first time via the simultaneous incorporation of PDA and poly(ethylenimine) (PEI) on Fe3O4 nanoparticles simply in one step to overcome almost all the disadvantages of “traditional” PDA adsorbents. The constructed PDA-based magnetic nanoparticles have an ultrathin shell layer (only about 3 nm, much thinner than that of other PDA adsorbents) and can withstand strong alkaline solutions (0.1 M NaOH, pH = 13), exhibiting an excellent alkali resistance. Remarkably, the nanoparticles show superior performance in smart and fast selective removal (>95% in just five minutes) of anionic dyes from dye mixtures and can maintain their high efficiency (>90%) even after 10 cycles, indicating the unprecedented selective adsorption capacity and the desirable recyclability. The adsorption process follows pseudo-second order reaction kinetics, as well as the Langmuir isotherm, indicating that anionic dyes are monolayer adsorbed on the hybrid by electrostatic interaction. In particular, the facile regeneration of the novel composite nanoparticles can be accomplished within only several minutes, demonstrating an excellent regeneration ability. Our study can provide new insights into utilizing mussel-inspired materials for environmental remediation and creating advanced magnetic materials for various promising applications.

Simply realizing “water diode” Janus membranes for multifunctional smart applications

A facile strategy for the preparation of multifunctional Janus membranes (JMs) was proposed, and excellent controllability of the multifunctional JMs was demonstrated in water collection, lossless transportation, decontamination, and on-off control. This novel strategy will accelerate the evolution of JMs from a scientific concept to usable materials for the “real” world.

A bio-inspired CO2-philic network membrane for enhanced sustainable gas separation

For the first time, the exciting reaction between the bio-inspired dopamine and the epoxy functional poly(ethylene oxide) (PEO) at elevated temperatures was found and utilized for fabricating dopamine/poly(ethylene oxide) (PEO) network membranes for sustainable gas separation. The gas transport properties of the synthesized novel membrane were investigated aiming at energy (H2) purification and CO2 capture. The membrane was confirmed to be CO2 selective and exhibited relatively high selectivity especially for CO2/N2 separation. Importantly, the flexible incorporation of low-molecular-weight poly(ethylene glycol) dimethyl ether (PEGDME) into the swollen network membrane greatly improved the gas transport performance and the CO2 permeability was increased by 550%. Furthermore, the temperature and upstream pressure dependence of our developed membranes have been examined in detail. Surprisingly, the plasticization phenomena in the membranes at higher upstream pressure can be harnessed to enhance the gas transport performance by increasing both the CO2 permeability and the CO2/other tested gas selectivity mainly due to the network structure and CO2-philic character. This report will expedite the rapid discovery of new materials derived from bio-inspired dopamine for possibly solving energy and environmental issues.