Structural Engineering-Enabled Joule Heating Effect Cooperated with Capillary Effect Toward Fast Spreading of Droplets for High-Flux Separation of Viscous Emulsion.

Viscous emulsions with poor fluidity and high adhesion are extremely difficult to separate. Herein, high-flux separation of viscous emulsions is realized by developing structural engineered collagen fibers (CFs)-based composite membrane that featured 3D conductive hierarchical fiber structure with the spaced carbon nanofibers (CNFs) and activated carbon (AC) serving as conductive network and competitive adsorption-based demulsifying sites, respectively. The as-designed membrane structure boosts fast spreading of emulsion droplets on membrane surface aided by the synergistic effect of joule heat in situ generated by the spaced CNFs and the capillary effect derived from CFs, which guarantees the full contact of viscous emulsions with the spaced AC for achieving ultra-efficient demulsifying. The permeation of resultant oily filtrate is accelerated by the capillary effect of hierarchically fibrous structured CFs to exhibit fast transport kinetics, therefore accomplishing high-flux separation. The structural engineered membrane achieves high-performance separation toward different viscous emulsions (55.4-123.7 mPa·s) with separation efficiency >99.9% and flux high up to 259 L m-2 h-1 . The investigations provide a novel structural engineering strategy for realizing high-performance separation of viscous emulsions.

Water-oil dual-channels enabled exceptional anti-fouling performances for separation of emulsified oil pollutant.

Oil contamination has been an increasingly concerned environmental issue due to the large quantity of oily wastewater discharged by the industry. The extreme wettability-enabled single-channel separation strategy guarantees efficient separation of oil pollutant from wastewater. However, the ultra-high selective permeability forces the intercepted oil pollutant to form a blocking layer, which weakens the separation capability and slows the kinetics of permeable phase. As a consequence, the single-channel separation strategy fails to maintain a stable flux for a long-term separation process. Herein, we reported a brand-new water-oil dual-channels strategy for accomplishing an ultra-stable long-term separation of emulsified oil pollutant from oil-in-water nano-emulsion by engineering two drastically opposite extreme wettabilities (i.e. superhydrophilicity and superhydrophobicity) to build the water-oil dual-channels. The strategy established the superwetting transport channels to permit water and oil pollutant to permeate through their own channel. In this way, the generation of intercepted oil pollutant was prevented, which guaranteed an exceptional long-lasting (20 h) anti-fouling performance for successful achievement of an ultra-stable separation of oil contamination from oil-in-water nano-emulsion with high flux retention and high separation efficiency. Therefore, our investigations provided a new route for realizing ultra-stable long-term separation of emulsified oil pollutant from wastewater.

Collagen Fiber-Based Advanced Separation Materials: Recent Developments and Future Perspectives.

Separation plays a critical role in a broad range of industrial applications. Developing advanced separation materials is of great significance for the future development of separation technology. Collagen fibers (CFs), the typical structural proteins, exhibit unique structural hierarchy, amphiphilic wettability, and versatile chemical reactivity. These distinctive properties provide infinite possibilities for the rational design of advanced separation materials. During the past 2 decades, many progressive achievements in the development of CFs-derived advanced separation materials have been witnessed already. Herein, the CFs-based separation materials are focused on and the recent progresses in this topic are reviewed. CFs widely existing in animal skins display unique hierarchically fibrous structure, amphiphilicity-enabled surface wetting behaviors, multi-functionality guaranteed covalent/non-covalent reaction versatility. These outstanding merits of CFs bring great opportunities for realizing rational design of a variety of advanced separation materials that were capable of achieving high-performance separations to diverse specific targets, including oily pollutants, natural products, metal ions, anionic contaminants and proteins, etc. Besides, the important issues for the further development of CFs-based advanced separation materials are also discussed.

Tannin foam immobilized with ferric ions for efficient removal of ciprofloxacin at low concentrations.

The presence of ciprofloxacin (CIP) in natural water may cause potential threats to the environment. Adsorption is a convenient and efficient method to remove CIP from aqueous solution. Bayberry tannin (BT), a natural polyphenol, has been utilized in the synthesis of tannin foam (TF) due to its abundant polyphenolic hydroxyls to chelate with metal ions. The obtained TF was subsequently immobilized with Fe3+ via a facile chelative adsorption to fabricate functional tannin foam (TF-Fe), which was highly porous, with a porosity of 78.93%. The Fe species in the TF-Fe featured good dispersity, which were active for chelative adsorption of CIP. The adsorption of CIP on the TF-Fe was a pH-dependent process. At the optimized pH of 7.0, the TF-Fe provided the adsorption capacity of 91.8 mg g-1. When applied in removal of CIP at the low concentration of 2.0 µg mL-1, a high removal efficiency of 96.60% was still obtained, which was superior to commercial activated carbon (28.78%). The adsorption kinetics were well fitted by the pseudo-second-order rate model while the adsorption isotherms were well described by the Langmuir model. The TF-Fe was capable of recycling, which still maintained a high removal efficiency of 92.25% in the 5th cycle.

Insights into Regional Wetting Behaviors of Amphiphilic Collagen for Dual Separation of Emulsions.

Industrial manufacture generates a huge quantity of emulsion wastewater, which causes serious threats to the aquatic ecosystems. Water-in-oil (W/O) and oil-in-water (O/W) emulsions are two major types of emulsions discharged by industries. However, dual separation of W/O and O/W emulsions remains a challenging issue due to the contradictory permselectivity for separating the two emulsions. In the present investigation, the amphiphilicity-derived regional wetting mechanism of water and oil on the amphiphilic collagen fibers was revealed based on the combination of numerous experiments and molecular dynamics (MD) simulations. Electrostatic interactions and van der Waals force were manifested to be the driving forces of regional wetting in the hydrophilic and hydrophobic regions, respectively. The regional wetting endowed amphiphilic collagen fibers with underwater oleophobicity and underoil hydrophilicity, which enabled dual separation of emulsions by selectively retaining the dispersed water phase of W/O emulsions in the hydrophilic regions while the dispersed oil phase of O/W emulsions in the hydrophobic regions. The achieved separation efficiency was higher than 99.98%, and the flux reached 3337.6 L m-2 h-1. Initial wetting status significantly affects the regional wetting-enabled dual separation. Based on the MD simulations, amphiphilic intramolecular conformations of tropocollagen were suggested to be the origins of regional wetting on collagen fibers. Our findings may pave the way for developing high-performance dual separation materials that are promising to be utilized for the practical treatment of emulsion wastewater.

Zeolitic imidazolate framework-8 templated synthesis of a heterogeneous Pd catalyst for remediation of chlorophenols pollution.

Herein, a heterogeneous Pd catalyst was prepared by embedding Pd nanoparticles in a highly porous nitrogen-doped mesoporous carbon (NMCs) synthesized by the ZIF-8 template. The as-prepared Pd/NMC catalyst was efficient and recyclable in mild catalytic hydrodechlorination of 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol, showing superior performances to those of the activated carbon-supported Pd commercial catalysts.

Encapsulating NiCo2O4 inside metal-organic framework sandwiched graphene oxide 2D composite nanosheets for high-performance lithium-ion batteries.

Ternary transition metal oxides are promising candidates for developing high-performance lithium-ion batteries. In the present investigation, we explored sandwiched composite nanosheets by encapsulating NiCo2O4 nanoparticles inside the pores of ZIF-67 crystals that were in situ grown on both surfaces of graphene oxide (GO). SEM and TEM observations confirmed the successful construction of the sophisticated architecture. For the designed electrode structure, the scaffold of GO provided a fast conductive highway for the encapsulated NiCo2O4 nanoparticles, while the porous and elastic framework of ZIF-67 together with the flexible GO guaranteed efficient accommodation to the volumetric change of NiCo2O4. Moreover, the highly porous composite nanosheets are suitable for electrolyte infiltration, with enhanced ionic transportation kinetics. Accordingly, the reversible capacity of NiCo2O4@ZIF-67/GO was high up to 1025 mA h g-1 and 740 mA h g-1 after 80 cycles at 0.5 and 2.0 A g-1, respectively. At the current density of 4.0 and 8.0 A g-1, the capacity was still retained at 500 and 320 mA h g-1, respectively. Other analyses further manifested that the distinctive structure of NiCo2O4@ZIF-67/GO enhanced the charge transportation kinetics in comparison with the control sample of NiCo2O4@ZIF-67. Our strategy provided a new concept for developing high-performance electrode materials of lithium-ion batteries.

Recyclable Amphiphilic Metal Nanoparticle Colloid Enabled Atmospheric Oxidation of Alcohols.

Developing amphiphilic colloid catalysts is essentially important for realizing environmentally benign biphasic catalysis under atmospheric conditions. Herein, a linear structured plant polyphenol was employed as an amphiphilic stabilizer for preparing a series of amphiphilic Pd nanoparticles (PdNPs) colloids. For the as-prepared PdNPs colloids, the phenolic hydroxyls of plant polyphenols were responsible for the stabilization of PdNPs, whereas the rigid aromatic scaffold of plant polyphenols effectively suppressed the PdNPs from aggregation by providing a high steric effect. Thanks to the coexistence of hydrophilic phenolic hydroxyls and hydrophobic aromatic rings, the plant polyphenols induced tunable amphiphilic properties into the PdNPs, allowing an easier wetting of PdNPs with the substrate molecules. By tuning the content of plant polyphenols in the colloid, the particle size (3.17-4.73 nm) and the dispersity of the PdNPs were facilely controlled. When applied for atmospheric oxidation of insoluble alcohols in water by air, the amphiphilic PdNPs preferentially absorbed the alcohol substrates to create a relatively high-substrate-concentration microenvironment, which improved the mass transfer in the biphasic catalysis, allowing the proceeding of low-temperature (50 °C) atmospheric oxidation of diverse alcohols with high catalytic conversion, including aliphatic alcohols, cyclic aliphatic alcohols, and aromatic alcohols. Furthermore, the amphiphilic PdNPs colloid also exhibited excellent reusability with a conversion yield high up to 97.96% in the fifth cycle. In contrast, the control catalysts of poly(vinylpyrrolidone)- and poly(ethylene glycol)-stabilized PdNPs were completely inactivated in the fifth cycle. As a consequence, our findings provided a new route for developing an environmentally benign aqueous colloid catalyst that is both highly active and recyclable for mild biphasic oxidation reaction systems.