Fei Zha

A prewetting induced underwater superoleophobic or underoil (super) hydrophobic waste potato residue-coated mesh for selective efficient oil/water separation

Oil/water separation has recently become a worldwide challenge due to expanding industrial oily wastewater and frequent oil spill accidents. The development of a low-cost, biobased, and environmentally friendly material has been attempted to treat environmentally sensitive water pollution caused by oils. Herein, prewetting induced underwater superoleophobic or underoil (super) hydrophobic waste potato residue coated-mesh (PRCM) without any further chemical modification was demonstrated for the first time for selective oil/water separation, which was fabricated by spraying waste potato residue powders (PRP) and waterborne polyurethane (PU) mixtures on a stainless steel mesh. After the PRCM is prewetted with water, water can be removed from the light oil/water mixture by gravity with high separation efficiency. On the other hand, heavy oil can be removed from the oil/water mixture by gravity via the heavy oil prewetted PRCM. The as-prepared PRCM showed a high separation efficiency of above 96.5% for a series of light or heavy oil–water mixtures. In addition, the PRCMs maintained a high separation efficiency of over 98.0% and a stable recyclability even after 40 separation cycles for a kerosene–water mixture. Furthermore, the as-prepared PRCM exhibited excellent environmental stability under a series of harsh conditions that were used for the separation of mixtures of oil and various corrosive materials, including strong acidic, alkaline and salt aqueous solutions.

Underwater superoleophobic palygorskite coated meshes for efficient oil/water separation

Oil/water separation has recently become a global challenging task due to frequent oil spill accidents and increasing industrial oily waste water. Here, we demonstrate for the first time underwater superoleophobic palygorskite coated meshes, which were fabricated by spraying palygorskite and polyurethane mixtures on copper mesh substrates. The underwater superoleophobic meshes were then used to study gravity driven oil/water separation for a series of oil/water mixtures, where only the water from the oil/water mixture is allowed to permeate through the mesh. A separation efficiency of up to 99.6% could be achieved through the coated mesh for the kerosene–water mixture. In addition, the palygorskite coated mesh still maintained a high separation efficiency of over 99.0% and stable recyclability after 50 separation cycles with the surface morphology of the palygorskite coated mesh nearly unchanged. Furthermore, the palygorskite coated meshes exhibit excellent environmental stability under a series of harsh conditions, which are used for the separation of mixtures of oil and various corrosive and active aqueous solutions, including strong acidic, alkaline, or salt aqueous solutions, even hot water. The fabrication approach presented here can be applied for coating large surface areas and to develop a large-scale oil/water separation facility for oil and various corrosive and active aqueous mixtures.

Robust superhydrophobic attapulgite coated polyurethane sponge for efficient immiscible oil/water mixture and emulsion separation

Separation of oil/water mixtures has become an increasingly important subject worldwide because of frequent oil spill incidents and industrial oily wastewater. The filter materials for the mixtures separation need to collect first and then filter, which is energy-intensive and cumbersome. Utilization of adsorbents appears to be an economical and direct way for mixture disposal. In this study, the superhydrophobic polyurethane (PU) sponge is fabricated by coating superhydrophobic attapulgite (APT) onto its skeleton surface. The coated PU sponges exhibit robust superhydrophobicity and high adsorption capability under a series of harsh conditions, which are used for the separation of mixtures of oil and various corrosive solutions and hot water. Moreover, the coated PU sponges can selectively adsorb oils from mixtures under extreme and harsh turbulent conditions. Furthermore, the coated PU sponge connected to a vacuum system could remove up to 3200 times its self-weight in kerosene within 20 s under a vacuum degree of about 30 kPa. More importantly, the coated PU sponges can separate tiny oil droplets from surfactant-stabilized oil-in-water emulsions with a separation efficiency of over 99.87% by employing a compression and agitation procedure. All of these characteristics make the coated PU sponge a promising adsorbent for realizing oil and organic pollutant removal in realistic aquatic environments.

A facile one-step spray-coating process for the fabrication of a superhydrophobic attapulgite coated mesh for use in oil/water separation

Oil/water separation is a worldwide problem due to the increasing emission of industrial oily waste water and the frequent oil spill accidents. Herein, we demonstrate, for the first time, superhydrophobic attapulgite coated mesh films for gravity driven oil water separation, which were fabricated by a facile one-step spray-coating process. The as-prepared attapulgite coated mesh films show both superhydrophobic and superoleophilic properties simultaneously with a high water contact angle of 155° ± 1° and an oil contact angle of 0°. Thus, they can be used to separate a series of oil/water mixtures, such as kerosene, chloroform, and petroleum ether with separation efficiency up to 97% for the kerosene/water mixture. In addition, the as-prepared coated mesh still maintained separation efficiency above 94% and stable recyclability after 40 separation cycles with the surface morphology of the attapulgite coated mesh nearly unchanged. Besides, the separation mechanism for the oil/water mixture was elaborated by interpreting the different states of water droplet on the surface before and during separation, which has been discussed scarcely. Furthermore, the as-prepared attapulgite coated mesh could keep its superhydrophobic property under various harsh conditions, not only for pure water but also for corrosive acidic, alkaline and salt solutions, which suggests attractive potential for practical oil/water separation in industry and everyday life.

Facile Spray-Coating Process for the Fabrication of Tunable Adhesive Superhydrophobic Surfaces with Heterogeneous Chemical Compositions Used for Selective Transportation of Microdroplets with Different Volumes

In this paper, tunable adhesive superhydrophobic ZnO surfaces have been fabricated successfully by spraying ZnO nanoparticle (NP) suspensions onto desired substrates. We regulate the spray-coating process by changing the mass percentage of hydrophobic ZnO NPs (which were achieved by modifying hydrophilic ZnO NPs with stearic acid) in the hydrophobic/hydrophilic ZnO NP mixtures to control heterogeneous chemical composition of the ZnO surfaces. Thus, the water adhesion on the same superhydrophobic ZnO surface could be effectively tuned by controlling the surface chemical composition without altering the surface morphology. Compared with the conventional tunable adhesive superhydrophobic surfaces, on which there were only three different water sliding angle values: lower than 10°, 90° (the water droplet is firmly pinned on the surface at any tilted angles), and the value between the two ones, the water adhesion on the superhydrophobic ZnO surfaces has been tuned effectively, on which the sliding angle is controlled from 2 ± 1° to 9 ± 1°, 21 ± 2°, 39 ± 3°, and 90°. Accordingly, the adhesive force can be adjusted from extremely low (∼2.5 μN) to very high (∼111.6 μN). On the basis of the different adhesive forces of the tunable adhesive superhydrophobic surfaces, the selective transportation of microdroplets with different volumes was achieved, which has never been reported before. In addition, we demonstrated a proof of selective transportation of microdroplets with different volumes for application in the droplet-based microreactors via our tunable adhesive superhydrophobic surfaces for the quantitative detection of AgNO3 and NaOH. The results reported herein realize the selective transportation of microdroplets with different volumes and we believe that this method would potentially be used in many important applications, such as selective water droplet transportation, biomolecular quantitative detection and droplet-based biodetection.

Underoil superhydrophilic desert sand layer for efficient gravity-directed water-in-oil emulsions separation with high flux

Efficient and rapid separation of emulsified oil/water mixtures is urgently needed and still remains a worldwide challenge. Even though traditional superhydrophobic/superoleophilic filtration membranes have demonstrated to be effective for separation of water-in-oil emulsions, they still suffer from complicated fabrication procedures and lower flux, resulting from their nanoscale pore size. Herein, green desert sands (50 μm to 1 mm) with under-oil superhydrophilicity were introduced, for the first time, to develop into a layer for efficient gravity-directed separation of various water-in-oil emulsions, which could avoid not only sophisticated filtration membranes fabrication process but also the use of expensive low energy materials of fluorosilane involved in traditional superhydrophobic materials. It is worth mentioning that the sand layer could serve as an adsorbent material with under-oil superhydrophilicity, achieving ultrafast gravity-driven separation of tiny water droplets from various water-in-oil emulsions with flux as high as 2342 L m−2 h even though the interspacing between the sand particles is greater than the size of emulsified droplets. Moreover, the sand can be abundantly obtained from deserts, which is another advantage that the current filtrate materials do not possess. In summary, this study provides a general avenue to design under-oil superhydrophilic materials for rapid separation of water-in-oil emulsions. Such an approach can provide some new perspectives for fabrication of novel emulsion-separating materials.

Oxidation of Styrene with Molecular Oxygen Catalyzed by Polymer‐Supported O‐Aminobenzoic Acid Salicylaldehyde Schiff‐Base Copper(II) Complex

Schiff‐base complexes of copper supported on chloromethylated polystyrene as a catalyst have been studied in the oxidation of styrene with molecular oxygen. The main products are benzaldehyde and the epoxide of styrene. Compared with the unsupported copper complex, the polymer supported complex has more effective catalytic activity, and could be easily separated and reused. The influences of reaction temperature and the amount of catalyst have also been investigated.

Preparation and catalytic oxidation by polymer supported 4-(2-pyridylazo) rosorcinol–metal complexes

Abstract Polymer-supported 4-(2-pyridylazo) rosorcinol–metal complexes (PS-PAR-M, M=Cu, Co, Ni, Fe) were prepared and characterized by IR, ICP, XPS, and used in the oxidation of ethylbenzene as catalyst. In comparison with their catalytic activities, PS-PAR-Cu was a more effective catalyst for the oxidation of ethylbenzene without solvent. The influences of reaction temperature, the amount of catalyst and substrate concentration, as well as reaction time on the oxidation of ethylbenzene have been investigated. The reaction optimum conditions have been obtained.

Facile fabrication of superhydrophobic meshes with different water adhesion and their influence on oil/water separation

The control of water adhesion is important for superhydrophobic surfaces in numerous applications. Compared with the abundant research on oil/water separation through the use of superhydrophobic materials, research relating to the influence of the water adhesion of superhydrophobic materials on their oil/water separation performance is extremely rare. Herein, superhydrophobic ZnO coated meshes with different water adhesion were successfully prepared by spraying ZnO nanoparticles (NPs) on a stainless steel mesh. By simply changing the percentage of hydrophobic ZnO NPs in the hydrophobic/hydrophilic ZnO NP mixture, superhydrophobic ZnO meshes with different water adhesion have been fabricated successfully. In addition, the separation mechanism for oil/water mixtures is elaborated by interpreting the different states of a water droplet on the surface before and during separation. Furthermore, the influence of the water adhesive property of superhydrophobic meshes on their oil/water separation performance is studied. To the best of our knowledge, this issue has scarcely been considered. It is found that the influence of the adhesive property of the superhydrophobic meshes on their oil/water separation performance can be neglected. The superhydrophobic ZnO coated meshes whether with low or high water adhesion showed nearly the same separation efficiency, which is up to 98.5% for a kerosene and water mixture. The water intrusion pressure and oil flux study exhibit that the low adhesive meshes show a little higher water intrusion pressure and oil flux than the high adhesive meshes. This report assesses the influence of the water adhesion of superhydrophobic materials on their oil/water separation performance, which not only helps us to further understand the mechanism of oil/water separation, but also to design and prepare superhydrophobic surfaces for the effective separation of water from oil.

Oxidation of Cyclohexene with Oxygen Catalyzed by Supported Dinuclear Schiff-Base Complex

Oxidation of cyclohexene, using chloromethylated polystyrene supported dinuclear Schiff-base complexes (PS-DD-M, where M= Cu2+, Co2+, Ni2+ and Mn2+, respectively) as catalyst and molecular oxygen as oxidant, was studied. In the oxidation reaction, cyclohexene was oxidized to 7-oxabicyclo[4,1,0]heptane, 2-cyclohexene-1-ol, 2-cyclohexene-1-one and 2-cyclohexene-1-hydroperoxide. It was found that the conversion of cyclohexene decreases in the order of PS-DD-Cu> PS-DD-Mn>PS-DD-Co>PS-DD-Ni, but the turnover number decreases with PS-DD-Ni>PS-DD-Mn>PS-DD-Co>PS-DD-Cu. A maximum conversion of 43% was observed for PS-DD-Cu/O2 system after a reaction of 10 h at 343 K as catalyst: substrate = 2 mg: 2 mL.