Jiang Cheng

Inspired by Stenocara Beetles: From Water Collection to High-Efficiency Water-in-Oil Emulsion Separation

Inspired by the water-collecting mechanism of the Stenocara beetles back structure, we prepared a superhydrophilic bumps-superhydrophobic/superoleophilic stainless steel mesh (SBS-SSM) filter via a facile and environmentally friendly method. Specifically, hydrophilic silica microparticles are assembled on the as-cleaned stainless steel mesh surface, followed by further spin-coating with a fluoropolymer/SiO2 nanoparticle solution. On the special surface of SBS-SSM, attributed to the steep surface energy gradient, the superhydrophilic bumps (hydrophilic silica microparticles) are able to capture emulsified water droplets and collect water from the emulsion even when their size is smaller than the pore size of the stainless steel mesh. The oil portion of the water-in-oil emulsion therefore permeates through pores of the superhydrophobic/superoleophilic mesh coating freely and gets purified. We demonstrated an oil recovery purity up to 99.95 wt % for surfactant-stabilized water-in-oil emulsions on the biomimetic SBS-SSM filter, which is superior to that of the traditional superhydrophobic/superoleophilic stainless steel mesh (S-SSM) filter lacking the superhydrophilic bump structure. Together with a facile and environmentally friendly coating strategy, this tool shows great application potential for water-in-oil emulsion separation and oil purification.

Durably Antibacterial and Bacterially Antiadhesive Cotton Fabrics Coated by Cationic Fluorinated Polymers

Considerable attention has been devoted to producing antibacterial fabrics due to their very wide applications in medicine, hygiene, hospital, etc. However, the poor antibacterial durability and bad bacterial antiadhesion capacity of most existing antibacterial fabrics limit their applications. In this work, a series of antibacterial and polymeric quaternary ammonium monomers with different alkyl chain length were successfully synthesized to copolymerize with fluorine-containing and other acrylic monomers to generate cationic fluorinated polymer emulsions and durably antibacterial and bacterially antiadhesive cotton fabrics. The relation between antibacterial constituent and its antibacterial activity was investigated. The study indicated that the alkyl chain length and contents of the antibacterial monomers, as well as the add-on percentage of polymer greatly influenced the antibacterial activities of the fabrics. In addition, it was found that incorporation of fluorine component into the polymer greatly enhanced the antibacterial activity and bacterial antiadhesion of the treated fabrics due to the low surface energy induced hydrophobicity. Finally, antibacterial and antiadhesive models of action of the obtained fabrics were illustrated.

Nature-Inspired Strategy toward Superhydrophobic Fabrics for Versatile Oil/Water Separation

Phytic acid, which is a naturally occurring component that is widely found in many plants, can strongly bond toxic mineral elements in the human body, because of its six phosphate groups. Some of the metal ions present the property of bonding with phytic acid to form insoluble coordination complexes aggregations, even at room temperature. Herein, a superhydrophobic cotton fabric was prepared using a novel and facile nature-inspired strategy that introduced phytic acid metal complex aggregations to generate rough hierarchical structures on a fabric surface, followed by PDMS modification. This superhydrophobic surface can be constructed not only on cotton fabric, but also on filter paper, polyethylene terephthalate (PET) fabric, and sponge. AgI, FeIII, CeIII, ZrIV, and SnIV are very commendatory ions in our study. Taking phytic acid-FeIII-based superhydrophobic fabric as an example, it showed excellent resistance to ultraviolet (UV) irradiation, high temperature, and organic solvent immersion, and it has good resistance to mechanical wear and abrasion. The superhydrophobic/superoleophilic fabric was successfully used to separate oil/water mixtures with separation efficiencies as high as 99.5%. We envision that these superantiwetting fabrics, modified with phytic acid-metal complexes and PDMS, are environmentally friendly, low cost, sustainable, and easy to scale up, and thereby exhibit great potentials in practical applications.

Emission, mass balance, and distribution characteristics of PCDD/Fs and heavy metals during cocombustion of sewage sludge and coal in power plants.

The emission, mass balance, and distribution characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) as well as those of heavy metals (Hg, Cd, Pb, Cr, and Cu) were investigated during the cocombustion of 5%, 10%, 15%, and 20% sewage sludge (SS) in a pulverized coal power plant. The PCDD/F emissions increased from 7.00 to 32.72 pg I-TEQ/Nm(3) as the amount of SS in the mixed fuel (MF) increased. High sulfur content and relatively low chlorine levels in MF resulted in lower PCDD/F emissions. SS exhibited a remarkable difference in congener profiles compared with flue gas, bottom ash, and fly ash. The negative dioxin mass balance indicated that the cofiring of SS with coal in power plants was not a source but a sink of dioxins. The concentrations and emission factors of heavy metals in flue gas and bottom ash, as well as fly ash, all exhibited a tendency to increase with increasing input values of heavy metals in MF. The distribution characteristics of the investigated heavy metals were primarily dependent on the evaporative properties of these metals. The availability of chlorine could alter the heavy metal distribution behavior. The emitted pollutants in the power plant were below the legal limits.

Evaluation of PCDD/Fs and metals emission from a circulating fluidized bed incinerator co-combusting sewage sludge with coal

The emission characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and heavy metals were evaluated during co-combustion of sewage sludge with coal from a circulating fluidized bed incinerator. The stack gas, slag and fly ash samples were sampled and analyzed. The gas-cleaning system consisted of electrostatic precipitators and a semi-dry scrubber. Results showed that the stack gas and fly ash exhibited mean dioxin levels of 9.4 pg I-TEQ/Nm3 and 11.65 pg I-TEQ/g, respectively, and showed great similarities in congener profiles. By contrast, the slag presented a mean dioxin level of 0.15 pg I-TEQ/g and a remarkable difference in congener profiles compared with those of the stack gas and fly ash. Co-combusting sewage sludge with coal was able to reduce PCDD/Fs emissions significantly in comparison with sewage sludge mono-combustion. The leaching levels of Hg, Pb, Cd, Ni, Cr, Cu, and As in the fly ash and slag were much lower than the limits of the environmental protection standard in China. These suggest that the co-combustion of sewage sludge and coal is an advisable treatment method from an environmental perspective.

Droplet Motion on a Shape Gradient Surface

We demonstrate a facile method to induce water droplet motion on an wedge-shaped superhydrophobic copper surface combining with a poly(dimethylsiloxane) (PDMS) oil layer on it. The unbalanced interfacial tension from the shape gradient offers the actuating force. The superhydrophobicity critically eliminates the droplet contact line pinning and the slippery PDMS oil layer lubricates the droplet motion, which makes the droplet move easily. The maximum velocity and furthest position of droplet motion were recorded and found to be influenced by the gradient angle. The mechanism of droplet motion on the shape gradient surface is systematically discussed, and the theoretical model analysis is well matched with the experimental results.

Cure kinetics and chemorheological behavior of a wind epoxy resin system and its viscoelastic properties reinforced by glass fiber matt with process of vacuum assisted resin transfer molding

In order to investigate the processability of a wind epoxy resin for the vacuum-assisted resin transfer molding (VARTM) process, a differential scanning calorimeter and rheometry instrument were applied to characterize the curing properties and study the chemorheological behavior to obtain a better understanding of the resin system in order to define the implementation of the process. The curing temperature parameters were established along with a cure kinetic model to predict the cure behavior. In addition, the influence of the gelation and vitrification was also examined by rheological methods. No obvious vitrification appeared in the epoxy system and the apparent active energy of the cure reaction calculated by gel time was almost the same as the differential scanning calorimetry result. What is more, the viscoelastic properties of the composite reinforced by glass fiber matt was characterized through dynamic mechanical analysis, and it proved that post-cure was necessary to ensure complete cure and that the stiffness increased several magnitudes after glass fiber reinforcement.

Thermal Properties and Crystallite Morphology of Nylon 66 Modified with a Novel Biphenyl Aromatic Liquid Crystalline Epoxy Resin

In order to improve the thermal properties of important engineering plastics, a novel kind of liquid crystalline epoxy resin (LCER), 3,3′,5,5′-Tetramethylbiphenyl-4,4′-diyl bis(4-(oxiran-2-ylmethoxy)benzoate) (M1) was introduced to blend with nylon 66 (M2) at high temperature. The effects of M1 on chemical modification and crystallite morphology of M2 were investigated by rheometry, thermo gravimetric analysis (TGA), dynamic differential scanning calorimetry (DSC) and polarized optical microscopy (POM). TGA results showed that the initial decomposition temperature of M2 increased by about 8 °C by adding 7% wt M1, indicating the improvement of thermal stability. DSC results illustrated that the melting point of composites decreased by 12 °C compared to M2 as the content of M1 increased, showing the improvement of processing property. POM measurements confirmed that dimension of nylon-66 spherulites and crystallization region decreased because of the addition of liquid crystalline epoxy M1.

Mechano-Chemical Preparation and Application of Mulberry-Like CaCo3/SiO2 Composite Particles in Superhydrophobic Films

This study focuses on preparation of mulberry-like CaCO3/SiO2 composite particles with a mechanochemical method and their application in superhydrophobic films. Silicon dioxide nanoparticles were adhered to calcium carbonate microparticles to form mulberry-like composite particles through vigorous stirring, which prevented agglomeration of silicon dioxide nanoparticles and maintained their nanocharacteristics. Then, hexamethyldisilazane was employed for hydrophobic modification of the mulberry-like CaCO3/SiO2 composite particles. The effect of CaCO3/SiO2 mass ratios, stirring speed, reaction temperature, and amount of modifying reagent on morphology and lipophilicity of composite particles was studied. Moreover, the superhydrophobic films with excellent film properties were obtained by through combination of mulberry-like CaCO3/SiO2 hydrophobic composite particles and RTV silicon rubber. The water contact angle and sliding angle of the superhydrophobic surface were measured to be 170 ± 2.5° and 4°, respectively. This approach proves to be ideal for substantial improvement of the self-cleaning property of RTV silicon rubber anti-pollution flashover coating.

Preparation, characterization, and properties of novel bisphenol-A type novolac epoxy-polyurethane polymer with high thermal stability

In this study a series of modified bisphenol-A type novolac epoxy resins (MNEPs) were synthesized from bisphenol-A type novolac epoxy resin (NEP) and propionic acid (PA) by a one-step ring-opening reaction process in the presence of tetramethylammonium bromide as catalyst. Fourier transform infrared and 1 H-NMR were employed to confirm the chemical structures of the MNEPs. The spectra results indicated that MNEPs with different hydroxyl contents were obtained successfully by different ring-opening rates of NEP. In addition, Intercross-linked epoxy-polyurethane composites (MNEP-PUs) were also obtained by curing reaction among MNEP, cross linker polyisocyanate IL1351 and phthalic anhydride(PHA). The thermal stability of MNEP-PUs and the conventional polyol PU A450/IL1351 were determined and compared. The thermal analysis demonstrated that the obtained MNEP-PUs exhibited much better thermal stability than the conventional polyurethane system A450/IL1351, and the thermal stability of MNEP-PUs was correlated to the content of MNEP. Moreover, physico-chemical properties of MNEP-PUs such as pencil hardness, adhesive attraction, solvent resistance were reported. It demonstrated that incorporating MNEP into MNEP-PUs as inherent hardness of MNEP-PUs could greatly improve pencil hardness, adhesive attraction, water, acid and alkali resistance of MNEP-PUs.