Recent developments on catalytic membrane for gas cleaning

© 2019 Elsevier B.V. Catalytic membrane, a novel membrane separation technology that combines catalysis and separation, exhibits significant potential in gas purification such as formaldehyde, toluene and nitrogen oxides (NOx). The catalytic membrane can remove solid particles through membrane separation and degrade gaseous pollutants to clean gas via a catalytic reaction to achieve green emissions. In this review, we discussed the recent developments of catalytic membranes from two aspects: preparation of catalytic membrane and its application in gas cleaning. Catalytic membranes are divided into organic catalytic membranes and inorganic catalytic membranes depending on the substrate materials. The organic catalytic membranes which are used for low temperature operation (less than 300 °C) are prepared by modifying the polymers or doping catalytic components into the polymers through coating, grafting, or in situ growth of catalysts on polymeric membrane. Inorganic catalytic membranes are used at higher temperature (higher than 500 °C). The catalyst and inorganic membrane can be integrated through conventional deposition methods, such as chemical (physical) vapor deposition and wet chemical deposition. The application progress of catalytic membrane is focused on purifying indoor air and industrial exhaust to remove formaldehyde, toluene, NOx and PM2.5, which are also summarized. Perspectives on the future developments of the catalytic membranes are provided in terms of material manufacturing and process optimization

Transmission of sodium chloride in PDMS membrane during Pervaporation based on polymer relaxation

Polydimethylsiloxane (PDMS) composite membrane is used for treating pharmaceutical wastewater containing NaCl and solvent. In this study, the influence of feed concentrations of NaCl and isobutanol, process temperature and membrane microstructures on salt rejection are evaluated. Microstructures of PDMS membrane before and after separation are characterized by nuclear magnetic resonance (NMR), energy dispersive X-ray spectroscopy (EDS), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Positron annihilation life-time spectroscopy (PALS). The PV results show that NaCl will not spontaneously enter PDMS membrane without isobutanol. However, while NaCl feed concentration is 13 wt%, salt rejection of PDMS membrane drops from 100% to 99.09% with increasing feed concentration of isobutanol (up to 7 wt%). On the contrary, a higher temperature increases salt rejection of PDMS membrane and NaCl permeation through PDMS membrane is not through a vapor permeate process. Due to the relaxation of PDMS polymer chain, when PDMS cross-linking ratio is 0.1, the salt rejection increases from 99.87% to 100% with its thickness increasing from 10 ?m to 17.5 ?m. While the cross-linking ratio rises to 0.2, the salt rejection is 100% with the PDMS layer thickness of 10 ?m. The relationship between relaxation of polymer chains and transport of NaCl in PDMS membrane is an excellent guidance and will be beneficial for the treatment of saline organic wastewater

Continuous and complete conversion of high concentration p-nitrophenol in a flow-through membrane reactor

Here, we report on a green and effective method for the continuous and complete conversion of high concentrations of p-nitrophenol (PNP) using a flow-through membrane reactor and less NaBH4. The catalytic membrane was successfully fabricated by loading Pd nanoparticles onto the surface of a branched TiO2 nanorod-functionalized ceramic membrane. The modification with branched TiO2 nanorods can significantly improve the loading amount of Pd nanoparticles onto ceramic membranes, resulting in enhanced catalytic performance. With 6 mg of Pd, 93 L m−2 hr−1 of flux density and 8.04 cm2 of membrane surface area in the flow-through membrane reactor, PNP at a concentration of 4,000 ppm can be converted to high-value p-aminophenol using less NaBH4 (using a molar ratio of NaBH4:PNP of 9.6) within 24 s at 30°C. More importantly, the conversion can be continuously and stably performed for 240 min

Factors that affect the growth and photosynthesis of the filamentous green algae, Chaetomorpha valida, in static sea cucumber aquaculture ponds with high salinity and high pH

Chaetomorpha valida, dominant filamentous green algae, can be harmful to sea cucumber growth in aquaculture ponds of China. In order to understand the environmental factors affecting the growth of C. valida in sea cucumber aquaculture ecosystems, a combination of field investigations and laboratory experiments were conducted. Field surveys over one year revealed that C. valida survived in sea cucumber aquaculture ponds in salinities ranging from 24.3 ± 0.01‰ to 32.0 ± 0.02‰ and a pH range of 7.5 ± 0.02–8.6 ± 0.04. The high salinity and pH during the period of low C. valida biomass from January to May lay the foundation for its rapid growth in the following months of June to October. Many factors interact in the field environment, thus, laboratory experiments were conducted to determine the isolated effects of pH and salinity on C. valida growth. In laboratory experiments, samples were incubated under different salinity and pH conditions at 25 °C, with a light intensity of 108 μmol photon·m−2·s−1, and a photoperiod of 12 L:12 D. Results showed that salinity and pH significantly affect the growth and Fv/Fm (quantum yield of photosynthesis) of C. valida (p < 0.01). C. valida grew the longest at a salinity of 34‰ and a pH of 8.0. At 34‰ salinity, C. valida grew to 26.44 ± 5.89 cm in 16 days. At a pH of 8.0, C. valida grew to 67.96 ± 4.45 cm in 32 days. Fv/Fm was 0.635 ± 0.002 at a salinity of 32‰, and 0.550 ± 0.006 to 0.660± 0.001 at pH 7.0 to 8.5. Based on these results, we conclude that C. valida can bloom in sea cucumber ponds due to the high salinity and pH of coastal sea waters, which promote growth and maintain the photosynthetic activity of C. valida

Review of advanced road materials, structures, equipment, and detection technologies

As a vital and integral component of transportation infrastructure, pavement has a direct and tangible impact on socio-economic sustainability. In recent years, an influx of groundbreaking and state-of-the-art materials, structures, equipment, and detection technologies related to road engineering have continually and progressively emerged, reshaping the landscape of pavement systems. There is a pressing and growing need for a timely summarization of the current research status and a clear identification of future research directions in these advanced and evolving technologies. Therefore, Journal of Road Engineering has undertaken the significant initiative of introducing a comprehensive review paper with the overarching theme of “advanced road materials, structures, equipment, and detection technologies”. This extensive and insightful review meticulously gathers and synthesizes research findings from 39 distinguished scholars, all of whom are affiliated with 19 renowned universities or research institutions specializing in the diverse and multidimensional field of highway engineering. It covers the current state and anticipates future development directions in the four major and interconnected domains of road engineering: advanced road materials, advanced road structures and performance evaluation, advanced road construction equipment and technology, and advanced road detection and assessment technologies

Transmission of butanol isomers in pervaporation based on series resistance model

Pervaporation (PV) has shown great potential in the separation of butanol aqueous solutions due to their economic and environmental benefits. This work applies polydimethylsiloxane (PDMS) composite membrane to separate four butanol isomers (n-butanol, isobutanol, sec-butanol and tert-butanol) in aqueous solution. Based on physical and chemical properties of butanol isomers, such as solubility, polarity and interaction parameter, we systematically study the transmission difference in the pervaporation process. The influence of feed concentration, temperature and permeate pressure on membrane performance of PDMS composite membrane are investigated. The results show that the contact angles of butanol isomers on the PDMS layer are 51°, 42.7°, 37.7°, 29.1° and the fluxes at 40 °C are 237.6 g m-2 h-1, 245.4 g m-2 h-1, 224.1 g m-2 h-1, 169.4 g m-2 h-1 for n-butanol, isobutanol, sec-butanol, and tert-butanol, respectively. Moreover, the similar compatibility principle is introduced to the series resistance model so the process simulation matches well with the antagonistic effect of water molecules on mass transfer of butanol isomers. The permeation activation energy is negative, indicating that the dissolution dominates the dissolution and diffusion process. In addition, low vacuum is not conducive to the separation of n-butanol from water. The research on isomers separation through pervaporation may pave a way to separate other solvents of similar properties

Effects of Boride Orientation and Si Content on High-Temperature Oxidation Resistance of Directionally Solidified Fe–B Alloys

In this work, the as-cast directionally solidified (DS) Fe–B alloys with various Si contents and different boride orientation were designed and fabricated, and the as-cast microstructures and static oxidation behaviors of the DS Fe–B alloys were investigated extensively. The as-cast microstructure of the DS Fe–B alloys consists of the well-oriented Fe2B columnar grains and α-Fe, which are strongly refined by Si addition. The oxidation interface of the scales in the DS Fe–B alloy with 3.50 wt.% Si demonstrates an obvious saw-tooth shaped structure and is embedded into the alternating distributed columnar layer structures of the DS Fe–B alloy with oriented Fe2B and α-Fe matrix, which is beneficial to improve the anti-peeling performance of the oxide film compared with lower amounts of Si addition in DS Fe–B alloys with oriented Fe2B [002] orientation parallel to the oxidation direction (i.e., oxidation diffusion direction, labeled as Fe2B// sample). In the DS Fe–B alloys with oriented Fe2B [002] orientation vertical to the oxidation direction (i.e., labeled as Fe2B⊥ sample), due to the blocking and barrier effect of laminated-structure boride, Si is mainly enriched in the lower part of the oxide film to form a dense SiO2 thin layer adhered to layered boride. As a result, the internal SiO2 thin layer plays an obstructed and shielded role in oxidation of the substrate, which hinders the further internal diffusion of oxygen ions and improves the anti-oxidation performance of the Fe2B⊥ sample, making the average anti-oxidation performance better than that of the Fe2B// sample

A Highly Sensitive and High-Resolution Resonant MEMS Electrostatic Field Microsensor Based on Electrostatic Stiffness Perturbation

This paper proposes a highly sensitive and high-resolution resonant MEMS electrostatic field sensor based on electrostatic stiffness perturbation, which uses resonant frequency as an output signal to eliminate the feedthrough interference from the driving voltage. The sensor is composed of a resonator, driving electrode, detection electrode, transition electrode, and electrostatic field sensing plate. The working principle is that when there is an electrostatic field, an induction charge will appear at the surface of the electrostatic field sensing plate and induce electrostatic stiffness on the resonator, which will cause a resonant frequency shift. The resonant frequency is used as the output signal of the microsensor. The characteristics of the electrostatic field sensor are analyzed with a theoretical model and verified by finite element simulation. A device prototype is fabricated based on the Silicon on Insulator (SOI) process and tested under vacuum conditions. The results indicate that the sensitivity of the sensor is 0.1384Hz/(kV/m) and the resolution is better than 10 V/m

Effect of Silicon Content on Microstructures and Properties of Directionally Solidified Fe-B Alloy

In order to investigate the effect of Si content on the microstructures and properties of directionally solidified (DS) Fe-B alloy, a scanning electron microscope (SEM) with an energy dispersive spectrum (EDS), and X-ray diffraction have been employed to investigate the as-cast microstructures of DS Fe-B alloy. The results show that Si can strongly refine the columnar microstructures of the DS Fe-B alloy, and the columnar grain thickness of the oriented Fe2B is reduced with the increase of Si addition. In addition, Si is mainly distributed in the ferrite matrix, almost does not dissolve in boride, and seems to segregate in the center of the columnar ferrite to cause a strong solid solution strengthening and refinement effect on the matrix, thus raising the microhardness of the matrix and bulk hardness of the DS Fe-B alloy

Detection and Identification of Leachables in Vaccine from Plastic Packaging Materials Using UPLC-QTOF MS with Self-Built Polymer Additives Library

The direct contact of plastic parts with the medical products raises the possibility that plastic-related contaminants (leachables) may be present in the finished medical product. The leachable components from plastic materials may impact the safety and efficacy of the final medical product, so identification and determination of the leachables are essential for the safety assessment of medical products. A method to identify main leachables-polymer additives in medical products was developed by ultraperformance liquid chromatography-quadrupole time-of-flight-mass spectrometry (UPLC-QTOF MS) and a self-built library. The library contains 174 additives and the information on their names, formulas, structures, retention times, fragments, classifications, origin, and corresponding MS^E and MSMS spectra. The reliability of the construction process of the library was guaranteed by the system stability and suitability test. Identification parameters of library application, such as mass error, retention times, fragments, and isotope pattern, were evaluated. Leachables in real vaccine and the intermediates were identified using automatic library searching. In vaccine, the peak <i>m</i>/<i>z</i> 239.0887 that could not be assigned by the library was identified as dimethyl 2-hydroxy-1,3-cyclohexanedicarboxylate using a series of elucidation tools. As a result, the concentrations of leachables in vaccine and the intermediates ranged from 0.85 to 21.91 μg/L