Low Flux Research Articles

Efficient Phosphate Ions Removal Using Multi-Layered Poly(allylamine hydrochloride)/ Poly(styrene sulfonate) Incorporated Electrospun Cellulose Membrane

Phosphate ion removal in wastewater via nanofiltration is a major challenge in wastewater treatment. In this study, cellulose acetate (CA) incorporated with graphene oxide/ sodium dodecyl sulphate (GO/SDS) and poly(allylamine hydrochloride)/poly(styrene sulfonate) (PAH/PSS) were synthesized using the electrospinning method. The membranes were characterized using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle, and field emission scanning electron microscope (FESEM). In addition, a multi-layered electrospun cellulose membrane was stacked using a layer-by-layer (LbL) technique to produce a functional ultra-filtration membrane for enhanced phosphate ions removal. The results showed that the modified membranes had better hydrophilicity and lower flux rates as compared to the unmodified membrane. The incorporation of compressed multi-layered for both unmodified and modified membranes also indicated increased phosphate ions removal efficiency up to 18.99 % and 43.08 %, respectively. In addition, post-filtration revealed that phosphate was adsorbed onto the three-layer modified membrane. PAH/PSS-modified CA/GO/SDS membrane is an innovative modification of the cellulose membrane for the phosphate-contaminated water system.

Experimental study of pool boiling heat transfer on mini-pillar surfaces with different hydrophobic dot arrays

In this study, we conducted experimental research on the pool boiling performance of mini-pillar surfaces with different hydrophobic dot arrays. The experimental results show that the distribution and total area of hydrophobic dot arrays on pillar tops significantly influence the boiling performance of mini-pillar surfaces. In comparison with the mini-pillar surface without wettability modification, introducing hydrophobic dot arrays on the pillar tops can improve the bubble nucleation density and diminish the wall superheat at boiling onset. Therefore, the boiling performance of mini-pillar surfaces can be gradually improved by increasing the total area of hydrophobic dot arrays at low heat fluxes. However, a further increase in the total area of hydrophobic dot arrays may lead to the reduction of the bubble departure frequency at high heat fluxes, which is not conducive to the segregation of the liquid and vapor pathways. The experimental results indicated that when the total area of hydrophobic pillar tops accounts for 10.24 % of the projected area of the mini-pillar surfaces, an optimal enhancement is achieved, and the optimal enhancement of boiling performance on the mini-pillar surfaces with hydrophobic dot arrays results from a suitable balance between promoting the bubble nucleation and maintaining higher bubble departure frequency.

Tackling residual tensile stress in AlN-on-Si nucleation layers via the controlled Si(111) surface nitridation

This work is devoted to the study of the influence of controlled Si(111) surface nitridation on the epitaxial growth of AlN-on-Si nucleation layers with reduced tensile stress on ordered crystalline silicon nitride phase. The Si(111) surface nitridation process was performed at low ammonia flux and substrate temperatures in the range of 700–900 °C and was studied using RHEED and STM techniques. A universal criterion, namely the stage of the nitridation process completion is introduced, taking into account the influence of substrate temperature, ammonia flux and nitridation time. The 100 nm AlN nucleation layer on silicon substrates grown by ammonia molecular beam epitaxy is studied using AFM, XRD, HR-TEM and Raman spectroscopy techniques. The Raman data show that reducing the nitridation temperature from 900 °C to 700 °C not only deteriorates the crystalline quality of the subsequent AlN nucleation layers, but also reduces the residual tensile stress by almost 30 %. In the present contribution, micro-Raman spectroscopy is used to determine the nature of the defects formed during the high temperature growth of the AlN nucleation layers and confirms them to be inversion domains. The HR-TEM technique was used to study the AlN/Si interface in AlN-on-Si nucleation layers grown on a nitridated silicon surface at 700 °C and 900 °C at the optimum stage of the nitridation process completion. HR-TEM images of AlN nucleation layers revealed regions with different AlN/Si(111) interfaces: 1) AlN/amorph-Si3N4/Si, 2) AlN/SiN(8 × 8)/Si, and 3) AlN/Si with a sharp interface boundary. Using fast Fourier transform image analysis, it is shown that the presence of amorphous Si3N4 phase inclusions in the AlN/Si interface boundary introduces tensile stresses in the AlN nucleation layer which can be reduced by lowering the nitridation temperature. The results obtained clearly show that one of the causes of cracks in III-nitride layers grown on silicon substrates is the formation of tensile AlN layers with a high content of the amorphous Si3N4 phase at the AlN/Si interface, which is characteristic of silicon nitridation at elevated temperatures (> 700 °C).

Damage regularity and multifractal analysis of sol-gel reflection coating of KDP crystal under low UV irradiation flux.

This study employed multifractal analysis to investigate the changes in surface morphology of SiO2 anti-reflective coatings prepared on KDP substrates using the sol-gel method, under various conditions of ultraviolet (UV) irradiance. The coatings were successfully fabricated, and the chemical structure of the SiO2 sol was comprehensively characterized using Solid-State Nuclear Magnetic Resonance (SSNMR) technology. Under low UV irradiance (4 J/cm2), repeated experiments revealed a crack-induced mechanism of surface fatigue damage. Utilizing Scanning Electron Microscopy (SEM), the study discovered the induction effect of initial crack defects in UV-damaged coatings and established a damage model. Furthermore, Atomic Force Microscopy (AFM) was used to acquire images of the coatings' surface morphology at different damage levels, which were analyzed using the multifractal spectrum f(α). This analysis confirmed the multifractal nature of the coatings both before and after damage. This study identified significant effects of UV irradiation on the width of the multifractal spectrum and Δf, indicating that the SiO2 anti-reflective coatings exhibit multifractal characteristics under various damage states. The coatings displayed a pattern of decreasing and then increasing singularity spectrum width, height distribution unevenness, and surface roughness with increasing damage. This study demonstrates that multifractal analysis is an effective tool for describing the complexity of the surface morphology of sol-gel-derived anti-reflective coatings for the first time and for validating their multifractal properties across different stages of UV damage. HIGHLIGHTS: Damage dynamic process of KDP crystal sol-gel coating was described by SEM&AFM; The crack propagation mechanism of sol-gel coating under UV radiation is proposed; The damage evolution of sol-gel coating was described by multifractal analysis.

Role of phytoplankton composition on exudation of dissolved organic carbon in the Bay of Bengal

Phytoplankton in the marine environment exudates part of the primary production as dissolved organic carbon (DOC) into the surrounding waters. The rate of exudation of DOC is depended on the hydrographic condition, nutrient availability, phytoplankton composition, and their size structure. To examine this, samples were collected from the coastal and offshore regions where different hydrographic conditions exists in the Bay of Bengal. The coastal waters were relatively low saline, rich in inorganic nutrients, high phytoplankton biomass (Chl-a) and primary production in the coastal compared to offshore regions. The photic zone integrated Chl-a displayed insignificant difference between coastal and offshore regions whereas higher photic zone integrated primary production was observed in the former than latter region. Dominance of microplankton was observed in the coastal waters associating with high inorganic nitrogen concentrations, in contrast, picoplankton dominated in the offshore region associating with low inorganic nitrogen but high organic nitrogen concentrations. Due to high surface-to-volume ratio of picoplankton, ∼45% of the primary production exudated as DOC in the offshore compared to the coastal region (∼12%) due to dominance of microplankton. The sum of primary production and DOC exudation, called total primary production, was almost equal in the coastal and offshore regions. The mean phytoplankton biomass normalized primary production (pB) in the Bay of Bengal was low (17 ± 8 mgC mgChl-a−1 d−1) compared to Arabian Sea (37 ± 5 mgC mgChl-a−1 d−1). In contrast pB estimated based on total primary production is close (30 ± 16 mgC mgChla−1 d−1) to that of the Arabian Sea (37 ± 5 mgC mgChl-a−1 d−1) suggesting that the Bay of Bengal is equally productive compared to that of Arabian Sea than hitherto hypothesized due to strong stratification and less nutrients input in the former basin. The low sinking carbon flux observed below the photic zone is attributed to the release of primary production as DOC. The released DOC from the phytoplankton may support heterotrophic activity as evidenced by the existence of strong net heterotrophy in the Bay of Bengal. This may lead to the time lag between primary and export productions. None of these processes were incorporated into the numerical models resulting in inaccurate simulations of carbon cycling in the northern Indian Ocean. Modifications in the models by incorporating these processes may improve model simulations for a better understanding the modifications in biogeochemical processes due to climate change in the Bay of Bengal.

Thermal and Dynamo Evolution of the Lunar Core Based on the Transport Properties of Fe‐S‐P Alloys

AbstractPaleomagnetic analyses have suggested that the lunar magnetic field underwent a significant change from 4.25 to 3.19 Ga, indicating the rapid transition of the lunar dynamo mechanism. We used the van der Pauw (vdP) method to measure the electrical resistivity of Fe‐S‐P alloys under conditions relevant to the lunar core and estimated the thermal conductivity of the Fe‐S‐P lunar core. These values were incorporated into thermal and dynamo models to investigate the evolution of the lunar core. Our model indicates that the inner core began to grow as early as 4.35 Ga, the solidification regime switched at 3.50 Ga, and the thermal dynamo ceased between 3.78 and 3.51 Ga. The cessation of the dynamo could be due to a low buoyancy flux and insufficient entropy dissipation. Thermal and compositional dynamos cannot sustain the ancient strength of the Moon's magnetic field, and require other energy sources.

Preparation of antifouling reverse osmosis membrane with polyacrylic acid brushes based on polydopamine coating assisted atom transfer radical polymerization

An antifouling polyamide (PA) reverse osmosis (RO) membrane was fabricated in this work by incorporating polyacrylic acid (PAA) brushes onto the membrane surface via polydopamine (PDA)-assisted atom transfer radical polymerization (ATRP). Specifically, a PDA intermediate layer containing the initiator 2-bromoisobutyryl bromide (BIBB) for polymerization was coated on original membrane surface. Then, acrylic acid (AA) was controllably incorporated on the membrane surface in the form of PAA brushes by regulating ATRP reaction time. The PDA-assisted polymerization was mild to the separation layer, and BIBB could be immobilized on the membrane surface with even distribution and controllable density. It was demonstrated that the water contact angle and surface roughness of the RO membranes with PAA brushes was reduced, while the negative charge and hydrophilicity were increased. Simultaneously, the water flux of the membrane was enhanced by 27.8% and the NaCl rejection was maintained compared with that of virgin membrane. Moreover, the modified membrane presented a higher flux recovery ratio and a lower flux decline ratio when lysozyme, bovine serum albumin, humic acid, and sodium alginate were used as model foulants. Besides, the membrane exhibited a satisfactory long-term performance stability. Our work provides a gentle and controllable strategy for the fabrication of antifouling RO membranes with enhanced water permeability and maintained salt rejection, which is crucial for increasing the efficiency of RO processes.

Hydrogel Coated Mesh with Controlled Flux for Oil/Water Separation.

Superwetting surfaces are often applied in oil/water separation. Hydrogels have been widely prepared as superhydrophilic/underwater superoleophobic materials for oil/water separation since they are naturally hydrophilic. Hydrogels usually need to be combined with porous substrates such as stainless steel mesh (SSM) due to their poor mechanical properties. However, it is usually inevitable that the pores of the substrate are clogged during the actual preparation process, leading to a significant decrease in the flux, which limits its effective application. In this study, acrylic acid (AA), chitosan (CS) and modified silica were utilized to form a layer of dual-network PAA/CS@SiO2 hydrogel by photopolymerization on SSM, followed by a simple and novel ultrasonic-assisted pore-making method to generate numerous pores in situ on the surface of the hydrogel-coated mesh, which led to an increase in water flux from 0 to 70,000 L m-2 h-1 without decreasing the separation efficiency. After 100 separations of a mixture of n-hexane and water, the flux was still higher than 50,000 L m-2 h-1 with a separation efficiency above 99%, which is superior to most of hydrogel-coated meshes reported so far. Moreover, the prepared PAA/CS@SiO2 hydrogel-coated mesh also has good environmental stability, low swelling, and self-cleaning properties. We believe that the strategy of this study will provide a simple new perspective when hydrogels block the substrate pores, resulting in low water flux.

Effect of agricultural management system (“cash crop”, “livestock” and “climate optimized”) on nitrous oxide and ammonia emissions

AbstractThe study aimed to measure soil-atmosphere N2O fluxes and their controlling factors, as well as NH3 emissions and yields for two soils (silt loam and clay loam) in three management systems over two years under subsequent wheat and maize cultivation. The management systems were characterized as follows: (1) cash crop (C) with mineral fertilizer and conventional tillage; (2) livestock (L) with biogas residue fertilization and its incorporation prior to sowing in maize and reduced tillage; and (3) climate optimized (O) with minimum tillage, 8-year crop rotation, with biogas residue fertilization, in maize without incorporation in clay loam soil or incorporation by strip-tillage prior to seeding in silt loam soil. Stable isotope ratios of N2O and mineral N were determined to identify N2O processes. Within the organically fertilized maize treatments, cumulative N2O fluxes were highest in the O-system treatments of both sites (4.0 to 9.4 kg N ha− 1 a− 1), i.e. more than twice as high as in the L-system (1.5 to 3.1 kg N ha− 1 a− 1). Below root-strip till fertilizer application did not enhance N2O fluxes. Fluxes with mineral fertilization of wheat (1.1 to 3.1 kg N ha− 1 a− 1) were not different from those with organic fertilization. Isotopic values of emitted N2O revealed that bacterial denitrification dominated most of the peak flux events, while the N2O/(N2 + N2O) ratio of denitrification was mostly between 0.1 and 0.5. It can be concluded that, contrary to the intention to lower greenhouse gas fluxes by the O-system management, the highest N2O fluxes occurred in the O-system without biogas digestate incorporation in maize. With respect to NH3 fluxes, we could confirm that the application of digestate application in growing crops without incorporation or late incorporation in fertilization before sowing induces high fluxes. The beneficial aspects of the O-system including more stable soil structure and resource conservation, are thus potentially counteracted by increased N2O and NH3 emissions.

Single-frame transmission and phase imaging using off-axis holography with undetected photons

Imaging with undetected photons relies upon nonlinear interferometry to extract the spatial image from an infrared probe beam and reveal it in the interference pattern of an easier-to-detect visible beam. Typically, the transmission and phase images are extracted using phase-shifting techniques and combining interferograms from multiple frames. Here we show that off-axis digital holography enables reconstruction of both transmission and phase images at the infrared wavelength from a single interferogram, and hence a single frame, recorded in the visible. This eliminates the need for phase stepping and multiple acquisitions, thereby greatly reducing total measurement time for imaging with long acquisition times at low flux or enabling video-rate imaging at higher flux. With this single-frame acquisition technique, we are able to reconstruct transmission images of an object in the infrared beam with a signal-to-noise ratio of 3.680±0.004\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$3.680\\,\\pm \\,0.004$$\\end{document} at 10 frames per second, and record a dynamic scene in the infrared beam at 33 frames per second.

Combined X-ray Diffraction Analysis and Quantum Chemical Interpretation of the Effect of Thermal Neutrons on the Geometry and Electronic Properties of CdTe

Objective: Substantiation of the result of the interaction of thermal neutrons with CdTe crystals by quantum-chemical methods and comparison of the experimental results with the results of quantum-chemical calculations. Methods: Single crystal samples of cadmium telluride (CdTe) were obtained by a modified Bridgman method. The plates cut from the single crystal were subjected to mechanical grinding with abrasive paper of the type P1,200-P4,000, mechanical polishing with silver paste. To clean the surface of the plate from contamination, it was washed in ethyl alcohol. In the experimental part of the work, the influence of low thermal neutron fluxes on the structural parameters of CdTe was studied. The samples were irradiated with a thermal neutron flux in the range from 2.64×107 neutron/cm2 to 1.85×109 neutron/cm2. To study the structure of CdTe crystals, the method of X-ray structural analysis was used, using a DRON-3 X-ray diffractometer. In the second part of the work, computer modeling of the process of interaction of thermal neutrons on CdTe crystals was carried out. Results: X-ray diffraction analysis of the crystals showed that as a result of irradiation with low thermal neutron fluxes, the structural parameters of CdTe improve, as evidenced by the ordering of the crystallites. In addition, in this region of the thermal neutron flux the resistance of the crystals decreases. Conclusion: Calculations of the crystal lattice parameters of CdTe are in good agreement with experimental data. The electronic and optical properties of CdTe have been studied. A decrease in the band gap after irradiation with thermal neutrons has been shown.

Thermal regulation enhancement in multi-story office buildings: Integrating phase change materials into inter-floor void formers

Addressing the thermal loss from building envelopes is a crucial challenge and requires the exploration of various mitigation strategies. This study employs comprehensive 3D computational fluid dynamics simulations to investigate the incorporation of various bio-based Phase Change Materials (PCMs) including CrodaTherm (CT) 19, CT21, and CT24W, within inter-floor void formers between the roof-floor boundary in multi-story office buildings to optimize energy management during inactive periods in one of the adjacent units. Aside from the PCM type, the void former shape, its placement, and the combinations of PCMs and insulating layers are examined through heat flux and solid fraction plots as well as liquid fraction contours. Results highlight the exceptional performance of CT24W-integrated void formers, achieving a remarkable 36.74 % reduction in the 48-h average heat flux in comparison with the case without void formers, and offering lower heat flux values than the scenario with insulating layers for 89.38 h (endurance time). Based on the findings, with identical PCM volumes, the semi-ellipsoid PCM-integrated void former provides 11.07 % lower heat flux and 27.56 % longer endurance time compared to the one with a spherical shape. The results underscore PCM integration as a superior strategy over standalone insulation for managing thermal loss between apartment floors.

Effects of Wind Speed and Heat Flux on De-Icing Characteristics of Wind Turbine Blade Airfoil Surface

The icing on wind turbines reduces their aerodynamic performance and can cause other safety issues. Accordingly, in this paper, the de-icing characteristics of a wind turbine blade airfoil under different conditions are investigated using numerical simulation. The findings indicate that when the de-icing time is 10 s, the peak ice thickness on the leading edge of the airfoil surface decreases from 0.28 mm to 0.068 mm and from 0.77 mm to 0.45 mm at low (5 m/s) and high (15 m/s) wind speeds, respectively. This is due to the fact that the ice melting rate is much greater than the icing rate at low wind speeds, while the icing rate increases at high wind speeds. When the de-icing time is 20 s, ice accretion on the leading edge of the airfoil is completely melted. At a low heat flux (8000 W/m2) and high heat flux (12,000 W/m2), the peak ice thickness decreases by 31.2% and 64.9%, respectively. With an increase in de-icing time and heat flux, the peak thickness of runback ice increases. This is due to an increase in runback ice as a result of more ice melting on the leading edge of the airfoil. The surface temperature in the ice-free area is significantly higher than that in the ice-melting area, due to high thermal resistance in the ice-free area. This study will provide guidance for the thermal distribution and coating layout of a wind turbine blade airfoil to make the anti-/de-icing technology more efficient and energy-saving.

Mitigating nitrous oxide emissions from low carbon to nitrogen ratio wastewater treatment: Utilizing sugarcane bagasse fermentation liquid for constructed wetlands

Sugarcane bagasse was recycled to produce fermentation liquid (FL) as a supplementary carbon source that was added to constructed wetlands (CWs) for regulating influent carbon to nitrogen ratio (C/N), and then being applied to investigate nitrogen transformations and greenhouse gas emissions. Results showed that this FL achieved faster NO3−-N removal and lower N2O fluxes than sucrose did, and the lowest N2O flux (67.6 μg m−2h−1) was achieved when FL was added to CWs in a C/N of 3. In contrast, CH4 emissions were higher by the FL addition than by the sucrose addition, although the fluxes under both additions were in a lower range of 0.06–0.17 mg m−2h−1. The utilization of FL also induced significant variations in microbial communities and increased the abundance of denitrification genes. Results showed the application of FL from sugarcane bagasse can be an effective strategy for improving nitrogen removal and mitigating N2O emissions in CWs.

Application of the NCAR FastEddy® Microscale Model to a Lake Breeze Front

This study investigates how urban environments influence boundary layer processes during the passage of a Great Salt Lake breeze using a multi-scale modeling system, NCAR’s WRF-Coupled GPU-accelerated FastEddy® (FE) model. Motivated by the need for sub-10 m scale decision support tools for uncrewed aerial systems (UAS), the FE model was used to simulate turbulent flows around urban structures at 5 m horizontal resolution with a 9 km × 9 km domain centered on the Salt Lake City International Airport. FE was one-way nested within a 1 km resolution Weather Research and Forecasting (WRF) domain spanning 400 × 400 km. Focused on the late morning lake breeze on 3 June 2022, an FE simulation was compared with WRF outputs and validated using surface and radar observations. The FE simulation revealed low sensible heat flux and cool near-surface temperatures, attributed to a relatively low specification of thermal roughness suitable for previously tested FE applications. Lake breeze characteristics were minimally affected, as FE effectively resolved interactions between the lake breeze and urban-induced turbulent eddies, providing insights into fine-scale boundary layer processes. FE’s GPU acceleration ensured efficient simulations, underscoring its potential for aiding decision support in UAS operations in complex urban environments.

The primary carbon metabolism in cyanobacteria and its regulation.

Cyanobacteria are the only prokaryotes capable of performing oxygenic photosynthesis. Many cyanobacterial strains can live in different trophic modes, ranging from photoautotrophic and heterotrophic to mixotrophic growth. However, the regulatory mechanisms allowing a flexible switch between these lifestyles are poorly understood. As anabolic fixation of CO2 in the Calvin-Benson-Bassham (CBB) cycle and catabolic sugar-degradation pathways share intermediates and enzymatic capacity, a tight regulatory network is required to enable simultaneous opposed metabolic fluxes. The Entner-Doudoroff (ED) pathway was recently predicted as one glycolytic route, which cooperates with other pathways in glycogen breakdown. Despite low carbon flux through the ED pathway, metabolite analyses of mutants deficient in the ED pathway revealed a distinct phenotype pointing at a strong regulatory impact of this route. The small Cp12 protein downregulates the CBB cycle in darkness by inhibiting phosphoribulokinase and glyceraldehyde 3-phosphate dehydrogenase. New results of metabolomic and redox level analyses on strains with Cp12 variants extend the known role of Cp12 regulation towards the acclimation to external glucose supply under diurnal conditions as well as to fluctuations in CO2 levels in the light. Moreover, carbon and nitrogen metabolism are closely linked to maintain an essential C/N homeostasis. The small protein PirC was shown to be an important regulator of phosphoglycerate mutase, which identified this enzyme as central branching point for carbon allocation from CBB cycle towards lower glycolysis. Altered metabolite levels in the mutant ΔpirC during nitrogen starvation experiments confirm this regulatory mechanism. The elucidation of novel mechanisms regulating carbon allocation at crucial metabolic branching points could identify ways for targeted redirection of carbon flow towards desired compounds, and thus help to further establish cyanobacteria as green cell factories for biotechnological applications with concurrent utilization of sunlight and CO2.

Electrochemical advanced oxidation of PFOA by Ti4O7 reactive electrochemical membrane anode

In recent years, per and polyfluoroalkyl substances (PFAS) have garnered significant attention due to their persistent and harmful effects on the environment and human health. Traditional treatment methods often fall short of effectively removing PFAS from water, prompting the need for innovative techniques. One promising approach is electrochemical advanced oxidation, based on highly reactive chemical species generated through electrochemical reactions to degrade organic pollutants. In this study, a specific reactive electrochemical membrane (REM) anode was used to degrade perfluorooctanoic acid (PFOA). The anode is a tubular Ti4O7-based REM (mixture of Ti4O7 and Ti5O9 Magneli phases) with a water permeability of 3300 L m−2 h−1 bar−1. The impact of various operating parameters, including current density, flux through REM, and feed concentration, on PFOA degradation efficiency was investigated. It was found that higher current densities, feed concentrations and lower flux through REM led to increased PFOA removal rates. With this type of REM, a total degradation of PFOA was observed at PFOA flux (passing throw the REM) under 0.2 g h−1 m−2 even at the lowest current density (71 A/m2). The degradation mechanism was investigated by evaluating the generated by-products after several degradation cycles, and the results confirmed that the degradation occurs via the decomposition cycle of CF2. Energy consumption has been taken into account, as it is the major limitation of advanced oxidation processes, exhibiting value under 5 kWh/g for the lowest current density and the highest PFOA flux. The originality of this study relies on the use of a specific anode; a tubular shape Ti4O7-based REM (by Saint Gobain Company). Such concentric REM reactor is optimal for the treatment of recalcitrant effluent containing PFOA as it significantly improved mass transfer leading to a very interesting energy efficient system that can easily be scale up.

Convection Heat-Transfer Characteristics of Supercritical Pressure RP-3 in Horizontal Microchannels

To enhance the heat-transfer performance of scramjet engines, a numerical simulation was conducted on the heat-transfer process of RP-3 aviation kerosene under supercritical pressure within a horizontal micro-fine circular tube. The intrinsic mechanism of the heat-transfer process was analyzed, summarizing the impacts of mass flux, inlet temperature, and gravitational acceleration. Furthermore, four commonly used buoyancy criterion numbers were compared and evaluated. The results indicate that the heat-transfer process can be divided into five phases: heating inlet phase, normal heat-transfer phase, heat-transfer deterioration phase, heat-transfer enhancement phase, and high-temperature normal heat-transfer phase. The heating inlet phase is significantly influenced by the inlet temperature, while the heat-transfer deterioration is affected both by the thermal property variations of the aviation kerosene and the buoyancy effects. Lower mass flux and hypergravity conditions all exacerbate heat-transfer deterioration. Inlet temperature, however, does not affect the heat-transfer pattern. Among the criteria, Grq/Grth provides the best prediction of buoyancy effects in horizontal circular tubes.

Enhanced water permeability and antifouling properties of cross-linked graphene oxide composite membranes with tunable d-spacings

Low flux and membrane fouling are major challenges in membrane distillation (MD) for treating concentrated wastewater. This study compared the performance of GO composite membranes with different interlayer distances, by covalently bonding the terminal amine groups of ethylenediamine (EDA) and 1,12-diaminododecane (DADD) with the carboxyl groups present on the GO sheets. The results indicated that the GO-DADD/PTFE membrane, with longer carbon chain cross-linking, achieved the highest flux and antifouling properties. At 70 °C, the pure water flux reached 68.5 kg/m2·h, and the fluxes for treating NaCl, HA containing NaCl, and BSA containing NaCl were 29.8 %, 37.1 %, and 38.5 % higher than the uncrosslinked GO/PTFE, and 95.7 %, 121.2 %, and 146.9 % higher than the PTFE membrane, respectively. Through mathematical models for mass and heat transfer, the study identified the key to this enhancement as the increased d-spacing within the GO layer due to cross-linking, which weakened the Kelvin effect and enhanced the vapor partial pressure on the hot side. The unique surface structure and electrostatic interactions induced by long-chain cross-linking further boosted the antifouling effect. These modifications not only overcome the typical trade-off between retention rates and flux but also offer a scalable and efficient solution for advanced membrane distillation applications.

Flame synthesis of nanoparticles based on high flux electrostatic atomization burner.

This study presents an innovative electrostatic spray flame synthesis (ESFS) reactor that combines the advantages of electrostatic spray and flame synthesis for precise spray control and efficient single-step continuous synthesis. To overcome the limitations of conventional ESFS systems, which often suffer from low atomized precursor flux, we successfully demonstrated a high-flux disk electrostatic atomizer coupled low-swirl flame reactor, achieving a precursor flux of up to 30 ml/h about 30 times higher than that of typical ESFS devices. The atomized precursor being rapidly carried away from the burner is undergoing high-temperature pyrolysis and particle formation through lifted premixed turbulent flames. The ESFS system provides extensive control over parameters such as flame temperature, equivalence ratio, residence time, initial droplet sizes, and precursor concentrations. For illustrative purposes, the ESFS system was utilized to synthesize silica nanoparticles, demonstrating the capability of synthesizing nanoparticles with various properties. By manipulating the collection position and height, the particle size has made a substantial leap from the nanoscale to the micrometer level. This remarkable achievement underscores the system's enormous potential for precise particle size regulation and one-step synthesis of complex structured thin films.