Dewatering Research Articles

Synergistic removal of tetracycline in water with highly stable Lac immobilized on magnetic metal-organic framework

The arbitrary discharge of tetracycline (TC) residuals has seriously influenced the ecosystem and human health. Laccase (Lac)-based biodegradation technology is considered a more effective way to remove TC due to its high catalytic efficiency and less by-product. Nevertheless, free Lac suffers from poor stability, easy inactivation and difficult recovery, restricting its application. Immobilization of Lac is considered an efficient strategy for addressing these obstacles. In this study, a magnetic metal-organic framework of Fe3O4@SiO2@UiO-66-NH2 (MMOF) was prepared and used as a carrier to immobilize Lac (Lac@MMOF) for TC degradation. Benefiting from the multiple binding sites, adsorption, and protection effect of MMOF, Lac@MMOF displayed a wider pH application range (2–7) and better thermal (15–85 °C), repeatability, and storage stability than free Lac. Furthermore, owing to the synergism of MOF adsorption and Lac biocatalysis, the removal rate of Lac@MMOF for TC could be up to 98 % at pH = 7 within 1 hr, which was 1.29 and 1.24 times that of free Lac and MMOF, respectively. More importantly, Lac@MMOF could easily be separated from aqueous solution under a magnetic field and maintained good removal performance (80 %) after five cycles. The degradation products were identified by applying LC-MS/MS, and possible degradation mechanisms and pathways were proposed. Finally, the antibacterial activity of intermediate products was evaluated using Escherichia coli, which revealed that the toxicity of TC was reduced effectively by the degradation of Lac@MMOF. Overall, Lac@MMOF is a green alternative for residual antibiotic removal in water.

Highly dispersed BiVO4 nanoparticles supported by pseudoboehmite for effective removal of antibiotics

BiVO4/pseudoboehmite (PB) composite catalysts were innovatively prepared using the cost-effective PB as support by a facile hydrothermal method. BiVO4 nanoparticles with an average size of 12 nm are highly dispersed on the surface of PB. Compared to pure BiVO4, the composite BiVO4/6 %PB exhibits high specific surface area (32.9 m2/g) about double that of pure BiVO4 (15.1 m2/g) which can provide more adsorption and photocatalytic reaction sites. Meanwhile, the composite has enhanced photogenerated electron-hole separation and transfer efficiency. As a result, it has a superior performance of antibiotics removal in water than pure BiVO4. The tetracycline hydrochloride (TCH) removal efficiency of BiVO4/6 %PB can reach 87 % within 2 h with high stability (<7 % decay after four cycles) under LED lamp (380–780 nm) irradiation as well as high selectivity. Specifically, the adsorption efficiency and photocatalytic rate constant are respectively triple and double that of pure BiVO4. Simultaneously, the BiVO4/6 %PB also possesses high removal efficiency of amoxicillin (76 %). Our results indicate that the selection of cost-effective PB as catalyst support offers a new solution to solve the aggregation problem of BiVO4 nanoparticles and the composite obtained contributes to an economic and efficient BiVO4-based photocatalyst for antibiotics removal in sewage treatment.

Geothermometrical calculations of thermal waters affected by secondary processes: The case of Sierra Elvira (Spain)

Geothermometrical calculations in thermal systems are often limited by the presence of secondary processes that modify the chemistry of the deep reservoir fluid during the ascent to the surface (e.g., mixing, degasification). The effect of secondary processes can be avoided by applying some techniques to reconstruct the chemical equilibrium at depth and the fluid original composition. However, the reconstruction of thermal waters mixed with cold surficial waters is complicated when the dilution factors are unknown. For that case, here, we propose to use an approach consisting of the simulation of a concentration process that removed different amounts of water from the thermal solutions until the equilibrium temperatures of anhydrite and quartz converge for the waters affected by mixing in unknown proportions. Using classical geothermometers and geothermometrical modeling, including the water removal process and CO2 degasification, a temperature range of 78 ± 9 °C at depth has been established for the Sierra Elvira geothermal system whose waters are in chemical equilibrium with respect to calcite, dolomite, anhydrite, quartz, illite, pyrophyllite and beidellite-K. The good agreement in the temperatures obtained for the different thermal fluids of the system suggests a common reservoir for all of them. The methodology used in this study can be applied to other geothermal systems in carbonate rocks affected by mixing.

Neutron tomography analysis of permeability‐enhancing additives in refractory castables

AbstractPolymeric fibers are often used as a drying additive for refractory castables because they can increase their permeability, reducing the risk of pressurization that is believed to trigger explosive spalling. Despite the potential of synthetic polymers to be engineered and obtain desired properties, the required parameters for inducing permeability enhancement remain unclear. This inhibits the development of novel designed drying additives and improvement of the numerical models. This work investigates the effect of polypropylene (PP), polyethylene (PE) and cellulose fibers on the water transport in refractory castables through rapid neutron tomography, enabling the in situ visualization of the water distribution, the drying front advance and the size, intensity and duration of moisture accumulation. PE and cellulose fibers accelerate drying fronts earlier than PP, in which PE exhibits larger moisture accumulation, residual moisture behind its drying front and a slower drying rate at higher temperatures despite the early water removal initiation. In contrast, cellulose emerged as a better candidate, due to a swelling–shrinkage based mechanism. The neutron tomography observations unveil the dynamic and intricate effect of fibers in the permeability, emphasizing that safer industrial processes require a deeper understanding of the underlying mechanisms to develop better fibers and accurate numerical models.

Synthesis of Ag-HKUST-1 composites and adsorption performance of neutral red dye

HKSUT-1 is often used as an adsorbent because of its excellent adsorption properties. In this study, Ag+ was impregnated into the HKSUT-1 precursor solution using the impregnation method, with sodium borohydride (NaBH4) serving as the reducing agent. This was done to examine the removal efficiency of NR dye. The Ag-HKSUT-1 composites were prepared by varying the additions of AgNO3 and NaBH4. The morphology and structure of the Ag-HKSUT-1 composites were characterized by TG, FT-IR, BET and TEM. The adsorption performance of AH1 for neutral red dye in wastewater was investigated. The adsorption process was described by the Langmuir model and the pseudo-second-order kinetic model. The adsorption capacity of AH1 for NR dye at 298 K was calculated to be 64.59 mg/g, indicating that Ag-HKUST-1 effectively adsorbed NR dye. The adsorption process is driven by a chemisorption mechanism, where intermolecular forces between Ag-HKUST-1 and NR, electrostatic interactions, and π-π conjugation between benzene rings play key roles. The results enhance our understanding of the surface interactions between Ag-HKUST-1 and NR dyes and broaden the application of HKUST-1 as an adsorbent for pollutant removal in water.

Estimation of net accumulation and removal of fluorescent dissolved organic matter in different Baltic Sea water masses

This study aimed to detect non-conservative processes that affect the distribution of fluorescent dissolved organic matter (FDOM) in the Baltic Sea. An extensive data set comprised of 408 FDOM data, optical and physical profiles, and the development of a water masses balance model allowed us to ascertain the sources of mixing anomalies. These were seen as second-order deviations in the FDOM distribution as a function of salinity in three layers: surface water, Baltic Sea Winter Water, and deep water. The difference between modeled and measured FDOM values at three different excitation/emission wavelengths allowed to show the strength of non-conservative processes, such as photochemical and microbial decomposition (negative residual values) or extracellular release of dissolved organic matter from phytoplankton, heterotrophic uptake and release from anoxic sediments (positive residual values). Humic-like FDOM fractions displayed positive residuals in all seasons for intermediate and deep layers and negative residuals in surface waters. Largest accumulation rates of humic-like fractions were reached in the Gulf of Gdańsk during summer in intermediate and deep layers, while the greatest removal in surface waters was observed during spring in the Bornholm and Gotland Basins and during summer in the Gulf of Gdańsk, probably due to photodegradation. Positive residuals of the protein-like fraction were observed at the surface in summer and autumn in the Gulf of Gdańsk, probably linked to the abundance of phytoplankton and also due to the low molecular weight by-products of photodegradation of humic-like components. Spatial transects revealed an increase in humic-like residuals with depth and a strong correlation with apparent oxygen utilization, increasing with higher fluorescence and exhibiting an asymptotic trend. A relationship was found between the protein-like fractions and phytoplankton biomass proxies. A generalized concept for FDOM cycling in the Baltic Sea was proposed, highlighting photobleaching as the dominant non-linear process determining the efficiency of humic-like FDOM removal. The protein-like component was found to be more efficiently taken up by aerobic prokaryotes at the surface. Microbial utilization and reworking of organic matter, release from sediments, and a decade-long stagnation of bottom water masses, all contribute to the observed accumulation of FDOM in mesohaline deep waters below the permanent pycnocline in the Baltic Sea.

Impact of biochar synergized bacteria on Mn2+ and NH4+-N removal and CO2 immobilization in water by enhanced extracellular electron transfer

Mn2+ and NH4+-N contamination in water by Mn slag leakage is urgent to be resolved. Biochar synergistic strains is considered to be a promising approach to remove pollution with high concentration, however, the specific oxidation and electron transfer processes are rarely elucidated in detail. In this study, under different biochar (BC) additions, NH4+-N concentration and pH ranges, removal efficiency of Mn2+, NH4+-N and COD had reached at 99.7 %-100 %, 100 % and 90.3–96.2 % by the BC & strain AL-6 system (co-system), respectively, and the nitrification processes was completed. Meanwhile, the electrochemical analysis showed that BC had strong tendency to donate, accept and transfer electrons, and electrons transfer property was more responsible for the removal process. Further, the electrical conductivity of co-system was enhanced upon reaction with Mn2+ and NH4+-N, suggesting that co-system promoted the electron transfer processes for pollutants removal. Concretely, Raman spectroscopy specified that conductive graphite region of biochar accelerated electron transfer behavior in the system. As well as, 2D-COS and characterization analyses indicated that C-C and CC functional groups, O2•− radicals, and semiquinone radicals could promote the oxidation of manganese. Eventually, manganese presented 2+ and high valence state was adsorbed on the surface of the co-system. In addition, BC facilitated strain AL-6 to convert organic carbon into CO2 and transfer electrons for N metabolism, and over time, CO2 and N2O could also be absorbed by BC. This study further dissected the efficiency on the Mn-contaminated water bodies and mechanism process by co-system and provided potential value in mitigating climate change.

Enhancing subsequent kraft fiber dewatering properties by using fiber polyamide-epichlorohydrin (PAE) treatment to prepare a dry pulp product,

The energy needed for the dewatering and drying of wet paper web represents around half of the energy consumption of papermaking processes. The present work examined whether the dewatering and drying of paper could be enhanced during a previous pulp drying process by pretreating the fibers with polyamide-epichlorohydrin (PAE). According to the hypothesis, the cured PAE restrains swelling and water absorption of water-wetted fibers by forming a fiber-bound, self-crosslinked polymer-network on the fiber surfaces. The hypothesis was tested by adding PAE to never-dried kraft pulp slurry followed by pulp thickening, drying, and final curing of the PAE-resin. After this, the PAE-treated fibers were dispersed in water, and their water retention values (WRV) and Shopper-Riegler values (○SR) were measured. The PAE pretreatments notably decreased the fibers´ WRV and ○SR, indicating improved water removal of paper web in the paper machine forming and drying section. Compared to chemical crosslinking pretreatments, which also can be used to decrease fibers WRV and ○SR-value, a notable advantage of PAE-pretreatment is milder required curing conditions of the PAE, which makes implementation of the method easier in practice. Due to decreased fiber-to-fiber bonding capability, the PAE-treated specialty fibers could take advantage especially as a bulking aid of paperboard, tissue, and absorbent materials.

Flame retardant mechanism-inspired fabrication of all-biomass-derived porous carbons for zinc-ion hybrid supercapacitors

Phosphorus-doped porous carbon materials, sourced from biomass, are becoming increasingly recognized as excellent electrode materials for zinc-ion hybrid supercapacitors (ZHSC). However, existing fabrication methods often involve complexities, a reliance on specialized equipment, and high costs. In this study, we successfully used bamboo fibers and phytic acid to prepare phosphorus-doped porous carbon with a high specific surface area. Our method, which takes advantage of the flame-retardant effect of phytic acid on biomass, eliminates the need for additional water removal steps or pore-forming agents. As such, it offers benefits such as simplicity, cost-effectiveness, environmental sustainability, and adaptability, relying solely on biomass for phosphorus doping and pore formation. The resulting phosphorus-doped porous carbon has a high specific surface area of up to 1229 m2 g−1. Correspondingly, the ZHSC fabricated using this carbon reaches a specific capacity of 109 mAh g−1 in a 2 M ZnSO4 electrolyte. Additionally, a quasi-solid-state flexible ZHSC based on this carbon was successfully manufactured, achieving a maximum energy density of 60 Wh kg−1 and a maximum power density of 1653 W kg−1. These performance metrics surpass those of some similar ZHSCs, underscoring the efficacy of our material fabrication method in producing superior electrode materials for ZHSCs.

Highly Efficient Removal of 2,4,5-Trichlorophenoxyacetic Acid by Adsorption and Photocatalysis Using Nanomaterials with Surface Coating by the Cationic Surfactant.

Extensive removal of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) using titania (TiO2) nanoparticles by adsorption and photocatalysis with a surface coating by cetyltrimethylammonium bromide (CTAB) is reported. The CTAB-coated TiO2 nanoparticles (CCTN) were characterized by FT-IR, zeta-potential measurements, and UV-vis diffuse reflectance spectroscopy (UV-vis-DRS). 2,4,5-T removal increased significantly after surface modification with CTAB compared with bare TiO2 nanoparticles. Optimal parameters affecting 2,4,5-T removal were found to be pH 4, CCTN dosage 10 mg/mL, and adsorption time 180 min. The maximum adsorptive removal of 2,4,5-T using CCTN reached 96.2% while highest adsorption capacity was 13.4 mg/g. CCTN was also found to be an excellent photocatalyst that achieved degradation efficiency of 99.2% with an initial concentration of 25 mg/L. The removal mechanisms of 2,4,5-T using CCTN by both adsorption and photocatalysis are discussed in detail based on changes in functional group vibrations and surface charge. Our results indicate that CCTN is an excellent material for 2,4,5-T removal in water by both adsorption and photocatalysis.

The removal mechanism of lead from wastewater on pharmaceutical sludge-based biochar

This study aims to enhance the resource utilization of waste sludge and mitigate the environmental risks associated with Pb2+ contamination. Municipal sludge biochar (MBC) and pharmaceutical sludge biochar (PBC) were selected as the experimental subjects. The experiment systematically investigated the influential factors affecting adsorption, including adsorbent dosage, reaction time, and pH. The physicochemical attributes of the biochar (BC) were assessed through techniques such as scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and point of zero charge analysis. The Pb2+ adsorption process was described by the pseudo-second-order kinetic model and Freundlich isotherm model, the highest adsorption capacities were established as 18.56 mg/g and 19.07 mg/g for MBC and PBC, respectively. The adsorption of Pb2+ on BCs is related to chemical and physical adsorption mechanisms. Ligand bonding, monolayer chemisorption, electrostatic interactions and pore filling were considered as possible mechanisms involved in the adsorption system. It was shown that MBC and PBC are efficient adsorbents for the Pb2+ removal in water.

Adsorption efficiency and in-situ catalytic thermal degradation behaviour of microplastics from water over Fe-modified lignin-based magnetic biochar

The efficient removal and degradation of microplastics are critical for protecting aquatic ecosystems. Herein, Fe-modified magnetic biochar (MBC) was synthesized as an adsorbent for removing microplastics in water. The effects of lignin/Fe salt mass ratios, adsorbent amount, adsorption time, adsorption temperature, solution pH, and presence of coexisting anions on adsorption efficiency were investigated. The thermal degradation behaviour and recycling characteristic of microplastics was also explored. Results showed that MBC has a developed pore structure, superparamagnetic property, and abundant oxygen-containing functional groups. The removal efficiency of polystyrene microplastics using MBC-11 was 99 %, with an adsorption capacity of 68.57 mg/g, which was 25 times higher than that of unmodified lignin biochar. The kinetics of the adsorption process followed the pseudo-first kinetic model, and the equilibrium data best fitted the Freundlich model. Thermodynamic results confirmed that adsorption over MBC was a spontaneous, heat-absorbing, and entropy-increasing process. The adsorption mechanism of PS by biochar was mainly via electrostatic and hydrophobic interactions and pore throttle. The thermal-degradation products of PS were mainly hydrocarbons, including styrene, benzene, and toluene, owing to the enhanced β-scission, H-shift, and methylation reactions at MBC catalytic sites. This study provides a scientific basis for the development of control technologies for microplastics removal in water.

Dewatering and valorizing lake sediments by electroosmotic dewatering for lakes restoration.

Dredging eutrophic lake sediments can improve water quality, but it also requires dewatering and valorizing the dredged material to avoid wasting resources like phosphorus. This study experimentally investigated the basic mechanism and performance of electroosmotic dewatering of 1-L dredged sediments using different electric currents (20mA, 40mA, and 60mA) after gravity filtration. The dewatering performance, moisture content and distribution, effect of electrochemical reaction on dewaterability, energy consumption, and changes in metals and phosphorus (P) distribution and pH values were analyzed. The results indicated that electroosmotic dewatering effectively decreased sediment mass by predominantly eliminating free and a portion of interstitial water, with reductions ranging from 7 to 20%. The optimal duration and current should, however, be considered to balance water removal and energy consumption. Higher moisture removal occurred with 40mA for 24h and 60mA for 6h, while the energy consumption obtained with 60mA (0.201 kWh/kg water removed) was significantly lower than that of applying 40mA for 24h (0.473 kWh/kg water removed), with the assistance of ohmic heating, resulting in reduced viscosity and water release from capillaries. The tested conditions did not significantly extract heavy metals or P from the sediments, which may facilitate the disposal of the removed water back into the lake and the utilization of the treated sediments for different purposes. This technology is easy to operate and suitable for the treatment of dredged sediments, and the dewatering result is comparable to low pressurized filtration but at low energy consumption.

Composite 2D Material-Based Pervaporation Membranes for Liquid Separation: A Review.

Today, chemistry and nanotechnology cover molecular separations in liquid and gas states by aiding in the design of new nano-sized materials. In this regard, the synthesis and application of two-dimensional (2D) nanomaterials are current fields of research in which structurally defined 2D materials are being used in membrane separation either in self-standing membranes or composites with polymer phases. For instance, pervaporation (PV), as a highly selective technology for liquid separation, benefits from using 2D materials to selectively transport water or other solvent molecules. Therefore, this review paper offers an interesting update in revising the ongoing progress of PV membranes using 2D materials in several applications, including solvent purification (the removal of water from organic systems), organics removal (the removal of organic molecules diluted in water systems), and desalination (selective water transport from seawater). In general, recent reports from the past 3 years have been discussed and analyzed. Attention has been devoted to the proposed strategies and fabrication of membranes for the inclusion of 2D materials into polymer phases. Finally, the future trends and current research gaps are declared for the scientists in the field.

Engineering of ceramic membranes with superhydrophobic pores for different size water droplets removal from water-in-oil emulsions

Superhydrophobic (SHB) ceramic membrane surfaces have proved their superiority in water-in-oil (W/O) emulsion separation. However, the construction of ceramic membranes with SHB pores remains challenging and the interaction between the SHB pores and water droplets is still unclear. Herein, by growing uniform ZnO nanoclusters (NCs) onto the SiC grains of a symmetric SiC ceramic membrane and then grafting with triethoxy(octyl)silane, a series of ZnO NCs@SiC membranes with SHB pores were prepared. Prior to secondary hydrothermal synthesis ZnO NCs, the small-sized ZnO nanoparticles (NPs) were grown onto the SiC grains via a sol–gel process. All the ZnO NCs@SiC membranes with SHB pores showed improved water removal performance from W/O emulsions compared with that of the pristine membrane. The optimal membrane with SHB pores displayed a pore size of 0.19 μm with a water contact angle of 163.96°. The smaller water droplets in W/O emulsions, the membrane pores are easier to be polluted. When separating a 1000 ppm W/O emulsion with a water droplet size of 500 nm at a transmembrane pressure of 0.5 bar, the water rejection reached 98.90 %, and the steady-state oil flux was 92.99 L·m−2·h−1. Based on the separation experiments, the separation mechanism was revealed. This work provides significant perceptions into constructing SHB pores of ceramic membranes, which might be useful for other possible applications.

Development of Robust Freeze-Drying Process for Long-Term Stability of rVSV-SARS-CoV-2 Vaccine.

The thermostability of vaccines, particularly enveloped viral vectored vaccines, remains a challenge to their delivery wherever needed. The freeze-drying of viral vectored vaccines is a promising approach but remains challenging due to the water removal process from the outer and inner parts of the virus. In the case of enveloped viruses, freeze-drying induces increased stress on the envelope, which often leads to the inactivation of the virus. In this study, we designed a method to freeze-dry a recombinant vesicular stomatitis virus (VSV) expressing the SARS-CoV-2 spike glycoprotein. Since the envelope of VSV is composed of 50% lipids and 50% protein, the formulation study focused on both the protein and lipid portions of the vector. Formulations were prepared primarily using sucrose, trehalose, and sorbitol as cryoprotectants; mannitol as a lyoprotectant; and histidine as a buffer. Initially, the infectivity of rVSV-SARS-CoV-2 and the cake stability were investigated at different final moisture content levels. High recovery of the infectious viral titer (~0.5 to 1 log loss) was found at 3-6% moisture content, with no deterioration in the freeze-dried cakes. To further minimize infectious viral titer loss, the composition and concentration of the excipients were studied. An increase from 5 to 10% in both the cryoprotectants and lyoprotectant, together with the addition of 0.5% gelatin, resulted in the improved recovery of the infectious virus titer and stable cake formation. Moreover, the secondary drying temperature of the freeze-drying process showed a significant impact on the infectivity of rVSV-SARS-CoV-2. The infectivity of the vector declined drastically when the temperature was raised above 20 °C. Throughout a long-term stability study, formulations containing 10% sugar (sucrose/trehalose), 10% mannitol, 0.5% gelatin, and 10 mM histidine showed satisfactory stability for six months at 2-8 °C. The development of this freeze-drying process and the optimized formulation minimize the need for a costly cold chain distribution system.

Study on the synthesis of ordered mesoporous alumina with high specific surface area using inorganic aluminum sources and its adsorption performance for carbon dioxide

In this work, inexpensive aluminum nitrate was used as the raw material and ammonium carbonate as the precipitant. Ordered mesoporous alumina (OMA) with a high surface area was synthesized using suitable template agents and auxiliary agents. The synthesized materials underwent characterization via X-ray powder diffraction (XRD), N2 adsorption-desorption (BET), transmission electron microscopy (TEM), and other analytical techniques. The effects of various template agents, aging durations, calcination methods, and calcination temperatures on the structure of the synthesized OMA were investigated. Key factors influencing the formation of inorganic precursors, the self-assembly of template agents with inorganic precursors, and the pore formation process (involving template agent and water removal) during synthesis were analyzed. Using the synthesized OMA as the substrate and triethylenetetramine (TETA) as the modifier, the impact of modified materials on CO2 adsorption performance was assessed. The results showed that OMA prepared with P123 as the template agent and ammonium dihydrogen phosphate as the auxiliary agent exhibited a specific surface area of 545.2 m2/g, an average pore diameter of 3.8 nm, and a pore volume of 1.01 cm3/g. The addition of auxiliary agents significantly increased the specific surface area of the synthesized material. The modified TETA-OMA, with a loading capacity of 50 %, achieved an adsorption capacity of 216.25 mg/g at an intake flow rate of 20 mL/min and an adsorption temperature of 40 °C. After six cycles of adsorption-desorption recycling, minimal changes were observed in the adsorption performance, indicating excellent regeneration capability. The synthesized high-surface-area ordered mesoporous alumina holds potential for industrial applications.

Additives Depletion by Water Contamination and Its Influences on Engine Oil Performance

Water enters engine oil in different ways and moves in the lubrication system causing an increase in wear, oil degradation and additives depletion. It has been proposed that water in the lubricants can transfer from dissolved to free phase leading to additives depletion in the oil. Different additives in the lubricants can easily latch to water molecules forming reverse micelles. The separation of reverse micelles from the oil causes additives depletion. This experimental and analytical study aims to investigate how the separation of free water above the saturation level can diminish the efficiency of additives in engine oils. The effect of varied levels of water on oil performance and its additives was investigated in this study. A new saturation method was used to determine the water saturation level in engine oil at different temperatures. The results reveal a decrease in additive concentration with increased separation of free water from the oil. Free water separation from engine oil is expected to reclaim the tribological performance, however, the results demonstrate that tribological performance after the separation of free water from the oil has been affected. The study showed not only does the removal of free water diminish the efficiency of additives due to additives depletion (≈ 10 wt%), but also the remaining dissolved water which is ≈ 2600 ppm can also affect wear and tribofilm chemistry. The results prove that two main mechanisms influence oil performance expressed as additives depletion by free water and remaining dissolved water.

Examining Invasion‐Percolation Across the Cathode Layered Assembly in Polymer Electrolyte Membrane Fuel Cells: Oxygen Resistance, Wettability and Cracks

AbstractEfficient evacuation of water generated by oxygen reduction reaction is necessary to increase catalyst utilization in polymer electrolyte membrane Fuel Cells. However, analysis of two‐phase transport is challenged by the wide range of pore sizes present in the membrane electrode assembly (MEA), varying from 10–100 nm in the catalyst layer (CL), 10–1000 nm in the microporous layer (MPL) and 10 μm in the gas diffusion layer (GDL). In this work, a novel multiscale invasion‐percolation model accounting for the cathode CL, MPL and GDL is presented. Saturation in the macroporous GDL is modeled through an all‐or‐nothing invasion law (empty/filled), while a macroscopic description in terms of the capillary pressure curve is adopted for the MPL and the CL. The oxygen transport resistance across the cathode MEA is quantified using the computed saturation distributions. Among other conclusions, the results show that MPL addition is crucial to avoid local flooding at the CL/GDL interface, providing localized access points to the GDL rather than massively invading interfacial macropores. However, excessive MPL hydrophobicity can cause CL flooding. Water removal from the CL can be enhanced by using a more hydrophilic MPL, a hydrophobic CL or the addition of a moderate volume fraction of cracks. Oxygen transport can be further improved by modulating the arrangement of water in the GDL with patterned wettability, provided that the number of MPL cracks is low.

Estimation of Soil Organic Matter Based on Spectral Indices Combined with Water Removal Algorithm

Soil moisture strongly interferes with the spectra of soil organic matter (SOM) in the near-infrared region, which reduces the correlation between organic matter and spectra and decreases accuracy in the prediction of SOM. In this study, we explored the feasibility of two types of spectral indices, two- and three-band mixed (SI) and three-band spectral indices (SI3), and two water removal algorithms, direct standardization (DS) and external parameter orthogonalization (EPO), to estimate SOM in wet soils using a total of 192 soil samples at six water content gradients. The estimation accuracies of spectral indices combined with water removal algorithms were better than those of full spectral data combined with water removal algorithms: the prediction accuracies of SI-EPO (R2 = 0.735, RMSEp = 3.4102 g/kg) were higher than those of EPO (R2 = 0.63, RMSEp = 4.1021 g/kg), and those of SI-DS (R2 = 0.70, RMSEp = 3.7085 g/kg) were higher than those of DS (R2 = 0.61, RMSEp = 4.2806 g/kg); SI3-EPO (R2 = 0.752, RMSEp = 3.1344 g/kg) was better than SI-EPO; both EPO and DS effectively mitigated the influence of soil moisture, with EPO demonstrating superior performance in small-sample prediction scenarios. This study introduces a novel approach to counteract the impact of soil moisture on SOM estimation.