High Removal Capability Research Articles

Porous chitosan/biocarbon composite membrane as the electrode material for the electrosorption of uranium from aqueous solution

The radioactive pollution owing to the discharge of effluents containing radionuclides brings serious toxicological effects on the ecological environment. In this work, the chitosan (CS) and biomass-resourced porous activated carbons (BC) composite membranes (CS/BC) were used as the electrodes for the electrosorption of U(VI) from aqueous solutions. The capacitive characteristic and electrosorption performance of the composite electrodes was systematically investigated. The CV curves of the CS/BC membrane showed normal dependency of scan-rate and U(VI) concentration, reflecting good removal capacity and kinetic rate for U(VI) electrosorption. The CS: BC mass ratios had significant effects on U(VI) electrosorption performance, and the CS/BC-2 is the best among various CS/BC electrodes owing to its good match of functional groups and mesoporous structure. The CS/BC-2 presented high removal capability of for U(VI) electrosorption (207.6 mg/g at the voltage of 0.9 V and pH 4.0, based on Langmuir model). The electrosorption involves in electrical double-layer formation, ion-exchange, complexation and physisorption. The cyclic electrosorption-desorption results and the XPS characterization further clarified this mechanism. The CS/BC-2 could also selectively adsorbed U(VI) from other co-existed metal ions in electrosorption. The results revealed the potential application of electrosorption process by using CS/BC electrodes in U(VI) solution for the cleanup of environmental pollution.

Elemental mercury capture from flue gas by magnetic recyclable Fe6Mn1-xCexOy sorbent. Part 1. Performance evaluation and regeneration

A series of Ce doped Fe-Mn magnetic sorbents (Fe6Mn1-xCexOy) were prepared by using the co-precipitation method. The mercury removal performance evaluation and thermal regeneration of Fe6Mn1-xCexOy sorbent was conducted in a fixed-bed system. Combining with the characterization of N2 adsorption, X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and X-ray photoelectron spectroscopy (XPS), the structure–activity relationship and the mechanism of circulating mercury removal by Fe6Mn1-xCexOy sorbent was analyzed. The results show that the Fe6Mn0.8Ce0.2Oy sorbent displays the best mercury removal capability, because Ce doping modifies the pore structure of sorbent, but excessive Ce addition reduces the active component of Mn. Both O2 in flue gas and low temperature are beneficial to mercury removal by Fe6Mn0.8Ce0.2Oy sorbent, because O2 can supplement the consumed lattice oxygen and Ce doping promotes the oxidation activity of lattice oxygen at low temperature. During mercury removal process, gas phase Hg0 is oxidized to Hg2+ by Mn4+ reducing to Mn3+, and combining with adsorbed O to form HgO. During thermal regeneration, part of Mn3+ is re-oxidized to Mn4+ by O2 in flue gas as well as Ce3+. After 6 cycles of mercury removal and thermal regeneration, the Fe6Mn0.8Ce0.2Oy sorbent still keep stable magnetism and high mercury removal capability. Therefore, the Fe6Mn0.8Ce0.2Oy sorbent is a promising sorbent for cyclic mercury removal from coal-fired flue gas.

Numerical study and experimental verification on spray cooling with nanoencapsulated phase-change material slurry (NPCMS)

Spray cooling is an efficient cooling method with high heatflux removal capability. In this study, we propose a spray cooling regime with nanoencapsulated phase-change material slurry (NPCMS), aiming to improve the coolant's heat capacity. We develop a three-dimensional model of spray cooling of NPCMS based on DPM and Lagrangian Wall Film (LWF) models. Also, the equivalent heat capacity method is integrated in LWF model to characterize the solid-liquid phase change of NPCMS. In addition, the experiment of spray cooling of NPCMS is conducted to verify our model. The influences of initial temperature of NPCMS and dynamic properties on flow and heat transfer of NPCMS are discussed. The results show that NPCMS greatly improves the heat transfer coefficient within the phase-change temperature range, especially the coefficient at the stagnation point of heated surface, but reduces the uniformity of heat transfer. The optimal heat transfer performance occurs when the initial temperature of NPCMS is 301 K, 0.9 K lower than the peak temperature of phase change. The heat transfer coefficient at the center of wall is almost twice of that of the water due to latent heat absorption. Lower surface tension and viscosity are beneficial to improving spray cooling performance.

Visible light-activated NGQD/nsC3N4/Bi2WO6 microsphere composite for effluent organic matter treatment

The diminishing availability of clean water resources has led to a high demand for advanced, effective wastewater effluent reclamation techniques. In this study, a new microsphere composite of nitrogen-doped graphene oxide quantum dots, nanosheet C3N4, and Bi2WO6 was synthesized and characterized to examine its feasibility as a visible light-activated photocatalyst for wastewater reclamation. At the optimal dose of 1 g•L−1 under 6 h of illumination, the composite exhibited a high removal capability for effluent organic matter (82.8 ± 1.6%). Its high performance and stability over multiple cycles are attributed to two factors: (1) its harvesting ability over a wide range of the visible light region and (2) its ability to separate photoinduced charge carriers effectively, which is driven by the efficient interfacial contact of the hosts and inclusion of the photosensitized nitrogen-doped graphene oxide quantum dots in the structural network. The complex effluent organic matter removal process of the compound was further examined by fluorescence spectroscopy and size exclusion chromatography. Fluorescence spectroscopy showed that humic-like components with a higher degree of aromatic condensation and greater molecular size were preferentially removed by photocatalysis. Protein-like components were removed more rapidly than the humic-like components due to the synergetic effects of OH and 1O2 on the rapid decomposition of low-molecular-weight compounds. Size exclusion chromatography revealed that the photocatalytic system preferentially removed larger molecules via adsorption and oxidation; however, smaller size fractions might be produced via the breakdown of biopolymer and humic substance fractions in effluent organic matter.

Fe3O4@Mesoporous-SiO2@Chitosan@Polyaniline Core–Shell Nanoparticles as Recyclable Adsorbents and Reductants for Hexavalent Chromium

In this work, we designed the Fe3O4@mesoporous-SiO2@chitosan@polyaniline core–shell nanoparticles (Fe3O4@mSiO2@CS@PANI, hence abbr. FSCP), which can be used to capture Cr(VI) in wastewater. Rapid adsorption behavior and high removal capability (249.6 mg Cr(VI) per gram of FSCP) were exhibited by this material. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that Cr(VI) was adsorbed and in situ reduced on FSCP at pH 2. Adsorption was facilitated by the electrostatic attraction of HCrO4– and −N+═C–/–N+H–, while the active −NH–/–N+H– sparked the reduction of Cr(VI) to Cr(III). Moreover, the coordination of the resulting Cr(III) with the amino group promoted adsorption, thus achieving detoxification of Cr(VI) in wastewater. After eight recycling experiments, the Cr(VI) removal efficiency of this material is still more than 90%, indicating that this material has excellent stability and good application potential. Therefore, this magnetic adsorbent offers a potential solution for the successful handling of chromium-containing wastewater.

Gradient wick channels for enhanced flow boiling HTC and delayed CHF

Liquid supply to wick structures of flow boiling surfaces is fundamentally restricted by the capillary limit at which the pressure drop of the wicked liquid surpasses texture-amplified capillary forces. Gradient wick structures partially decouple permeability and capillary pressure, thereby delaying the capillary limit. In this study, gradient wick channels facilitating out-of-plane liquid delivery are introduced to postpone the capillary limit and thus enhance the two-phase flow boiling heat transfer coefficient (HTC) and delay critical heat flux (CHF). Here, the permeability of the gradient wick channels is augmented by large-pore-size meshes employed near the bulk fluid while capillary pressure is maximized by small-pore-size meshes utilized near the hot boiling surface. This combination of wick structures enables to preferentially guide the cooling liquid, deionized water, from the far-field cold liquid toward the bottom hot substrate. The spatial distribution of individual gradient wick channels promotes separate liquid-vapor pathways, thus facilitating the vapor escape process. Experiments conducted here reveal that the flow boiling performance metrics of the proposed heat sink leveraging the gradient wick channels outperform those of the homogenous wick channels and solid fin channels. The proposed heat sink demonstrates a strong liquid mass flux dependency due to a combination of convective boiling and amplified wickability effects. The enhanced convective boiling could be related to surface roughness, a high number of active nucleation sites, and a large surface area available through tortuous passages of wick channels. At higher mass flow rates, effective capillary pressure available for out-of-plane wicking action also increases, thereby further boosting the wickability effect and associated heat transfer processes. This could meaningfully delay the CHF. In fact, the CHF limit was not observed on the gradient wick channel surfaces in the mass flux and wall superheat range studied. The experimental results indicated a maximum heat flux of 870 W/cm2 with a gradient wick channel heat sink, a 60% improvement compared with a plain copper surface. Furthermore, a maximum HTC of 1000 kW/m2-K at a wall superheat of 3 °C was observed, a three-fold enhancement compared with that of the plain surface. The proposed gradient wick channel topology offers new pathways for designing innovative surface technologies with high heat removal capabilities, thereby potentially improving the energy economy in myriad modern energy applications.

Self-Anticoagulant Nanocomposite Spheres for the Removal of Bilirubin from Whole Blood: A Step toward a Wearable Artificial Liver.

Current therapy for liver failure and concomitant hyperbilirubinemia faces the challenge of poor hemocompatibility and bleeding risks associated with the anticoagulant injection. Herein, heparin-mimetic biomacromolecule (HepMBm) with a similar degree of sulfation and anticoagulant properties to heparin was synthesized by imitating the structure of natural biomacromolecule heparin. Then HepMBm was used to prepare nanocomposite spheres based on reduced graphene oxide (rGO). The formation of a dual-network structure in the spheres endowed the spheres with improved dimensional stability. The proposed spheres exhibited outstanding blood compatibilities and excellent self-anticoagulant properties. The bilirubin adsorption experiments and whole blood bilirubin removal assay indicated that the spheres exhibited high bilirubin removal capability from whole blood (The removal ratio was 99.69%.). The spheres open new routes for a therapeutic strategy without a plasma separation system and heparin pump, which may be a step toward a lightweight wearable artificial liver.

A multifunctional hierarchical porous SiO2/GO membrane for high efficiency oil/water separation and dye removal

Removing contaminants from wastewater is critical to secure the global water supply. Membrane technologies for water purification are exceptionally attractive due to their high efficiency and low energy consumption. The traditional porous polymer films, however, are easy to be fouled by the organic pollutants, causing pore blockage and deteriorated separation performance. We herein report the rational design of a porous SiO2/GO hybrid membrane by coupling graphene oxide (GO) nanosheets with SiO2 nanoparticles and using ethylenediamine to crosslink them, for efficient oil/water separation and dye removal. The SiO2 nanoparticles provide an excellent hydrophilicity and underwater superoleophobicity interface, resulting in efficient and antifouling oil/water separation with an outstanding rejection rate over 99.4% for different types of oil; and the hierarchical scaffold, formed from the hydrophilic GO nanosheets embedded with SiO2 nanoparticles, greatly facilitates the rapid permeation of water with a high flux rate of up to 2387 L m−2 h−1 for pure water and 470 L m−2 h−1 for oil/water separation. Moreover, the abundant functional groups on the GO surface also render this membrane with a high removal capability for dye blocking, enabling it to remove soluble pollutants in molecular dimensions as well. This design strategy not only provides an outstanding membrane for water purification but also sheds light on the design of multi-purpose functional membranes for a variety of energy and environment-related applications.

Fundamental study on sustainable treatment system of mine water using magnetized solid catalyst

In the mine exploration sites, sustainable treatment system of mine water with energy saving and minimized chemical additives is required. Since most of the mine water contains highly-concentrated ferrous ion, it is necessary to study on the removal method of iron ions. We propose the system consisting of two processes; precipitation process by air oxidation using solid catalyst-modified magnetite and separation process combining gravitational sedimentation and magnetic separation using a permanent magnet. Firstly, in the precipitation process (a former process of the system), we succeeded to prepare solid catalyst-modified magnetite. Air oxidation using solid catalyst-modified magnetite using Fe2(SO4)3 as a starting material showed high iron removal capability. Secondly, in the separation process (latter process of the system), solid catalyst-modified magnetite using Fe2(SO4)3 as a starting material can be separated by a superconducting bulk magnet and a permanent magnet.

Hydro-Seq enables contamination-free high-throughput single-cell RNA-sequencing for circulating tumor cells

Molecular analysis of circulating tumor cells (CTCs) at single-cell resolution offers great promise for cancer diagnostics and therapeutics from simple liquid biopsy. Recent development of massively parallel single-cell RNA-sequencing (scRNA-seq) provides a powerful method to resolve the cellular heterogeneity from gene expression and pathway regulation analysis. However, the scarcity of CTCs and the massive contamination of blood cells limit the utility of currently available technologies. Here, we present Hydro-Seq, a scalable hydrodynamic scRNA-seq barcoding technique, for high-throughput CTC analysis. High cell-capture efficiency and contamination removal capability of Hydro-Seq enables successful scRNA-seq of 666 CTCs from 21 breast cancer patient samples at high throughput. We identify breast cancer drug targets for hormone and targeted therapies and tracked individual cells that express markers of cancer stem cells (CSCs) as well as of epithelial/mesenchymal cell state transitions. Transcriptome analysis of these cells provides insights into monitoring target therapeutics and processes underlying tumor metastasis.

Bacterial community shifts evaluation in the sediments of Puyang River and its nitrogen removal capabilities exploration by resuscitation promoting factor

Identifying indigenous bacterial community and exploring the potential of native microorganisms are crucial for in situ bioremediation of nitrogenous pollutants in water bodies. This study evaluated the bacterial communities of sediment samples from a nitrogen polluted river, and revealed the possible environmental factors shaping the bacterial populations. Importantly, viable but non-culturable bacteria which possessed nitrogen removal capabilities in indigenous population of the sediments were explored by resuscitation promoting factor (Rpf). It was found that the sediments from upstream (URS) and lower stream (LRS) of Puyang river showed both different pollutants levels and bacterial community. Nitrate nitrogen, organic carbon and ammonium nitrogen probably had a significant effect on bacterial compositions between URS and LRS. From URS and LRS, a total of thirteen strains with heterotrophic nitrification ability were resuscitated by Rpf addition, which belonged to genera Bacillus, Pseudomonas, Stenotrophomonas and Acinetobacter. Among them, the strain Pseudomonas sp. SSPR1 was found to display high removal capabilities of simultaneous nitrification and denitrification, and the average ammonium and nitrate removal rates were 2.23 and 0.86 mg/(L·h), respectively. These resuscitated strains could be considered to be used for biological nitrogen removal in rivers and their receiving water bodies.

Treatment of real aquaculture wastewater from a fishery utilizing phytoremediation with microalgae

AbstractBACKGROUNDIn this study, five microalgal species (Chlorella vulgaris, Chlorococcum sp. GD, Parachlorella kessleri TY, Scenedesmus quadricauda, and Scenedesmus obliquus) were cultivated in batch mode to evaluate their respective potential for the treatment of real aquaculture wastewater from a fishery. Subsequently, the microalga with the best performance was cultivated with different initial inoculation concentrations to evaluate the effect of initial inoculation on pollutant removal efficiency.RESULTSWhen real aquaculture wastewater was inoculated with exogenous microalgae, the growth of both indigenous microalgae and bacteria was significantly inhibited. Pollutant removal was closely related to exogenous inoculation of microalgae. Parachlorella kessleri TY had high growth potential and pollutant removal capability in aquaculture wastewater, compared with the other four microalgae. When the wastewater was inoculated with low biomass concentrations of P. kessleri TY (50–100 mg L−1), it grew well and degraded most of the encountered pollutant. In particular, P. kessleri TY with 100 mg L−1 of inoculation concentration removed 94.4% of COD, 96.2% of ammonium, 99% of nitrite, 94.3% of nitrate, and 95.6% of phosphorus after 3 days of cultivation.CONCLUSIONSBoth the screening for microalgal species and the regulation of initial inoculation concentrations are promising approaches to enhance pollutant removal efficiency from real aquaculture wastewater. © 2018 Society of Chemical Industry

Isolation and Identification of Potent Probiotics with High Lead Removal Capability

Probiotics play an effective and significant role in human health. The aim of this study was to isolate potential probiotics from Egyptian sources. Among the 14 different bacterial isolates recovered from 8 different sources on Man-Rogosa-Sharp (MRS) agar medium, 5 isolates exhibited tolerance to pH 3 and survived at bile concentration of 0.3% for 3h. The selected isolates were resistant to amikacin, vancomycin, ciprofloxacin and bacitracin. In addition, they showed high antibacterial activity against 7 pathogens. Hydrophobicity usingxylene and toluene showed high hydrophobic property for M isolate with toluene and xylene (80.43±0.95% and 78.2±0.73%, respectively). The potent isolate was identified by 16S rRNA gene as Lactobacillus plantarum strain M (KY508300). This strain was able to remove 71.28 ± 0.4 % of lead (1mg/ml) after 5min. The probiotic strain M showed count stability in yoghurt up to 21 days. The characteristic features of L. plantarum strain M as potent probiotics entitled it to be used in industrial and environmental applications.

Self-Template Etching Synthesis of Urchin-Like Fe3O4 Microspheres for Enhanced Heavy Metal Ions Removal

Hierachical Fe3O4 microspheres with superparamagnetic properties are attractive for their superior structural, water-dispersible, and magnetic separation merits. Here self-template etching route was developed to create optimal porous structure in superparamagnetic Fe3O4 microspheres by using the oxalic acid (H2C2O4) as etching agent. A plausible formation mechanism of the urchin-like Fe3O4 microspheres was proposed based on systematic investigation of the etching process, which involved two stages including pore-forming step based on size-selective etching and pore-expanding step based on further etching. The as-synthesized Fe3O4 microspheres exhibited urchin-like structure with specific surface area and pore-size tunable, water-dispersible, and superparamagnetic properties. The optimal urchin-like Fe3O4 microspheres demonstrated superior performance including fast magnetic separation and high removal capabilities for the heavy metals ions like Pb2+ (112.8 mg g-1) and Cr(VI) (68.7 mg g-1). This work will shed new light on the synthesis of urchin-like microspheres for superior performance.

A sustainable adsorbent for phosphate removal: modifying multi-walled carbon nanotubes with chitosan

Phosphorus, a major culprit for eutrophication of aquatic environments, is dissolved in water primarily in the form of phosphate; hence, it is difficult to remove, and different materials are being investigated, aiming at high removal capabilities. Meanwhile, recovery capability must also be considered, since phosphorus present in wastewater may serve as a potential alternative resource for the mineral phosphorus. Carbon nanotubes are promising for the treatment of phosphate pollution; however, studies about their removal potential are limited. Herein, multi-walled carbon nanotubes were modified with chitosan through simply cross-linking to obtain a novel adsorbent for phosphate removal. Our data show that a maximum adsorption as high as 36.1 ± 0.3 mg P g−1 was achieved in 30 min at pH 3 and 293 K. The adsorption capacity of the composite (chitosan/multi-walled carbon nanotubes) could be maintained at 94–98% even after 5 adsorption–desorption cycles. An exothermic process was obtained, according to the Freundlich isotherm model. Based on the reported performance, the composite has a great advantage compared with other novel adsorbents for phosphate removal, indicating that the composite is a highly potential material to treat phosphorus-induced eutrophication of water bodies.

Effect of pH and aging temperature on the phosphorus removal properties of layered hydroxide synthesized from zinc acetate

ABSTRACTZinc hydroxide acetate (ZHA) is a promising material for anion exchange applications because it has a layered structure with intercalating CH3COO− and H2O. ZHA can be synthesized through a direct precipitation method by adding sodium hydroxide solution to a Zn(OCOCH3)2 solution. In this study, ZHAs were synthesized under various conditions and tested as phosphorous removal agents. The ZHA precipitates were obtained at pH 6, 7, and 9. They were then aged at 25°C, 60°C, 90°C, and 120°C under hydrothermal conditions. At pH 6, nearly pure single-phase ZHAs were obtained regardless of the aging temperature. On the other hand, most of the ZHAs that were prepared at higher pH and aged at higher temperature were transformed to ZnO. For the phosphorous removal experiments, the single-phase ZHA precipitates removed approximately 99% of the phosphate ions in a 100 mg L−1 phosphorous solution, and the phosphorus removal efficiency decreased with increasing amounts of ZnO. Therefore, ZHAs that were prepared at lower pH and aged at lower temperatures contained little to no ZnO, thereby showing high phosphorous removal capabilities.

Adsorption and regeneration of expanded graphite modified by CTAB-KBr/H3PO4 for marine oil pollution.

The cleaning-up of viscous oil spilled in ocean is a global challenge, especially in Bohai, due to its slow current movement and poor self-purification capacity. Frequent oil-spill accidents not only cause severe and long-term damages to marine ecosystems, but also lead to a great loss of valuable resources. To eliminate the environmental pollution of oil spills, an efficient and environment-friendly oil-recovery approach is necessary. In this study,1expanded graphite (EG) modified by CTAB-KBr/H3PO4 was synthesized via composite intercalation agents of CTAB-KBr and natural flake graphite, followed by the activation of phosphoric acid at low temperature. The resultant modified expanded graphite (M-EG) obtained an interconnected and continuous open microstructure with lower polarity surface, more and larger pores, and increased surface hydrophobicity. Due to these characteristics, M-EG exhibited a superior adsorption capacity towards marine oil. The saturated adsorption capacities of M-EG were as large as 7.44g/g for engine oil, 6.12g/g for crude oil, 5.34g/g for diesel oil and 4.10g/g for gasoline oil in 120min, exceeding the capacity of pristine EG. Furthermore, M-EG maintained good removal efficiency under different adsorption conditions, such as temperature, oil types, and sodium salt concentration. In addition, oils sorbed into M-EG could be recovered either by a simple compression or filtration-drying treatment with a recovery ratio of 58-83%. However, filtration-drying treatment shows better performance in preserving microstructures of M-EG, which ensures the adsorbents can be recycled several times. High removal capability, fast adsorption efficiency, excellent stability and good recycling performance make M-EG an ideal candidate for treating marine oil pollution in practical application.

Isolation and characterization of a Bacillus amyloliquefaciens strain with zearalenone removal ability and its probiotic potential.

Zearalenone (ZEN) is a non-steroidal estrogenic mycotoxin produced by Fusarium species, which has been shown to be associated with reproductive disorders in livestock, and to a lesser extent with hyperoestrogenic syndromes in humans. The aim of this study was to characterize a Bacillus amyloliquefaciens strain with ZEN removal ability. A pure culture of a strain designated LN isolated from moldy corn samples showed a high ZEN removal capability. Based on microscopic observations, biochemical characteristics, and phylogenetic analysis of the 16S rRNA gene sequence, LN was identified as B. amyloliquefaciens. After incubation of B. amyloliquefaciens LN in Luria-Bertani (LB) medium containing 3.5 ppm of ZEN, the ZEN concentration fell below the detection limit within 24 h. In ZEN-contaminated corn meal medium, B. amyloliquefaciens LN decreased ZEN concentration by 92% after 36 h of incubation. In phosphate-buffered saline (PBS) containing 5 ppm of ZEN, B. amyloliquefaciens LN reduced the ZEN concentration from 5 ppm to 3.28 ppm immediately after coming into contact with ZEN, and further reduced the ZEN concentration to 0.36 ppm after 4 h of incubation. The amounts of ZEN adsorbed by the cells of B. amyloliquefaciens LN did not increase with the extension of incubation time, indicating that B. amyloliquefaciens LN not only possessed ZEN adsorption ability, but also exhibited the ability to degrade ZEN. In addition, B. amyloliquefaciens LN was non-hemolytic, non-enterotoxin producing, and displayed probiotic characteristics including acidic tolerance, bile salt tolerance, and anti-pathogenic activities. These findings suggest that B. amyloliquefaciens LN has a potential to be used as a feed additive to reduce the concentrations of ZEN in feedstuffs.

Expanded Graphite Modified by CTAB-KBr/H3PO4 for Highly Efficient Adsorption of Dyes

Expanded graphite (EG) modified by CTAB-KBr/H3PO4 was synthesized via composite intercalation agent of CTAB-KBr and natural flake graphite, followed by the activation of phosphoric acid under low temperature. The resultant modified expanded graphite (M-EG) architectures showed an interconnected and continuous open microstructure, in which the number, size and volume of the pores were larger than the EG before modification. Due to their unique structural characteristics, the resulting M-EG exhibited a wide applicability and superior adsorption capacity toward dyes. The saturated adsorption capacities of M-EG were as large as 159.71 mg/g for acid brilliant blue, 48.06 mg/g for methylene blue, 56.73 mg/g for disperse yellow and 81.73 mg/g for acid red with the time of 40, 60, 50 and 50 min respectively, exceeding largely the corresponding pristine EG. Furthermore, it is surprising that the M-EG under different adsorption conditions of temperature, initial pH and metal ions still maintain good removal efficiency and more importantly, the M-EG can be easily separated and do not generate secondary contaminants. Adsorption dynamics indicated pseudo second-order model was more suitable for the investigated adsorption process, which is controlled by chemical adsorption involving uptake of acid brilliant blue onto M-EG through functional groups, but not the only factor. Adsorption isotherm indicated the adsorption process from Langmuir model to Temkin model. According to Dubinin–Radushkevich model, the calculated mean free energy implied chemisorption between M-EG and acid brilliant blue. High removal capability, fast adsorption efficiency, excellent stability and broad applicability make M-EG ideal candidates for dyes removal in practical application.

The Limitations of the Application of Darcy Law in Serpentine Flow Field

One of most common flow fields used in proton exchange membrane (PEM) fuel cells is the serpentine flow field. Diffusion (which is caused by concentration gradient) and convection (which is caused by pressure gradient) are two major transport mechanisms in the serpentine flow field. In the serpentine flow field, there is a pressure difference between two adjacent channels that leads to an under-land cross-flow through the porous media of the gas diffusion layer (GDL) from the higher pressure channel to the lower pressure channel. High under-land cross-flow rate leads to a high oxygen concentration under the land area and a high water removal capability, but it causes a high pressure drop at the same time. Most researchers use Darcy law in their modeling to predict the under-land cross-flow rate, and the inertial effect is neglected. At low velocity, the inertial force can be neglected, so the relation between pressure gradient and velocity inside the GDL is linear. However, the inertial force becomes important at high velocity, and the relation between pressure drop and velocity inside the GDL is no longer linear, so Darcy law is not applicable. Thereby, the modified Darcy Law which includes the inertial effect is developed. Non-Darcy effect is defined as the ratio of the inertial effect to the sum of the inertial effect and the viscous effect, and it is used as a benchmark for accounting the importance of the inertial effect. In this study, our numerical modeling applied Darcy law and modified Darcy law in the single serpentine flow field, respectively. When non-Darcy effect is no less than 5%, Darcy law over-predicts the cross-flow rate by more than 10% compared to the modified Darcy law. Criterions of the application range of Darcy law in the single serpentine flow field are found with the dimensional analysis as well. From the experimental results, Darcy law significantly under-estimates the pressure drop in the single serpentine flow field, which has narrow land, high permeability and high inertial coefficient.