Carbon Fiber Brush Research Articles

Highly efficient treatment of tetracycline using coupled electro-Fenton and electrocoagulation process: Mechanism and toxicity assessment

In this study, a novel carbon fiber brush (CFB) electrode was designed using carbon fiber filaments and conductive metals. It was used as the cathode to construct an efficient coupled electro-Fenton and electrocoagulation (EF-EC) process for tetracycline (TC) treatment. An optimal 97.9% removal rate of 10 mg L−1 TC was achieved within 20 min. The coupled process is less pH-dependent and more effective in treating TC compared to the traditional individual electro-Fenton (EF) or electrocoagulation (EC) process, achieving efficient TC removal under neutral pH conditions. The removal rate of 10 mg L−1 TC consistently remained above 92% at 20 min after ten cycle experiments using the same electrodes in a Fe-CFB system (92.7–97.9%), indicating excellent reusability and stability of the CFB cathode. Mechanism analysis showed both EF and EC processes were involved in the system. Radicals (such as •OH and SO4−•) generated by EF contributed to the degradation of TC, yielding nine intermediates. Coagulants (such as Fe(OH)3) generated by EC contributed to the removal of TC. Toxicity prediction results indicated that over half of the nine intermediates exhibited lower biotoxicity compared to TC. This study provides a feasible alternative cathode for the efficient treatment of TC using EF-EC process.

Evaluating the feasibility of carbon fiber brush for improving biohydrogen production in acidogenic dark fermentation

Dark fermentation is a promising technology for biohydrogen (bioH2) production. Augmenting the dark fermentation process with conductive materials has drawn significant research interests improving the bioH2 yield. This study evaluated the feasibility of using carbon fiber brush (CB) as an additive to increase the efficiency of mesophilic dark fermentation using glucose as substrate and heat-shock pretreated anaerobic sludge as inoculum. Effect of electrode packing density on bioH2 yield, soluble metabolite product formation, and substrate degradation was investigated. Maximal bioH2 yield of 334.6 mL/g-glucose was obtained using medium-sized CB with 72.5% higher than the control (194 mL/g-glucose) and butyrate-type fermentation was the dominant metabolic pathway. Further, enhanced concentrations of proteins and polysaccharides on CB biofilm suggested the critical role of extracellular polymeric substances in microbial electron transfer. This was supported via electron transport activity in CB biofilm. Finally, microbial community analysis revealed a selective enrichment of the potentially electroactive Clostridium_sensu_stricto_1 on the CB (56.6%) compared to 40.9% abundance in control. Insights gained from this study demonstrated that CB aided dark fermentation can be an economical and environmentally benign strategy for improving bioH2 yield.

Laser powder bed fusion recoater selection guide—Comparison of resulting powder bed properties and part quality

Spreading devices used to create powder layers in the laser powder bed fusion of metals (PBF-LB/M) were found to have a significant impact on the additive manufacturing process. However, previous research primarily focused on theoretical investigations, including recoater concepts that are not available on the market, while no comprehensive comparison of commercially available spreading devices currently exists. The aim of this study is therefore to examine the powder bed properties and part qualities that can be achieved with the three most common types of recoater: carbon fiber brushes, polymer lips, and high speed steel (HSS) blades. Identical build jobs were produced using each of the spreading devices. Their capabilities were assessed by nine evaluation criteria, including dimensional, metallurgical, and mechanical properties and criticality of particles abraded from the spreading devices. Based on these quantitative findings, a spreading device selection guide was compiled for the benefit of PBF-LB/M practitioners. All recoaters yielded processes with high stability and part properties that were on a par with or even outperformed the nominal values from the literature. However, the HSS blade was found to provide higher accuracy and stability in steady-state processes. In turn, the brush and lip are better suited for parameter development and design studies. Additionally, the lip was found to have economic benefits over the brush, while the brush was deemed an effective all-rounder.

Improved net energy recovery in a sludge anaerobic digestion process by coupling an electrochemical system: electrode material and its impact on suspended microbial community.

Despite its great potential to recover energy from waste sludge, anaerobic digestion (AD) still needs to solve issues such as slow hydrolysis and H2 inhibition. This study investigated the effects of coupling microbial electrolysis cell (MEC) with AD on the CH4 yield. Results and analysis show that the CH4 yield was significantly improved in MEC-AD reactors by two factors, i.e., enhanced and accelerated hydrolysis and acidogenesis, and enrichment of hydrogenotrophic methanogens in suspended culture. Compared with graphite rod and carbon fiber brush, carbon felt (CF) as an electrode showed the best performance in terms of net energy output. The CH4 yield of MEC-AD-CF was 40.2 L CH4/kg VS, 92.3% higher than in the control group, and the VS removal rate was also increased by 47.2%. Acetoclastic methanogens were dominant in the control AD reactor, while the relative abundance of Methanobacterium, which is electroactive and known as hydrogenotrophic methanogen, increased to 24.6% in MEC-AD with CF as electrodes.

Zinc-based metal organic framework on carbon fiber brush as a novel anode of yeast-based microbial fuel cell

A microbial fuel cell (MFC) is an eco-friendly device that uses living microorganisms' catalytic activity for energy harvesting. The power output of this device is still far from the targeted one. An improvement to the power can be accessed via the use of biocompatible high surface area anode materials. Metal-organic frameworks (MOFs) have a high surface area, crystalline, and can be prepared in different morphologies. MOF demonstrated excellent performance in various energy conversion/storage devices. For the first time, a standalone carbon fiber brush electrode modified with Zn-MOF is constructed via a simple hydrothermal approach. The prepared electrodes were investigated as the anode of yeast-based MFC. The MFC with Zn-MOF carbon fiber brush exhibited maximum current and power densities of 317 mA/m2 and 73.7 mW/m2, which are twofold those obtained using bare carbon brush anodes. The significant improvement in the MFC performance with modified carbon fiber brush would be related to the role of the Zn-MOF in facilitating the electron transfer between the anode and the yeast cells and thus promoting bio electrocatalytic activity as confirmed from the redox peaks that appeared during the cyclic voltammetry (CV) of the modified electrodes and supported by electrochemical impedance spectroscopy (EIS).

Horizontal carbon fiber brush amendment and maximum radius of influence prediction: A novel soil bioelectrochemical system for extending the range of petroleum hydrocarbons degradation

Horizontal carbon fiber brush amendment and maximum radius of influence prediction: A novel soil bioelectrochemical system for extending the range of petroleum hydrocarbons degradation

Optimization of bioenergy generation and chemical oxygen demand reduction in dual-chamber microbial fuel cells using active soil microbes

This study focused on the optimization of a dual-chamber microbial fuel cell (MFC) system using carbon fiber brush and titanium electrodes, meat processing wastewater as substrate, and active soil microbes as biocatalyst. Significant findings revealed promising results on the MFC performance. The active soil microbes contain viable bacteria that worked effectively in the anode chambers. Peak open-circuit voltages (OCV) of the MFCs were as high as 1.05 V using titanium mesh and 1.03 V using carbon fiber brush. In closed-circuit conditions, the current obtained were 1.04 mA and 1.38 mA, and the power densities were 1.22 Wm−2 and 0.34 Wm−2, correspondingly. The power densities were normalized based on the surface areas of the anodes. The bioenergy generation profiles also revealed the MFCs can produce peak potentials of 30.109 kJ and 19.415 kJ using carbon fiber brush and titanium mesh, respectively. Furthermore, the results showed that the reduction in chemical oxygen demand (COD) was highest at 24.32 percent using carbon brush and lowest at 13.34 percent using titanium mesh electrodes.

Conductive carrier promotes synchronous biofilm formation and granulation of anammox bacteria

The extracellular electron transfer capability of some anaerobic ammonium oxidation (anammox) bacteria was confirmed in recent years. However, the effect of conductive carriers on the synchronous formation of anammox biofilm and granules is rarely reported. Anammox biofilm and granules with compact and stable structures accelerate the initiation and enhance the stability of the anammox process. In this study, we found that the conductive carbon fiber brush (CB) carrier promoted synchronous biofilm formation and granulation of anammox bacteria in the internal circulation immobilized blanket (ICIB) reactor. Compared with polyurethane sponge and zeolite carrier, the ICIB reactor packed with CB carrier can be operated under the highest total nitrogen loading rate of 6.53 kg-N/(m3·d) and maintain the effluents NH4+-N and NO2−-N at less than 1 mM. The volatile suspended solids concentration in the ICIB reactor packed with conductive carrier increased from 5.17 ± 0.40 g/L of inoculum sludge to 24.24 ± 1.20 g/L of biofilm, and the average particle size of granules increased from 222.09 µm to 879.80 µm in 150 days. Fluorescence in situ hybridization analysis showed that anammox bacteria prevailed in the biofilm and granules. The analysis of extracellular polymeric substances indicated that protein and humic acid-like substances played an important role in the formation of anammox biofilm and granules. Microbiome analysis showed that the relative abundance of Candidatus Jettenia was increased from 0.18% to 38.15% in the biofilm from CB carrier during start-up stage. This study provides a strategy for rapid anammox biofilm and granules enrichment and carrier selection of anammox process.

Development and comprehensive characterization of low-cost hybrid clay based ceramic membrane for power enhancement in plant based microbial fuel cells (PMFCs)

A variety of low-cost hybrid clay based ceramic membranes were developed for application in plant based microbial fuel cells (PMFCs). The membranes were prepared by using locally available clay mixed with varying concentrations of sodium carbonate, sodium metasilicate, boric acid, bentonite, and fly ash. Physiochemical characterization was carried out by using TGA, XRD, FESEM, FTIR, flexural strength test, water uptake, proton conductivity, oxygen and acetate diffusion and compared with Nafion117. Performance of ceramic membranes in PMFCs was evaluated by using the plant E. aureum with carbon fiber brush electrode. Membrane having composition of clay-55%, bentonite-15%, flyash-15%, Na2Co3-8%, Na2Sio3-2%, H3Bo3-5% exhibited maximum power density of 22.38 mW m−2 which was 78% higher than control (100% clay) with a decrease in internal resistance from 346 Ω to 234 Ω. The study demonstrates that the addition of bentonite, fly ash, Na2Co3, Na2Sio3 and H3Bo3 with clay at a concentration of 15%, 15%, 8%, 2%, and 5% respectively improved membrane cation transport ability, reducing oxygen diffusion and substrate crossover at the same time. The membrane demonstrated extreme stability for long term operations involving more than six months’ period. The low cost of production of clay based ceramic membrane at ₹1279/ft2 can be a good alternative to highly priced commercially available proton exchange membranes.

Operating life assessment of a carbon fibre brush seal through endurance testing

While brush seals have been studied for almost forty years, carbon fibre brush seals have only recently drawn interest for their excellent leakage performance, combined with low friction. Their suitability for oil sealing applications has been acknowledged in the aeronautical field, specifically for civil aircraft gas turbine engines. This paper focuses on the endurance of optimally designed brush seals in an environment simulating the bearing chamber working conditions. They underwent a wide range of differential pressures and rotational speeds in long runs ranging from 100 to 300 h. A semi-empirical performance prediction model was developed based on these results, allowing estimation of the leakage performance beyond the recorded data. In addition, the presence of lubrication oil largely increases seal life, despite initial leakage performance degradation due to hydrodynamic lift. Finally, a visual inspection with a high precision microscope revealed uprooting of the carbon fibres. This phenomenon may well be the biggest cause of performance degradation, rather than fibre material losses, which were ultimately deemed unquantifiable.

A feasibility investigation of a pilot-scale bioelectrochemical coupled anaerobic digestion system with centric electrode module for real membrane manufacturing wastewater treatment

The large-scale application of bioelectrochemical coupled anaerobic digestion (BES-AD) is limited by the matching of electrode configuration and the applicability of real wastewater. In this study, a pilot-scale BES-AD system with an effective system volume of 5 m3 and a 1 m3 volume of a carbon fiber brush electrode module was constructed and tested for treatment of the membrane manufacturing wastewater. The results showed that the BOD5/COD of the wastewater was increased from 0.238 to 0.398 when the applied voltage was 0.9 V. The pollutants such as N, N-Dimethylacetamide and glycerol in wastewater were degraded significantly. The microorganisms in the electrode modules were spatially enriched. The fermenters (Norank_f__ML635J-40_aquatic_group, 6.55 %; unclassified_f__Propionibacteriaceae, 5.25 %) and degraders (Corynebacterium, 29.31 %) were mostly enriched at the bottom, while electroactive bacteria (Pseudomonas, 29.39 %, Geobacter, 7.86 %) were mostly enriched at the top. Combined with the economical construction and operation cost ($1708.8/m3 and $0.76/m3) of the BES-AD system.

Investigating the effect of powder recoater blade material on the mechanical properties of parts manufactured using a powder-bed fusion process

As additive manufacturing (AM) technology grows, more industries are learning how to utilize it for their specific applications. Powder bed fusion-based AM processes such as Direct metal laser solidification (DMLS) allow manufacturers to design more intricate or lightweight parts that could not be made with traditional tools. DMLS expands the capabilities of manufacturing, but the recoater blade that spreads powder presents challenges in printing delicate details such as lattice structures and high aspect ratio features. Hard steel or ceramic blades are often used to compact powder to create smooth, even layers that result in higher strength values of parts. However, small structures can be damaged by these blade types. Alternatively, a softer rubber or carbon fiber brush can be used to make the printing process easier by not breaking the small, printed features. On the other hand, parts made with softer blades are expected to have less strength and more defects. To compare the mechanical properties of finished parts due to blade type, 3 blade materials, high-speed steel (HSS), silicone rubber, and carbon fiber brush, were compared in this study. Tensile bars, cubes, and Voronoi lattice structure pucks were printed and analyzed for tensile properties, optical density analysis, as well as compression strength or toughness. These tests are often completed by original equipment manufacturers (OEM’s) in the AM industry to qualify the machine’s process. There were no significant tensile strength differences noticed of parts based on blade type and the values were all within the tolerance of OEM specifications. Optical density analysis indicated that the rubber blade builds have a higher number of large defects, greater than 75 μ m, and the brush blade has a higher number of small defects, less than 75 μ m in size. The HSS blade has zero defects greater than 90 μ m. There was no significant difference in maximum compression strength for the three blades, but the HSS blade produces parts with a standard deviation of toughness that is half of the other two blades. Inconsistencies shown in the soft blade builds may be due to the nature of the soft blades wearing faster over time during each build, however, the soft recoater blades can be a useful option if the application allows for occasional inconsistency.

The Application of Sediment Microbial Fuel Cells in Aquacultural Sediment Remediation

To successfully apply sediment microbial fuel cells (SMFCs) in remediating aquacultural sediments and water bodies on a large scale, SMFC systems with different electrode materials (carbon fiber brush, graphite felt, and carbon fiber cloth) and structural forms were constructed, and the advantages and disadvantages of various electrodes were compared in terms of electricity generation, pollutant removal, and application cost. The results revealed that (1) introducing SMFCs accelerated the removal of pollutants from the overlying water, promoted the degradation of organic matter and the fixation of phosphorus in the sediments, and inhibited water eutrophication and algal blooms; (2) SMFC systems with carbon fiber brushes and graphite felt electrodes exhibited better electricity generation, but the smooth surface of the carbon fiber cloth was not conducive to microbial attachment, leading to a relatively low electrode power density; and (3) the low external resistance accelerated electron transfer and increased the pollutant removal rate.

One-Step Preparation of a Superhydrophobic Surface by Electric Discharge Machining with a Carbon Fiber Brush Electrode

Superhydrophobic surfaces are extremely susceptible to damage, which can lead to a sharp decrease in their service life and physical properties. Therefore, developing methods to impart superhydrophobic surfaces with excellent wear resistance is crucial. In this article, a flexible carbon fiber brush was utilized as an electrode to fabricate micro-/nano-structures on a grooved surface via electric discharge machining in one step, resulting in a superhydrophobic coating with excellent wear resistance. Carbon fiber brushes exhibit several notable properties, including excellent flexibility, conductivity, and high temperature resistance. Carbon fiber brushes can adapt to the complex inner walls of grooves. Many nano-structures were fabricated on the grooves via pulse discharge, which resulted in a superhydrophobic surface with excellent wear resistance. The contact angle (CA) and sliding angle of the surface after discharge were 156.3 and 2°, respectively. The processed surface exhibits superior corrosion resistance compared to the stainless-steel substrate. The influence of the micro-groove shapes on wear resistance was tested. The results showed that, after 500 cm of wear, the shallow grooves retained their superhydrophobicity with a CA of 150.1°.

Fe2+, Fe3+, Co2+ as highly efficient cocatalysts in the homogeneous electro-Fenton process for enhanced treatment of real pharmaceutical wastewater

The electro-Fenton process (EFP) has been known as an effective process with highly outstanding oxidation power. In this study, the real pharmaceutical wastewater was successfully mineralized via EFP by using boron-doped diamond (BDD) anode and carbon-fiber brush cathode (CFB) with Fe2+/Fe3+/Co2+ cocatalysts. The effect of various parameters, including the electrode, ratio of cocatalysts, current density, pH, and O2 flow rate, was investigated. The TOC and COD removal efficiencies of 92% and 93%, respectively, were achieved. For the increase in biodegradability, BOD5/COD ratio increased from 0.1 to 0.69 after 2 h in the presence of Fe2+/Fe3+/Co2+ cocatalysts under optimal conditions in a batch experiment (current density of 17 mA cm−2, initial pH of 3, a Fe2+/Fe3+/Co2+ ratio of 1:1:2, O2 flow rate of 0.5 L min−1). In comparison, TOC and COD removal efficiencies were reached 81% and 85% after 10 h of reaction in a continuous-flow condition, respectively. The oxidation of pharmaceutical organic pollutants was mainly found by the electrochemically produced hydroxyl (OH) and sulfate (SO4−) radicals, followed by pseudo-first-order kinetics. Hence, EFP demonstrated the feasibility of potential technology for the treatment of real pharmaceutical wastewater.

The impact of different types of high surface area brush fibers with different electrical conductivity and biocompatibility on the rates of methane generation in anaerobic digestion

The addition of electrically conductive materials may enhance anaerobic digestion (AD) efficiency by promoting direct interspecies electron transfer (DIET) between electroactive microorganisms, but an equivalent enhancement can also be achieved using non-conductive materials. Four high surface area brush materials were added to AD reactors: non-conductive horsehair (HB) and polyester (PB), and conductive carbon fiber (CB) and stainless steel (SB) brushes. Reactors with the polyester material showed lower methane production (68 ± 5 mL/g CODfed) than the other non-conductive material (horsehair) and the conductive (graphite or stainless steel) materials (83 ± 3 mL/g CODfed) (p < 0.05). This difference was due in part to the higher biomass concentrations using horsehair or carbon (135 ± 43 mg) than polyester or stainless steel or materials (26 ± 1 mg). A microbial community analysis indicated that the relative abundance of electroactive microorganisms was not directly related to enhanced AD performance. These results show that non-conductive materials such as horsehair can produce the same AD enhancement as conductive materials (carbon or stainless steel). However, if the material, such as polyester, does not have good biomass retention, it will not enhance methane production. Thus, electrical conductivity alone was not responsible for enhancing AD performance. Polyester, which has been frequently used as a non-conductive control material in DIET studies, should not be used for this purpose due to its poor biocompatibility as shown by low biomass retention in AD tests.

Decolorization of Methyl Orange using a Double-chamber Microbial Fuel Cell with the Use of Soil Microorganisms

In this study, the decolorization of methyl orange was carried out in a double chamber microbial fuel cell. Microbial fuel cells (MFC’s) have been widely studied using various materials and operating conditions, these bioelectrochemical devices that use exoelectrogenic bacteria as biocatalysts have shown great potential to oxidize a variety of substrates while simultaneously generating electricity. Soil microorganisms consisting of lactic acid bacteria, Saccharomyces, Rhizobium, Rhodopseudomonas, Rhodobacter, Actinomycetes, and fungi were obtained from a concentrated soil microbial inoculant. Comparatively, the results of the experiments showed that using titanium mesh, the open circuit voltage and the power density of the MFC in close-circuit condition were 1.005 V and 1.223 Wm−2 while using carbon fiber brushes, values were 0.992 V and 0.338 Wm−2. On the other hand, results also revealed that the system with carbon fiber brush electrodes is more effective in decolorizing methyl orange at a maximum of 78 percent removal efficiency. In 10 hours of continuous operation, the concentration of methyl orange reduced from 0.10-0.022 mM.

Addition of a carbon fiber brush improves anaerobic digestion compared to external voltage application

Two methods were examined to improve methane production efficiency in anaerobic digestion (AD) based on adding a large amount of surface area using a single electrically conductive carbon brush, or by adding electrodes as done in microbial electrolysis cells (MECs) to form a hybrid AD-MEC. To examine the impact of surface area relative to electrodes, AD reactors were fitted with a single large brush without electrodes (FB), half a large brush with two electrodes with an applied voltage (0.8 V) and operated in closed circuit (HB-CC) or open circuit (HB-OC) mode, or only two electrodes with a closed circuit and no large brush (NB-CC) (equivalent to an MEC). The three configurations with a half or full brush all had improved performance as shown by 57-82% higher methane generation rate parameters in the Gompertz model compared to NB-CC. The retained biomass was much higher in the reactors with large brush, which likely contributed to the rapid consumption of volatile fatty acids (VFAs) and therefore improved AD performance. A different microbial community structure was formed in the large-size brushes compared to the electrodes. Methanothrix was predominant in the biofilm of large-size carbon brush, while Geobacter (anode) and Methanobacterium (cathode) were highly abundant in the electrode biofilms. These results demonstrate that adding a high surface area carbon fiber brush will be a more effective method of improving AD performance than using MEC electrodes with an applied voltage.

An open-structured carbon fiber brush electrode for efficient hydrogen evolution by inducing oriented bubble transport

Hydrogen, as a promising energy carrier to alleviate the global issues of energy crisis, has arisen a worldwide concern. However, the lack of management of the produced bubbles on electrode surface is one of the critical barriers for hydrogen evolution reaction (HER) since insufficient bubble removal causes the blockage of the active sites, increased ohmic resistance in the electrolyte and deficient ion transfer from the bulk solution to the electrode surface. In this study, an open-structured carbon fiber brush electrode (CFB) that can be produced by simply twisting a folded Ti wire fitted with carbon fibers was proposed. As a proof-of-concept demonstration, an earth-abundant electrocatalyst, MoS2 nanosheets was loaded on the CFB via solvothermal method to fabricate the HER electrode (MoS2⊥CFB). This structure not only ensures a uniform electrocatalyst distribution throughout the exterior and internal electrode surface but also ensures an improved exposure of active sites and a sufficient reaction ion supply by inducing oriented hydrogen bubble transport during the electrochemical process. Additionally, the open structure of CFB accelerates fluid flow around the electrode, which also guarantees a sufficient proton supply and hydrogen bubble removal. As a results, MoS2⊥CFB exhibits a 3.7 times higher current density at an overpotential of 400 mV and prominent durability as compared with the same catalyst growing on the common carbon cloth substrate.

Experimental characterization of friction and heat generation of carbon fibre brush seals for aero-engines

Brush seals have been extensively studied for the last thirty years as an advanced sealing solution for gas turbine engines. The research is always aimed towards the reduction of the leakage flow, that has direct repercussions on the specific fuel consumption, the thrust-to-weight ratio, and the emission of pollutants. In addition, the sealing device must cope with side effects related to higher interface speeds, rotordynamics issues, or durability. Brush seals main assets are their excellent leakage performance with low friction properties compared to other contact seals like lip seals, and their ability to withstand rotor radial excursion without permanent damage. However, proper design optimization cannot be performed without the inclusion of the tribological performance. This paper presents a parametric investigation of the friction properties of carbon fibre brush seals as a function of the fibre pack geometry and the rotational speed. Carbon fibre and commonly used metallic brush seals present fundamentally different behaviour in presence of differential pressure or rotational speed. This paper also proposes an alternative method to predict the brush seal torque, based on measurements with a torque sensor. Heat generation was also evaluated with a thermographic camera. Both methods ensured consistency between results.