PAN-based Activated Carbon Fibers Research Articles

Facile Preparation of Polyacrylonitrile-Based Activated Carbon Fiber Felts for Effective Adsorption of Dipropyl Sulfide.

Activated carbon fibers (ACFs) derived from various polymeric fibers with the characteristics of a high specific surface area, developed pore structure, and good flexibility are promising for the new generation of chemical protection clothing. In this paper, a polyacrylonitrile-based ACF felt was prepared via the process of liquid phase pre-oxidation, along with a one-step carbonization and chemical activation method. The obtained ACF felt exhibited a large specific surface area of 2219.48 m2/g and pore volume of 1.168 cm3/g, as well as abundant polar groups on the surface. Owing to the developed pore structure and elaborated surface chemical property, the ACF felt possessed an intriguing adsorption performance for a chemical warfare agent simulant dipropyl sulfide (DPS), with the highest adsorption capacity being 202.38 mg/g. The effects of the initial concentration of DPS and temperature on the adsorption performance of ACF felt were investigated. Meanwhile, a plausible adsorption mechanism was proposed based on the kinetic analysis and fitting of different adsorption isotherm models. The results demonstrated that the adsorption process of DPS onto ACF felt could be well fitted with a pseudo-second-order equation, indicating a synergistic effect of chemical adsorption and physical adsorption. We anticipate that this work could be helpful to the design and development of advanced ACF felts for the application of breathable chemical protection clothing.

Application of textile (PAN-based) activated carbon fibers decorated with silver nanoparticles in water treatment

Introduction: Water treatment deficit and poor health, hygiene and sanitation infrastructure can contribute to disease transmission by dissemination of contaminants and microorganisms. As an alternative, carbon-based materials coated with antimicrobial molecules have been proposed for water treatment, but few supporting data are available so far. Hence, this study investigates the potential use of PAN-based activated carbon fibers (ACF) decorated with silver nanoparticles in water treatment.Methods: Silver nanoparticles were incorporated into the material using a cheap and electroless method. Field emission scanning electron microscopy (FEGSEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) characterized the whole material. The textile was mounted on a water filter prototype and had its capacity to remove bacterial (Escherichia coli) and fungal (Candida albicans, Aspergillus niger and Penicillium funiculosum) cells evaluated. Composition and toxicity of the filtered water were determined.Results: Water filtered by Ag@ACF for 2 and 24 h contained 0.254 mg/L and 0.964 mg/L Ag, respectively. Ag@ACF filtering successfully removed E. coli, C. albicans, and A. niger from the suspensions, but not P. funiculosum. Treated water was non-toxic for Vero cells and Drosophila melanogaster, but toxic for Raphidocelis subcapitata. Ag@ACF showed efficient microbial elimination when applied in water treatment. Silver nanoparticles released in aqueous medium may be responsible for R. subcapitata toxicity. Future studies should be conducted to reduce silver nanoparticles release from the carbon fiber.

Adsorption characteristics of nitrate ion by sodium carbonate activated PAN-based activated carbon fiber

In this study, polyacrylonitrile (PAN)-based carbon fiber with high nitrogen content was activated at 800 °C with sodium carbonate and heat-treated at 950 °C to prepare activated carbon fiber (ACF), and the results of nitrate ion adsorption on the prepared ACF are presented. CHN elemental analysis, XPS measurement, and Boehm titration were used to determine the nitrogen content and surface functional groups of ACF. It is discussed that the total amount of nitrogen decreases, whereas quaternary nitrogen (N-Q) increases upon heat treatment. The decrease in adsorption capacity of the prepared activated carbon under different storage conditions is shown. It is observed that the adsorption capacity of nitrate ion at equilibrium pH (pHe) 5 is halved after 5 weeks, and the decrease in adsorption capacity at pHe 3 is suppressed. The adsorption isotherms of the prepared ACF are shown using the Langmuir equation. The effect of pH on the adsorption capacity of the prepared ACF is compared with that of ACF before heat treatment and zinc chloride-activated powdered activated carbon. The adsorption capacity of ACF without heat treatment at 950 °C decreases as the pHe of the solution increases, and the pH of the nitrate solution including ACF after heat treatment is stable at pHe 4–5.

Effect of beating degree of fiber on the development of porosity in polyacrylonitrile-based activated carbon fiber paper

Activated carbon fiber paper (ACFP) has the potential for adsorption due to their high surface area and low through resistance. In this work, free-standing ACFP was developed from fibrillated polyacrylonitrile (PAN) fiber through wet forming process combined with subsequent pre-oxidation, carbonization and CO2 activation. A PFI refiner was used to prepare fibrillated PAN fibers with a beating degree of 7, 11, 25 and 60 oSR, respectively. As expected, PAN fibers with high beating degree improved surface area and fine fiber content, which resulted in the dense structure and low porosity of paper, thus influencing later stabilization and pyrolysis, as well as final properties of ACFP. With the increase of beating degree, the oxygen content of pre-oxidized PAN paper increased, but the cyclization index first decreased and then increased. ACFP with higher beating degree possessed higher BET surface area, pore volume and CO2 uptake capacity. ACFP, prepared from freeze-dried PAN paper, performed better in physicochemical properties than that from plate-press drier under the same beating degree. This study exhibited that ACFP can be a special material featured by scale production, lightweight, and high microporosity of chemical adsorption and separation.

Efficient adsorption and porous features from activated carbon felts activated by the eutectic of Na2CO3 and K2CO3 with vapor

In this work, a cost-effective eutectic mixture of Na2CO3 and K2CO3 was developed for preparing PAN-based activated carbon fibers (ACFs). Rapid activation (15 min) was achieved when using pre-oxygenated PAN felts as carbon source and a low amount (mass fraction of 0.5%) of the eutectic and water vapor as synergistic activating agents. The prepared ACFs exhibited high specific surface area (2175.0 m2/g), excellent benzene adsorption capacity (704.5 mg/g), and iodine adsorption capacity (2231.0 mg/g). Hierarchical structure of micropores and mesopores provided sites for gas adsorption. This study is expected to realize the industrial production of ACFs at a low cost.

The role of H2O in the removal of methane mercaptan (CH3SH) on Cu/C-PAN catalyst

Methane mercaptan (CH3SH) is a common organic sulfur in smelting flue gas, which has significant harm to the environment, industrial production and human health. Therefore, research on the purification of CH3SH has received extensive attention. Herein, we focused on the role of H2O in the removal of CH3SH, and revealed that H2O promotes the adsorption of CH3SH at low temperature and promotes its hydrolysis at high temperature, which significantly improves the removal of CH3SH. In this study, the polyacrylonitrile-based activated carbon fiber was prepared by electrospinning, with the diameter of about 300~400 nm. Cu, Fe and Mn were loaded by impregnation method, and the CH3SH removal efficiency were compared. The combination of characterization results by HR-TEM, XRD, XPS, NH3-TPD and activity evaluation as well as DFT calculation results finally revealed the removal mechanism of CH3SH with the participation of H2O.

Phosphate Ion Adsorption Properties of PAN-Based Activated Carbon Fiber Prepared with Na2CO3 Activation

Phosphate Ion Adsorption Properties of PAN-Based Activated Carbon Fiber Prepared with Na2CO3 Activation

Modification of polyacrylonitrile-based activated carbon fibers and their p-nitrophenol adsorption and degradation properties

Activated carbon fibers (ACFs) are widely used adsorbent materials for wastewater treatment. In this study, polyacrylonitrile-based ACFs (PAN–ACF) were modified with oxalic acid to promote their adsorption of p-nitrophenol (PNP) in wastewater. The obtained results revealed that the adsorption efficiency of the modified ACFs amounted to 98.05%. The photocatalytic degradation of PNP by ACFs loaded with nano-TiO2 and nano-ZnO photocatalysts was examined as well; under ultraviolet (UV) light irradiation, their PNP removal rates reached 99.85% and 98.31%, respectively. Moreover, the effects of pH, PNP concentration, and catalyst concentration on the PNP adsorption efficiency were systematically investigated. By conducting kinetic studies, it was found that the PNP adsorption on the PAN–ACF surface followed a pseudo-first-order model, while the PAN–ACF/TiO2 and PAN–ACF/ZnO obeyed a pseudo-second-order model, and all samples followed the Langmuir adsorption isotherm. Additionally, an integrated high-pressure microwave reactor was designed and fabricated, and the possibility of degrading PNP through the microwave-assisted catalytic oxidation by PAN–ACF/TiO2 was considered. The results of this work suggest that the novel modified PAN–ACF, PAN–ACF/TiO2 and PAN–ACF/ZnO adsorbents are promising materials for the removal of PNP-based pollutants from wastewater due to their facile application procedure, low fabrication costs, and good scale-up abilities.

Preparation of polyacrylonitrile-based activated carbon fiber for CS2 adsorption

Polyacrylonitrile (PAN)-based activated carbon fiber (ACF) was prepared by CO2 and KOH activation method, respectively, and used for the adsorption of CS2 at room temperature. The adsorbents were characterized by scanning electron microscope, CO2-temperature-programmed desorption and Fourier transform infrared spectroscopy. The adsorption activity of ACF prepared by different conditions (preoxidation process, carbonization temperature, CO2 activation temperature and time, carbon/KOH ratio, KOH activation temperature and time) was studied. The best breakthrough adsorption capacity of CS2 was 55.63 mgS/g when the ACF was activated by CO2 [ACF(I700)-CO2(900 + 90)]. The best breakthrough adsorption capacity of CS2 was 49.52 mgS/g when the activator was KOH [ACF(I700)-KOH(1:1 + 900 + 60)].

Phosphate ion adsorption properties of PAN-based activated carbon fibers prepared with K2CO3 activation

Adsorbents for phosphate ion removal were prepared with K2CO3 activation and heat treatment at 950 °C from polyacrylonitrile-based carbon fiber (PAN-CF). Comparative tests for specific surface area and pore structures, elemental and nitrogen species analysis, and phosphate ion adsorption experiments demonstrated that K(3)-Δ, which was activated with K2CO3/PAN-CF weight ratio of 3 and then treated at 950 °C, exhibited larger amount of quaternized-nitrogen (0.46 wt%) and equilibrium adsorption amount (0.23 mmol/g) among the prepared adsorbents. The experimental data for phosphate adsorption of K(3)-Δ was well fitted to Langmuir adsorption isotherms and pseudo-second-order kinetic model. As for regeneration performance, K(3)-Δ still remained more than 60% adsorption amount of the fresh adsorbent after rejuvenation treatment.

Bead chain structure RFC/ACF by electrospinning for supercapacitors

PurposeThe purpose of this paper is to prepare a spherical modifier-modified activated carbon fiber of high specific capacitance intended for electrode materials of supercapacitor.Design/methodology/approachIn this study, phenolic-based microspheres are taken as modifiers to prepare PAN-based fiber composites by electrospinning, pre-oxidation and carbonization. Pearl-chain structures appear in RFC/ACF composites, and pure polyacrylonitrile fibers show a dense network. The shape and cross-linking degree are large. After the addition of the phenolic-based microspheres, the composite material exhibits a layered pearlite chain structure with a large porosity, and the RFC/ACF composite material is derived because of the existence of a large number of bead chain structures in the composite material. The density increases, the volume declines and the mass after being assembled into a supercapacitor as a positive electrode material decreases. The specific surface area of RFC/ACF composites is increased as compared to pure fibers. The increase in specific surface area could facilitate the diffusion of electrolyte ions in the material. Owing to the large number of bead chains, plenty of pore channels are provided for the diffusion of electrolyte ions, which is conducive to enhancing the electrochemical performance of the composite and improving the RFC/ACF composite and the specific capacitance of the material. The methods of electrochemical testing on symmetric supercapacitors (as positive electrodes) are three-electrode cyclic voltammetry, alternating current impedance and cycle stability.FindingsThe specific capacitance value of the composite material was found to be 389.2 F/g, and the specific capacitance of the electrode operating at a higher current density of 20 mA/cm2 was 11.87 F/g (the amount of the microsphere modifier added was 0.3 g). Using this material as a positive electrode to assemble into asymmetrical supercapacitor, after 2,000 cycles, the specific capacitance retention rate was 87.46 per cent, indicating excellent cycle stability performance. This result can be attributed to the fact that the modifier embedded in the fiber changes the porosity between the fibers, while improving the utilization of the carbon fibers and making it easier for electrolyte ions to enter the interior of the composites, thereby increasing the capacitance of the composites.Originality/valueThe modified PAN-based activated carbon fibers in the study had high specific surface area and significantly high specific capacitance, which makes it applicable as an efficient and environment-friendly absorbent, as well as an advanced electrode material for supercapacitor.

NO Adsorption and Removal at Low Temperature by Adsorption Catalyst (Ce–Fe–Mn/ACFN)

FM/ACFN and Ce-doped CFM/ACFN low-temperature catalysts are prepared by an impregnation method that takes polyacrylonitrile-based activated carbon fiber modified with nitric acid as the carrier. The catalysts are characterized by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The effects of temperature, oxygen, and sulfur dioxide on the adsorption and removal of NO by catalyst are studied by laboratory gas distribution. Results show that the addition of metal oxide can increase the ability of chemical adsorption of NO by ACFN by 2.5%, and the ability of catalytic reduction of NO can be increased by up to 14%. Under the condition of oxygen and ammonia as reducing agent at 250 °C, the ability of metal-oxide-loaded ACFN to catalyze the reduction of NO can reach up to 68%. The addition of Ce does not completely inhibit the decrease of the ability of the catalyst in treating NO under sulfur-containing conditions, but it can maintain the catalyst’s reducing ability at a relatively stable level, and the presence of SO2 will reduce the redox capacity of ACFN itself.

Carbon Dioxide Adsorption on Porous and Functionalized Activated Carbon Fibers

Polyacrylonitrile-based activated carbon fibers (ACFs), modified using potassium hydroxide (KOH) or tetraethylenepentamine (TEPA), were investigated for carbon dioxide (CO2) adsorption, which is one of the promising alleviation approaches for global warming. The CO2 adsorption isotherms were measured, and the values of isosteric heat of adsorption were calculated. The results showed that the KOH-modified ACFs exhibited a great deal of pore volume, and a specific surface area of 1565 m2/g was obtained. KOH activation made nitrogen atoms easily able to escape from the surface of ACFs. On the other hand, the surface area and pore volume of ACFs modified with TEPA were significantly reduced, which can be attributed to the closing or blocking of micropores by the N-groups. The CO2 adsorption on the ACF samples was via exothermic reactions and was a type of physical adsorption, where the CO2 adsorption occurred on heterogeneous surfaces. The CO2 uptakes at 1 atm and 25 °C on KOH-activated ACFs reached 2.74 mmole/g. This study observed that microporosity and surface oxygen functionalities were highly associated with the CO2 uptake, implying the existence of O-C coordination, accompanied with physical adsorption. Well cyclability of the adsorbents for CO2 adsorption was observed, with a performance decay of less than 5% over up to ten adsorption-desorption cycles.

Chemical grafting of sulfo groups onto carbon fibers

We proposed the brominated carbon cloth that made of polyacrylonitrile-based activated carbon fibers (PAN-ACFs) as a precursor to chemically and uniformly graft SO3H groups to prepare the solid acid catalyst. The thermal and catalytic properties of the sulfonated PAN-ACFs were examined by IR controlled catalytic measurements and thermal analysis. The catalytic test results showed that the sulfonated surface remarkably improved the operating efficiency in isopropanol dehydration by decreasing the reaction temperature. All PAN-ACFs with grafted SO3H groups prepared through brominated precursors can converse 100% of isopropanol into propylene at moderate temperature. They showed the highest catalytic activity compared to PAN-ACFs sulfonated with oleum and chlorosulfonic acid, which conversed only 40% and 70% of isopropanol into propylene and deactivated at the higher temperatures in the reaction medium.

Modified polyacrylonitrile-based activated carbon fibers applied in supercapacitor

Purpose The purpose of this paper is to prepare a new modified activated carbon fibers (ACFs) of high specific capacitance used for electrode material of supercapacitor. Design/methodology/approach In this study, the specific capacitance of ACF was significantly increased by using the phenolic resin microspheres and melamine as modifiers to prepare modified PAN-based activated carbon fibers (MACFs) via electrospinning, pre-oxidation and carbonization. The symmetrical supercapacitor (using MACF as electrode) and hybrid supercapacitor (using MACF and activated carbon as electrodes) were tested in term of electrochemical properties by cyclic voltammetry, AC impedance and cycle stability test. Findings It was found that the specific capacitance value of the modified fibers were increased to 167 Fg-1 by adding modifiers (i.e. 20 wt.% microspheres and 15 wt.% melamine) compared to that of unmodified fibers (86.17 Fg-1). Specific capacitance of modified electrode material had little degradation over 10,000 cycles. This result can be attributed to that the modifiers embedded into the fibers changed the original morphology and enhanced the specific surface area of the fibers. Originality/value The modified ACFs in our study had high specific surface area and significantly high specific capacitance, which can be applied as efficient and environmental absorbent, and advanced electrode material of supercapacitor.

Microstructure of polyacrylonitrile-based activated carbon fibers prepared from solvent-free coagulation process

Polyacrylonitrile precursor fibers prepared using a solvent-free coagulation process were stabilized, carbonized, and physically activated bycarbon dioxide into activated carbon fibers (ACFs). The activation temperature varied from 600 to 900◦C while the activation time was 1 h. Atomicforce microscopy was used to observe the surface morphology, as well as the surface roughness of the ACFs. Higher pyrolysis temperature formedrougher surfaces, and increased the pore sizes. Meanwhile, Fourier transform infrared spectroscopy revealed more conversion of oxygen containingfunctional groups to carbonaceous materials as the activation temperature increased. Moreover, the microstructure properties were thoroughlycharacterized by the X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) studies. XRD analysis showed that the activationof the ACFs shrank the ordered structure, reducing the D-spacing from 0.358 to 0.347 nm for the fibers prepared at activation temperatures of600 to 900◦C. Meanwhile, XPS analysis concluded that that the oxygen containing functional groups were still retained even at high activationtemperatures while the nitrogen containing functional groups were reduced during the high temperature activation in the CO2 atmosphere.

Fabrication of high surface area PAN-based activated carbon fibers using response surface methodology

This study reports on the modeling and optimization of the iodine number of activated carbon fiber (ACF), using response surface methodology (RSM) based on the full factorial design (FFD). The individual and the interaction effects of the effective factors such as activation temperature (800, 900 and 1000 °C), time (1, 2 and 3 h), and activator type (KOH and NaOH) on the iodine number of the ACF were investigated in the optimization section. The FFD analysis confirmed that activation temperature and time were the main significant variables affecting the iodine number. High regression coefficient between the variables and the iodine number (R 2=0.9170) indicates excellent evaluation of experimental data by quadratic polynomial model. The RSM model predicted the 1028 value of the highest iodine number at conditions of 920 °C activation temperature, and 2.20 h of the time with used KOH for activator in activation process. The obtained FFD results confirmed that the selected RSM model presented acceptable performance for evaluating the involved factors and prediction of the ACF iodine number. The ACF produced under optimized conditions was characterized by pore structure analysis, scanning electron microscopy (SEM), and N2 adsorption/desorption isotherm. The obtained results showed that the produced ACF has developed porous structure and fibrous shape.

Asymmetric Electrodes Constructed with PAN-Based Activated Carbon Fiber in Capacitive Deionization

Capacitive deionization (CDI) method has drawn much attention for its low energy consumption, low pollution, and convenient manipulation. Activated carbon fibers (ACFs) possess high adsorption ability and can be used as CDI electrode material. Herein, two kinds of PAN-based ACFs with different specific surface area (SSA) were used for the CDI electrodes. The CDI performance was investigated; especially asymmetric electrodes’ effect was evaluated. The results demonstrated that PAN-based ACFs showed a high electrosorption rate (complete electrosorption in less than half an hour) and moderate electrosorption capacity (up to 0.2 mmol/g). CDI experiments with asymmetric electrodes displayed a variation in electrosorption capacity between forward voltage and reverse voltage. It can be attributed to the electrical double layer (EDL) overlap effect and inner pore potential; thus the ions with smaller hydrated ionic radius can be adsorbed more easily.

Polyacrylonitrile-Based Activated Carbon Fiber/SnO<sub>2 </sub>Composites via Different Synthetic Methods

Polyacrylonitrile-based activated carbon fiber (PAN-ACF)/SnO2 composites were synthesized by sol-gel and in-situ chemical synthesis method, respectively, and characterized by XRD, TGA, and SEM. The electrochemical properties of the resultant composites as negative electrodes in lithium-ion battery were also studied to investage the influence of different synthetic methods on the structure and electrochemical properties of the composites. The results show that the SnO2 in the composites prepared by both methods has a tetragonal rutile structure but the structure and electrochemical properties are different. With the similar composition, the composites prepared by in-situ method have uniform distribution of SnO2 particles, and exhibit better cyclic performance than those made by sol-gel method. The capacity of PAN-ACF/SnO2 composites with SnO2 content of 42.9% prepared by in-situ method remains 401.2 mAh g-1 after 50 charge/discharge cycles at a current density of 50 mAh g-1.

Preparation and characterization of antibacterial polyacrylonitrile-based activated carbon fiber supporting Nano-ZnO

Polyacrylonitrile(PAN)-based activated carbon fiber(PACF) supporting nano-ZnO(PACF/nano-ZnO) was prepared by spin, pretreatment, carbonization, and KOH chemical activation at an activation temperature of 950 °C for 40 min. Nano-ZnO content, distribution and antibacterial properties of the PACF/nano-ZnO were studied. The pore structure and surface properties of the PACF/nano-ZnO were studied by Brunauer-Emmett-Teller(BET), N2/77 K isothermal adsorption. The specific surface area increased markedly after the activation process and it was several hundred times greater than that before the process. The PACF/nano-ZnO shows a strong adsorption for Staphylococcus aureus(S. aureus) and Escherichia coli(E. coli) and antibacterial activity against them. As an experimental result, antibacterial properties of PACF/nano-ZnO increased with increasing the concentration of nano-ZnO particles, which suggests it is a promising antibacterial material.