Traditional Chemical Activation Research Articles

Heterostructure of Fe2O3 doped Alstonia Scholaris wood waste derived activated carbon based electrode for supercapacitor applications

The production of environmentally friendly and long-lasting supercapacitor electrodes employing activated carbons obtained from industrial wood waste from Alstonia Scholaris by traditional chemical activation using H2SO4 at High temperature activation is shown in this paper. The new traits of metal oxide (Fe2O3) doped Alstonia Scholaris wood derived activated carbon employing a slow precipitation technique. The produced activated carbon and the Fe2O3 doped activated carbon samples were examined using a variety of analytical methods, including XRD, FESEM, TEM-HRTEM, elemental mapping, N2 adsorption-desorption, Raman, XPS, and VSM. The BET result of prepared Fe2O3 doped activated carbon exhibits high surface area of 443 m2g−1. However, the assembled ASC cell exhibits high energy density of 38 Wh/kg and power density of 3181 W/kg. This work focuses on an innovative, straightforward process for producing low cost activated carbon from waste wood sources, which might have useful applications in the energy storage system.

Deep Eutectic Solvent‐Induced Polyacrylonitrile‐Derived Hierarchical Porous Carbon for Zinc‐Ion Hybrid Supercapacitors

AbstractHierarchical porous carbon that possesses large surface area and high porosity has become an important electrode material for supercapacitors. However, some unavoidable issues like complex approach and environmental pollution involved in traditional chemical activation restrict the sustainable development of carbons. Herein, a green, low‐cost, and safe urea‐zinc chloride deep eutectic solvent (DES) is proposed to prepare polyacrylonitrile derived three‐dimensional carbon nanosphere (D‐PC). Specially, the D‐PC efficiently accelerates electrolyte ions migration and enhances charge storage due to its interconnected ionic pathways and large accessible active surfaces. When employing the D‐PC as positive electrode of zinc‐ion hybrid supercapacitors, a high specific capacitance of 261.5 F g−1 at 0.2 A g−1 along with a cycling stability of 91.3 % after 10000 cycles at 5 A g−1. Meanwhile, such device holds the maximum energy/power density of 93.9 Wh kg−1/16.7 kW kg−1 at 0.2 A g−1/20 A g−1, respectively. Thanks to the unique physicochemical properties of as‐obtained D‐PC, an ultrahigh areal capacitance of 2.2 F cm−2 also can be achieved at a mass loading of 23 mg cm−2. The satisfying structure and performance highlight the potential of DESs in the design of functional carbons.

Preparation of Highly Porous Graphitic Activated Carbon as Electrode Materials for Supercapacitors by Hydrothermal Pretreatment-Assisted Chemical Activation.

The obstruction of traditional chemical activation lies in the addition of excessive catalysts to prepare the highly porous graphitic activated carbon (HPGAC), we propose the hydrothermal pretreatment-assisted chemical activation method to synthesize HPGAC as electrode materials using a small amount of Na-based catalysts (20 wt %). Hydrolysis accompanied by the strong depolymerization and reorganization of the coal framework is beneficial to the removal of different kinds of oxygen-containing structures (including cross-linking bonds, functional groups, and heterocycles) from lignite; thus, the deoxidization effect of hydrothermal carbonization (HTC) on hydrochar gradually strengthens with the increase in pretreatment temperature from 180 to 300 °C, resulting in the formation of a lot of disordered nanostructures and a smooth and compact surface. In the subsequent chemical activation stage, the microstructure of hydrochar is beneficial to the formation of a lot of graphene-like sheets and developed micropores even under a small amount of Na-based catalysts (20 wt %). The as-obtained C-HTC-300 with a highly ordered microstructure and a high specific surface area (SBET) of 1945.33 m2/g has an excellent electrochemical performance. Compared with a large consumption of catalyst for synthesizing HPGAC in traditional chemical activation, the hydrothermal pretreatment-assisted method meets the environmental protection and low-cost preparation requirements.

One-step construction of hierarchically porous carbon nanorods with extraordinary capacitive behavior

The construction of hierarchically porous carbon nanorods (HPCNs) is realized via the one-step template-directing coupled with the activation methodology. The heteroatom (S and N) incorporation into the carbon skeleton is also realized during the preparation process because of the enrichment of S and N-containing organic compounds in the pitch precursor. The optimization of pore size distribution and specific surface area is performed by controlling the mass ratio of raw materials. The contributions of chemical activation and template-directing are mainly dedicated to generating the micropore and mesopore channels, respectively. Compared to the traditional chemical activation process, the employment of the amount of active agent in this work is reduced dramatically. Benefiting from the robust microarchitecture associated with hierarchical pore channels, HPCNs deliver the much enhanced capacitive behavior than the commercial activated carbon and counterparts derived from the pure template-directing and chemical activation methods, respectively. The great compatibility of gravimetric and areal capacitances can be simultaneously guaranteed even when the areal mass loading of the electrode is as high as 10 mg cm−2. Besides, the high-efficient conversion of pitch into the capacitive electrode material is also a new route for the high value-added utilization of pitch.

Sonication-assisted reactivation process: A new method to enhance traditional chemical activation technology

Abstract In order to further enhance the adsorption properties of activated carbon fiber, sonication is introduced into the process of activator impregnation on the basis of traditional chemical reactivation technology. The novel process of sonication-assisted chemical reactivation is proposed for the first time in this paper. This novel process probe a new developing route for the surface structure modification of activated carbon fiber, which also provides a new idea to enhance the traditional chemical activation technology. In this study, viscose-based activated carbon fiber is used as research object, and low concentration formaldehyde gas is used as adsorbate. The research of the novel reactivation process is researched by four activators of phosphoric acid, zinc chloride, perhydrol and nitric acid, which commonly used in chemical activation processes of industrial production. The results indicate that the novel reactivation process assisted by sonication has an obvious improvement on the pore volume of micropores and mesopores at the range of 2–5 nm, meanwhile, the content of surface functional groups increase significantly. Besides, formaldehyde adsorption properties enhanced significantly after treated by the novel reactivation process. In particular, the formaldehyde adsorption rate increased by 90.05% when phosphoric acid used as activator.

A novel melt infiltration method promoting porosity development of low-rank coal derived activated carbon as supercapacitor electrode materials

Abstract Focusing on the bottlenecks of traditional physical or chemical activation methods for the preparation of activated carbons, we report a simple and scalable melt infiltration strategy assisted with CO2 activation for the preparation of activated carbons from Chinese large-scale reserve Zhundong coal. The preparation is achieved by the melt infiltration of a small amount of anhydrous FeCl3 (10–20 wt%) into the coal framework and subsequent CO2-assisted physical activation during which the encapsulated iron species play the dual role of pore-forming templates and activating catalysts. The as-obtained MI-AC-2 possesses a partially hierarchical pore structure with a high specific surface area of 1872 m2 g−1, five times more than the activated carbon prepared by solely physical activation, which endows the constructed MI-AC-2 electrode with good supercapacitive performances. Relative to the large consumption of activation agents used in a traditional chemical activation process, such a new method with low-cost resource materials and the low-dose FeCl3 additive paves a scalable way to loading metal precursor into coal/biomass for the preparation of high-porosity activated carbons. This work also provides a simple and efficient strategy to encapsulate active materials into external matrix or substrate.

Effect of microwave treatment onto activated carbon produced from pecan nut shells for Tartrazine removal from aqueous media

The processes used to fabricate carbonaceous materials with sorption capacity are expensive and require the exploitation of natural resources. The use of microwave treatment for activated carbons is an innovative and cheaper method than traditional chemical activation. To develop a sustainable carbonaceous material with sorption properties, the present study used four methods to prepare activated carbon using pecan nut shells, an agricultural waste, as an alternative precursor instead of conventional materials such as coconut shells or wood. The preparation methods were: carbonisation (NAC), carbonisation/water activation (NAC-H2O), carbonisation/microwave treatment (NAC-MW) and carbonisation/activation/microwave treatment (NAC-H2O-MW). The prepared material was characterised by pHPZC and total ash content determination, BET surface area analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis. The sorption equilibrium time for the Tartrazine dye sorption was determined. The prepared activated carbons that presented the best sorption capacity were NAC-H2O (8.2 mg/g) and NAC-MW (5.1 mg/g); the sorption equilibrium time was 24 h for both materials. The sorption experiments showed a good fitting to pseudo second order equation and to Freundlich model.

Effect of microwave treatment onto activated carbon produced from pecan nut shells for Tartrazine removal from aqueous media

The processes used to fabricate carbonaceous materials with sorption capacity are expensive and require the exploitation of natural resources. The use of microwave treatment for activated carbons is an innovative and cheaper method than traditional chemical activation. To develop a sustainable carbonaceous material with sorption properties, the present study used four methods to prepare activated carbon using pecan nut shells, an agricultural waste, as an alternative precursor instead of conventional materials such as coconut shells or wood. The preparation methods were: carbonisation (NAC), carbonisation/water activation (NAC-H2O), carbonisation/microwave treatment (NAC-MW) and carbonisation/activation/microwave treatment (NAC-H2O-MW). The prepared material was characterised by pHPZC and total ash content determination, BET surface area analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis. The sorption equilibrium time for the Tartrazine dye sorption was determined. The prepared activated carbons that presented the best sorption capacity were NAC-H2O (8.2 mg/g) and NAC-MW (5.1 mg/g); the sorption equilibrium time was 24 h for both materials. The sorption experiments showed a good fitting to pseudo second order equation and to Freundlich model.

New strategy to prepare ultramicroporous carbon by ionic activation for superior CO2 capture

Traditional chemical activation methods to prepare porous carbons adsorbents consume large amounts of activating agent through physical mixing. Herein, we developed a new strategy to prepare microporous carbons with uniform ultramicropores (∼0.57 nm) through ionic activation method by using potassium carboxylate as an activating agent, which was uniformly incorporated onto the surface of hydrothermally prepared hydrochar. The ultramicroporous carbon adsorbent developed by this new method showed high CO2 uptakes of 5.87 and 3.82 mmol g−1 at 0 and 25 °C, respectively. We demonstrated that small amounts of uniformly distributed potassium carboxylate contributed to the development of ultramicroporosity. This research paves the way for a new route to prepare ultramicroporous carbons as efficient CO2 adsorbents by using significantly lower amounts of activating agents and hence the process may be not only cost-effective but also avoids negative impacts of traditional chemical activation.

Pozzolanicity of fly ash modified by fluidized bed reactor–vapor deposition

Fly ash (FA) can improve the workability and durability of concrete. However, the utilization of FA is usually limited due to its low pozzolanic activity. In this study, a fluidized bed reactor was designed to modify FA by the fluidized bed reactor–vapor deposition (FBR-VD), using NaOH solution as the activation material. We investigated the pozzolanicity of FBR-VD modified FA (MFA), and the workability of cement paste. The results were compared against traditional chemical activation method, using Ca(OH)2, NaOH, Na2SO4, or NaCl. The microstructures and hydration products were analyzed by scanning electron microscopy (SEM), and thermogravimetric–differential scanning calorimetry (TG-DSC). The experimental results show that FBR-VD accelerates the early-age pozzolanic reaction of FA, without affecting the workability of the paste. The 7-day and 28-day activity indices of the paste and mortar with MFA were higher than those with raw FA, while the 60-day activity index of the paste became even close to that without FA. The SEM results indicate that FBR-VD can make the activation material coat onto the surfaces of the FA particles, breaking down part of the Si–O and Al–O bonds in the FA. The remaining NaOH crystals on the FA surface also promote the growth of Ca(OH)2 crystals during the hydration process, so the FA particles are fixed tightly to the hardened cement paste, resulting in a higher compressive strength. TG-DSC shows that the MFA has a stronger effect on consuming the Ca(OH)2 in the paste than traditional activation materials and methods, indicating an enhanced pozzolanic activity of the FA.

Solvent-free derivatization of oxidized single-walled carbon nanotubes and nanodiamond with aminobenzo-crown ethers

ABSTRACTWe report on a one-step amide derivatization of two carbon nanomaterials (CNM) containing carboxylic functional groups, which are oxidized single-walled carbon nanotubes (SWNTs) and nanodiamond (ND), with amino-substituted crown ethers, namely, 4′-aminobenzo-15-crown-5 and 4′-aminobenzo-18-crown-6. The functionalization procedure proposed is based on thermal activation of COOH groups instead of traditional chemical activation, is fast and facile, does not require the use of organic solvents and can be considered as ecologically friendly. The nanohybrids of crown ethers with SWNTs and ND were characterized by means of Fourier-transform infrared and Raman spectroscopy, scanning and transmission electron microscopy, as well as thermogravimetric analysis and solubility tests in toluene and propanol. The approach proposed allows for a facile preparation of crown ether-functionalized SWNTs and ND without contamination with other chemical reagents, solvents and detergents, which might be especially important for a broad spectrum of applications ranging from nanoelectronics to nanomedicine.

Mechanochemical and chemical activation of lignocellulosic material to prepare powdered activated carbons for adsorption applications

This work presents a solvent-free mechanochemical approach toward controlled preparation of powdered activated carbons from lignocellulosic residue (horse chestnut shell, CS). The physicochemical changes of the biomass during mechanochemical and chemical activation with K2CO3 and the properties of the final materials obtained after pyrolysis at 700°C have been investigated by means of thermogravimetric analysis (TG–DTG), scanning electron microscopy (SEM), X-ray diffraction (XRD), N2 adsorption–desorption, infrared and micro-Raman spectroscopy. The results indicated that the mechanochemical activation is superior to the traditional chemical activation in terms of specific surface area, pore development and the degree of structural order of the activated carbons. Furthermore, it has been observed that the later parameters depend on the milling time and the maximal BET surface area (1040m2/g) and total pore volume (1.01cm3/g) of the resulting mesoporous material can be obtained after 3h milling of the raw material/K2CO3 mixture. In addition, malachite green oxalate (MGO) adsorption capacities of the carbons were also examined and adsorption uptake up to 250mg/g is observed. This study demonstrates the potential use of CS as a precursor in the preparation of activated carbon for adsorption applications and opens up new ways for activation of lignocellulosic materials under ball-milling conditions.

Preparation and Characterization of Polypropylene Non-woven Fabrics Prepared by Melt-blown Spinning for Filtration Membranes

Polypropylene (PP) non-woven fabrics have been widely used as filtration membranes in wastewater purification with industrial applications due to their low cost, good mechanical strength, and high thermal and chemical stability. The membrane fouling behavior depends strongly on the physical and mechanical properties of the membrane, including pore size, porosity, morphology, and hydrophilicity. 1-5 In general, PP non-woven fabrics have poor hydrophilicity; this has limited their application in the biomedical field. It is therefore necessary to develop PP non-woven fabrics with improved surface hydrophilicity to increase the scope of their use. Plasma treatment, an environmentally friendly alternative to traditional chemical activation, only changes the uppermost atomic layers of a membrane surface without affecting the bulk properties of the polymer. 6-12 To perform as a functional membrane, the PP non-woven fabrics must have a porosity of ≤ 1 μm, remove > 95% of impurities, and possess a morphology for surface filtration. However, the porosity of traditional membranes prepared from non-woven fabrics is ≥ 5 μm and exhibit a depth filtration mechanism. The fibers prepared by melt-blown spinning have usually 8-15 μm porosity, which is reduced to 1-2 μm after heat treatment. 13-15 In this study, PP nonwoven fabrics were prepared by a melt-blown spinning process. To control the porosity and impart hydrophilicity, the PP non-woven fabrics were treated with heat and plasma processes. The mechanical properties, contact angle, water flux, average pore size, average pore pressure, and particle removal efficiency of these PP nonwoven fabrics were investigated. PP non-woven fabrics were prepared by melt-blown spinning. However, the resulting PP non-woven fabrics have a large pore size and low hydrophilicity, making them unsuitable for use as filtration membranes. The PP non-woven fabrics were subsequently treated with heat and plasma processes to control porosity and impart hydrophilicity. 16,17 Figure 1 shows SEM micrographs of the PP non-woven fabrics before and after heat treatment. Figure 1 shows the increase in the fiber sizes of the PP non-woven fabrics from 2-7 μm to 4-11 μm before and after the heat treatment. This was due to the densification effect. 18,19

Preparation of Sludge Activated Carbon Adsorbent and its Engineering Simulation Study to Removing Odor

Wastewater is purified in wastewater treatment plant, but this process produce a large amount of surplus sludge and odor including hydrogen sulfide, ammonia and so on. To candle water pollution, the wastewater treatment process leads to serious secondary pollution to environment. This paper mainly studied two problems. The first is using surplus sludge to prepare sludge activated carbon adsorbents. The second is using the product to remove the obnoxious gas in wastewater treatment plants. By analyzing the basic properties of surplus sludge and obnoxious gas, the surplus sludge was used to prepared activated carbon adsorbent by traditional chemical activation method. Final purpose is controlling waste by waste and achieving recycling. Meantime, the deodorization transfer process of sludge activated carbon adsorption was emulated and the adsorption capacity of the adsorbent in normal temperature was found out through the experiment. Besides, by optimizing the filling applicator of the sludge activated carbon, we obtained the operating parameter using the adsorbent to remove hydrogen sulfide and optimizing parameter of adsorbent filling applicator. Thus some reliable technology parameters can be offered for engineering application design and operating.

Experimental Design To Optimize the Preparation of Activated Carbons from Herb Residues by Vacuum and Traditional ZnCl2 Chemical Activation

Doehlert matrix was used to optimize the experimental conditions for the preparation of activated carbons from herb residues by vacuum chemical activation and traditional chemical activation using ZnCl2 as activation agent. The effects of activation temperature and impregnation ratio, the most influential factors of ZnCl2 chemical activation, were studied. The obtained activated carbons were characterized by total yield and methylene blue and iodine adsorption value. Each response has been described by a second-order model, and the predicted model presented a good agreement with experimental data. The results showed that activated carbons prepared by vacuum chemical activation have higher yield and better adsorption capacity. The removal percentages of methylene blue for the two optimal activated carbons and a commercial activated carbon were determined. The activated carbon prepared by vacuum chemical activation exhibited the highest methylene blue removal efficiency.

Various Treated Conditions to Prepare Porous Activated Carbon Fiber for Application in Supercapacitor Electrodes

Porous activated carbon fiber (ACF) is prepared from oxidized polyacrylonitrile (PAN) fiber through three activation methods, which are traditional chemical activation, traditional physical activation, and ameliorative chemical activation. The samples under various high temperature heat treatments are used as electrode for the supercapacitor. The structure and electrochemical properties of these samples are then characterized by nitrogen adsorption at 77 K, X-ray diffraction (XRD), Raman spectrum, electron spectroscopy for chemical analysis (ECSA), Fourier transform infrared spectrometer (FTIR), cyclic voltammetry (CV), and galvanotactic charge/discharge, respectively. Once formed by the ameliorative chemical activation method, which is used for the electrodes of supercapacitors, the samples exhibited excellent capacitance characteristics in the 1 M H2SO4 electrolyte and showed a high specific capacitance of 158 F/g, which is higher than the two traditional activation methods. HP20−1/3−900 presents a high...

Preparation of Activated Carbon by Chemical Activation under Vacuum

Activated carbons especially used for gaseous adsorption were prepared from Chinesefir sawdust by zinc chloride activation under vacuum condition. The micropore structure, adsorption properties, and surface morphology of activated carbons obtained under atmosphere and vacuum were investigated. The prepared activated carbons were characterized by SEM, FTIR, and nitrogen adsorption. It was found that the structure of the starting material is kept after activation. The activated carbon prepared under vacuum exhibited higher values of the BET surface area (up to 1079 m2 g(-1)) and total pore volume (up to 0.5665 cm3 g(-1)) than those of the activated carbon obtained under atmosphere. This was attributed to the effect of vacuum condition that reduces oxygen in the system and limits the secondary reaction of the organic vapor. The prepared activated carbon has well-developed microstructure and high microporosity. According to the data obtained, Chinese fir sawdust is a suitable precursor for activated carbon preparation. The obtained activated carbon could be used as a low-cost adsorbent with favorable surface properties. Compared with the traditional chemical activation, vacuum condition demands less energy consumption, simultaneity, and biomass-oil is collected in the procedure more conveniently. FTIR analysis showed that heat treatment would result in the aromatization of the carbon structure.