Surface Area Of Activated Carbon Research Articles

Removal of COD from petroleum refinery wastewater by adsorption using activated carbon derived from avocado plant

In the present work, removing of COD from wastewater generated via Al-Diwanya petroleum refinery plant located in Iraq by adsorption with activated carbon (AC) derived from avocado seeds was successfully performed via a two-step approach. In the first step, AC was prepared from avocado seeds via impregnating with H3PO4 at 400 °C where effects of H3PO4 concentration and calcination time on the specific surface area of AC were studied. Additionally, properties of the prepared AC were examined by XRD, SEM, and FTIR to knowledge the features of the internal structure of AC. Results showed that the prepared AC has mesopores structure with pore diameters in the range between 30.07 and 50.8 µm. Increasing the weight percent of H3PO4 led to an increase in the specific surface area of AC to reach a maximum value beyond which a decrease in the specific surface area was happened with further increasing in H3PO4 percent. Increasing the time resulted in an increase in the AC specific surface area to reach a maximum value beyond which a decrease in specific surface area was happened. The best value of AC specific surface area was 436.6 m2/g which obtained at 70 %H3PO4 and 4 h. At the second step, the performance of the prepared AC in removing of COD by adsorption process was evaluated via studying the effects of three operating parameters, namely adsorbent dosage (1–5 g/L), pH (3–9), and shaking speed (100–400 rpm) on the removal of COD(RE%) using a response surface methodology (RSM). Increasing AC dosage led to an increase in RE% while increasing each of pH and shaking speed resulted in lowering RE%. The optimum conditions for higher RE% were AC dosage of 5 g/L, pH of 3, and shaking speed of 100 rpm in which a removal efficiency of 94.54 % was obtained. The degradation of COD with time was found to obey a second order kinetic confirming the chemisorption is the rate limiting step in the adsorption process.

Revealing the mechanism of oxygen-containing functional groups on the capacitive behavior of activated carbon

O-doping is important to regulate the electrochemical behavior of activated carbon (AC) used in supercapacitors. However, the clear mechanism and relationship of O-doping on the capacitance behavior of AC seem contradictory and remain undisclosed. This is because when O-doping is carried out, it often causes changes in the physical and chemical properties such as defect state, structure, and specific surface area of AC. The superposition of these factors on capacitance behavior complicates the research problem. Here, a low-temperature oxidation method was adopted to achieve doping of different forms of O-functional groups on the AC with minimal effect on its structure and specific surface area. It can be found that the effect of O-doping on the double-layer capacitance of AC is relatively small, but positively correlated with the pseudocapacitance. This is because the functional groups C-O and COOH by O-doping can not only improve the wettability between the electrolyte and AC, but also combine with cations in the electrolyte to enhance the pseudo capacitance. The influence mechanism of O-doping on the capacitance behavior of AC has been verified in different electrode systems and aqueous electrolytes. This study provides theoretical support for rational O-doping to enhance the electrochemical performance of AC.

Zinc Chloride as a Catalyst in Hydrothermal Carbonization of Cocoa Pods Husk

In this study, we have successfully synthesized a high surface area of activated carbons (ACs) from cocoa pod husk (CPH) by using a combination of hydrothermal carbonization (HTC) and chemical activation in the presence of ZnCl2 as both of catalyst as well as activating agent. During HTC, the effect of HTC temperature (200 and 225 °C) and ZnCl2 to biomass mass ratio (1:1, 2:1, 3:1) as a catalyst to the characteristics of the obtained hydrochar (HC) and ACs were investigated. The obtained hydrochar (HCs) was then processed by using ZnCl2 chemical activation with a fixed HC to ZnCl2 mass ratio of 1:4 and the mixture was pyrolyzed at 600 °C for 1 h under an inert atmosphere. The results showed that the addition of catalyst during HTC presented different AC morphology, where the carbon samples were decorated with carbon microspheres. An increase of surface area was observed, where the ACs synthesized from catalyzed HC at biomass to ZnCl2 ratio of 1:3 at temperature 200 °C gave a higher surface area of 1954 m2/g compared to that of without catalyst (1165 m2/g). The catalysis effect was more profound at the HTC temperature of 200 °C compared to 225 °C, as reflected in the significant increase of AC surface area. The addition of a catalyst creates ACs with narrow pore distribution compared to that of synthesized in the absence of a catalyst. It was also observed that the ACs from catalyzed hydrochar possessed higher oxygenated functional groups (OFG) than those without catalysts.

Sustainable production of porous carbon from biomass: Influence of pre-carbonization on pore evolution and environment impact

Pre-carbonization is one frequently used pre-treatment for production of activated carbon (AC) from activation of biomass, which impacts not only nature of AC but also composition of bio-oil and gases in activation of biomass. In this study, activation of sawdust/cellulose/lignin directly or via pre-carbonization were conducted, with a particular focus on effects of pre-carbonization on evolution of the various products and environment. The results indicated that the pre-carbonization removed significant portion of aliphatic structures, creating difficulty for developing pores from the resulting biochar. This, however, enhanced overall yields of AC and gases at expense of bio-oil with K2C2O4, CO2 or H2O as activators. The high yield and high specific surface area of AC could not be obtained simultaneously and needs to be balanced in application. In converse, ZnCl2 or H3PO4 as activators generated more AC with developed pore structures via direct activation of biomass, as they catalyzed the dehydration of aliphatic structures in biomass, but not in biochar. The life cycle assessment (LCA) indicated that the pre-carbonization led to a higher impact to environment and energy consumption than the direct activation. ZnCl2 and CO2 showed the smallest influence on the fossil fuel depletion and global warming. Direct activation exhibited lower environmental impact in the production of AC with more developed pore structures, rendering it a more desirable route for production of AC.

Orange peel as a biosource for the synthesis of activated carbon and its application in hydrogen storage

AbstractBACKGROUNDThe reduction of fossil fuels and the environmental threats caused by their combustion has diverted the attention of the scientific community to search for renewable and environmentally safe energy sources. There are some advances in the development of activated carbons (ACs) from different wastes for use as adsorbents in hydrogen storage. In the present work, different ACs were synthesized using a domestic residue (orange peel) as a carbon source.RESULTSTo obtain these carbonaceous materials, a chemical activation was performed using phosphoric acid (50 wt%) as activating agent. Different synthesis conditions, acid/precursor ratio and contact time between them were used. The materials obtained through the revaluation of waste were applied to the adsorption of hydrogen as an alternative in the use of green hydrogen. Hydrogen adsorption was related to some textural properties of ACs, such as specific surface area and meso/microporosity. All the materials obtained have a high specific surface area (between 1000 and 1400 m2 g−1) and meso‐ and microporosity. X‐ray powder diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and Raman spectroscopy analyses were performed to characterize these materials.CONCLUSIONAdsorption increases practically linearly with respect to the specific surface area of ACs. Synergy can be observed between mesopores and micropores since increasing both microporosity and mesoporosity increases hydrogen storage. The highest adsorption capacity was 3.3 wt% at −196.15 °C and 10 bar. © 2023 Society of Chemical Industry (SCI).

Revealing the causes of degradation of an asymmetric ionic liquid supercapacitor with a composite polyaniline/carbon electrode

The extended window of electrochemical stability of ionic liquids and the high specific capacitance values of activated carbon (AC)/conductive polymer (polyaniline, Pani) composite materials are promising approaches to improve the performance of supercapacitors (SC).In this work, we studied the stability of an asymmetric AC//Pani-C cell with 1 M solution of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) in acetonitrile as an electrolyte. Pani-C (56 wt% of Pani) composite was prepared by oxidative polymerization of aniline in the presence of high surface area AC (SBET = 2300 m2‧g−1). Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission and scanning electron microscopies data confirmed the formation of Pani-C composite. Combination of cyclic voltammetry, galvanostatic charge/discharge method, and electrochemical impedance spectroscopy in 2- and 3-electrode cell configurations gave information about anodic (1 V vs. Ti) and cathodic (−1.8 V vs. Ti) potential limits of electrochemical stability, and potential of zero charge of Pani-C and AC.From these data, optimal mass ratio of Pani-C and AC electrodes was obtained for asymmetric SC assembly. It was found that after 500 charge/discharge cycles, the capacitance of the asymmetric AC//Pani-C SC decreased by 15% from 46.8 to 39.9 F·g−1 as a result of Pani-C degradation. The specific capacitance of AC remained virtually unchanged (decreased from 144 to 141 F·g−1), while that of Pani-C decreased by 8.7% from 230 to 210 F·g−1. Electrochemical measurements showed that degradation is accompanied by an increase in the working potential window of Pani-C (from 0.85 V to 0.97 V) and a shift in Emin…Emax working potentials from 0.15 … 1 to 0.52 … 1.49 V vs. Ti in the beginning and in the end of stability test, respectively. The last region is related to the potential for non-conductive pernigraniline formation (1.3 V vs. Ti). It was shown that the main reason of AC//Pani-C SC capacitance decay is a gradual increase in the operating potential window with a constantly shifts towards anodic values of positive Pani-C electrode, which resulted in accumulation of nonconductive polymer form that does not participate in charge accumulation.

Novel adsorbent for malachite green from okra stalks waste: synthesis, kinetics and equilibrium studies

In this study, malachite green (MG) removal was performed with activated carbon synthesized from okra stalks by microwave assisted chemical activation method. In the synthesis of activated carbon, the effects of gas in the microwave, activation, and impregnation rate were investigated. The synthesized activated carbon characterization was investigated using BET, FT-IR, and SEM analyses. The activated carbon surface area achieved was 759.453 m2 g−1. In addition, the surface area of activated carbon synthesized using the conventional method was17.766 m2 g−1. The effect of the initial solution concentration on MG adsorption was investigated. According to the kinetic and equilibrium data, it was found that the adsorption process best fitted the pseudo-second order kinetic model and the Langmuir isotherm. According to the equilibrium data, the maximum adsorption capacity (q max) of the monolayer was 119.05 mg g−1. In addition, MG adsorption was investigated by the experimental design method. The adsorption capacity at the determined optimum conditions was 99.63 mg g−1. All results show that activated carbon synthesized from waste biomass by combining the conventional method with microwave-assisted impregnation is a cheap and environmentally friendly adsorbent.

Adsorption of Methylene blue onto hydrophobic activated carbon

Activated carbon (AC) was prepared from date palm leaflets using NaOH activation. AC was oxidized using concentrated HNO3 to produce oxidized activated carbon (ON). Alkylamines including methylamine (M), dimethylamine (DM), ethylamine (E), diethylamine (DE), and diisopropylamine (DIP) were covalently immobilized onto ON to produce ONM, ONDM, ONE, ONDE, and ONDIP hydrophobic activated carbons, respectively. The surface area of AC (588 m2/g) decreased on oxidation with a further decrease on functionalization. These carbons were tested for methylene blue (MB) adsorption. Initial pH 7 was found optimum for the adsorption of MB. The hydrophobic activated carbons show faster adsorption (except for ONDE), than AC with adsorption data following well a pseudo-second-order kinetic model. The rate of adsorption increased with temperature rise. The activation energy, Ea, was less than 42 kJ/mol indicating physical adsorption. Equilibrium adsorption follows L-type isotherm with the adsorption data following well the Langmuir model. The adsorption capacity of MB follows the order of ONDIP > ONE > ONDM > AC > ON > ONM > ONDE. Thermodynamic parameters indicate spontaneous and endothermic adsorption. Carbon reuse for MB adsorption was more efficient for ONDIP, ONE, and ONDM than AC

Characterization of physicochemical properties of activated carbons prepared from penicillin mycelial residues and its adsorption properties for VOCs

In this study, adhering to the concept of "treat waste with waste", the physicochemical properties of activated carbons (ACs) prepared from penicillin mycelial residues (PMR) was characterized, and the adsorption performance of ACs for VOCs was explored. The results showed that AC230–1 exhibited the largest specific surface area (2187.50 m2/g), while AC290–0.5 exhibited the largest microporous surface area (1624.81 m2/g). With the increase of KOH ratio, microporous surface area of ACs decreased gradually, and the pore size distribution of ACs gradually developed to large micropores and mesopores. XRD and Raman results showed that AC290–0.5 had better graphite microcrystalline structure and stability. FT-IR results showed that ACs had similar surface functional groups, and XPS results indicated that AC290–0.5 contained more CO, C-OH, and abundant N-containing functional groups, which could effectively improve the adsorption capacity of ACs for VOCs. AC290–0.5 exhibited the highest dichloromethane (DCM) saturation adsorption capacity (204.83 mg/g), trichloroethylene (TCE) saturation adsorption capacity (732.59 mg/g) and chlorobenzene (CLB) saturation adsorption capacity (735.90 mg/g). The Y–N model could perfectly fit the adsorption breakthrough curve of ACs for VOCs, and adsorption kinetics indicated that the adsorption of ACs for VOCs was mainly physical adsorption. The microporous and surface chemical group of AC were the main factors that determined its adsorption capacity for VOCs.

Modification of Activated Carbon and Its Application in Selective Hydrogenation of Naphthalene.

The MoS2/ACx catalyst for hydrogenation of naphthalene to tetralin was prepared with untreated and modified activated carbon (ACx) as support and characterized by X-ray powder diffraction, Brunauer-Emmett-Teller, scanning electron microscopy, temperature-programmed desorption of ammonia, X-ray photoelectron spectroscopy, and scaning transmission electron microscopy. The results show that the modification of activated carbon by HNO3 changes the physical and chemical properties of activated carbon (AC), which mainly increases the micropore surface area of AC from 1091 to 1209 m2/g, increases the micropore volume of AC from 0.444 to 0.487 cm3/g, increases the oxygen-containing functional groups of AC from 5.46 to 7.52, and increases the acidity of catalysts from 365.7 to 559.2 mmol/g. The modified catalyst showed good catalytic performance, and the appropriate HNO3 concentration is very important for the modified of activated carbon. Among all the catalysts used in this study, the MoS2/AC3 catalyst could achieve the highest yield of tetralin. It can be attributed to the moderate acidity of the catalyst, reducing the cracking of hydrogenation products. Also, the proper hydrogenation activity of MoS2 and the appropriate increase of oxygen-containing functional groups on the surface of modified activated carbon are beneficial to the dispersion of active components on the support, increasing the yield of tetralin. The catalytic performance of MoS2/AC3 is better than that of MoS2/Al2O3 catalyst, and the two catalysts show different hydrogenation paths of naphthalene.

Enhanced capacitive deionization properties of activated carbon doped with carbon nanotube-bridged molybdenum disulfide

The shortage of freshwater supplies has restricted societal development. Capacitive deionization (CDI) is an emerging technology for desalination of seawater or brackish water, the performance of which is highly dependent on electrode materials. In this work, a molybdenum disulfide/carbon nanotube composite (CNTs-b-MoS2) with high capacitance was successfully synthesized using a hydrothermal method. The composite exhibited a specific capacitance of 112.79 F g−1. To reduce costs and determine the practicality of using CNTs-b-MoS2 for CDI, we combined activated carbon (AC) with CNTs-b-MoS2 as a CDI electrode. The research demonstrated that after doping with 5% (mass ratio) CNTs-b-MoS2, the specific capacitance and electrosorption capacity of AC were significantly improved and the maximum desalination capacity of CNTs-b-MoS2/AC reached 8.19 mg g−1. The low dosage of CNTs-b-MoS2 combined with the high specific surface area of AC avoided the shortcomings of CNTs-b-MoS2, namely low specific surface area and high cost. Moreover, the outstanding conductivity of CNTs-b-MoS2 improved the conductivity and enhanced the adsorption capacity of AC, giving CNTs-b-MoS2/AC potential as an advanced, low-cost CDI electrode material.

Rice husk-derived activated carbon electrode in redox-active electrolyte – New approach for enhancing supercapacitor performance

Processing of renewable, abundant, and low-cost biomass into porous carbon materials for application in supercapacitor electrodes has been attracting interest in last years. In this study, activated carbons (ACs) were produced via carbonization of rice husk followed by the chemical activation with KOH. SEM, Raman spectroscopy, XPS, and low temperature nitrogen physisorption were used to characterize the morphology, defectiveness, surface composition and textural parameters of the synthesized ACs. Activation significantly increased the specific surface area of AC up to 2700 m2·g−1 forming a well-developed porous structure favorable for charge accumulation. The electrochemical performance of ACs was tested in the 1 M Na2SO4 and 1 M Na2SO4 + 0.03 M K3Fe[CN]6 electrolytes by cyclic voltammetry, galvanostatic charge – discharge measurements and impedance spectroscopy. The addition of redox-active K3Fe[CN]6 to the conventional 1 M Na2SO4 electrolyte noticeably (in 3.6 times) increased the specific capacitance of the AC-based electrode up to 400 F·g−1 at a current density of 0.5 A·g−1. The high capacitance retentions of 99.6 % in 1 M Na2SO4 and 97.7 % in 1 M Na2SO4 + 0.03 M K3Fe[CN]6 after 5000 charge–discharge cycles, developed microporosity and high electrochemical performance make the rice husk-derived AC a promising electrode material for energy storage applications. At a current density of 0.5 A·g−1 the symmetric AC2-based supercapacitor with the redox-active electrolyte delivered an energy density of 16.7 Wh·kg−1 at power density of 0.4 kW·kg−1.

Microporous Activated Carbon from Pisum sativum Pods Using Various Activation Methods and Tested for Adsorption of Acid Orange 7 Dye from Water.

Highlights•Pisum sativum pods was used for producing porous activated carbon materials.•Two chemical methods and two gases were used in the activation processes.•Higher performances were achieved by applying ZnCl2 and CO2 for activation.•The products exhibited large surface areas and high AO7 dye adsorption performances.•RMS study of the AO7 dye removal by produced material was reported.This work demonstrates the preparation of high-surface-area activated carbon (AC) from Pisum sativum pods using ZnCl2 and KOH as activating agents. The influence of CO2 and N2 gases during the carbonization process on the porosity of AC were studied. The highest specific surface area of AC was estimated at 1300 to 1500 m2/g, which presented characteristics of microporous materials. SEM micrographs revealed that chemical activation using an impregnation reagent ZnCl2 increases the porosity of the AC, which in turn leads to an increase in the surface area, and the SEM image showed that particle size diameter ranged between 48.88 and 69.95 nm. The performance of prepared AC for adsorption of Acid Orange 7 (AO7) dye was tested. The results showed that the adsorption percentage by AC (2.5 g/L) was equal to 94.76% after just 15 min, and the percentage of removal increased to be ~100% after 60 min. The maximum adsorption capacity was 473.93 mg g−1. A Langmuir model (LM) shows the best-fitted equilibrium isotherm, and the kinetic data fitted better to the pseudo-second-order and Film diffusion models. The removal of AO7 dye using AC from Pisum sativum pods was optimized using a response factor model (RSM), and the results were reported.

Nitrogen doped activated carbon derived from chitosan/hexamethylenetetramine: structural and CO2 adsorption properties

Chitosan and chitosan/hexamethylenetetramine (HMT) macrospheres were prepared respectively by dropping the solution of chitosan and chitosan/HMT (in wt/wt ratios of 1:1 and 1:3) in aq. NaOH solution. Here, HMT served as an additional nitrogen precursor for in situ N-doping with chitosan derived activated carbon (AC). The as-formed macrospheres were impregnated using ZnCl2, freeze-dried and carbonized at 500 °C under inert atmosphere to yield ACs of size ranging from 2.5 to 2.8 mm. All the samples were characterized using SEM, EDS, CHNS Analyzer, TGA, FT-IR, Raman, XRD and BET surface area analyzer. All the samples showed mesoporous characteristics. The surface area of the AC without HMT, with 1:1 HMT and 1:3 HMT were 391.502, 259.017 and 111.717 m2/g respectively. Similarly, the pore volumes of AC without HMT, with 1:1 HMT and 1:3 HMT were 0.138, 0.095 and 0.075 cc/g respectively. The chitosan/HMT derived AC possessed higher N-content and better thermal stability, however exhibited lower surface properties with increasing HMT content. The CO2 adsorption capacity of chitosan derived AC was 97.98 mg/g while that of AC with 1:1 HMT and 1:3 HMT were 72.95 mg/g, 55.11 mg/g respectively at 25 °C and 1 bar. Deterioration in adsorption capacity of chitosan/HMT derived AC may be attributed to the physical cross-linking of chitosan polymer chains induced by increase in pH with addition of HMT and also the intermolecular H-bonding interaction between HMT and chitosan, which in turn reduces the surface area of as-formed N-doped ACs progressively.

Electrochemical Performance of Symmetric Supercapacitor Based on Activated Carbon Biomass TiO2 Nanocomposites

A supercapacitor (SC) is an energy storage device with high energy density, high power density, long life cycle and a bundant material in nature.. Activated carbon based on coconut shell waste (ACCS) is one of the most promising supercapacitor base materials due to its abundance in nature, environmentally friendly, and high surface area. Activated carbon based on coconut shell (ACCS) waste is a potential material as a supercapacitor base material. This is because ACCS has undergone chemical and physical activation, has a high surface area, is abundant in nature, and is environmentally friendly. However, ACCS has common ionic transport diffusion, resulting in inefficient utilization of activated carbon surface area. Therefore, ACCS composite with TiO2 material is needed. TiO2 material with a small particle size can be used to reduce the aggregation so it can increase the electrolyte to an active redox site. Therefore, this research was conducted to obtain information about the most optimum activation method for ACCS biomass and the supercapacitors enhancement with ACCS-TiO2 composite to obtain great ionic diffusion performance and an effective surface area utilization. In brief, the experiment was started by preparing the composite solutions with various compositions of TiO2 (0%, 10%, 15%, and 20%). The deposition was carried out using the doctor blade technique on the aluminum foil based substrate and the liquid electrolyte of 1 M Et4NBF4 was injected between the electrodes. The crystal structure, morphology, and elemental analysis of the composite were identified using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX), respectively. Charge Discharge was applied to measure the electrical performance of the device. The highest performance of symmetric supercapacitor was performed by TiO2 15% that able to show its cyclic reversibility at the voltage range of 0-2 V, generated a specific capacitance of 53.10 F g-1 with the power density and maximum energy density of 367.05 W kg-1 and 26.15 Wh kg-1, respectively. Over 50 cycles, its maximum energy density was decreased to 24.83 Wh kg-1 with the capacity retention of 94.64 %.

Impacts of cooking, pyrolysis and HTC pretreatments of noodles waste on evolution of products in activation

Cooking and other thermal treatments like hydrothermal carbonization (HTC) and pyrolysis might impact the evolution of varied products in the activation of noodles. In this study, raw noodles were pretreated via cooking at 100 °C, pyrolysis at 500 °C and HTC at 260 °C, and subsequently activated with K2C2O4 at 800 °C. Correlation of the varied pretreatments with nature of the resulting activated carbon (AC), bio-oil and gases was paid particular attention. The results showed that cooking treatment enhanced the formation of mesopores in AC, but decreased overall yields of bio-oil and gases from 82.0 to 80.3 wt% during the activation. HTC pretreatment decreased the production of both AC and gases, but remarkably enhanced bio-oil formation. Pyrolysis increased aromatization degree of biochar and suppressed cracking reactions in activation, producing the highest overall yields of AC. However, pyrolysis and HTC destroyed sugars in noodles and reduced the occurrence of reactions for transformation of the functionalities like -OH, -C-H, C=O and C-O-C, which hindered development of pores. The highest specific surface area of AC from direct activation of raw noodles thus showed superior capability for the adsorption of tetracycline (TC) from aqueous solution. Life cycle analysis (LCA) indicated that HTC plus activation showed the least environmental impact, although the lowest yields and specific surface area of AC was obtained via this route. The results of this study will be interested to anyone working in the general field of bioenergy science and engineering.

An Efficient, Multi‐element AC/TiO2/WO3 Photocatalyst for the Degradation of Tetracycline Hydrochloride

AbstractIn this study, a simple one‐step hydrothermal synthesis of three‐element complex system photocatalyst technology is systematically studied. The results show that due to the complex heterojunction formed by titanium dioxide (TiO2), tungsten trioxide (WO3) and activated carbon (AC) and the strong adsorption performance of AC, the catalytic efficiency and cycle stability of the composite have been significantly improved. The excellent electron transport ability of AC is conducive to the separation of carriers, so that the electron transfer between AC/TiO2 and AC/WO3 can make it achieve a heterojunction effect similar to TiO2/WO3. The rich specific surface area of AC and the pores of the “labyrinth” structure can provide a higher concentration of degradable substances inside the catalyst, and the degraded substances are quickly transferred to the active site for degradation. Therefore, by controlling the mass ratio of AC/TiO2/WO3, a photocatalyst with high catalytic efficiency and strong cycle stability was successfully prepared (the degradation efficiency is above 95 %, and the degradation efficiency after 5 cycles is above 80 %).

The Activated Carbon with Pyrolle-N from Cotton Stalk for the Electrochemical Performance

Porous carbon materials have been applied in many fields for their advanced physical features. Using biomass waste material as the activated carbon (AC) source is of importance to keep the sustainable environment. The CO2 activation and KOH activation were adopted to create AC with the flexible porous structure and the former caused low surface area but with high nitrogen content of AC. The reversed results were formed with the KOH activation. The differences on specific surface area and nitrogen groups distribution were investigated by nitrogen sorption isotherm and X-ray photoluminescence spectroscopy. Their porous structure and framework were characterized with transmission electron microscope and Raman spectra. Electrochemical performance was evaluated by supercapacitance and oxygen evolution reaction (OER). Comparing to the CO2 activation, KOH activation improved surface area of AC and more functional groups on the carbon surface, which led to the enhancement of the electroactivity.

Sustainable process to produce activated carbon from Kraft lignin impregnated with H3PO4 using microwave pyrolysis

Currently, the demand for activated carbon (AC) has been growing thanks to its adsorption capacity to remove liquid and gaseous pollutants. Lignin is a biomass derived from an abundant renewable resource, rich in carbon, with potential applications in modern society. This work seeks to add greater value for the lignin, transforming it in AC and also to demonstrate the microwave pyrolysis effectiveness. ACs were obtained from Kraft lignin treated with different proportions of phosphoric acid in two different periods of time, using microwave pyrolysis in oxidizing atmosphere. The results of Fourier transform infrared spectroscopy and X-ray diffraction showed that the conversion of lignin to carbon material occurred successfully. The morphology of lignin, observed by scanning electron microscopy, showed a globular appearance and different diameters, which was converted into AC with very porous structures. Adsorption/desorption of N2 (BET) analyses showed that the AC presented high surface areas, between 635 and 1055 m2g-1, with the presence of micro and mesopores. The highest acid:lignin weight ratio favored higher values of AC surface area and pore volume. The maximum adsorption capacity of prepared AC was tested with methylene blue dye (MB) and amoxicillin (AMOX), and values of 140 and 220 mgg−1 were found, respectively. In the case of MB, the adsorption mechanism adjusted better to the Langmuir model and the AMOX to the Freundlich model.

Catalytic upgrading of ex-situ heavy coal tar over modified activated carbon

Commercial activated carbon (AC) was modified by steam activation (ST) and chemical activation (AT), and their catalytic upgrading of ex-situ heavy coal tar was investigated. The results show that both AT and ST methods could significantly increase the total surface area, promote the formation of mesopores, and further improve the catalytic upgrading performances. The light tar content was increased to 90.5% over AC-0.25ST and 85.0% over AC-2AT, respectively. The specific textural properties of AC exerted an obvious effect on the resultant tar quality, and a good linear relationship between light tar content and mesoporous surface area of AC was first revealed. The removal of minerals in AC is unbeneficial to the tar upgrading, suggesting that the minerals play a catalytic role. The modified ACs could obviously increase the contents of light oil and naphthalene oil, and the pitch content was declined to 9.5% over AC-0.25ST. H2 and CH4 yields were also remarkably increased during tar upgrading. The resultant ACs exhibited good selectivity to benzenes and naphthalenes during tar upgrading, along with a decrease in aliphatic compounds and more than 3-ring polycyclic aromatic hydrocarbons (PAHs), and 50.3% and 47.2% naphthalenes were acquired over the AC-0.25ST and AC-2AT, respectively. This study is expected to guide the preparation of upgrading catalysts and the products regulation during the catalytic upgrading of heavy coal tar.