Specific 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.

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).

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.

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 %).

Supercapacitors Based on Activated Carbons, Products of Rice Hull Processing

Rice hull ash (RHA) produced commercially by burning hulls of rice growing in the Krasnodar Krai, Russia, is characterized by a series of modern physicochemical investigation methods. The RHA is shown to contain amorphous silica (>70 wt %) and carbon (~8 wt %). Activated carbon (AC) is prepared by treating RHA with an alkali solution followed by annealing at 700°C. The specific surface area of AC is 1442 m2 g–1, with mesopores dominant in its structure. The AC is used as an electrode material in fabricating electric double-layer supercapacitors containing an aqueous 6 M KOH electrolyte or an organic 1 M Et4NBF4/PC electrolyte. The energy storage capacity of studied EDLCs are 299 and 131 F g–1, respectively.

Synthesis and characterization of modified activated carbon (MgO/AC) for methylene blue adsorption: optimization, equilibrium isotherm and kinetic studies.

Methylene blue (MB) is the cationic dye that is widely used for coloring cotton, wool, and silk. Since MB is harmful to human beings and toxic to microorganisms, there is the need to find cheap and efficient methods for removal of MB from wastewater prior to disposal into natural waters. In the present study, MB adsorption potential of MgO/AC prepared using a sol-gel-thermal deep-coating method was compared with the activated carbon (AC). The central composite design (CCD) as a method of the response surface methodology (RSM) was applied to minimize the number of runs and process optimization. The characterization of the microporous MgO/AC composite showed that the magnesium oxide nanoparticles were successfully coated on the AC and the BET specific surface area of AC and MgO/AC were 1,540 and 1,246 m2/g, respectively. The MB removal efficiency and the maximum adsorption capacity of AC and MgO/AC were 89.6, 97.5% and 571.7, 642.3 mg/g, respectively under optimum operational conditions of initial dye concentration of 100.9 mg/L, the adsorbent dosage of 69.4 mg/100 mL, pH of 10.2 and contact time of 149.1 min. According to an analysis of variance (ANOVA), the initial dye concentration and its interaction with the other effective factors have a large impact on adsorption efficiency. Furthermore, the mechanism of adsorption followed the Langmuir isotherm (R2 = 0.9935, Δqe = 2.9%) and adsorption kinetics fitted by the pseudo-second-order model (R2 = 0.9967, Δqe = 6.6%). Finally, our results suggest that the prepared MgO/AC is an efficient and promising material for dye wastewater treatment.

Removal of gas condensate from industrial wastewater using low‐cost adsorbents: Optimization by Box–Behnken design method

AbstractIn this study, three effective adsorbents such as Padina sanctae cruces algae (PSC), activated carbon (AC), and bentonite clay were used to remove gas condensates from industrial wastewater generated in the fourth refinery of South Pars Gas Complex in Iran. Physical and surface properties of the adsorbents were characterized using Brunauer–Emmett–Teller (BET), field‐emission scanning electron microscope, Fourier transform‐infrared spectroscopy, and energy dispersive X‐ray spectroscopy (EDAX) analyses. Also, droplet size distribution analysis was used to determine the size distribution of gas condensate droplets in the emulsion and to evaluate the emulsion stability. According to the BET analysis, the specific surface area of AC, PSC, and bentonite were obtained as 900.93, 0.0463, and 40.70 m2/g, respectively. To check the effect of different parameters on the removal efficiency of gas condensates, the Box–Behnken design method was used. Moreover, the optimal conditions for the removal of gas condensates included pH 9, temperature of 65°C, contact time of 120 min, and an adsorbent dosage of 5 g/L. Under such optimal conditions, the adsorption efficiencies using AC, PSC, and bentonite were obtained as 98.90%, 96.35%, and 97.24%, respectively. Furthermore, the maximum adsorption capacities of 1250, 54.95, and 99.01 mg/g were achieved using AC, PSC, and bentonite, respectively, in which AC showed the highest adsorption capacity ever achieved for the removal of gas condensate from wastewater. Besides, the thermodynamic study indicated that the sorption process was exothermic and spontaneous.

In Russian

In this work, we investigated granular and powder activated carbons (AC) – initial and waste with adsorbed impurities after purification of technical glycerin and subsequent washing with water. The aim of this work was to quantify the adsorbed impurities in the spent AC using thermal analysis (TA) and to work out the conditions for thermal regeneration of AC. TA of AC samples was carried out in an atmosphere of helium and air; the specific surface area of AC was measured by the method of low-temperature desorption of argon (SAr). It was established by the TA method that water is released in the temperature range of 20 – 170 °C, and glycerin – 170 – 400 °C. Spent AC contains up to 22.8 wt. % H2O and up to 44.6 wt. % C3H5(OH)3. Based on these data, it was proposed to regenerate spent coal by heating at 400 °C in air. In the case of a granular AC sample, the regeneration proceeds completely, while for a powder AC sample, the specific surface area with respect to argon is restored only by 22 %, from the initial 2170 m2/g. The adsorption isotherms of methylene blue (MB) of the initial samples are located higher than for the spent ones, since in the spent ones part of the surface is occupied by adsorbed glycerin. The SMB values calculated from the adsorption of methylene blue in the spent AC samples are strongly overestimated in comparison with SAr. Probably, MB displaces glycerin from the surface or interacts with it to form complexes.

Chestnut-Derived Activated Carbon as a Prospective Material for Energy Storage.

In this work, we present the preparation and characterization of biomass-derived activated carbon (AC) in view of its application as electrode material for electrochemical capacitors. Porous carbons are prepared by pyrolysis of chestnut seeds and subsequent activation of the obtained biochar. We investigate here two activation methods, namely, physical by CO2 and chemical using KOH. Morphology, structure and specific surface area (SSA) of synthesized activated carbons are investigated by Brunauer-Emmett-Teller (BET) technique and scanning electron microscopy (SEM). Electrochemical studies show a clear dependence between the activation method (influencing porosity and SSA of AC) and electric capacitance values as well as rate capability of investigated electrodes. It is shown that well-developed porosity and high surface area, achieved by the chemical activation process, result in outstanding electrochemical performance of the chestnut-derived porous carbons.

Promotion of Activated Carbon on the Nucleation and Growth Kinetics of Methane Hydrates.

Due to the hybrid effect of physical adsorption and hydration, methane storage capacity in pre-adsorbed water-activated carbon (PW-AC) under hydrate favorable conditions is impressive, and fast nucleation and growth kinetics are also anticipated. Those fantastic natures suggest the PW-AC-based hydrates to be a promising alternative for methane storage and transportation. However, hydrate formation refers to multiscale processes, the nucleation kinetics at molecule scale give rise to macrohydrate formation, and the presence of activated carbon (AC) causes this to be more complicated. Although adequate nucleation sites induced by abundant specific surface area and pore texture were reported to correspond to fast formation kinetics at macroperspective, the micronature behind that is still ambiguous. Here, we evaluated how methane would be adsorbed on PW-AC under hydrate favorable conditions to improve the understanding of hydrate fast nucleation and growth kinetics. Microbulges on AC surface were confirmed to provide numerous nucleation sites, suggesting the contribution of abundant specific surface area of AC to fast hydrate nucleation and growth kinetics. In addition, two-way convection of water and methane molecules in micropores induced by methane physical adsorption further increases gas–liquid contact at molecular scale, which may constitute the nature of confinement effect of nanopore space.

Influences of fine-grained NaCl particles on performance and denitration efficiency of activated carbon during sintering flue gas purification process.

Alkali metal chlorides emitted from sintering flue gas are easily adsorbed on the surface of activated carbon (AC) in the purification process. In this paper, NaCl particles adsorbing onto AC were simulated by impregnation method, and the size and morphology of NaCl particles were similar to those of NaCl-PM10 emitted from sintering flue gas. With the adsorption of NaCl particles, 2-10-μm pores of AC were filled, and the specific surface area of AC decreased. But NaCl led to the increase of acidic functional groups on the surface of AC. When 0.75 wt% NaCl was adsorbed, it was beneficial for AC catalytic denitration (de-NOx), because the chemical reaction was strengthened by acidic functional groups, so it showed a certain promotion of de-NOx efficiency. As 1.5 wt% NaCl and 3 wt% NaCl were adsorbed, NaCl had an inhibitory effect on AC de-NOx, which was because the specific surface area of AC decreased, and the prevention of physical adsorption played a major role. As a result, the de-NOx efficiency of AC adsorbed with 3 wt% NaCl decreased from 40.59 to 23.02% at 150 °C. Therefore, the absorption of NaCl fine particles on AC should not exceed 0.75 wt%.

Preparation and Thermal Properties of 1‐Hexadecanol‐Palmitic Acid Eutectic Mixture/Activated Carbon Composite Phase Change Material for Thermal Energy Storage

AbstractIn this study, a new kind of 1‐hexadecanol‐palmitic acid (HD‐PA) binary eutectic mixture and the composite phase change materials (PCMs) composed of HD‐PA absorbed into activated carbon (AC) pores with different mass percentage of 50, 55, 60, and 65% were prepared by vacuum impregnation method. The chemical structural, thermal stability and thermal durability of HD‐PA/AC composite phase change materials (CPCMs) with different mass fraction of HD‐PA was characterized by Fourier transformation infrared (FT‐IR) spectrometer, differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA), respectively. The specific surface area of AC were determined to be 760 m2 g−1 and abundant mesopores and micropores with the sizes at 1.8 and 0.6 nm were observed according to the N2 adsorption‐desorption measurement. DSC results showed that the onset melting temperature and latent heat of novel HD‐PA eutectic were 50.2 °C and 226.6 J g−1, respectively. The addition of AC to the PCM of binary HD‐PA eutectic can enhance its thermal stability, durability and thermal energy storage‐release rate. The form‐stable HD‐PA/AC CPCM can be used as energy storage materials in many fields owing to its good thermal properties and chemical stability.

Advanced Energy Storage System with Graphite/Copper Oxide Composite for High Energy Density

Recently high capacity energy storage devices are highlighted due to rapid growth of electric vehicles(EVs) and large-scale grid energy storage system. Especially Li ion batteries (LIBs) is the most suitable energy storage devices for EVs performing with high energy density. However, LIBs have some problems. The first is slow charging time issues owing to intrinsic reaction mechanism. The second is operating voltage range limit which is directly connected to energy density derived from revisable capacity of cathodic material. The last is cost of cathode materials because of their scarcity. To overcome these issues, we introduce hybrid energy storage system that delivers high energy density without sacrificing power density. This hybrid system is made up of expanded graphite/copper oxide composite (GCuO) as the negative electrode and activated carbon (AC) as the positive electrode. . The GCuO is high capacity materials by faradaic reaction. The AC provide large capacitance by non-faradaic reaction. Additionally, both the active materials are abundant and low price. So, this system shows the three types of energy storage mechanism: a Intercalation reaction derived from the expanded graphite, a conversion reaction from the copper oxide, and a physical adsorption/ desorption of ion the interface between the AC electrode and the electrolyte The GCuO is synthesized by a simple process, through heat treatment of the Cu ion complex and pristine graphite. While the Cu ion complex is thermal decomposed, H2 and CO2 gases are generated. These gases induce the graphite planes expanded, the gap between the planes is increased from 0.34nm to 0.40nm. Also, copper oxide is in-situ formed on the graphite plane. The expanded graphite has a lower Li+ ion intercalation barrier than pristine graphite. So the synthesized material leads to a fast diffusion of lithium ions on the anode. As a result, a high power density can be obtained by enhanced charge transfer between the electrode and the electrolyte. The copper oxide provides additional capacity to the anode. Structure of GCuO were confirmed with HR-TEM (High Resolution Transmission Electron Microscopy), EDS (Energy Dispersive Spectrometer), HR-XRD (High Resolution X-ray Diffraction) and Raman Spectroscopy. And the specific surface area of AC was characterized by BET(Brunauer-Emmett-Teller) analysis and the value was 2131m2 g-1. The large surface area provided large capacitance by the ion adsorption/desorption. The half-cell test was performed with Li metal electrode. The GCuO half-cell exhibited good specific capacity (~500 mAh g-1 at 0.2C) and life characteristics (83% capacity retention up to 250 cycles ). The AC half-cell showed specific capacity (~60 mAh g-1 at 1A g-1) and excelent cycle ability (98% capacity retention up to 500cycle). Before the full cell assembled, GCuO electrode needs to be pre-lithiation step under proper conditions since the positive electrode is not a lithium-ion source unlike the LIBs. The pre-lithiation is very effective for lowering the potential of the negative electrode and forming a stable SEI (Solid Electrolyte Interface) layer. Due to the lowered anode potential, a full cell had a wide operating potential window, which can obtain a higher energy density. In addition, the cycle characteristics of the cell were also enhanced by preventing additional loss of lithium-ion in the electrolyte . The volume change of copper oxide occurs while the copper oxide lithiation / delithiation. The lithiated CuO (enlarged CuO) makes graphite planes gap expanded. Accordingly, repetitive charging/discharging of GCuO can improve the hybrid system’s performance. The full cell with repetitive pre-lithiation has a higher energy density (~1.5 times) than the one pre-lithiated. Finally, optimized full cell shows high specific energy of about 210 Wh kg-1 at specific power of 270W kg-1 , which is equivalent to LIB’s energy density performance and the specific energy remain 70Wh kg-1 when the specific power of 10kW kg-1 within the voltage range of 1.0~4.0V. In addition, the optimized full cell showed excellent energy efficiency over 90%, which is better than that of LIBs with 80%. In conclusion, GCuO is outstanding and promising anode active material for hybrid energy storage system.

Removal of nitrate using activated carbon-based electrodes for capacitive deionization

Abstract The removal performance of nitrate using capacitive deionization (CDI) of activated carbon (AC)-based electrodes were studied. The AC electrode was prepared and the effect of cell voltage, flow rate and initial solution concentration on ion removal were investigated. Furthermore, the AC was modified with phosphoric acid (ACP) and the surface structure of AC and ACP were analyzed. The results showed that the specific surface area of AC increased by 10.71% after the modification. The mesopore ratio and micropore ratio increased by 14.69% and 24.06%, respectively. The optimal conditions of AC electrode was a voltage of 1.4 V and flow rate of 20 mL/min while the ACP electrode was a voltage of 1.4 V and flow rate of 10 mL/min. The electrosorption capacity of ACP electrode was improved and the unit of electrosorption load was high to 19.28 mg/L. For the AC or ACP electrode, the nitrate removal efficiency decreases with the increase in the initial feed solutions, but the unit electrosorption load gradually increased with the improvement of initial feed solutions' concentration and the ACP electrode was superior to the AC electrode. Therefore, the ACP electrode would be suitable for the application of CDI on the nitrate removal.

Activated Carbon Prepared from Alternanthera philoxeroides Biomass by One-step K2CO3 Activation

Activated carbons (ACs) were prepared from Alternanthera philoxeroides (AP) by K2CO3 one-step mixing activation. The effects of the mixing mass ratio of K2CO3 to AP, activation temperature, N2 flow rate, and period on the yield and specific surface area of ACs were investigated. The results showed that the surface area and pore volume of ACs were closely related to activation conditions and that the activation temperature was the main factor influencing the surface area and pore volume. The activation conditions only had a slight effect on the yield of ACs, which varied between 13.5% and 19.5%. The surface area of 1799.8 m2/g was obtained at a K2CO3 to AP mass ratio of 2:1, activation temperature of 900 °C, activation time of 2 h, and N2 flow rate of 60 cm3/min. The surface morphology of ACs were characterized with scanning electron microscopy (SEM), and the recovered K2CO3 was characterized with powder X-ray diffractometry (XRD). The SEM images of the ACs also showed that the activation temperature had an obvious effect on the porous structure.