Search

Electrochemical hydrogen storage is considered as the safest mode compared to the other storage forms, which is why it has attracted a significant research attention in the past decade. Carbon-based porous mediums offer many benefits that favor hydrogen adsorption in it. The presented work investigates the feasibility of coconut shell derived activated carbon for hydrogen adsorption by ascertaining its physical and chemical characteristics. The procedure employed for characterization is disclosed. Brunauer-Emmett-Teller (BET) surface area, average crystalline size of the activated carbon was found to be 51.7 m2/g and average crystalline size using X-Ray Diffraction (XRD) to be 10.69nm, respectively, which is comparable with the published data in literature. The scanning electron microscopy illustration of the field emission revealed the presence of well-developed pores on the surface of the sample activated carbon. The Fourier Transform Infrared Analysis (FTIR) spectrum was employed to determine the existence of essential functional groups. The ultraviolet–visible spectroscopy (UV–V) is used to confirm the presence of π- π* transition within the activated carbon. Working in the similar direction, the presented work is an experimental investigation on ionic hydrogen storage in an activated carbon electrode integrated in a modified reversible polymer electrolyte fuel cell (PEMFC) for transport applications that is carried out. The ingress and egress of hydrogen within the developed PEMFC of 6.25 cm2 active area successfully stored 559.65mAh/g during charging and give out 510.51 mAh/g while discharging. The result analysis revealed the feasibility of the coconut shell based activated carbon to be a suitable candidate for hydrogen storage applications. [ABSTRACT FROM AUTHOR]

Activated carbons exhibit a high grade of porosity, which together with structural stability, regenerability and cyclability makes them capable of achieving excellent hydrogen adsorption capacity. A further advantage comes from the ease of production and the use of recyclable and biocompatible materials. A simple way to produce activated carbons from amorphous cellulose involves procedures in which a pyrolysis process is combined with physical activation in CO 2. We used this approach by optimizing the production process tuning the activation times. The aim is to evaluate the influence of this process parameter on the formation of the specific surface area, the pore volume and fraction of micropores with a typical size <2 nm. The influence of these structural parameters on the hydrogen adsorption properties was then evaluated. The textural and adsorption characteristics were investigated using a commercial volumetric apparatus (ASAP 2460, Micromeritics) at −196 °C and pressures between 0 and 1 bar, while the morphological properties were investigated using scanning electron microscopy. The results show that the nanostructured samples are characterized by a very high degree of ultra-microporosity (<0.7 nm) with an average pore size between 0.5 and 0.6 nm and a high specific surface area, reaching maximum values around 1500 m2/g and micropore volume up to 0.58 cc/g. These morphological characteristics strongly influence the hydrogen adsorption properties, where the molecules adsorbed reach values very close to the coverage of ideal monolayer. The synthesized activated carbon samples show a higher hydrogen adsorption capacity than similar commercial materials tested under the same thermodynamic conditions. [Display omitted] • Easily tuning of ultra-microporosity. • Precursor influence on storage performance. • Hierarchical porous carbons and possibility hydrogen storage at low pressure. • Fully reversible hydrogen physisorption. • Amorphous cellulose as sustainable solution. [ABSTRACT FROM AUTHOR]

• Municipal GW can be used as a sustainable and low-cost precursor to generate AC. • Activation process enhanced the surface area and internal micro-mesoporous structure. • Higher activation temperature has significant influence on AC characteristics. • No significant difference in AC characteristics generated in 1-step and 2-step. • Carbon structure, thermal stability of synthetic AC is comparable to commercial AC. This research aims to investigate the potential of the municipal garden waste as a new precursor to generate activated carbon by CO 2 activation. TGA analysis shows the distinctive thermal degradation nature of garden waste. The activation of the garden waste enhanced its surface area where well-developed internal micro-mesoporous structure is also noticed. The results suggest that most of the volatiles decomposed at temperatures beyond 450 °C. A decrease in char yield, increase in surface area and pore volume and weakening of oxygen and hydrogen-containing groups were observed at higher pyrolysis temperatures. Raman and XRD support the amorphous and porous graphitic structure of carbon. Carbonization temperature of 500 °C and activation temperature of 800 °C were shown to produce the better-quality AC where highest surface area of 363.32 m2/g and highest pore volume of 0.095 cm3/g was achieved. Compared to the pyrolysis temperature, pyrolysis steps did not have notable contribution to the AC characteristics. [ABSTRACT FROM AUTHOR]

Coal and biomass are two important carbonaceous feedstocks for producing carbon materials. Distinct composition of them might affect pore development of resulting activated carbon (AC) during activation. This was investigated herein via activating anthracite coal and poplar biomass via physical activation (activators: CO 2 and H 2 O) and chemical activation (activators: K 2 C 2 O 4 and ZnCl 2) under the same conditions. The results indicated that the activation of highly aromatic coal produced much higher yield of AC than that from poplar sawdust (ca. 90 % versus ca. 25–37 %). Nonetheless, this was at the cost of limited development of pore structure of AC-coal (121.1 m2g-1 with K 2 C 2 O 4 and 190.8 m2g-1 with H 2 O as an activator). Conversely, abundant aliphatics in poplar created more developed pore structures in AC-poplar (949.0 m2g-1 with K 2 C 2 O 4 and 588.6 m2g-1 with H 2 O), which also enhanced yields of AC-poplar through condensation reactions catalyzed with ZnCl 2 (AC yield: 33.7 % vs 22.8 % from blank experiment). The fused ring structures in coal were hardly activated via cracking with K 2 C 2 O 4. However, H 2 O could oxidize some carbonaceous organics on AC-coal, introducing oxygen-containing species, further cracking of which formed pores. This was an important route for generating pore structures in AC-coal. [Display omitted] • Highly fused aromatic rings in coal inhibit pore development via physical/chemical activation. • Aliphatic structures in poplar are main contributor to pores but diminishes solid yield. • H 2 O is more active than CO 2 for creating pores via cracking/gasification of poplar or coal. • H 2 O oxidizes coal to generate aliphatic O-containing species and then forms pores via cracking. • Ethers, ketones and esters/lactones in coal are cracked over K 2 C 2 O 4 or ZnCl 2 , forming limited pores. [ABSTRACT FROM AUTHOR]

Because of its high adsorption capacity, activated carbon is frequently employed as an effective adsorbent. Activated carbon is a main element for treatment of wastewater, groundwater and water purification. The activating agents greatly affects the porosity and surface area of the produced activated carbon. In this study, the use of agricultural leftovers for the production of activated carbon is discussed in detail. The pyrolysis stage is investigated in relation to a number of process variables. The effects of physical and chemical activation circumstances on the properties of activated carbon are discussed. Under controlled process conditions, many active carbons with Brunauer–Emmett–Teller surface areas ranging from 250 to 2,410 m2/g and pore volumes ranging from 0.022 to 91.4 cm3/g were produced. A review of reaction kinetic modelling applied to pyrolysis of agricultural wastes is also carried out. In this study, effort has been given to show the preparation of activated carbon from various agricultural residues. Also the comparisons of different activated carbon prepared from various agricultural residues have been shown. In the present review, the preparation of activated carbon by treating with different chemicals has also been incorporated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyrolysis of four types of citrus wastes was studied; • The derived biochars and activated carbons could be used as Cu(II) adsorbents; • The adsorption capacity of the biochars are comparable with the literature. A route based on pyrolysis and physical activation with H 2 O and CO 2 was proposed to reuse citrus waste traditionally discarded. The citrus wastes were orange peel (OP), mandarine peel (MP), rangpur lime peel (RLP), and sweet lime peel (SLP). The main aim was to use the solid products of this new route as adsorbents for Cu(II) ions. Copper ions are among the most important water pollutants due to their non-degradability, toxicity, and bioaccumulation, facilitating their inclusion and long persistence in the food chain. Besides the solid products, the liquid and gaseous fractions were evaluated for possible applications. Results showed that the citrus waste composition favored the thermochemical treatment. In addition, the following yields were obtained from the pyrolysis process: approximately 30 % wt. of biochar, 40 % wt. of non-condensable gases, and 30 % wt. of bio-oil. The biochars did not present a high specific surface area. Nevertheless, activated carbons with CO 2 and H 2 O presented specific surface areas of 212.4 m2/g and 399.4 m2/g, respectively, and reached Cu(II) adsorption capacities of 28.2 mg g−1 and 27.8 mg g−1. The adsorption kinetic study revealed that the equilibrium was attained at 60 min and the pseudo-second-order model presented a better fit to the experimental data. The main generated gases were CO 2 , which could be employed as an activating agent for activated carbon production. d -limonene, used for food and medicinal purposes, was the main constituent of the bio-oil. [ABSTRACT FROM AUTHOR]

The generation of liquid waste containing dyes and complex organic compounds is a problem in the textile industries. In this work, we evaluated the use of macadamia nut residue as a precursor of a biochar for the treatment of these effluents through the adsorption process. The macadamia nut endocarp undergoes a sequential treatment involving pyrolysis at 600 °C followed by physical activation with CO 2 and H 2 O vapor at 700 °C. Characterization of the resulting macadamia nut residue-derived biochar (MB) is accomplished through various techniques, including X-ray diffractometry (XRD), thermogravimetric analysis (TGA), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), nitrogen physisorption analysis and the pH at the zero charge point (pH ZCP). Performance studies reveal that pH exerts minimal influence on the adsorption phenomenon. The Elovich kinetic model effectively describes the adsorption kinetics for both β-naphthol and Reactive Black 5 (RB5), with adjusted coefficients of determination (R2 adj) of 0.99 and 0.94, respectively. Further analysis using the intraparticle diffusion model demonstrates that β-naphthol adsorption kinetics involve multiple mechanisms, while RB5 adsorption is predominantly governed by intraparticle diffusion. Equilibrium adsorption data for both adsorbates fit well with the Sips isothermal model, yielding maximum adsorption capacities of q max β-naphthol = 15.16 mg∙g−1 and q max RB5 = 3.08 mg∙g−1 at 55 °C. The adsorption process for both compounds is spontaneous and endothermic, based on the enthalpy values, it can be inferred that the β-naphthol adsorption is governed by weak van der Waals forces, indicating physisorption. As for RB5, the enthalpy value suggests that the phenomenon occurs due to electrostatic interactions between the molecule and the surface groups with higher energy involved. This study highlights the potential of macadamia nut residue biomass as a precursor for biochar, demonstrating its favorable attributes for application as an effective adsorbent material in the removal of organic compounds such as β-naphthol and RB5 from wastewater streams within the textile industry. [Display omitted] • Macadamia biochar as a potential support for catalytic materials and dyes removal. • Accurate adsorption kinetics described by the Elovich model for β-naphthol and RB5. • Study unveils the nature of adsorption interactions in textile wastewater treatment. • Promising results highlight residue-derived biochar as an eco-friendly solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Self-doped porous activated biochar derived from Venice lagoon's Sargassum brown macroalgae. • Thermochemical carbonization followed by CO 2 physical activation. • ABS exhibits a remarkable specific surface area of 821 m2/g and heteroatoms (N, O, and S) doping. • ABS-based electrodes reached energy densities in supercapacitor of 12.4 Wh kg−1 at 57.4 W kg−1. • Flexible solid-state supercapacitor displayed a remarkable 97% specific capacitance retention. In this study, self-doped porous activated biochar derived from Venice lagoon's Sargassum brown macroalgae (ABS) has been successfully prepared through thermochemical carbonization (pyrolysis) followed by CO 2 physical activation and used as electrodes for supercapacitor (SC) applications. The ABS exhibits a remarkable specific surface area of 821 m2g–1 and heteroatoms (N, O, and S) doping, both key features to attain high-performance carbon-based SC electrodes. The electrochemical performances of ABS-based SCs were assessed in three different electrolytes. Two are aqueous (i.e., 1 M H 2 SO 4 and 8 M NaNO 3), while the third one is the prototypical organic, namely 1 M TEABF 4 in acetonitrile. In these three electrolytes, the ABS-based electrodes exhibited specific capacitance values (C g) of 109.5, 79.0, and 64.3Fg–1, respectively, at a current density of 0.1 Ag–1. The capacitive performance resulted in SC energy densities of 3.45 Wh kg−1 at 22.5 W kg−1, 6.3 Wh kg−1 at 36.1 W kg−1, and 12.4 Wh kg−1 at 57.4 W kg−1 and maximum power densities of 147, 222, and 378 kW kg−1 in the acidic, quasi-neutral aqueous electrolyte and organic electrolyte, respectively. The ABS electrodes were used to realize a flexible solid-state SC based on the sulfonated polyether ether ketone (SPEEK):functionalized niobium disulfide flakes (f-NbS 2) composite membrane. The flexible solid-state SC displayed a remarkable 97% C g retention even under various mechanical stresses, including bending up to 1000 times and folding angles up to 180°, while keeping a Coulombic efficiency above 98%. This study reveals ABS as a promising sustainable source of active materials for SCs. The remarkable performance of ABS-based SCs can be attributed to their multi-scale porosity, heteroatom doping, and enhanced surface wettability, providing abundant active sites for charge accumulation, and efficient electrolyte diffusion, thus highlighting its potential as a sustainable solution for energy storage applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly porous activated carbon was synthesized through physical method. • Biomass from Strychnos Potatorum was used as a raw material. • Symmetric supercapacitor devices exhibit a specific capacitance of 281 F g−1 at 0.2 A g−1. • Excellent retention of more than 98.2 % after 5000 cycles. Herein, low-cost activated carbon (AC) prepared from Strychnos Potatorum shells using CO 2 as an activating agent via physical activation technique. Waste biomass-derived AC have the merits of excellent conductivity and highly porous with high-surface area. Electrochemical assessments indicated that the prepared Strychnos Potatorum derived activated carbon (SPAC) electrode exhibited superior electrochemical performance. The experimental data showed that the specific capacitance of 352.5 F g−1 at 0.5 A g−1 and retained 140 F g−1 at 20 A g−1. Symmetric supercapacitors SPAC//SPAC device displayed an impressive specific capacitance of 147 F g−1 at 0.1 A g−1 and an energy density of 20.41 W h kg−1 at 100 W kg−1 and retained 2.7 Wh kg−1 at 10000 W kg−1. Furthermore, these supercapacitors demonstrated exceptional cyclability, maintaining capacity retention of 92.3 % over 10,000 charge–discharge cycles at 1 A g−1. This research work underscores the promising potential of AC materials derived from Strychnos Potatorum shells in development of high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • The CO 2 /H 2 O co-activation and the NO-char reaction are systematically studied. • The mechanism of the synergistic activation of CO 2 and H 2 O is described. • C − O promotes the conversion of NO. • The co-activated carbon has many micropores, oxygen groups and ordered structures. • The co-activated carbon has high adsorption and reducing properties. Adsorption and reduction of NO by coal-based activated carbon has the advantages of cleanliness, wide distribution of raw materials and low cost. In this paper, activated carbons with 30, 50 and 70 wt% burn-off rates were prepared via physical activation of Zhundong coal by CO 2 , H 2 O and 40 % H 2 O/60 % CO 2 at 700 °C, and NO removal rates were tested in both temperature-programmed and isothermal experiments. The synergistic effects of CO 2 /H 2 O co-activation on the morphology, pore and chemical structures of activated carbons and the adsorption and reduction of NO by activated carbon are systematically investigated for the first time. The results show that the pore size distribution and functional group contents of activated carbons varied with the burn-off rate. At a low burn-off rate of 30 wt%, the H 2 O/CO 2 co-activated carbon exhibits the best adsorption and reduction performance for NO among all samples, which may be attributed to its largest microporous area and abundant oxygen-containing functional groups. As the burn-off rate increased, the micropores were deeply etched, enlarged and/or merged to form mesoporous structures, leading to a decrease in the number of micropores and the NO conversion. At the same burn-off rate and similar specific surface area, the NO conversion increases with increasing C − O content, suggesting that NO reduction is encouraged by C − O enrichment. Coal-based porous carbons from H 2 O/CO 2 co-activation at a low burn-off rate has the advantage of high adsorption and reduction performance for NO. In addition, the effect of active metal elements in coal-based activated carbon on the catalytic reduction of NO was briefly discussed. A novel synergistic activation method was used to prepare activated carbon for reduction of NO at moderate temperatures and the synergistic mechanism is proposed. [ABSTRACT FROM AUTHOR]

As the most commonly used method for industrial activated carbon preparation, physical activation is usually accompanied by significant loss of raw materials, especially when the pore structure of activated carbon is well developed. This not only reduces yields, but also increases costs. To enhance both yield and pore structure of activated carbon, we proposed a facile and scalable method called "fast pyrolysis-physical activation". After fast pyrolysis, although the initial pore volume of the semi-coke decreases, the rapid release of volatiles promotes the increase of mesopore and macropore volumes and the development of micron-scale cracks, which is beneficial for CO 2 mass transfer and reduces diffusion resistance. Therefore, compared to slow pyrolysis, the activated carbon produced through this method has a higher pore volume (increased by 25.9 %–30.0 %) and a larger S BET (increased by 26.7 %–38.3 %), while the yield remains almost unchanged. Consequently, due to the increase in pore volume and high yield of the activated carbon, the CO 2 adsorption capacity (25 °C, 1 bar) of ACB-K700 increases from 2.02 mmol/g to 2.37 mmol/g compared to ACB-M700, and the total CO 2 adsorption capacity of activated carbon prepared from the same mass of raw coal (1 g) increases from 1.07 mmol to 1.16 mmol. Due to the pre-formed pores inside the semi-coke, the gas activator molecules are able to penetrate deep into the particles, which not only reduces the ineffective etching that occurs on the surface, but also promotes the development of pore structure. In conclusion, this study provides a new pore development model for physical activation, and also provides a new method to produce activated carbon rapidly and massively, while the pore structure is well developed. • A new pore-forming mechanism is proposed based on fast pyrolysis-physical activation. • The S BET significantly increases by 26.7–38.3 % at similar yields (49.12–53.01 %). • The rapid escape of volatiles increases the pore volume for semi-coke. • Pre-formed pores in the semi-coke reduces ineffective etching of activator. • The CO 2 absorption capacity at 25 °C and 1 bar can be up to 2.37 mmol/g. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) is produced by a physical or chemical activation process. Physical activation methods are commonly adopted in industry because of their low production costs, but the insufficiency of activating agent diffusibility into core parts of the particles and microdomains of carbon materials causes a lower activation yield and degree of pore development, compared with chemical activation methods. To increase the activating agent diffusibility and corresponding degree of pore development, we propose a novel pressurized physical activation method. Pressurization afforded remarkable increases in specific surface area and total pore volume of the prepared AC, compared with atmospheric pressure. Additionally, in AC prepared by this method, pore size distribution analysis revealed characteristic development of micropores of about 1.6 nm; such micropores did not appear in AC under conventional atmospheric physical activation. Furthermore, observations of particles and their microdomains showed that pressurization increased the activating agent diffusibility in carbon particles, but not at the microdomain level. This innovative pressurized physical activation can produce AC with highly developed pores (specific surface area >2600 m2/g) and a unique pore size distribution due to the improved activating agent diffusibility in carbon particles. [Display omitted] • Pressurized physical activation promoted pore development of activated carbons. • Specific surface area >2600 m2/g was achieved by pressurized physical activation. • Pressurization can afford unique pore size distribution. • Pressurization improved gas diffusibility in carbon particle, but not in microdomain. [ABSTRACT FROM AUTHOR]

This study investigated the alternative cheap eco-friendly materials date palm (Phoenix dactylifera) fibers for the preparation of activated carbon (AC) by physical activation with CO2 at different parameters of pyrolysis: pyrolysis temperature, the particle size and the duration of pyrolysis. The physical characterization (porosity and surface) was determined by the adsorption–desorption of nitrogen at 77 K (BET) and Dubinin–Radushkevich (D-R) equations, as well as the analysis by scanning electron microscopy. The chemical characterization (surface function), which was carried out by the Boehm titration, the pH zero-point charge (pHzpc) and Fourier transform infrared spectroscopy, confirmed the acidic character of the material. The adsorption of phenol from aqueous solutions onto the prepared AC was investigated. The adsorption process followed the Langmuir isotherm model with a maximum adsorption capacity of 31.75 mg g–1 for date palm fibers. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the latest advancement in physical and chemical activation strategies for ultra-high performance concrete (UHPC), addressing challenges such as high autogenous shrinkage, insufficient hydration, and inadequate steel fibers utilization, to further enhance its performance and achieve broader application. Firstly, an in-depth discussion is provided on physical activation strategies, encompassing design methodologies, nanomaterials, mixing, casting, and curing regimes. Subsequently, the discourse comprehensively covers chemical activation strategies, including active nanomaterials, multi-cementitious material systems, chemical admixtures and alkali-activator. Throughout this investigation, particular emphasis is placed on identifying research gaps within various activation strategies to foster more profound subsequent research and encourage innovative contributions to civil engineering. Finally, a focused discussion is provided on the influence of synergistic physical and chemical activation on UHPC performance. This comprehensive review serves as a crucial reference for deep research and broader application of UHPC in engineering, offering valuable insights for further exploration and optimization of the UHPC performance. [ABSTRACT FROM AUTHOR]

Many experimental studies have shown the feasibility of using biomass precursors to produce activated carbon, often improving the properties obtained from traditional materials. However, hardly any models focus on the development of porosity during the process. Among the so-called pore models, the random pore model (RPM) is the most popular and accurately predicts the evolution of the porous structure due to pore growth and coalescence. However, in activation processes with a low degree of conversion, in which pore formation is the dominant mechanism, the RPM does not correctly predict the evolution of the specific surface area since it does not consider the appearance and creation of new porosity. In this work, a new model is proposed that predicts the specific surface area created due to the formation of new pores. Subsequently, it is combined with the determination of the variation of the specific surface area predicted by the RPM due to the growth and coalescence of existing pores. The validation of the new pore evolution model with activated carbon samples obtained at different conversions shows that the model proposed adequately predicts the specific surface area and pore distribution evolution throughout the activation process. [Display omitted] [ABSTRACT FROM AUTHOR]

• AC successfully prepared from a low-cost bio-adsorbent and agro-industrial waste. • ACs were modified by chemical (three types) and physical (two types) activations. • Operational parameters of adsorption were optimized using ACs for DCF removal. • GP modelling and MD simulation performed for selected AC in adsorption process. This work aims at the preparation of AC from chemical activation (H 3 PO 4 , KOH, and HCl) and physical activation (thermal treatment under N 2 atmosphere at 500 and 700 °C) of Astragalus Mongholicus (AM) (a low-cost bio-adsorbent and agro-industrial waste), used as carbon precursor. The obtained materials were further applied in the adsorption of diclofenac (DCF) from water/wastewater. The physicochemical properties of the as-prepared ACs and commercial activated carbons (CAC) were evaluated by SEM, XRD, FT-IR, and BET analyses, revealing the high surface area and mesoporous proportion of AC when compared to CAC. Adsorption results showed that the efficiency of AC-700 °C (774 m2 g−1) for DCF removal (92.29%) was greater than that of AC-500 °C (648 m2 g−1, 83.5%), AC-H 3 PO 4 (596 m2 g−1, 80.8%), AC-KOH (450 m2 g−1, 59.3%), AC-HCl (156 m2 g−1, 29.8%) and CAC (455 m2 g−1, 67.8%). The optimization of effective parameters in adsorption was examined at a laboratory-scale using the selected AC-700 °C. The Langmuir isotherm and the pseudo-second-order model fitted well the experimental data. The regeneration efficiency was maintained at 96% (DI-water) and 97% (heating) after three cycles. Besides, genetic programming (GP) and molecular dynamics (MD) simulations were applied to predict the adsorption behavior of DCF from aqueous phase as well as in the ACs structure. It was found that the adsorption mechanisms involved were electrostatic interaction, cation–π interaction, and π–π electron interaction. [ABSTRACT FROM AUTHOR]

• Residue after supercritical extraction of hops as precursor for activated bio-carbons production. • This study developed activated bio-carbons to remove NO 2. • The most favorable conditions for NO 2 removal from air stream were specified. • The maximum adsorption capacity obtained 79.2 mg/g ads. Production of activated bio-carbons from the residue of supercritical extraction of hops has been described. The precursor was first subjected to pyrolysis at 500 and 700 °C in nitrogen atmosphere. The bio-chars were next subjected to physical activation at 700 and 800 °C in carbon dioxide atmosphere. The effects of pyrolysis and activation temperature on the physicochemical properties and sorption capacity toward NO 2 were established. The results have shown that by physical activation of residue of supercritical extraction of hops it is possible to produce bio-sorbents with very high capacity towards NO 2, reaching maximum 79.2 mg/g. It has been proved that the effectiveness of NO 2 removal to large extent depends on the conditions of adsorption. The presence of steam in the stream of gases and preliminary wetting of the adsorbent bed have positive effect on the adsorption of NO 2 by the bio-sorbents obtained. [ABSTRACT FROM AUTHOR]

Polymeric carbon/activated carbon aerogels were synthesized through sol-gel polycondensation reaction followed by the carbonization at 800 °C under Argon (Ar) atmosphere and subsequent physical activation under CO 2 environment at different temperatures with different degrees of burn-off. Significant increase in BET specific surface area (SSA) from 537 to 1775 m2g−1 and pore volume from 0.24 to 0.94 cm3g−1 was observed after physical activation while the pore size remained constant (around 2 nm). Morphological characterization of the carbon and activated carbons was conducted using X-ray diffraction (XRD) and Raman spectroscopy. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to investigate the effect of thermal treatment (surface cleaning) on the chemical composition of carbon samples. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to analyse the capacitive and resistive behaviour of non-activated/activated/and surface cleaned activated carbons employed as electroactive material in a two electrode symmetrical electrochemical capacitor (EC) cell with 6 M KOH solution used as the electrolyte. CV measurements showed improved specific capacitance (SC) of 197 Fg−1 for activated carbon as compared to the SC of 136 Fg−1 when non-activated carbon was used as electroactive material at a scan rate of 5 mVs−1. Reduction in SC from 197 Fg−1 to 163 Fg−1 was witnessed after surface cleaning at elevated temperatures due to the reduction of surface oxygen function groups. The result of EIS measurements showed low internal resistance for all carbon samples indicating that the polymeric carbons possess a highly conductive three dimensional crosslinked structure. Because of their preferred properties such as controlled porosity, exceptionally high specific surface area, high conductivity and desirable capacitive behaviour, these materials have shown potential to be adopted as electrode materials in electrochemical capacitors. • Polymeric carbon/activated carbon aerogels were synthesized through sol-gel polycondensation reaction. • Significant increase in BET SSA from 537 to 1775 m2g−1 was observed after physical activation using CO 2. • Improved SC of 197 Fg−1 was achieved after activation as compare to 136 Fg−1 for non-activated carbon aerogels. • Significant decrease in contact angle was observed when carbon substrate was substituted with activated carbon. [ABSTRACT FROM AUTHOR]

Vinasse has been successfully used as carbon and non-metals precursor for the synthesis of N-S-doped nanoporous carbon materials. The procedure involves the hydrothermal treatment of vinasse (HTV), and subsequent physical activation with CO 2 in absence (VP) and presence of cobalt (VPCo). The N 2 physisorption and SEM images showed the development of porous in the material, with BET surface area values ranging from 7.17 (HTV) to 734 m2 g−1 (VPCo), and the formation of carbon-spheres. Spectroscopy techniques (FTIR and XPS) demonstrated the insertion of nitrogen and sulfur elements, as well as the presence of cobalt into the carbon lattice. The electrocatalytic activity experiments toward the oxygen reduction and evolution reactions, and hydrazine oxidation reaction were superior for VPCo, which gave onset values of 0.91, 1.60 and 0.36 V vs. RHE, respectively. Additionally, VP was selective for H 2 O 2 , while VPCo catalyzed ORR via a four-electron pathway. Image 1 • Sugarcane vinasse was successfully converted into carbon via hydrothermal treatment. • The vinasse acted both as carbon and non-metal precursor (nitrogen and sulfur). • CO 2 -physical activation enhanced the porosity of the materials. • Selective materials toward H 2 O 2 production and total O 2 reduction were prepared. • Decorated the material with cobalt improved its activity toward all reactions. [ABSTRACT FROM AUTHOR]

Recently, the global industrial and transportation sectors are trying to reduce their dependence on petroleum products and replace them with renewable and environmentally friendly sources because of crude oil depletion and the problem of climate warming caused by the unrestrained release of carbon dioxide and other greenhouse gases due to the combustion of petroleum- fuels. As a result, many scientists and researchers are promoting the development of new alternate sources with low cost and little environmental impact. The International Energy Agency (IEA) sets a high goal of obtaining 6% of the global energy supply from renewable energy sources by 2030. Biofuel is a form of biodegradable alternative fuel that can be synthesized from various vegetable and animal fatty sources using heterogynous catalysts. Activated carbon (AC) is a porous substance with distinct physical and chemical characteristics that has found widespread use in a variety of activities, especially in the catalytic process of biofuel production. Therefore In this review, the different lignocellulosic biomass raw materials bio-resources used in the production of activated carbon were reviewed and several examples detained including Durian shells, Palm kernel shells, Almond stone, Bamboo, Banana peel, Orange peel, Peanut shell, Rice husk, Sugar cane bagasse, and Waste tea. The techniques of activated carbon production were reviewed including physical, chemical, and microwave-assisted methods. However, chemical activation is more economical, as the activation takes place at low temperatures and in a relatively short time to give activated carbon its own high porosity and large surface area. The parameters influencing the properties of the produced activated carbon were monitored including the effect of activation temperature, activation time, and the impregnation ratio. The role of different activating agents on the effectiveness of activated carbon produced from different resources was studied. The best specifications for the production of activated carbon were determined, the degree of crystallinity, porosity, and surface area were controlled, and a report on the factors affecting them was determined. The costs of preparing activated carbon from various sources and raw materials had to be considered in the first place. [Display omitted] • Activated carbon has impressive properties during diverse applications. • Chemically activated carbon has narrow porous structure and high surface area. • Activated carbon is more ecofriendly and less toxic for environment. • Activated carbon functionalizing increased its activity in biodiesel production. • Activated carbon commercialization is important for industrial applicability. [ABSTRACT FROM AUTHOR]

In this study, activated polymer-based hard carbons (APHs) were prepared for supercapacitor electrode applications under various carbonization and activation conditions. The crystallite size of the APHs was adjusted by changing the heating rate during the carbonization process. The surface morphologies and structural characteristics of the APHs were observed by SEM and XRD, respectively. The N 2 adsorption isotherm characteristics at 77 K were confirmed by BET and BJH equations. From the results, the specific surface areas and total pore volumes of the APHs were determined to be 790–1620 m2/g and 0.31–0.68 cm3/g, respectively. It was also observed that pore structure depended on crystallite size and CO 2 activation conditions. Also, the carbonization conditions could control the crystal structure and pore structure of the APHs. A small crystallite size produced APHs with the high specific surface area, and large crystallite size produced APHs with uniform pore size distribution. The analysis of electrochemical characteristics also found that the specific capacity increased from 8 to 108 F/g. Based on these results, we were able to determine the pore characteristics of APHs by controlling the carbonization and activation conditions, which consequently allowed us to manufacture the APHs with advanced electrochemical properties. [ABSTRACT FROM AUTHOR]

Highlights • Activated carbons with surface areas over 3000 m2 g−1 can be prepared through simple CO 2 activation. • Micropores develop through two distinctive steps during activation. • The prepared carbons exhibit a high gravimetric capacitance of approximately 80 F g−1. • A carbon with an optimized bimodal pore system exhibited good rate performance. Abstract Activated carbons for electrodes of non-aqueous electric double layer capacitors were prepared from composites of poly(methymethacrylate) particles and phenolic resins. Their surface areas can be increased up to 3000 m2 g−1 through simple CO 2 activation. Through the characterization of pore properties of the resulting carbons, it was found that the activation process appears to be composed of two steps. The pore properties of the activated carbons were optimized to maximize their performances as electrodes for non-aqueous electric double layer capacitor electrodes. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Microporous activated carbon pellets have been prepared from date stone without the use of binder. • Binderless activated carbon was used as supercapacitor in water treatment: capacitive deionization. • The capacitive deionisation electrosorptive performance of the activated carbons was evaluated. Abstract Microporous activated carbon pellets have been prepared from date stone without the use of a binder. These pellets were tested as electrodes for capacitive deionization. The activation process involved two steps. First, a pyrolysis of the date stone was conducted to a temperature of 1000 °C under nitrogen flow. Then, the obtained carbon monoliths were physically activated at 900 °C under CO 2 flow. Elemental analysis, BET, SEM, mercury porosimetry, conductivity measurement and electrochemical performance testing carried out to characterize the structure and the properties of activated carbon pellets. The activated carbon exhibited predominant microporosity with a specific surface area of 896 m2 g−1 which leads to the highest specific capacitance 270.90 F/g. The performance of activated carbon electrode at 900 °C in capacitive deionization (CDI) test was also examined. [ABSTRACT FROM AUTHOR]

Abstract This work aims at shedding light on how the microporous texture of porous carbons influences their electrochemical behavior when used as anodes for Li-ion batteries. To this aim, a synthetic hard carbon (carbon xerogel, CX), prepared from a resorcinol-formaldehyde precursor gel, underwent several post-synthesis treatments in order to modulate its micropore to total pore volume ratio. The micropore volume was either expanded by physical activation or decreased using chemical vapor deposition (CVD) of a carbon layer. Several variables other than the micropore texture of the obtained carbons, which could influence their behavior as anode active materials for Li-ion batteries, such as the particle size or the electrode characteristics, were carefully controlled. The thickness of electrode coatings and the pore texture of the active material-binder composite were analyzed. It was shown that CX-binder composites resulting from water-based slurries preserve the microporosity of the starting materials. Detailed electrochemical characterization of the electrodes prepared with carbon xerogels displaying various defined micropore textures was performed. A clear linear dependency could be evidenced between the Li+ insertion and de-insertion in half-cell configuration with the increase of the volume of supermicropores (0.7–2 nm), demonstrating the effect of micropore enlargement by activation on the storage capacity, provided the maximum charge potential value is set at 3.0 V vs. Li+/Li. Graphical abstract Image 1 Highlights • The microporosity of a macroporous carbon xerogel was selectively modulated. • The micropore texture was characterized by combined N 2 and CO 2 adsorption measurements. • Using a water-soluble binder to prepare electrodes allows for keeping the micropores accessible. • The volume of supermicropores strongly influences Li+ ions insertion and de-insertion. [ABSTRACT FROM AUTHOR]

Activated bio-char prepared from the pyrolysis and CO 2 -based physical activation of Sargassum macro-algae was developed as a sustainable and cost-effective adsorbent for malachite green (MG) and methylene blue (MB) adsorption. Prepared activated bio-char was characterized with CHNS, FESEM, Raman, FT-IR and N 2 adsorption/desorption methods. Langmuir isotherm and pseudo second order kinetics model best fitted equilibrium and kinetics data. The maximum adsorption capacity for MG and MB were 500 and 204.8 mg/g. The effect of solution pH and temperature on adsorption efficiency was studied and discussed. Acid treatment easily regenerated the adsorbent. After 5 cycles, the MB and MG adsorption efficiency reached 89 % and 78 %, respectively. A Density Functional Theory (DFT) calculation showed that pH-N-(CH 3) 2 of MB was strongly attracted to the -COOH functional groups in activated bio-char. For MG, the order of preferred interactions between the ph-N-(CH 3) 2 groups and the functional groups of adsorbent was -CONH 2 >-COOH>-COH. [Display omitted] • Mesoporous Sargassum macroalgae-derived activated biochar with high surface area. • A green and low-cost adsorbent with diverse functional groups and S/N doped carbons. • Regeneration of the adsorbent with acid treatment. • Investigation of the nature of adsorbent-adsorbate interactions by DFT calculation. [ABSTRACT FROM AUTHOR]

Physical activation of biomass with H 2 O or CO 2 is an important method for producing activated carbon (AC). Activation of biomass with CO 2 or H 2 O follows varied mechanisms and the use of mixed CO 2 /H 2 O might show potential synergistic effects for creating pores. This was investigated by activation of lignin-derived biochar with H 2 O, CO 2 and their mixture. The results demonstrated that H 2 O as an activator was much more effective than CO 2 for generation of pores (804.1 m2g−1 versus 516.1 m2g−1in CO 2), especially mesopores (40% versus 14% in CO 2). This was achieved via enhancing cracking/gasification reactions of the biochar with H 2 O. The synergistic effect of CO 2 and H 2 O for activation of the lignin-derived biochar was insignificant as cracking/gasification reactions were not enhanced, leading to remarkably lower specific surface area of the AC (674.8 m2g−1) than that with H 2 O as an activator alone. Competitive adsorption of CO 2 and H 2 O existed and preferable adsorption of CO 2 hindered deoxygenation of the biochar with H 2 O. The in-situ IR characterization indicated that CO 2 presence suppressed decarbonylation reactions, retaining more oxygen species in form of C O, while it was the opposite in H 2 O. Additionally, activation with H 2 O formed numerous round-shape dents on surface of activated carbon, while the activation with CO 2 formed the characteristic round edges. The AC activated with H 2 O showed superior capability for adsorption of phenol than that activated with CO 2 or mixed H 2 O/CO 2. [Display omitted] • H 2 O is more effective than CO 2 for cracking, forming less activated carbon (AC). • Synergistic effect of CO 2 /H 2 O is insignificant as creating pores are not enhanced via cracking. • Competitive while preferable adsorption of CO 2 hinders activation with H 2 O. • CO 2 is not as active as H 2 O for cracking of C O in intermediates and for creating pores. • AC activated with H 2 O is superior for adsorbing phenol. [ABSTRACT FROM AUTHOR]

The leather industry converts waste from the meat industry (animal skin/hide) into a value-added product namely, leather. However, during this process large amount of both solid and liquid waste is generated. Efficient and eco-friendly methods are required for the utilization and safe disposal of these solid waste as it causes severe environmental concerns. In this review, we have focussed on the effective utilization of leather solid waste by converting it into activated carbon and finding various possible potential applications of this activated carbon. Compared to other biowaste-derived carbon (eggshell, banana peel, and orange peel) leather solid waste-derived carbon is rich in nitrogen content and has a high surface area, low cost, easy availability, and a simple synthesis method, hence these characteristics make leather solid waste-derived activated carbon a potential material for various applications such as energy storage, wastewater treatment, rubber sole preparation, dye adsorption, etc. Thus, the objective of this review is to compile the various strategies available for the effective utilization of leather solid waste as activated carbon for a sustainable future. The preparation of activated carbon from tannery solid waste using different activation methods, the properties of the prepared activated carbon, and their potential applications in various fields have been discussed in detail. [Display omitted] Synopsis: Leathers solid waste derived activated carbon for various potential application. • Leather solid waste-derived activated carbon has a high surface area of 2247 m2 g−1. • Leather solid waste-derived activated carbon is rich in nitrogen content. • The leather industry is producing huge amounts of solid and liquid waste. • Preparation of activated carbon from leather solid waste is simple and cost-effective. • Leather solid waste is an excellent starting material for activated carbon preparation. [ABSTRACT FROM AUTHOR]

In recent years, the growth of environmental protection policies has generated an increase in the global demand for activated carbon, the most widely used adsorbent in many industrial sectors, and with good prospects of implementation in others such as energy storage (electrodes in supercapacitors) and agriculture (fertilizer production). This demand is driving by the search for renewable, abundant and low-cost precursor materials, as an alternative to traditional fossil sources. This study investigates the production of activated carbon from barley straw using physical activation method with two different activating agents, carbon dioxide and steam. Experimental tests under different conditions at each stage of the process, carbonization and activation, have been conducted in order to maximize the BET surface area and microporosity of the final product. During the carbonization stage, temperature and heating rate have been found to be the most relevant factors, while activation temperature and hold time played this role during activation. Optimal conditions for the activation stage were obtained at 800 °C and a hold time of 1 h in the case of activation with carbon dioxide and at 700 °C and a hold time of 1 h in the case of activation with steam. The maximum BET surface area and micropore volume achieved by carbon dioxide activation were of 789 m 2 /g and 0.3268 cm 3 /g while for steam activation were 552 m 2 /g and 0.2304 cm 3 /g, which represent respectively an increase of more than 43% and 42% for the case of activation with carbon dioxide. [ABSTRACT FROM AUTHOR]

Two series of carbons were prepared from Agave americana fibres (A) mixed with mimosa Tannin (T) at different T to A weight ratios W  = 0/4; 1/3; 2/2; 3/1 and 4/0. The first series, CTAW, was produced by direct pyrolysis of the precursors (T, A, or blends) and the second one, CHTAW, was produced in two steps, hydrothermal carbonisation (HTC) and then pyrolysis. Materials from the CHTAW series presented higher surface areas, H/C atomic ratios and carbon yields than those of the CTAW series. CHTA2/2 was next activated with CO 2 during 1, 2 or 3 h. The appropriate selection of the synthesis conditions allowed obtaining high-surface area activated carbons (ACs) with similar carbon yields and average pore diameters as non-activated, low-surface area, carbon materials. CHTA2/2 activated for 2 h was tested for tetracycline (TC) adsorption, and the equilibrium was reached much faster than for a reference commercial AC due to the presence of macropores and mesopores provided by carbonised A. TC adsorption was spontaneous, and adsorption kinetics was adequately fitted by a pseudo-second-order model. TC adsorption essentially depends on surface area, and the results reported herein are in the range of those reported in the open literature. [ABSTRACT FROM AUTHOR]

In this work, hierarchically porous nitrogen-doped carbon materials (PNCs) are prepared through a physical activation process by using carbon dioxide as an activating agent and polyaniline as a precursor. The morphology, porous property, and chemical attribute of PNCs are investigated through different technical methods, such as scanning electron microscopy, nitrogen adsorption–desorption measurement, and X-ray photoelectron spectroscopy. The textural property of PNCs can be tuned by varying the activation time. PNCs display high specific surface areas (1030–2900 m 2 g −1 ) and large pore volumes (0.66–1.87 cm 3 g −1 ). When taken as adsorbents for gas capture, PNCs exhibit high carbon dioxide capture capacities (17.2–21.5 wt% at 273 K and 1.0 bar) and good selective adsorption of carbon dioxide over nitrogen or methane. The superior performance can be ascribed to the high porosity, suitable pore size, and the presence of nitrogen functional groups. [ABSTRACT FROM AUTHOR]

This work presents a first approach concerning the use of Tectona Grandis tree sawdust (from East Timor) for high activated carbon production, by physical activation with carbon dioxide at different temperatures. The activated carbons (AC) obtained exhibit a well-developed porous structure with a pore size distribution varying from micro to mesopores. Selected AC was successfully evaluated for pesticide removal, specific to 4-chloro-2-methylphenoxyacetic acid, from the liquid phase. The results presented are very promising, allowing to establish that Tectona Grandis sawdust is as an excellent precursor for the basic AC production and allow to expect good performance of theses adsorbents on the removal of a broad range of pollutants. It should also be noted that, this achievement is very relevant for developing countries, such East Timor, where Tectona Grandis sawdust is available and may constitute a source of income creating a handle to the technical and industrial development of this region. [ABSTRACT FROM AUTHOR]

A novel micro-mesoporous activated carbon (SBL AC-700) is synthesized from subabul (Leucaena leucocephala) sawdust waste by direct single-stage physical activation at 700 °C for 1 h for carbon capture applications. The synthesized AC is characterized to explore various physiochemical properties like elemental composition, surface morphology and crystallinity, presence of functional groups, surface area, pore size, and pore volume. Additionally, emphasis is given to exploring the thermophysical aspects of the novel AC, the literature regarding which is scarce in the open domain. The CO 2 adsorption study is carried out for a 0–1 bar pressure for temperatures ranging from 0 to 75 °C. The analysis revealed that the AC possesses a surface area of 590 m2/g and pore volume and width of 0.27 cm3/g and 1.85 nm, corresponding to a 70% microporosity with a well-developed porous structure. At 25 °C and 1 bar, a CO 2 uptake of 40.54 cm3/g is achieved, corresponding to an increment of 6–202% compared to other commercials, chemically and physically activated carbons. Moreover, SBL AC-700 has a thermal conductivity of 0.095 W/m K, 8–131% higher than other benchmarks ACs and much lower specific heat of 0.82 kJ/kg K corresponding to lesser regeneration energy requirements. Experimental data are fitted with various isotherm models, i.e., Langmuir, Freundlich, Sips, R–P, and Toth, out of which R–P and Toth models exhibit the best fit. In continuation, adsorption kinetics is studied to explore the dynamic performance of the SBL AC-700 by using Pseudo-first-order, Pseudo-second-order, Elovich, and intraparticle diffusion kinetic models. [Display omitted] • AC SBL AC-700 from subabul sawdust waste is synthesized successfully. • Novel AC is prepared by eco-friendly single-step direct CO 2 activation. • The ability of CO 2 uptake at 25 °C and 1 bar is 40.54 cm3/g. • SBL AC-700 has a thermal conductivity of 0.095 W/m K, 8–131% higher than other ACs. • Isotherm, kinetics, and thermodynamic modeling is done for the AC-CO 2 pair. [ABSTRACT FROM AUTHOR]

To improve the utilization value of coal resources and optimize the production process of coal-based activated carbon, an L 9 (34) orthogonal experiment was designed to study the comprehensive effects of the carbonization temperature, heating rate, activation time and activator type on the specific surface area and iodine value of activated carbon prepared by physical activation, as well as the surface chemical and crystal properties. The results showed that large amounts of C–H and oxygen functional groups from the raw materials were lost in the process of preparing the activated carbon, and CaCO 3 generated CaS through a two-step reaction. The raw materials were nonporous or macroporous materials, while the activated carbon developed a microporous structure. The same optimal working conditions were obtained when the iodine value and the specific surface area were used as the optimization target, as follows: 800 °C for carbonization, 10 °C/min for heating rate, 75 min for activation time, and steam + CO 2 as the activator. Finally, activated carbon was prepared under the optimal experimental conditions. The results showed that this activated carbon had the highest specific surface area and iodine value. In addition, the iodine value had a good linear relationship with the specific surface area. [Display omitted] • Time was the greatest factor, followed by the heating rate, temperature and activator. • Steam and CO 2 coactivation had a better activation effect. • The same results were obtained when the iodine value and BET were used as the optimization target. • Carbonization formed cracks and pits, and activation formed a developed pore structure. • CaCO 3 was converted into CaS during activated carbon preparation. [ABSTRACT FROM AUTHOR]

A wheat and hemp lignin, obtained from a soda pulping-precipitation process, was carbonized at 800 °C under N 2 atmosphere. The resulting carbon material was thermally activated under oxidative atmosphere at four different temperatures (150, 200, 300 and 350 °C). The materials prepared at higher activation temperatures (300 and 350 °C) have proven their potential in the elimination of 4-nitrophenol (4-NP) from aqueous model solutions (5 g L −1 ) when using catalytic wet peroxide oxidation (CWPO). In these conditions we were able to remove around 70% of 4-NP after 24 h, with an efficient H 2 O 2 decomposition, in experiments conducted at relatively mild operating conditions (atmospheric pressure, 50 °C, pH = 3, catalyst load = 2.5 g L −1 and [H 2 O 2 ] 0 = 17.8 g L −1 ). By increasing the working temperature to 80 °C, complete 4-NP removal was obtained within 48 h (against 93% 4-NP removal at 50 °C), with an efficiency of H 2 O 2 consumption of 70% and a significant mineralization (61%). On the other hand, the materials prepared at lower activation temperatures (150 and 200 °C), with higher basicity, promote the faster but inefficient H 2 O 2 decomposition, 4-NP removal being lower than 25% after 24 h at 50 °C in CWPO. This can be attributed to the formation of species other than HO radicals during H 2 O 2 decomposition, the recombination of the formed radicals into non-reactive species and a poor adsorption capacity. [ABSTRACT FROM AUTHOR]

Objective of this study was to investigate the mechanisms of 2,4-Dichlorophynoxy acetic acid (2,4-D) sorption on biochar in aqueous solutions. Sorption isotherm, kinetics, and desorption experiments were performed to identify the role of biochars’ feedstock and production conditions on 2,4-D sorption. Biochars were prepared from various green wastes (tea, burcucumber, and hardwood) at two pyrolytic temperatures (400 and 700 °C). The tea waste biochar produced at 700 °C was further activated with steam under a controlled flow. The sorption of 2,4-D was strongly dependent on the biochar properties such as specific surface area, surface functional groups, and microporosity. The steam activated biochar produced from tea waste showed the highest (58.8 mg g −1 ) 2,4-D sorption capacity, which was attributed to the high specific surface area (576 m 2 g −1 ). The mechanism of 2,4-D removal from aqueous solution by biochar is mainly attributed to the formation of heterogeneous sorption sites due to the steam activation. [ABSTRACT FROM AUTHOR]

Spouted bed technology was applied for the production of activated carbons from pistachio nut shells for the first time. Both of the pyrolysis and the gasification stages were carried out in the same spouted bed reactor. The produced bio-char and activated carbon were analyzed via scanning electron microscopy (SEM), Iodine number, and BET surface area. Temperature of 600 °C, hold time of 60 min, with particle size of 3.36–4.76 mm were the best conditions to produce a char with 430 m 2 g -1 . While the carbonization tests were carried out in a shorter time, BET surface area of the bio-chars were as large as those obtained in other reactors. BET surface area of the best produced activated carbon was 2596 m 2 g −1 with the burn-off 90 % at temperature 850 °C and 20 min activation. A comparison was made between the activated carbon characteristics produced in spouted bed reactor with those obtained previously in fixed bed reactors. According to the results, spouted bed reactors are suitable equipment for performing the both carbonization and gasification stages thanks to excellent mixing and high circulation rates of the materials inside a spouted bed. [ABSTRACT FROM AUTHOR]

Sulfur doped carbons were prepared through physical activation of sulfur containing resorcinol-formaldehyde resins. The sulfur doping level depended on the sulfuric acid addition amount during the synthesis of the resin, it was also found that the increase of sulfur content caused the enlargement of pores. The CO 2 adsorption tests were carried out at 273, 298 and 323 K, the influences of different activation conditions were investigated systematically. The adsorption amount at 1 bar reached 5.63, 3.69 and 2.33 mmol/g at 273, 298 and 323 K, respectively. The results also revealed that both sulfur doping and the porous characteristics had important influences on the CO 2 uptake. The sulfur doped carbon also showed a high initial isosteric adsorption heat of 48.8 kJ/mol, which is higher than that of undoped carbon and close to that of nitrogen doped carbon. It was concluded that sulfur doping could significantly enhance the interaction strength between CO 2 and carbon surface. [ABSTRACT FROM AUTHOR]

In present work, porous and electrically conductive activated carbon needle punched nonwoven web was produced by heating acrylic fibrous wastes under the layer of charcoal using novel single stage carbonization and physical activation. The influence of 800 °C, 1000 °C and 1200 °C carbonization temperature on physical and morphological properties of activated carbon web was studied from EDX, X-ray diffraction, SEM, X-ray tomography and BET analysis. Additionally, the electrical conductivity was also measured. At the end, the utility of prepared activated carbon web was investigated for electromagnetic shielding ability in high frequency (i.e. at 2.45 GHz) and low frequency regions (i.e. below 1.5 GHz) using waveguide method and coaxial transmission line method, respectively. The activated carbon web produced at 1200 °C showed maximum shielding effectiveness in both high and low frequency regions. For single layers of 1200 °C web, the electromagnetic shielding effectiveness of 63.26 dB, 66.75 dB, and 75.44 dB was found for respective frequencies of 600 MHz, 1 GHz, and 1.5 GHz. This behavior was attributed to the increased multiple internal reflections and stronger absorption of electromagnetic radiations in 1200 °C activated carbon web. [ABSTRACT FROM AUTHOR]

[Display omitted] • Free standing CO 2 activated electrode fabricated from carbonized palm tree fronds. • Enhanced specific capacitance after CO 2 activation. • CO 2 activated electrodes showed enhanced capacitive deionization of water. • Activated electrodes showed higher salt adsorption and quick regeneration. Water is essential for life and is one of the most important resources on Earth. However, pollution of water is a major concern, as it can have negative impact on both the environment and human health. Capacitive deionization (CDI) of water is being considered as one of the emerging water purification techniques for removal of ions and desalination. In this work, CDI performance of free-standing electrodes made of CO 2 activated carbon nanoparticles (AcNP) has been studied. These nanoparticles were produced from carbonized date palm fronds followed by ball milling. The AcNP were mixed with single wall carbon nanotubes and polymer binder; subsequently casted on glass substrate to fabricate highly conducting free-standing electrodes. The Brunauer–Emmett–Teller analysis of the AcNP in contrast to the un-activated carbon nanoparticles (UnAcNP) showed significant increase in the specific surface area, microspore and mesopore volume, total pore volume and average pore size. The specific capacitance values of the UnAcNP and AcNP electrodes were measured to be 8.75 and 50 Fg−1, respectively at a fixed scan rate of 5 mV/s. The electrochemical impedance spectroscopy measurement also showed that the CO 2 activation has reduced the charge transfer resistance of the fabricated electrode and enhanced its capacity. The CDI performance showed that the AcNP has a much higher salt absorption capacity of 6.30 mg/g in contrast to 0.032 mg/g for the UnAcNP sample. Moreover, average salt absorption rate was found to be 0.42 mg/g/min for AcNP in comparison to UnAcNP (0.0021 mg/g/min). The higher desalination capacity of the AcNP shows promising applications of plant-based carbon materials in water desalination and purification systems. [ABSTRACT FROM AUTHOR]

• Briquetting showed obvious influence on sludge pyrolysis. • Mechanical performance of cylindrical-shaped biochar decreased with the increase of activation temperature. • CO 2 -activated biochar showed higher adsorption capacity than steam-activated biochar. • Both physical and chemical adsorptions played important role in methylene blue adsorption. • The maximum adsorption capacity of 513.81 and 419.29 mg/g could be achieved by the CO 2 and steam-activated biochar. Sludge briquettes were prepared through briquetting (under the pressure of 25 MPa) of half-dried sewage sludge with moisture content of 30 wt%, and the cylindrical-shaped biochar (CSB) was obtained by subsequent pyrolysis (600 °C) and CO 2 /steam activation (650–950 °C). Briquetting process showed great influence on the pyrolysis of sewage sludge. The temperature range for the organic decomposition increased from 150 to 500 °C for the sludge without briquetting to 150–700 °C for the sludge briquette. The mechanical performance of CSBs was greatly influenced by activation temperature. The axial compressive strength of the CO 2 /steam activated CSBs were in the range of 17.8–22.2 kg·cm‑2 at the activation temperature of 650 °C and 800 °C, but dropped markedly when the activation temperature increased to 950 °C. CSBs were negatively charged and rich in oxygen/nitrogen-containing functional groups like –OH, –COOH, amines and amides, and the specific surface area of the optimal steam and CO 2 -activated CSB were 123.2 and 113.5 m2·g‑1, respectively. The prepared CSBs were applied in methylene blue (MB) adsorption, and the maximum adsorption capacity of 513.81 and 419.29 mg·g‑1 could be achieved by the CO 2 and steam-activated CSB, respectively. Both physical and chemical adsorptions played important role in the MB adsorption. Finally, the regeneration test showed that optimal samples of the CO 2 and steam-activated CSB still retained around 90 % of its original adsorption capacity after three cycles of adsorption-regeneration tests, but the mechanical performance dropped by 58.1 % and 47.8 %, respectively. [ABSTRACT FROM AUTHOR]

This study presents porous activated carbons, prepared by the physical activation of high-alkali Zhundong coal with CO 2 , H 2 O, or CO 2 /H 2 O, as supercapacitor electrode materials. The synergistic effect between CO 2 and H 2 O activation on the specific capacitance, morphology, pore and physicochemical structure, and supercapacitor performance of activated carbons was systematically investigated for the first time. A hierarchical porous structure is formed in carbon co-activated by CO 2 and H 2 O at 800 °C (TC C/H-800), which also has a rich graphite microcrystalline structure, long-range ordered graphite network, abundant oxygen- and nitrogen-containing functional groups and high char yield (about 70 wt%), all of which are desirable properties. Moreover, the TC C/H-800 electrode shows better electrochemical performance than electrodes based on carbon activated by CO 2 or H 2 O alone, and has an ideal coulombic efficiency (98.95% after 2000 cycles at 5 A g−1) and a good specific capacitance. The symmetrical TC C/H-800 supercapacitor reaches a 155.1 F g−1 specific capacitance at 0.5 A g−1. Meanwhile, its energy density is 21.54 Wh kg−1 at 500.00 W kg−1, with 92.97% of the initial discharge capacity retains after 10,000 cycles. Coal-based porous carbon activated by CO 2 and H 2 O synergistically has the advantages of low losses and low pollution. [Display omitted] • A synergistic effect occurs when CO 2 and H 2 O are co-activated for supercapacitors. • The mechanism of the synergistic activation of CO 2 and H 2 O is described. • The material performs better than other physical activation methods. • Co-activation of CO 2 and H 2 O has the advantages of low loss and low pollution. [ABSTRACT FROM AUTHOR]

The release of colored compounds containing wastewaters into the environment and surface water resources is known as a serious threat to public health and aquatic ecosystems. Accordingly, in the present study, cost-effective and efficient activated carbons (ACs) were prepared employing agricultural wastes (walnut shell) over a two-stage physical activation under CO2 at various activation temperature (700–1000 °C) and time (30–120 min). The prepared ACs were characterized by various analyses of SEM, XRD, FTIR, BET, and also their adsorption performance was checked via the measure of methylene blue (MB) number in order to determine selected activated carbon. According to the reported results, the AC produced at the activation temperature and time of 900 °C and 60 min, respectively, indicated better physicochemical properties and more favorable performance compared to others. The selected AC had the highest BET surface area (S BET) of 903.9 m2/g and the greatest adsorption capacity of 307.4 mg/g as the MB number. Furthermore, the adsorption capacity as iodine number and pH of point of zero charge (pH PZC) were reported to be 1150 mg/g and 4.6, respectively, for the selected AC. In the following, the performance of the selected AC was further evaluated as adsorption of synthetic (MB) and natural dyes from biologically treated wastewaters under different conditions. Maximum absorption capacity of the MB was obtained to be 307.45 mg/g at optimum conditions (the adsorbent dosage of 1 g/L, adsorbate concentration of 400 mg/L, contact time of 3 h, and agitation speed of 150 rpm). Moreover, the selected AC demonstrated appreciable performance at adsorbent dosage of 1 g/L and the contact time of 240 min using three biologically treated wastewaters. The highest adsorption capacity of 395.7 mg/g was obtained by the biologically treated baker's yeast wastewater as the adsorbate. The selected AC revealed the highest conformity with the Langmuir isotherm model (R2 = 0.9999) and the Pseudo-second-order kinetic model (R2 = 0.9994). • The walnut shell-based activated carbons (ACs) were physically synthesized. • The impact of activation temperature and time on the ACs properties was studied. • The AC performance was evaluated as natural dye removal from field samples. [ABSTRACT FROM AUTHOR]

Oil palm empty fruit bunches activated carbon of different parts (shaggy and core) were characterized as to convert waste of oil palm-based into value added products. Conventional step processes of physical activation were performed where activation was undertaken after the pyrolysis process (carbonization-activation process). The pyrolysis temperatures applied were 400, 450, and 500°C in inert condition under nitrogen flow. For the activation process, 600, 700, and 800°C with the presence of 15%, 60%, and 100% CO 2 and holding time of 30, 60, and 120 minutes were applied. Results showed that activation temperature, CO 2 percentage and holding time did dictate the changes of activated carbon yield, carbon content, and textural properties of the activated carbon core and shaggy EFB produces. The highest yield of activated carbon was obtained from 700°C (middle temperature), 60% CO 2 (middle percentage), and 30 mins holding time (shortest). However, the highest carbon content was detected from 600°C, 60% CO2, and 60 mins of activated carbon core EFB. The size of pore determined prove that the three parameter do not correlate with each other as the bigger pore diameter was derived from 700°C, 60% of CO 2 , and 60 mins holding time. Hence, the results revealed that there are differences of activated carbon properties when we separate EFB part into its core and shaggy. [ABSTRACT FROM AUTHOR]

Activated carbon was produced from palm kernel shell (PKS) and coconut shell (CS) through physical steam activation and chemical activation. The optimum activation temperature for physical activation is 800 o C and for chemical activation is 550 o C. The activated carbons produced also loaded with different metal oxides (BaO, MgO, CuO, TiO 2 and CeO 2 ). Both loaded and unloaded activated carbons are characterized using ultimate analysis, BET surface area measurement method, fourier transform infrared (FT-IR) analysis and x-ray diffraction (XRD) analysis. The BET surface area and pore volumes showed that the activated carbons prepared from PKS by chemical activation (PCAC) and from CS by physical activation (CPAC) were found to be much higher than others activated carbons. Hence, the metal oxides were loaded on these two activated carbons. The loaded and unloaded activated carbons produced will be tested for application of CO 2 adsorption from the simulated flue gas. [ABSTRACT FROM AUTHOR]

A technology for obtaining activated carbons by physical activation of hay with the use of microwave radiation is described. The effect of pyrolysis temperature on the textural parameters, acid–base character of the surface and sorption properties of activated carbons has been tested. The sorption properties of the activated carbons obtained were characterized by determination of nitrogen dioxide and hydrogen sulphide adsorption in dry and wet conditions. The final products were adsorbents of surface area ranging from 196 to 377 m 2 /g and pore volume from 0.14 to 0.24 cm 3 /g, showing basic character of the surface. The results obtained in our study have proved that suitable choice of the pyrolysis and activation procedure for hay with the use of microwave radiation permits production of adsorbents with good capacity toward toxic gases of acidic character. [ABSTRACT FROM AUTHOR]

Biochar is a carbon-rich material that is a co-product of the thermochemical conversion of biomass to liquid or gaseous products. A possible high-value application of biochar is the production of activated carbon. Biochar from biomass can be physically activated with a mild oxidant such as steam or carbon dioxide. A new model is proposed to describe the physical activation of pyrolytic biochar to activated carbon. The primary model assumption is that activation deepens but does not widen the pores. Measurements confirmed that the average pore diameter remained at about 1.9 nm. The new model successfully predicts the yield and specific surface area of activated carbon produced from olive residues. The pyrolysis conditions significantly impact the quality of the activated carbon. For example, biochar produced at higher heating rates contains more pores that, when cleared by physical activation with carbon dioxide, provide an activated carbon with a higher specific surface area, reaching about 1300 m2/g. [Display omitted] • New model for biochar physical activation to activated carbon. • Model assumes that physical activation deepens but does not widen the pores. • Model predicts yield and specific surface area of activated carbon. • Biochar production conditions affect the activated carbon specific area. [ABSTRACT FROM AUTHOR]

• Activated sludge char (ASC) was prepared through microwave-assisted one-step pyrolysis and physical activation. • Steam-ASC showed markedly higher H 2 S adsorption capacities (SHAC) than that of CO 2 -ASC. • A strong correlation between SHAC and the specific surface area of the steam-/CO 2 -ASC could be found. • Both physisorption and chemisorption played important roles in H 2 S adsorption by ASC. • Chemisorption of H 2 S could lead to the formation of sulfide, sulfate and sulfone. A one-step method which combined microwave pyrolysis and CO 2 /steam activation to prepare activated sludge char (ASC) for H 2 S adsorption was investigated. The adsorption properties of ASC prepared under different pyrolysis temperature, CO 2 /steam flow rate, residence time, and sludge moisture content were investigated by the characterization of proximate analysis, H 2 S adsorption kinetics, and iodine adsorption values (IAV) through orthogonal method. Results showed that steam-ASC showed better H 2 S adsorption performance than CO 2 -ASC at the pyrolysis/activation temperature of 500–700 °C. The optimal saturated H 2 S adsorption capacities (SHAC) of steam-ASC and CO 2 -ASC were 9.149 and 3.451 mg/g, respectively. There was a strong correlation (R 2 = 0.964) between SHAC and IAV of steam-/CO 2 -ASC. H 2 S adsorption related to pore diffusion, but less significant than physisorption and chemisorption. According to the H 2 S adsorption characteristics and textural characterization of the optimal steam-/CO 2 -ASC, the decrease of adsorption temperature, the increases of H 2 S concentration and ASC moisture content, and N 2 atmosphere (compared with air) could enhance SHAC. Sulfide, sulfate, and sulfone were formed in ASC during H 2 S adsorption, and the possible formation pathways were discussed. The results of this study indicated that one-step of simultaneous sludge pyrolysis and steam activation is a promising ASC preparation method for H 2 S adsorption. [Display omitted] [ABSTRACT FROM AUTHOR]

In this research, porous carbon rod-shaped has been successfully fabricated by using almond shell as a lignocellulosic starting material. The porous carbon rods were prepared using powdered almond shell plus chitosan as a binder that both of ingredients are agriculture and marine wastes. This homogeneous and readily moldable mixture was next forced through a stainless-steel cylindrical die using a uniaxial press at 30 °C while applying a pressure of 100 kPa during the 4 min of the run. The dried rods were later carbonized at different temperatures ranging from 500 to 800 °C and were then physically activated in an oxidizing gas flow (O 2 /Ar). This study well demonstrated that surface area increases with an increase in the carbonization temperature. While almond shell has low specific surface area and pore volume, the almond shell rods take advantage of an increased surface area from 43 to 67 m 2 /g and a pore volume of less than 0.1 cm 3 /g when the carbonization temperature increased from 500 to 800 °C. The surface area and pore volume of the physically activated rods have increased by 14% and 23%, respectively compared to non-activated ones. The stability of rods resulting from properties such as inheriting crack-free, crumbling and peeling off was tested using aqueous solution of methylene blue. By applying solid wastes, the porous carbon rod shaped in both liquid and gaseous phases, can be considered as a promising adsorbent and contributing to reach a clean environmental. The adsorption capacities of methylene blue and phenol demonstrated that porous carbon rod-shaped has a moderate adsorption capacity. [ABSTRACT FROM AUTHOR]

A review on the preparation of the activated carbon from agricultural waste material is presented. The physical properties such as proximate and ultimate analysis of agricultural waste material were reviewed. The chemical compositions such as cellulose, hemicelluloses and lignin contents were also discussed. The effects of various parameters on the preparation such as carbonization and activation temperature, time, types of activating agents and impregnation ratio were reviewed. Various physical and chemical processes for the activation of the agricultural residues and their effects on the textural properties such as surface area and pore volume were discussed. The low cost, renewable and relatively less expensive of the agricultural waste were found to be efficiently being converted into wealth. The uses of activated carbon derived from agricultural residues in many fields were evidently proven in the review. The reaction kinetic modeling on the pyrolysis and activation of agricultural wastes were also reviewed. [ABSTRACT FROM AUTHOR]