Methyl Red Adsorption on Biochar Obtained by Physical Activation of Caraway Seeds with Carbon Dioxide.

In this study carbon adsorbents were produced from caraway (Carum carvi L.) seeds, through direct and physical activation by carbon dioxide. The resulting biochar adsorbents were analyzed using low-temperature nitrogen adsorption-desorption isotherms and Boehm titration. Furthermore, the acid-base properties of the biochar samples obtained were examined, and the pH of their aqueous extracts was determined. The obtained adsorbents had a specific surface area ranging between 10 to 70 m2 /g. Resulting carbon materials exhibited a predominance of basic groups on their surfaces. The sorption capacities of methyl red for the samples varied from 3 to 20 mg/g. Conducted adsorption studies determined, that the adsorption kinetics of the dye on biochar materials followed a pseudo-second order model and the adsorption process was best described by the Freundlich isotherm, indicating the development of a multi-layer adsorbate on their surfaces. The effectiveness of adsorption in aqueous solutions of methyl red increased with the rise in process temperature. Moreover, the adsorption process was found to be spontaneous and endothermic based on thermodynamic investigations.

Insights into interoceptive and emotional processing: Lessons from studies on insular HD-tDCS.

Interoception, the processing of internal bodily signals, is proposed as the fundamental mechanism underlying emotional experiences. Interoceptive and emotional processing appear distorted in psychiatric disorders. However, our understanding of the neural structures involved in both processes remains limited. To explore the feasibility of enhancing interoception and emotion, we conducted two studies using high-definition transcranial direct current stimulation (HD-tDCS) applied to the right anterior insula. In study one, we compared the effects of anodal HD-tDCS and sham tDCS on interoceptive abilities (sensibility, confidence, accuracy, emotional evaluation) in 52 healthy subjects. Study two additionally included physical activation through ergometer cycling at the beginning of HD-tDCS and examined changes in interoceptive and emotional processing in 39 healthy adults. In both studies, HD-tDCS was applied in a single-blind cross-over online design with two separate sessions. Study one yielded no significant effects of HD-tDCS on interoceptive dimensions. In study two, significant improvements in interoceptive sensibility and confidence were observed over time with physical preactivation, while no differential effects were found between sham and insula stimulation. The expected enhancement of interoceptive and emotional processing following insula stimulation was not observed. We conclude that HD-tDCS targeting the insula does not consistently increase interoceptive or emotional variables. The observed increase in interoceptive sensibility may be attributed to the activation of the interoceptive network through physical activity or training effects. Future research on HD-tDCS involving interoceptive network structures could benefit from protocols targeting larger regions within the network, rather than focusing solely on insula stimulation.

Enhancing Interoceptive Abilities and Emotional Processing: Effects of HD-tDCS.

BACKGROUND: Interoception, the processing and integration of bodily signals, is crucial for emotional experiences and overall well-being. The interoceptive network, including the somatosensory cortices, has been recognized for its role in interoceptive and emotional processing. High-definition transcranial, direct-current stimulation (HD-tDCS) has been demonstrated to modulate brain activity in the primary somatosensory cortex (S1). Based on those findings, we hypothesized that anodal HD-tDCS over the right S1 would enhance interoceptive abilities and heighten emotional perception. METHODS: Thirty-six healthy adults participated in two sessions separated by at least one week. A 20-min HD-tDCS stimulation (2 mA), and a sham stimulation, were applied in randomized order. Both conditions involved pre-tDCS physical activation by ergometer cycling. Interoceptive abilities were assessed before and after both sessions using a heartbeat-perception and respiratory-load task. Emotional perception was measured using four matched international affective picture system (IAPS) picture sets presented randomly. RESULTS: Active HD-tDCS did not significantly improve interoceptive accuracy, interoceptive emotion evaluation, or interoceptive sensibility. However, a notable increase in cardiac interoceptive awareness was observed after active HD-tDCS. The expected enhancement of emotional processing was not observed. CONCLUSIONS: This study represents the first attempt to modulate interoceptive and emotional processing using HD-tDCS over S1. Although consistent enhancement was not observed, our findings provide insights into the modulation of interoceptive and emotional processes with HD-tDCS, suggesting avenues for further research. Further studies should consider the nuanced effects of stimulation techniques and the complex interplay between interoception and emotion.

Removal of Methyl Red from Aqueous Solution Using Biochar Derived from Fennel Seeds.

In this study, fennel (Foeniculum vulgare) seeds were used as a precursor to obtain carbon adsorbents through physical activation with carbon dioxide and chemical activation by impregnating the precursor with sodium carbonate. The physical activation involved the carbonization of the precursor at a temperature of 600 °C for 60 min and activation at a temperature of 800 °C for 30 min with carbon dioxide. Chemical activation included impregnation of the precursor with sodium carbonate at a mass ratio of a precursor to activator of 1:2. The mixture was activated in a nitrogen atmosphere with a flow rate at a temperature of 700 °C for 45 min. The resulting biochar samples were washed with 5% hydrochloric acid and subsequently rinsed with boiling distilled water. The biochar adsorbents were characterized using low-temperature nitrogen adsorption-desorption isotherms, Boehm titration, and pH measurements of their aqueous extracts. The specific surface area of the obtained adsorbents ranged from 89 to 345 m2/g. Biochar adsorbents exhibit a predominance of acidic groups over basic groups on their surfaces. The sorption capacities of the obtained samples towards an aqueous solution of methyl red range from 26 to 135 mg/g. Based on adsorption studies, it was found that the adsorption of the dye on the obtained biochar materials follows a pseudo-second-order model. The Freundlich isotherm best describes the studied process, indicating the formation of a multilayer of adsorbate on the adsorbent surface. The efficacy of adsorption in aqueous solutions of methyl red was found to increase with the elevation of the process temperature. Moreover, thermodynamic studies have shown that the adsorption process is spontaneous and endothermic. Consequently, this work provides a description of the physicochemical parameters of two biochars obtained by physical and chemical activation of a little-studied precursor-fennel seeds-and studies on their potential use as adsorbents for contaminants from the aqueous phase.

The Influence of Oxidation and Nitrogenation on the Physicochemical Properties and Sorption Capacity of Activated Biocarbons Prepared from the Elderberry Inflorescence.

The main objective of the study was to prepare a series of new activated biocarbons by means of physical and chemical activation of elderberry inflorescence. The influence of carbon matrix nitrogenation/oxidation on the physicochemical properties and sorption abilities of the carbonaceous materials was investigated. The impact of initial dye concentration, pH and temperature of the system on methylene blue and rhodamine B removal efficiency was checked. It was shown that activation of elderberry inflorescences with CO2 or H3PO4, and their further modification by introducing nitrogen or oxygen functional groups, allowed us obtain a wide range of materials that differ significantly in terms of the chemical nature of the surface, degree of specific surface development and the type of porous structure generated. The samples prepared by chemical activation proved to be very effective in terms of cationic dyes adsorption. The maximum sorption capacity toward methylene blue and rhodamine B reached the level of 277.8 and 98.1 mg/g, respectively. A better fit to the experimental data was achieved with a Langmuir isotherm than a Freundlich one. It was also shown that the efficiency of methylene blue and rhodamine B adsorption from aqueous solutions decreased with increasing temperature of the system.

Adsorption of Methyl Red and Methylene Blue on Carbon Bioadsorbents Obtained from Biogas Plant Waste Materials.

In this study, biocarbon was obtained from the waste material corn digest. Carbon adsorbents were obtained by physical activation of the precursor with CO2. Detailed physicochemical characterization of the biocarbon was carried out using low-temperature nitrogen adsorption/desorption, Boehm titration, zero-charge point (pHpzc) and iodine number. In addition, the sorption capacity of the biocarbon agents towards an aqueous solution of methylene blue and methyl red was determined, and the kinetics of the adsorption process were determined. The biocarbon adsorbents were characterized by an average developed specific surface area covering the range from 320 to 616 m2/g. The sorption capacity of the biocarbon adsorbents against methylene blue ranged from 40 mg/g to 146 mg/g, and for methyl red it covered the range from 31 mg/g to 113 mg/g. It was shown that the efficiency of organic dye removal by the obtained biocarbons depends on the initial concentration of the adsorbate solution, its mass, shaking rate, adsorbent-adsorbate contact time and temperature. The results obtained from the Langmuir and Freundlich kinetic models showed that the Langmuir model is the most suitable model for describing the adsorption of the studied pollutants on biocarbon. In turn, the adsorption kinetics of dyes is described according to the pseudo-second-order model. Adsorption studies also showed that as the process temperature increases, the removal efficiency of methylene blue and methyl red increases.

Assessment of the Porous Structure and Surface Chemistry of Activated Biocarbons Used for Methylene Blue Adsorption.

In the presented research, activated carbons from wheat bran were obtained as a result of pyrolysis and physical activation (CO2 or/and steam). In addition, the obtained materials were subjected to additional modification with superheated steam using the microwave radiation as an energy source. The detailed materials characterization was performed using low-temperature nitrogen adsorption/desorption, Raman spectroscopy, X-ray diffraction, thermal analysis (TG), Boehm's titration, point of zero charge (pHpzc), scanning electron microscopy (SEM) and FT-IR/ATR methods. Moreover, the sorption capacity towards methylene blue (MB) was determined. The activated carbons were characterized with a well-developed surface and pore structure (SBET = 339.6-594.0 m2/g; Vp = 0.157-0.356 cm3/g). Activation in the presence of steam and additional modification with microwave radiation resulted in much better development of the porous structure (SBET = 600.4 m2/g; Vp = 0.380 cm3/g). The materials were shown to possess amorphous structure and thermal stability up to the temperatures of ~450-500 °C. They have good adsorption capacity towards MB varying from 150 mg/g to 241 mg/g depending on activation manner. The adsorption can be described by the pseudo-second order model (R2 = 0.99) and fitted to the Langmuir isotherm.

Preparation of binder-less activated char briquettes from pyrolysis of sewage sludge for liquid-phase adsorption of methylene blue.

Binder-less activated char briquettes from sewage sludge were prepared and used for the liquid-phase adsorption of methylene blue. The properties of sludge char briquettes prepared under the different initial sludge moisture content, compression pressure, and heating rate were systematically investigated through the tests of thermogravimetric analysis (TGA), scanning electron microscopy (SEM), surface and mechanical properties, burn-off rates, methylene blue adsorption kinetics and isotherms. All of the prepared briquettes presented hierarchical structures and microporous/mesoporous characteristics, and the increase of initial sludge moisture content from 10 to 30 wt% resulted in a great increase of surface area (SBET), total pore volume (VT), apparent density, and a slight decrease of mechanical performance. The decrease of compression pressure markedly enhanced the equilibrium adsorption capacity (qe, exp), owing to the decreased diffusion resistance and blockage of diffusion pathways inside briquettes. In consideration of the mechanical performance and adsorption capacity, the optimum preparation condition was obtained at the initial moisture content of 30 wt%, compression pressure of 25 MPa, and heating rate of 10 °C/min, in which the axial compressive strength (ACS) and qe, exp of the prepared briquettes were as high as 22.2 ± 3.1 kg/m2 and 316.9 mg/g. The results also showed that the equilibrium adsorption data fit well into the pseudo-first order model system, and the adsorption isotherms followed the Langmuir isotherm model, suggesting that the adsorption process was attributed to physical adsorption, and was inclined to happen on the adsorption sites with the same energy level. Finally, the thermal regeneration tests demonstrated that the binder-less briquette had a good regeneration performance and was worthy of reusing for industrial applications.

A New Approach for Controlling Mesoporosity in Activated Carbon by the Consecutive Process of Air Oxidation, Thermal Destruction of Surface Functional Groups, and Carbon Activation (the OTA Method).

A new and simple method, based entirely on a physical approach, was proposed to produce activated carbon from longan fruit seed with controlled mesoporosity. This method, referred to as the OTA, consisted of three consecutive steps of (1) air oxidation of initial microporous activated carbon of about 30% char burn-off to introduce oxygen surface functional groups, (2) the thermal destruction of the functional groups by heating the oxidized carbon in a nitrogen atmosphere at a high temperature to increase the surface reactivity due to increased surface defects by bond disruption, and (3) the final reactivation of the resulting carbon in carbon dioxide. The formation of mesopores was achieved through the enlargement of the original micropores after heat treatment via the CO2 gasification, and at the same time new micropores were also produced, resulting in a larger increase in the percentage of mesopore volume and the total specific surface area, in comparison with the production of activated carbon by the conventional two-step activation method using the same activation time and temperature. For the activation temperatures of 850 and 900 °C and the activation time of up to 240 min, it was found that the porous properties of activated carbon increased with the increase in activation time and temperature for both preparation methods. A maximum volume of mesopores of 0.474 cm3/g, which accounts for 44.1% of the total pore volume, and a maximum BET surface area of 1773 m2/g was achieved using three cycles of the OTA method at the activation temperature of 850 °C and 60 min activation time for each preparation cycle. The two-step activation method yielded activated carbon with a maximum mesopore volume of 0.270 cm3/g (33.0% of total pore volume) and surface area of 1499 m2/g when the activation temperature of 900 °C and a comparable activation time of 240 min were employed. Production of activated carbon by the OTA method is superior to the two-step activation method for better and more precise control of mesopore development.

The Analysis of Pore Development and Formation of Surface Functional Groups in Bamboo-Based Activated Carbon during CO2 Activation.

Pore development and the formation of oxygen functional groups were studied for activated carbon prepared from bamboo (Bambusa bambos) using a two-step activation with CO2, as functions of carbonization temperature and activation conditions (time and temperature). Results show that activated carbon produced from bamboo contains mostly micropores in the pore size range of 0.65 to 1.4 nm. All porous properties of activated carbons increased with the increase in the activation temperature over the range from 850 to 950 °C, but decreased in the temperature range of 950 to 1000 °C, due principally to the merging of neighboring pores. The increase in the activation time also increased the porous properties linearly from 60 to 90 min, which then dropped from 90 to 120 min. It was found that the carbonization temperature played an important role in determining the number and distribution of active sites for CO2 gasification during the activation process. Empirical equations were proposed to conveniently predict all important porous properties of the prepared activated carbons in terms of carbonization temperature and activation conditions. Oxygen functional groups formed during the carbonization and activation steps of activated carbon synthesis and their contents were dependent on the preparation conditions employed. Using Boehm's titration technique, only phenolic and carboxylic groups were detected for the acid functional groups in both the chars and activated carbons in varying amounts. Empirical correlations were also developed to estimate the total contents of the acid and basic groups in activated carbons in terms of the carbonization temperature, activation time and temperature.

Potential Use of Waste Activated Sludge Hydrothermally Treated as a Renewable Fuel or Activated Carbon Precursor.

In this work, dewatered waste activated sludge (DWAS) was subjected to hydrothermal carbonization to obtain hydrochars that can be used as renewable solid fuels or activated carbon precursors. A central composite rotatable design was used to analyze the effect of temperature (140-220 °C) and reaction time (0.5-4 h) on the physicochemical properties of the products. The hydrochars exhibited increased heating values (up to 22.3 MJ/kg) and their air-activation provided carbons with a low BET area (100 m2/g). By contrast, chemical activation with K2CO3, KOH, FeCl3 and ZnCl2 gave carbons with a well-developed porous network (BET areas of 410-1030 m2/g) and substantial contents in mesopores (0.079-0.271 cm3/g) and micropores (0.136-0.398 cm3/g). The chemically activated carbons had a fairly good potential to adsorb emerging pollutants such as sulfamethoxazole, antipyrine and desipramine from the liquid phase. This was especially the case with KOH-activated hydrochars, which exhibited a maximum adsorption capacity of 412, 198 and 146 mg/g, respectively, for the previous pollutants.

High-performance of activated biocarbon based on agricultural biomass waste applied for 2,4-D herbicide removing from water: adsorption, kinetic and thermodynamic assessments.

Activated biocarbons were prepared using biomass wastes: sugarcane bagasse, coconut shell and endocarp of babassu coconut; as a renewable source of low-cost raw materials and without prior treatments. These activated biocarbons were characterized by textural analysis, solid-state 13C nuclear magnetic resonance spectroscopy, X-ray diffraction and scanning electronic microscopy. Textural analysis results revealed that those activated biocarbons were microporous, with specific surface area values of 547, 991 and 1,068 m2 g-1 from sugarcane bagasse, coconut shell and endocarp of babassu coconut, respectively. The innovation of this work was to evaluate which biomass residue was able to offer the best performance in removing 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from water by adsorption. Adsorption process of 2,4-D was investigated and the Langmuir and Redlich-Peterson models described best the adsorption process, with R2 values within 0.96-0.99. The 2,4-D removal performance were 97% and 99% for the coconut and babassu biocarbons, respectively. qM parameter values obtained from Langmuir model were 153.9, 233.0 and 235.5 mg g-1 using sugarcane bagasse, coconut shell and endocarp of babassu, respectively. In addition, the adsorption kinetics were described nicely by the second-order model and the Gibbs free energy parameter values were negative, pointing to a spontaneous adsorption, as well.

Stevia residue as new precursor of CO2-activated carbon: Optimization of preparation condition and adsorption study of triclosan.

The present work reports the preparation of CO2-activated carbon (AC) using Stevia rebaudiana (Bertoni) residue as a new carbon precursor. The experimental parameters were optimized via chemometrics tools to obtain an AC with high BET surface area (SBET). The found optimum condition was: activation temperature of 900 °C, CO2 flow of 165 cm3 g-1 and activation time of 60 min, providing an ACop with SBET of 874 m2 g-1. The ACop was characterized from several analytical techniques, which showed that it has heterogeneous morphology features and different surface chemical groups, predominating the acidic character. The adsorption performance of ACop for triclosan (TCS) removal from solution was investigated by kinetic, equilibrium and thermodynamic studies. The results showed that TCS adsorption process onto ACop is spontaneous and endothermic, wherein the mechanism occurs by different steps, which equally play important roles. Additionally, the monolayer adsorption capacity (Qm) was found to be 117.00 mg g-1.

Interdisciplinary care programme to improve self-management for cancer patients undergoing stem cell transplantation: a prospective non-randomised intervention study.

The purpose of this single-centre prospective non-randomised study was to evaluate the effectiveness of an interdisciplinary care programme to enhance self-management in patients with haematopoietic stem cell transplantation (HSCT). Patients undergoing HSCT, aged >14 years with informed consent were recruited (n = 79). Patients in the intervention group (IG) received standard care plus the SCION-HSCT intervention to counteract three problems after HSCT: muscle weakness, oral mucositis and malnutrition. Control group patients received standard care. Primary endpoint was global health-related quality of life (HRQoL) at discharge (EORTC QLQ C30 v. 3.0). Baseline characteristics were balanced between both groups, except physical performance (ECOG) being significantly lower for patients of the IG. At discharge, no group differences could be seen regarding HRQoL. Non-confirmatory post hoc analyses showed for patients of the IG a shorter duration of hospitalisation (MD -10.90; 95% CI -18.05 to -3.75) and increased activity during hospitalisation (MD 2.44; 95% CI 1.27-3.61). In conclusion, clinical effectiveness of the intervention could not be proven with respect to the aspired improvement of HRQoL. However, the nurse-led interdisciplinary caring programme could be carried out in every day ward routine. Further research should focus on working mechanisms of complex interventions aiming to improve HRQoL of patients undergoing HSCT.

Application of Activated Carbons Obtained from Polymer Waste for the Adsorption of Dyes from Aqueous Solutions.

Plastic waste disposal is a major environmental problem worldwide. One recycling method for polymeric materials is their conversion into carbon materials. Therefore, a process of obtaining activated carbons through the carbonization of waste CDs (as the selected carbon precursor) in an oxygen-free atmosphere, and then the physical activation of the obtained material with CO2, was developed. Dyes such as methylene blue (MB) and malachite green (MG) are commonly applied in industry, which contaminate the water environment to a large extent and have a harmful effect on living organisms; therefore, adsorption studies were carried out for these cationic dyes. The effects of the activation time on the physicochemical properties of the activated materials and the adsorption capacity of the dyes were investigated. The obtained microporous adsorbents were characterized by studying the porous structure based on low-temperature nitrogen adsorption/desorption, scanning electron microscopy (SEM-EDS), elemental analysis (CHNS), Raman spectroscopy, X-ray powder diffraction (XRD), infrared spectroscopy (ATR FT-IR), thermal analysis (TG, DTG, DTA), Boehm's titration method, and pHpzc (the point of zero charge) determination. Moreover, adsorption studies (equilibrium and kinetics) were carried out. The maximum adsorption capacities (qm exp) of MB and MG (349 mg g-1 and 274 mg g-1, respectively) were identified for the obtained material after 8 h of activation. The results show that the use of waste CDs as a carbon precursor facilitates the production of low-cost and effective adsorbents.

Removal of Organic Dyes, Polymers and Surfactants Using Carbonaceous Materials Derived from Walnut Shells.

A series of new granular carbonaceous adsorbents was prepared via single-stage physical and chemical activation of walnut shells. Their suitability for removing various types of organic pollutants (represented by dyes, surfactants and water-soluble polymers) from the liquid phase was assessed. The activation of the precursor was carried out with CO2 and H3PO4 using conventional heating. Activated biocarbons were characterized in terms of chemical composition, acidic-basic nature of the surface, textural and electrokinetic properties as well as thermal stability. Depending on the type of activating agent used during the activation procedure, the obtained biocarbons differed in terms of specific surface area (from 401 to 1361 m2/g) and the type of porous structure produced (microporosity contribution in the range of 45-75%). Adsorption tests proved that the effectiveness of removing organic pollutants from the liquid phase depended to a large extent on the type of prepared adsorbent as well as the chemical nature and the molecular size of the adsorbate used. The chemically activated sample showed greater removal efficiency in relation to all tested pollutants. Its maximum adsorption capacity for methylene blue, poly(acrylic acid), poly(ethylene glycol) and Triton X-100 reached the levels of 247.1, 680.9, 38.5 and 61.8 mg/g, respectively.

CO2 capture by microporous carbon based on Brazil nut shells.

The increase in burning, deforestation, and the exorbitant use of fossil fuels have contributed to the increase in carbon dioxide emissions; this gas is responsible for the intensification of the greenhouse effect and radical climate changes. In this way, it becomes necessary to find alternatives to reduce its emission. Porous carbon materials synthesized from lignocellulosic waste can be employed in technologies for capture and utilization of CO2 due to the advantages such as selectivity, low-cost synthesis, high surface area and pore volume, and thermal and chemical stability. Considering the availability of Brazil nut biomass residues in the Amazon region, this article proposes to synthesize activated carbon from the lignocellulosic residue using physical and chemical activation methods for CO2 capture. The analysis of N2 adsorption-desorption isotherms proves the predominance of a microporous structure when using the two synthesis methods described here. In physical activation, the surface area was 912 m2/g, while, in chemical activation, it was 1421 to 2730 m2/g. The sample treated via the chemical method (BS6-K1) showed better performance in CO2 adsorption, with adsorption results of 3.8 and 6 mmol/g of CO2 at 25 ℃ and 0 °C, respectively, at 101 kPa. CO2 adsorption capacity is due to the high volume of ultramicropores. It is believed that the microporous carbon material synthesized from Brazil nut residues is an alternative precursor for carbon materials used as CO2 capture.

Activation methods increase biochar's potential for heavy-metal adsorption and environmental remediation: A global meta-analysis.

Removal of heavy metals (HMs) by adsorption on biochar's surface has shown promising results in the remediation of contaminated soil and water. The adsorption capacity of biochar can be altered by pre- or post-pyrolysis activation; however, the effect of activation methods on biochar's adsorption capacity varies widely. Here, we conducted a meta-analysis to identify the most effective methods for activation to enhance HM removal by biochar using 321 paired observations from 50 published articles. Activation of biochar significantly improves the adsorption capacity and removal efficiency of HMs by 136 and 80 %, respectively. This study also attempts to find suitable feedstocks, pyrolysis conditions, and physicochemical properties of biochar for maximizing the effect of activation of biochar for HMs adsorption. Activation of agricultural wastes and under pyrolysis temperatures of 350-550 °C produces biochars that are the most effective for HM adsorption. Activation of biochars with a moderate particle size (0.25-0.80 mm), low N/C (<0.01) and H/C ratios (<0.03), and high surface area (> 100 m2 g-1) and pore volume (> 0.1 cm3 g-1) are the most desirable characteristics for enhancing HM adsorption. We conclude that pre-pyrolysis activation with metal salts/oxides was the most effective method of enhancing biochar's potential for adsorption and removal of a wide range of HMs. The results obtained from this study can be helpful in choosing appropriate methods of activations and the suitable choice of feedstocks and pyrolysis conditions. This will maximize HM adsorption on biochar surfaces, ultimately benefiting the remediation of contaminated environments.

Highly Porous Carbon Aerogels for High-Performance Supercapacitor Electrodes.

In recent years, porous carbon materials with high specific surface area and porosity have been developed to meet the commercial demands of supercapacitor applications. Carbon aerogels (CAs) with three-dimensional porous networks are promising materials for electrochemical energy storage applications. Physical activation using gaseous reagents provides controllable and eco-friendly processes due to homogeneous gas phase reaction and removal of unnecessary residue, whereas chemical activation produced wastes. In this work, we have prepared porous CAs activated by gaseous carbon dioxide, with efficient collisions between the carbon surface and the activating agent. Prepared CAs display botryoidal shapes resulting from aggregation of spherical carbon particles, whereas activated CAs (ACAs) display hollow space and irregular particles from activation reactions. ACAs have high specific surface areas (2503 m2 g-1) and large total pore volumes (1.604 cm3 g-1), which are key factors for achieving a high electrical double-layer capacitance. The present ACAs achieved a specific gravimetric capacitance of up to 89.1 F g-1 at a current density of 1 A g-1, along with a high capacitance retention of 93.2% after 3000 cycles.

Potential of agro-industrial residues from the Amazon region to produce activated carbon.

Thousands of tons of residual lignocellulosic biomass are produced and discarded by agroindustries in the Amazon. These biomasses could be harnessed and used in the preparation of activated carbon, in view of the growing demand for this product with high added value, however, little is known about their characteristics, in addition to their potential as precursors of activated carbon. Therefore, the aim of this work was to evaluate the potential of four different biomasses in the preparation and quality of activated carbon. Residues from the processing of the fruits of acai, babassu, Brazil nut, and oil palm were collected, characterized, carbonized, physically activated with CO2, and characterized. The contents of the total extractives, insoluble lignin, minerals, holocellulose, and elemental (CHNS-O) were analyzed. The surface area and surface morphology were determined from the AC produced, and adsorption tests for methylene blue and phenol were performed. The four biomasses showed potential for use in the preparation of CA; the residues presented high contents of lignin (21.83-55.76%) and carbon (46.49-53.79%). AC were predominantly microporous, although small mesopores could be observed. The AC had a surface area of 569.65-1101.26 m2 g-1, a high methylene blue (93-390 mg g-1), and phenol (159-595 mg g-1) adsorption capacities. Babassu-AC stood out compared to the AC of the other analyzed biomasses, reaching the best results.