Highly microporous activated carbons from biomass for CO 2 capture and effective micropores at different conditions

Morphological, sterical, and localized thermodynamics in the adsorption of CO2 by activated biocarbon from the white rot fungi Trametes gibbosa

The capture of CO2 by biochar has recently become one of the cornerstones of circular economy models for a sustainable society. In this work, we synthesized an activated biocarbon using Trametes gibbosa (BioACTG) in a one-step synthesis. We investigated CO2 adsorption mechanisms under five different temperatures using a statistical physics approach. The data was better represented by the multilayer model with two distinguished energies, providing more accurate values for the estimated parameters. According to the number of carbon dioxide molecules per site (n) and the densities of the receptor sites (Dzif), the tendency to form a second layer increased as the temperature increased. The adsorption of CO2 on BioACTG was exothermic (the values of Qasat = 15.5 mmol/g at 273 K decrease to 10.5 mmol/g at 353 K), and the temperature influenced CO2 as well as the morphological features of the process. A computational approach was used to investigate the electronic properties of the adsorbate, showing that its lowest unoccupied orbital (LUMO) heavily contributed to the high efficiency of the process which was ruled by pore diffusion mechanisms driven by energetic fluctuations. Other molecules present in CO2-rich mixtures were also investigated, showing that their concentration limited their competitiveness with CO2.

Crosslinked hydrogel-derived carbons activated by trace amounts of aqueous potassium carbonate for carbon dioxide adsorption

A new method for green synthesis of activated carbon using chitosan-based hydrogel precursors is reported. Chitosan-based hydrogel materials are designed to absorb trace amounts of non-toxic and non-corrosive activating agent K2CO3 from dilute aqueous solution. The K2CO3 impregnated hydrogels are further freeze-dried and converted to activated carbons with tuneable pore structure by a single-step pyrolysis. Activated carbon with highest pore volume of 0.76 cm3/g and surface area of 2026 m2/g is obtained by using K2CO3 as low as 0.23 g per gram of chitosan hydrogel. It can adsorb maximum CO2 of 4.2 mmol/g at 25 °C and 1 bar. This study demonstrates that biopolymer hydrogels impregnated with trace amounts of K2CO3 are excellent precursor materials to design high surface area carbons for CO2 capture.

Investigation of performance of potential adsorbents for emissions mitigation in a diesel generator

Globally, the release of greenhouse gases primarily carbon dioxide (CO2) emissions to our Earth's surface has climbed by  about 45% to its present atmospheric concentration rate of 420 parts per million (ppm) during the industrial era. An unprecedented rise in atmospheric CO2 concentration has been claimed to lead to significant factors such as global warming potential (GWP) and climate change effects.  An increase in atmospheric CO2 concentrations is  a  serious threat to the environment. Recent research efforts have focused on mitigating emissions from anthropogenic point sources. Adsorption-based post-combustion CO2 capture using solid adsorbents is the most effective and efficient method for mitigating gas adsorption in the exhaust system. In the current study, activated carbons are obtained from three potential biomass, namely, (i) coconut shell, (ii) rice husk, and (iii) eucalyptus wood, through a - single-stage activation method. The prepared activated carbon materials are analyzed using proximate and ultimate analyses. Further investigations are performed using different characterization techniques to ensure their adsorption efficiency. Adsorbents are packed one after the other in an in-house fabricated double adsorption chamber and coupled to the exhaust unit of a generator. Test experiments are conducted to examine adsorbents' capture efficiency in emissions mitigation. Adsorbents' adsorption parameters are evaluated in experimental investigations. At 2.5 bar and 50 °C, a maximum loading capacity of samples is achieved by 4.85 mmol/g, 4.58 mmol/g, and 5.96 mmol/g for coconut shell, rice husk, and eucalyptus wood adsorbents, respectively. With a post-combustion carbon adsorption chamber, CO2 and NO are captured about 40-64% and 38-58%, respectively, for all three adsorbents. The thermodynamic parameter of isosteric heat of adsorption value is below 40 kJ/mol, ensuring physisorption for all adsorbents.

Hydrothermal-enhanced pyrolysis for efficient NOX reduction and biochar valorization from food waste digestate

Pyrolysis has emerged as a promising technology for valorizing digestate resulting from the anaerobic digestion of food waste. However, the high NOX emissions during pyrolysis limit its application. This study proposed a hydrothermal coupled pyrolysis process to control the element transfer in digestate during biochar production. The efficient reduction of NOX emissions and the improvement of biochar adsorbability were realized. The hydrothermal process reduced the nitrogen content in solid digestate by 49.10 %-81.79 %, thus reducing the NOX precursors in syngas and the N-containing substances in bio-oil. Additionally, the specific surface area and the total pore volume of biochar were enhanced from 25 m2/g to 60-73 m2/g and 0.06 cm3/g to 0.12-0.14 cm3/g, respectively. More defects, oxygen-containing functional groups, and doped Ca on the biochar resulted in a high phosphate removal efficiency of 94 %. The proposed technology provides an efficient and environmentally friendly way to utilize the digestate.

Activated carbons-preparation, characterization and their application in CO2 capture: A review

In this paper, we provide a comprehensive review of the latest research trends in terms of the preparation, and characteristics of activated carbons regarding CO2 adsorption applications, with a special focus on future investigation paths. The reported current research trends are primarily closely related to the synthesis conditions (carbonization and physical or chemical activation process), to develop the microporosity and surface area, which are the most important factors affecting the effectiveness of adsorption. Furthermore, we emphasized the importance of regeneration techniques as a factor determining the actual technological and economic suitability of a given material for CO2 capture application. Consequently, this work provides a summary and potential directions for the development of activated carbons (AC). We attempt to create a thorough theoretical foundation for activated carbons while also focusing on identifying and specific statements of the most relevant ongoing research scope that might be advantageous to progress and pursue in the coming years.

Enhancement of CO2 adsorption on activated carbons produced from avocado seeds by combined solvothermal carbonization and thermal KOH activation

A new strategy for ultramicroporous activated carbons production from avocado seeds was developed. Combined solvothermal carbonization and thermal KOH activation were conducted. Solvothermal carbonizations were performed in a stainless-steel autoclave lined with Teflon at the temperature of 180 °C for 12 h in three different liquids (water, methanol, isopropyl alcohol). Chars were activated by KOH. The carbonization combined with activation took place in the oven at 850 °C for 1 h. All the samples were very good CO2 sorbents. The highest CO2 adsorption at a pressure of 1 bar was achieved for activated carbon produced using isopropanol. The best carbon dioxide adsorption was equal to 6.47 mmol/g at 0 °C and 4.35 mmol/g at 20 °C.

Effect of sucrose-based carbon foams as negative electrode additive on the performance of lead-acid batteries under high-rate partial-state-of-charge condition

Lead-acid batteries are noted for simple maintenance, long lifespan, stable quality, and high reliability, widely used in the field of energy storage. However, during the use of lead-acid batteries, the negative electrode is prone to irreversible sulfation, failing to meet the requirements of new applications such as maintenance-free hybrid vehicles and solar energy storage. In this study, in order to overcome the sulfation problem and improve the cycle life of lead-acid batteries, active carbon (AC) was selected as a foaming agent and foam fixing agent, and carbon foams (CF) with layered porous structure was prepared by mixing with molten sucrose. Sucrose as raw material is green and cheap, and the material preparation process is simple. The prepared CF material was then added as an additive to the negative electrode plate, and the electrochemical performance of the electrode plate and the battery was studied. The results proved that the addition of CF could effectively inhibit the sulfate formation of the negative electrode plate, with the 1.0 % CF negative electrode plate showing the best electrochemical performance. Specifically, according to the result of battery cycle testing, the simulated battery with CF had a cycle life of 3642 times, which was 2.87 times that of the blank group and 2.39 times of the AC group. Meanwhile, rate testing showed that the simulated battery with CF could maintain a high capacity even under high-rate discharge conditions.

Zeolites synthesis from phyllosilicates and their performance for CO2 adsorption

Five phyllosilicates (kaolinite, montmorillonite, saponite, sepiolite and palygorskite) have been selected as starting materials for the synthesis of zeolites. Among them, kaolinite and montmorillonite display the lowest Si/Al molar ratio leading to aluminosilicates with high crystallinity. Thus, the hydrothermal treatment under basic conditions forms 4A zeolite when kaolinite is used as starting material while 13X zeolite is obtained when montmorillonite is used as starting material. The microporosity and CO2-adsorption capacity of the prepared zeolites are directly related to its crystallinity. Thus, in order to improve it, raw phyllosilicates were subjected to a microwave-assisted treatment to remove undesired Mg or Fe-species, which have a negative effect in the assembling of the zeolites by hydrothermal basic conditions in a second step. The highest adsorption value was 3.85 mmol/g at 25 °C and 760 mm of Hg for Mont-A-B sample after the consecutive treatments.

Characterization of Bioadsorbents from Organic Municipal Waste

This article describes the production of bioadsorbents coming from seven different kinds of organic waste, produced in huge quantities in households, in a two-stage process. In order to determine the influence of the process parameters of carbonization (I stage) and activation with potassium hydroxide solution (II stage), the following analysis of the physicochemical properties of each sample at each stage processing was performed: base elemental composition, structure properties, surface morphology, thermal stability, crystallinity, and transmittance spectra characteristic bands. There was a lack of research on samples after each stage of waste processing in the literature. Addressing this allowed us to evaluate the transformative potential of each kind of organic waste included in the research and select the best waste for the production of bioadsorbents commonly used in environmental protection. Moreover, the results were compared with the ones in the literature. The utilization of particular kinds of organic waste seems to be especially important taking into account the strategy of waste management and sustainable development.

Upgrading recovered carbon black (rCB) from industrial-scale end-of-life tires (ELTs) pyrolysis to activated carbons: Material characterization and CO2 capture abilities

The current study presents for the first time how recovered carbon black (rCB) obtained directly from the industrial-scale end-of-life tires (ELTs) pyrolysis sector is applied as a precursor for activated carbons (ACs) with application in CO2 capture. The rCB shows better physical characteristics, including density and carbon structure, as well as chemical properties, such as a consistent composition and low impurity concentration, in comparison to the pyrolytic char. Potassium hydroxide and air in combination with heat treatment (500-900 °C) were applied as agents for the conventional chemical and physical activation of the material. The ACs were tested for their potential to capture CO2. Ultimate and proximate analysis, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), Raman spectroscopy, thermogravimetric analysis (TGA), and N2/CO2 gas adsorption/desorption isotherms were used as material characterization methods. Analysis revealed that KOH-activated carbon at 900 °C (AC-900K) exhibited the highest surface area and a pore volume that increased 6 and 3 times compared to pristine rCB. Moreover, the AC-900K possessed a well-developed dual porosity, corresponding to the 22% and 78% of micropore and mesopore volume, respectively. At 0 °C and 25 °C, AC-900K also showed a CO2 adsorption capacity equal to 30.90 cm3/g and 20.53 cm3/g at 1 bar, along with stable cyclic regeneration after 10 cycles. The high dependence of CO2 uptake on the micropore volume at width below 0.7-0.8 nm was identified. The selectivity towards CO2 in relation to N2 reached high values of 350.91 (CO2/N2 binary mixture) and 59.70 (15% CO2/85% N2).

Cellulose-Amine Porous Materials: The Effect of Activation Method on Structure, Textural Properties, CO2 Capture, and Recyclability

CO2 capture via physical adsorption on activated porous carbons represents a promising solution towards effective carbon emission mitigation. Additionally, production costs can be further decreased by utilising biomass as the main precursor and applying energy-efficient activation. In this work, we developed novel cellulose-based activated carbons modified with amines (diethylenetriamine (DETA), 1,2-bis(3-aminopropylamino)ethane (BAPE), and melamine (MELA)) with different numbers of nitrogen atoms as in situ N-doping precursors. We investigated the effect of hydrothermal and thermal activation on the development of their physicochemical properties, which significantly influence the resulting CO2 adsorption capacity. This process entailed an initial hydrothermal activation of biomass precursor and amines at 240 °C, resulting in C+DETA, C+BAPE and C+MELA materials. Thermal samples (C+DETA (P), C+BAPE (P), and C+MELA (P)) were synthesised from hydrothermal materials by subsequent KOH chemical activation and pyrolysis in an inert argon atmosphere. Their chemical and structural properties were characterised using elemental analysis (CHN), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). The calculated specific surface areas (SBET) for thermal products showed higher values (998 m2 g-1 for C+DETA (P), 1076 m2 g-1 for C+BAPE (P), and 1348 m2 g-1 for C+MELA (P)) compared to the hydrothermal products (769 m2 g-1 for C+DETA, 833 m2 g-1 for C+BAPE, and 1079 m2 g-1 for C+MELA). Carbon dioxide adsorption as measured by volumetric and gravimetric methods at 0 and 25 °C, respectively, showed the opposite trend, which can be attributed to the reduced content of primary adsorption sites in the form of amine groups in thermal products. N2 and CO2 adsorption measurements were carried out on hydrothermal (C) and pyrolysed cellulose (C (P)), which showed a several-fold reduction in adsorption properties compared to amine-modified materials. The recyclability of C+MELA, which showed the highest CO2 adsorption capacity (7.34 mmol g-1), was studied using argon purging and thermal regeneration over five adsorption/desorption cycles.

Chemical Activation of Banana Peel Waste-Derived Biochar Using KOH and Urea for CO2 Capture

This article describes the synthesis and characterization of porous carbon derived from waste banana peels by chemical activation with KOH or by activation KOH and urea modification. The as-synthesized samples were carefully characterized by various techniques. The prepared carbonaceous materials possess highly developed micropore and mesopore structures and high specific surface area (up to 2795 cm2/g for materials synthetized with KOH and 2718 cm2/g for activated carbons prepared with KOH and urea). A series of KOH-activated samples showed CO2 adsorption at 1 bar to 5.75 mmol/g at 0 °C and 3.74 mmol/g at 25 °C. The incorporation of nitrogen into the carbon sorbent structure increased the carbon uptake capacity of the resulting materials at 1 bar to 6.28 mmol/g and to 3.86 mmol/g at 0 °C and 25 °C, respectively. It was demonstrated that treatment with urea leads to a significant increase in nitrogen content and, consequently, CO2 adsorption, except for the material carbonized at 900 °C. At such a high temperature, almost complete decomposition of urea occurs. The results presented in this work could be used in the future for utilization of biomass such as banana peels as a low-cost adsorbent for CO2 capture, which could have a positive impact on the environment and human health protection.

Investigating the effectiveness of rice husk-derived low-cost activated carbon in removing environmental pollutants: a study of its characterization

The chemically activated biochar was produced through the pyrolysis of rice husk. Thermal gravimetric and elemental analysis were conducted to characterize the raw rice husk. The activated biochar product underwent evaluation through SEM, BET and, FT-IR analysis. This cost-effective activated carbon was utilized as an adsorbent for the elimination of environmental pollutants. At a temperature of 25 °C, the activated biochar product exhibited an impressive maximum CO2 adsorption capacity of 152 mg/g. This exceptional performance can be attributed to its notable surface area and porosity, measuring at 2,298 m2/g and 0.812 cm3/g, respectively. This product was also utilized to remove methyl red (MR) dye from an aqueous solution. The optimal parameters for the removal of MR were determined as follows: a pH of 6.0, a temperature of 25 °C, an initial MR concentration of 50 mg/L, and an adsorbent dosage of 0.4 g/L. At a duration of 140 min, the system attained its maximum equilibrium adsorption capacity, reaching a value of 62.06 mg/g. Furthermore, the calculated maximum MR removal efficiency stood at an impressive 99.31%. The thermodynamic studies demonstrated that the MR removal process was spontaneous, exothermic, and increased randomness. Kinetic studies suggested that the pseudo-second-order model can fit well.

Natural Products Derived Porous Carbons for CO2 Capture

As it is now established that global warming and climate change are a reality, international investments are pouring in and rightfully so for climate change mitigation. Carbon capture and separation (CCS) is therefore gaining paramount importance as it is considered one of the powerful solutions for global warming. Sorption on porous materials is a promising alternative to traditional carbon dioxide (CO2 ) capture technologies. Owing to their sustainable availability, economic viability, and important recyclability, natural products-derived porous carbons have emerged as favorable and competitive materials for CO2 sorption. Furthermore, the fabrication of high-quality value-added functional porous carbon-based materials using renewable precursors and waste materials is an environmentally friendly approach. This review provides crucial insights and analyses to enhance the understanding of the application of porous carbons in CO2 capture. Various methods for the synthesis of porous carbon, their structural characterization, and parameters that influence their sorption properties are discussed. The review also delves into the utilization of molecular dynamics (MD), Monte Carlo (MC), density functional theory (DFT), and machine learning techniques for simulating adsorption and validating experimental results. Lastly, the review provides future outlook and research directions for progressing the use of natural products-derived porous carbons for CO2 capture.

A novel approach to environmental pollution management/remediation techniques using derived advanced materials

The carbon dioxide (CO2) crisis is one of the world's most urgent issues. Meeting the worldwide targets set for CO2 capture and storage (CCS) is crucial. Because it may significantly reduce energy consumption compared to traditional amine-based adsorption capture, adsorption dependant CO2 capture is regarded as one of the most hopeful techniques in this paradigm. The expansion of unique, critical edge adsorbent materials has received most of the research attention to date, with the main objective of improving adsorption capacity and lifespan while lowering the temperature of adsorption, thereby lowering the energy demand of sorbent revival. There are specific materials needed for each step of the carbon cycle, including capture, regeneration, and conversion. The potential and efficiency of metal-organic frameworks (MOFs) in overcoming this obstacle have recently been proven through research. In this study, we pinpoint MOFs' precise structural and chemical characteristics that have contributed to their high capture capacity, effective regeneration and separation processes, and efficient catalytic conversions. As prospective materials for the next generation of energy storage and conversion applications, carbon-based compounds like graphene, carbon nanotubes, and fullerenes are receiving a lot of interest. Their distinctive physicochemical characteristics make them suitable for these popular study topics, including structural stability and flexibility, high porosity, and customizable physicochemical traits. It is possible to precisely design the interior of MOFs to include coordinatively unsaturated metal sites, certain heteroatoms, covalent functionalization, various building unit interactions, and integrated nanoscale metal catalysts. This is essential for the creation of MOFs with improved performance. Utilizing the accuracy of MOF chemistry, more complicated materials must be built to handle selectivity, capacity, and conversion all at once to achieve a comprehensive solution. This review summarizes, the most recent developments in adsorption-based CO2 combustion capture, the CO2 adsorption capacities of various classes of solid sorbents, and the significance of advanced carbon nanomaterials for environmental remediation and energy conversion. This review also addresses the difficulties and potential of developing carbon-based electrodes for energy conversion and storage applications.

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.

A comprehensive review of coconut-based porous materials for wastewater treatment and CO2 capture

For several decades, water pollution has become a major threat to aquatic and non-aquatic species, including humans. Different treatment techniques have already been proposed and implemented depending on wastewater characteristics. But many of these treatment techniques are expensive and inefficient. Adsorption-based techniques have shown impressive performances as an inexpensive treatment method previously. Coconut-based resources have been considered as adsorbents for wastewater treatment because of their abundance, low cost, and favorable surface properties. However, over the last decade, no comprehensive study has been published regarding biochar from coconut-based materials for wastewater treatment and CO2 capture. This review discusses biochar production technology for coconut-based materials, its modification and characterization, its utilization as an adsorbent for removing metals and organics from wastewater, and the associated removal mechanisms and the economic aspects of coconut-based biochar. Coconut-based materials are cheap and effective for removing various organic compounds such as pesticides, hormones, phenol, and phenolic compounds from solutions and capturing CO2 from air mainly through the pore-filling mechanism. Utilizing coconut-based biochars in a hybrid system that combines adsorption and other techniques, such as biotechnology or chemical coagulation is a promising way to increase their performance as an adsorbent in wastewater treatment.

Carbon Dioxide Capture by Adsorption in a Model Hydroxy-Modified Graphene Pore

Concerns regarding the environmental impact of increasing levels of anthropogenic carbon dioxide have led to a variety of studies examining solid surfaces for their ability to trap this greenhouse gas (GHG). Atmospheric or post-combustion carbon capture requires an efficient separation of carbon dioxide and nitrogen gas. We used the molecular mechanics MM3 parameter set (previously shown to provide good estimates of molecule-surface binding energies) to calculate theoretical surface binding energies for carbon dioxide ∆E(CO₂) and nitrogen ∆E(N₂). For efficient separation, differentiation of these two gas-surface adsorption energies is required. Examined structures based on graphene, carbon slit width pore, and carbon nanotube gave ∆E(CO₂) to ∆E(N₂) ratios of 1.7, 1.8, and 1.9, respectively. To enhance the CO₂ adsorption, we developed a model graphene surface pore lined with four hydroxy groups whose orientation allowed them to form hydrogen bonds with the oxygens in CO₂. Both the single-layer and double-layer versions of this pore gave significant enhancement in the ability to trap CO₂ preferentially to N₂. The two-layer version of this pore gave ∆E(CO₂) = 73 and ∆E(N₂) = 6.8 kJ/mol. The one- and two-layer versions of this novel pore averaged a ∆E(CO₂) to ∆E(N₂) ratio of 12.

Molecular Simulation of Argon Adsorption and Diffusion in a Microporous Carbon with Poroelastic Couplings

Neglected for a long time in molecular simulations of fluid adsorption and transport in microporous carbons, adsorption-induced deformations of the matrix have recently been shown to have important effects on both sorption isotherms and diffusion coefficients. Here we investigate in detail the behavior of a recently proposed 3D-connected mature kerogen model, as a generic model of aromatic microporous carbon with atomic H/C ∼ 0.5, in both chemical and mechanical equilibrium with argon at 243 K over an extended pressure range. We show that under these conditions the material exhibits some viscoelasticity, and simulations of hundreds of nanoseconds are required to accurately determine the equilibrium volumes and sorption loadings. We also show that neglecting matrix internal deformations and swelling can lead to underestimations of the loading by up to 19% (swelling only) and 28% (swelling and internal deformations). The volume of the matrix is shown to increase up to about 8% at the largest pressure considered (210 MPa), which induces an increase of about 33% of both pore volume and specific surface area via the creation of additional pores, yet does not significantly change the normalized pore size distribution. Volume swelling is also rationalized by using a well-known linearized microporomechanical model. Finally, we show that self-diffusivity decreases with applied pressure, following an almost perfectly linear evolution with the free volume. Quantitatively, neglecting swelling and internal deformations tends to reduce the computed self-diffusivities.

Activated biocarbons derived from molasses as new tailored CO2 adsorbents

An innovative and cost-effective method for enhancing CO₂ capture by modifying the textural properties of derived activated biocarbons was explored. A molasses solution was prepared with a sucrose concentration of 1 mol/dm³. A two-step synthesis process was involved, which includes the hydrothermal synthesis of spherical carbonaceous materials from molasses followed by chemical activation. The carbonaceous material to activation agent ratio was studied from 1 to 4. The CO₂ adsorption of all activated biocarbons was tested at 0, 10, and 20°C and a pressure of up to 1 bar. The results showed a significant correlation between CO₂ adsorption and the textural properties of the activated biocarbons. The activated biocarbon with the highest CO₂ adsorption of 7.1 mmol/g at 1 bar and 0°C was successfully produced by modifying with KOH. The selectivity of CO₂ over N₂ calculated on the basis of the Ideal Adsorbed Solution Theory was excellent (16.5). The Sips model was found to be the most suitable, and the isosteric heats of adsorption were also specified.

Design and Synthesis of N-Doped Porous Carbons for the Selective Carbon Dioxide Capture under Humid Flue Gas Conditions

The design of novel porous solid sorbents for carbon dioxide capture is critical in developing carbon capture and storage technology (CCS). We have synthesized a series of nitrogen-rich porous organic polymers (POPs) from crosslinking melamine and pyrrole monomers. The final polymer's nitrogen content was tuned by varying the melamine ratio compared to pyrrole. The resulting polymers were then pyrolyzed at 700 °C and 900 °C to produce high surface area nitrogen-doped porous carbons (NPCs) with different N/C ratios. The resulting NPCs showed good BET surface areas reaching 900 m² g^-1. Owing to the nitrogen-enriched skeleton and the micropore nature of the prepared NPCs, they exhibited CO₂ uptake capacities as high as 60 cm³ g^-1 at 273 K and 1 bar with significant CO₂/N₂ selectivity. The materials showed excellent and stable performance over five adsorption/desorption cycles in the dynamic separation of the ternary mixture of N₂/CO₂/H₂O. The method developed in this work and the synthesized NPCs' performance towards CO₂ capture highlight the unique properties of POPs as precursors for synthesizing nitrogen-doped porous carbons with a high nitrogen content and high yield.

Design of biomass-based N, S co-doped porous carbon via a straightforward post-treatment strategy for enhanced CO2 capture performance

Biomass-based adsorbents are considered to have great potential for CO₂ capture due to their low cost, high efficiency and exceptional sustainability. The aim of this work is to design a simple method for preparing biomass-based adsorbents with abundant active sites and large numbers of narrow micropores, so as to enhance CO₂ capture performance. Herein, N, S co-doped porous carbon (NSPC) was created utilizing walnut shell-based microporous carbon (WSMC) as the main framework and thiourea as N/S dopant through physical grinding and post-treatment process at a moderate temperature without any other reagents and steps. By altering the post-treatment parameters, a series of porous carbons with varying physico-chemical properties were prepared to discuss the roles of microporosity and N/S functional groups in CO₂ adsorption. NSPC with narrow micropore volume of 0.74 cm³ g^-1, N content of 4.89 % and S contents of 0.71 % demonstrated the highest CO₂ adsorption capacity of 7.26 (0 °C) and 5.51 mmol g^-1 (25 °C) at 1 bar. Meanwhile, a good selectivity of binary gas mixture CO₂/N₂ (15/85) of 29.72 and outstanding recyclability after ten cycles of almost 100 % adsorption capacity retention were achieved. The proposed post-treatment method was beneficial in maintaining the narrow micropores and forming N/S active sites, which together improve the CO₂ adsorption performance of NSPC. The novel NSPC displays amazing CO₂ adsorption characteristics, and the practical, affordable synthetic approach exhibits significant potential to produce highly effective CO₂ adsorbents on a broad scale.

Impact of KOH Activation on Rice Husk Derived Porous Activated Carbon for Carbon Capture at Flue Gas alike Temperatures with High CO2/N2 Selectivity

Metal-free porous activated carbon is an effective alternative to capture CO₂ due to its high surface area and textural advantages. In this regard, the present research work explores a suitable method for producing activated porous carbon with a high specific surface area through a two-step reaction involving rice husk and KOH at 600 °C for 1 h to capture CO₂. By varying the ratio of rice husk biomass to KOH, the texture and specific surface area of the activated porous carbon has been altered. A high surface area of ∼755 m²/g and a micropore volume of 0.243 cm³/g have been observed in the porous carbon produced with a KOH/biomass weight ratio of 3 (PAC2). Nitrogen contents in PAC1 and PAC2 were approximately 2.27 and 2.71 atom %, respectively. When compared with other materials, PAC2 has the highest CO₂ adsorption capability, reaching up to 3.13 mmol/g at 0 °C and 1.55 mmol/g at 50 °C. The isosteric heat of adsorption confirms the presence of both physisorption and chemisorption. The materials turn out to be highly CO₂/N₂ selective, with the highest selectivity of 131, proving that the samples are potential materials for capturing CO₂ from flue gases. These findings unequivocally show that porous activated carbon can be used to make CO₂ adsorption efficient, inexpensive, and, more importantly, extremely effective.

Carbon capture of biochar produced by microwave co-pyrolysis: adsorption capacity, kinetics, and benefits

Microwave co-pyrolysis of sewage sludge and leucaena wood was conducted to produce biochar as an adsorbent for CO₂ capture. Both microwave power level and blending ratio were crucial factors affecting the CO₂ adsorption capacity of biochar. At a power level of 150 W, the biochar produced by microwave co-pyrolysis of 25% sewage sludge and 75% leucaena wood possessed the highest CO₂ adsorption capacity. When the biochar was produced at 100 W, its CO₂ adsorption capacity was higher than predicted. Based on the proximate and elemental compositions of biochar, two equations were obtained to predict CO₂ adsorption capacity. The proximate composition of biochar can provide more precise prediction of CO₂ adsorption capacity than elemental composition according to the higher R² value provided. The blending ratio of 50% would be most appropriate to produce the biochar with acceptable reduction in CO₂ adsorption capacity and loss of quantity. The pseudo-second-order model would be most suitable for simulating the kinetic of CO₂ adsorption. The biochar produced from 1 metric tonne of sewage sludge and leucaena wood can offset carbon tax by 83 US dollars. Based on experimental results and findings, microwave co-pyrolysis should be a feasible technique to produce biochar possessing high CO₂ adsorption capacity.

Sewage sludge derived biochar for environmental improvement: Advances, challenges, and solutions

With the rapid growth yield of global sewage sludge, rational and effective treatment and disposal methods are becoming increasingly needed. Biochar preparation is an attractive option for sewage sludge treatment, the excellent physical and chemical properties of sludge derived biochar make it an attractive option for environmental improvement. Here, the current application state of sludge derived biochar was comprehensively reviewed, and the advances in the mechanism and capacity of sludge biochar in water contaminant removal, soil remediation, and carbon emission reduction were described, with particular attention to the key challenges involved, e.g., possible environmental risks and low efficiency. Several new strategies for overcoming sludge biochar application barriers to realize highly efficient environmental improvement were highlighted, including biochar modification, co-pyrolysis, feedstock selection and pretreatment. The insights offered in this review will facilitate further development of sewage sludge derived biochar, towards addressing the obstacles in its application in environmental improvement and global environmental crisis.

Valorization of Different Fractions from Butiá Pomace by Pyrolysis: H2 Generation and Use of the Biochars for CO2 Capture

This work valorizes butiá pomace (Butia capitata) using pyrolysis to prepare CO2 adsorbents. Different fractions of the pomace, like fibers, endocarps, almonds, and deoiled almonds, were characterized and later pyrolyzed at 700 °C. Gas, bio-oil, and biochar fractions were collected and characterized. The results revealed that biochar, bio-oil, and gas yields depended on the type of pomace fraction (fibers, endocarps, almonds, and deoiled almonds). The higher biochar yield was obtained by endocarps (31.9%wt.). Furthermore, the gas fraction generated at 700 °C presented an H2 content higher than 80%vol regardless of the butiá fraction used as raw material. The biochars presented specific surface areas reaching 220.4 m2 g-1. Additionally, the endocarp-derived biochar presented a CO2 adsorption capacity of 66.43 mg g-1 at 25 °C and 1 bar, showing that this material could be an effective adsorbent to capture this greenhouse gas. Moreover, this capacity was maintained for 5 cycles. Biochars produced from butiá precursors without activation resulted in a higher surface area and better performance than some activated carbons reported in the literature. The results highlighted that pyrolysis could provide a green solution for butiá agro-industrial wastes, generating H2 and an adsorbent for CO2.

A green approach towards sorption of CO2 on waste derived biochar

Carbon capture technologies have advanced in recent years to meet the ever-increasing quest to minimize excessive anthropogenic CO₂ emissions. The most promising option for CO₂ control has been identified as carbon capture and storage. Among the numerous sorbents, char generated from biomass thermal conversion has shown to be an efficient CO₂ adsorbent. This study examines various characteristics that can be used to increase the yield of biochar suited for carbon sequestration. This review gives recent research progress in the area, stressing the variations and consequences of various preparation processes on textural features such as surface area, pore size and sorption performance with respect to CO₂'s sorption capacity. The adjoining gaps discovered in this field have also been highlighted herewith, which will serve as future work possibility. It aims to analyse and describe the possibilities and potential of employing pristine and modified biochar as a medium of CO₂ capture. It also examines the parameters that influence biochar's CO₂ adsorption ability and pertinent challenges regarding the production of biochar-based CO₂ sorbent materials.

Multifunctional Loblolly Pine-Derived Superactivated Hydrochar: Effect of Hydrothermal Carbonization on Hydrogen and Electron Storage with Carbon Dioxide and Dye Removal

Pore modulation via hydrothermal carbonization (HTC) needs investigation due to its crucial effect on surface that influences its multirole utilization of such ultraporous sorbents in applications of energy storage- hydrogen and capacitive- as well as for pollutant abatement- carbon capture and dye removal. Hence, loblolly pine was hydrothermally carbonized followed by KOH activation to synthesize superactivated hydrochars (SAH). The resulting SAHs had specific surface area (SSA) 1462-1703 m²/g, total pore (TPV) and micropore volume (MPV) of 0.62-0.78 cm³/g and 0.33-0.49 cm³/g, respectively. The SAHs exhibit excellent multifunctional performance with remarkably high atmospheric CO₂ capture of 145.2 mg/g and high pressure cryogenic H₂ storage of 54.9 mg/g. The fabricated supercapacitor displayed substantial specific capacitance value of maximum 47.2 Fg^-1 at 1 A g^-1 in 6 M KOH and highest MB dye removal of 719.4 mg/g. Higher HTC temperature resulted in increased surface porosity as higher SSA, TPV benefitted H₂ storage and MB dye removal while superior MPV favored CO₂ capture. Moderate HTC temperature ensured higher mesopore-to-macropore volume ratio favoring electrochemical performance. Isotherm modelling of the adsorbates was compared using models: Langmuir, Freundlich, Langmuir- Freundlich and Temkin.

CO2 Capture over Activated Carbon Derived from Pulverized Semi-Coke

Pulverized semi-coke was employed as raw material to prepare activated carbon via steam activation and evaluated as a CO2 adsorbent. The effects of the preparation parameters including demineralization, activation temperature, activation time and steam flow on the structure and performance of the synthesized activated carbon were investigated. It was found that the microporous structure of activated carbon was greatly influenced by demineralization order and activation conditions. Demineralization before activation significantly increased the microporous structure of the activated carbon, which was ascribed to the removal of the inorganic fraction. Compared to the commercial activated carbon, activated carbon obtained by employing 150 mL/min steam to treat the demineralized pulverized semi-coke at 700 °C for 70 min possessed a higher CO2/N2 selectivity of 34.4 and good cyclic performance, which was due to its narrow microporosity of 0.55 nm. Furthermore, it was proved that a pore size of smaller than 1 nm is favorable for CO2 sorption.

Post-combustion CO2 capture via a variety of temperature ranges and material adsorption process: A review

Carbon dioxide (CO₂) emissions from fossil fuel combustion have been linked to increased average global temperatures, a global challenge for many decades. Mitigating CO₂ concentration in the atmosphere is a priority for the protection of the environment. This is a comparison of the three main technological categories available for CO₂ capture and storage. They include: oxy-fuel combustion, pre-combustion, and post-combustion. Each capture technology has inherent benefits and disadvantages in cost, implementation, and flexibility, but post-combustion CO₂ capture has demonstrated the most promising results in typical power plant configurations. This paper presents a review of different post-combustion CO₂ capture materials; solvents, membranes, and adsorbents, focusing on economical and environmentally safe low to high temperature solid adsorbents. Furthermore, the authors summarize the advantages and limitations of the materials investigated to provide insight into the challenges and opportunities currently facing the development of post-combustion CO₂ capture technologies. The solid sorbents currently available for CO₂ capture are also reviewed in detail, including physical and chemical properties, reactions, and current research efforts on improvement.

Microporous N-Doped Carbon Obtained from Salt Melt Pyrolysis of Chitosan toward Supercapacitor and Oxygen Reduction Catalysts

The direct carbonization of low-cost and abundant chitosan biopolymer in the presence of salt eutectics leads to highly microporous, N-doped nanostructures. The microporous structure is easily manufactured using eutectic mixture (ZnCl2-KCl) and chitosan. Potassium ions here can act as an intercalating agent, leading to the formation of lamellar carbon sheets, whereas zinc chloride generates significant porosity. Here, we present an efficient synthetic way for microporous carbon nanostructures production with a total nitrogen content of 8.7%. Preliminary studies were performed to show the possibility of the use of such material as a catalyst for supercapacitor and ORR. The textural properties enhanced capacitance, which stem from improved accessibility of previously blocked or inactive pores in the carbon structure, leading to the conclusion that porogen salts and molten salt strategies produce materials with tailor-made morphologies. The synergistic effect of the eutectic salt is seen in controlled porous structures and pore size, and the micropores boosting adsorption ability.

Advanced Material-oriented Biomass Precise Reconstruction: A Review on Porous Carbon with Inherited Natural Structure and Created Artificial Structure by Post-treatment

Manufacturing of porous carbon with biomass resources has been intensively investigated in recent decades. The diversity of biomass species and great variety of processing methods enable the structural richness of porous carbon as well as their wide applications. In this review, we specifically focused on the structure of biomass-derived porous carbon either inherited from natural biomass or created by post-treatment. The intrinsic structure of plant biomass was briefly introduced and the utilization of the unique structures at different length-scales were discussed. In term of post-treatment, the structural features of activated carbon by traditional physical and chemical activation were summarized and compared in a wide spectrum of biomass species, statistical analysis were performed to evaluate the effectiveness of different activation methods in creating specific pore structures. The similar pore structure of biomass-derived carbon and coal-derived carbon suggested a promising replacement with more sustainable biomass resources in producing porous carbon. In summary, using biomass as porous carbon precursor endows the flexibility of using its naturally patterned micro-structure and the tunability of controlled pore-creation by post treatment. This article is protected by copyright. All rights reserved.

Design and Preparation of Biomass-Derived Activated Carbon Loaded TiO2 Photocatalyst for Photocatalytic Degradation of Reactive Red 120 and Ofloxacin

The design and development of novel photocatalysts for treating toxic substances such as industrial waste, dyes, pesticides, and pharmaceutical wastes remain a challenging task even today. To this end, a biowaste pistachio-shell-derived activated carbon (AC) loaded TiO₂ (AC-TiO₂) nanocomposite was fabricated and effectively utilized towards the photocatalytic degradation of toxic azo dye Reactive Red 120 (RR 120) and ofloxacin (OFL) under UV-A light. The synthesized materials were characterized for their structural and surface morphology features through various spectroscopic and microscopic techniques, including high-resolution transmission electron microscope (HR-TEM), field emission scanning electron microscope (FE-SEM) along with energy dispersive spectra (EDS), diffuse reflectance spectra (DRS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, photoluminescence spectra (PL) and BET surface area measurements. AC-TiO₂ shows enhanced photocatalytic activity compared to bare TiO₂ due to the change in the bandgap energy and effective charge separation. The degradation rate of dyes was affected by the bandgap of the semiconductor, which was the result of the deposition weight percentage of AC onto the TiO₂. The presence of AC influences the photocatalytic activity of AC-TiO₂ composite towards RR 120 and OFL degradation. The presence of heteroatoms-enriched AC enhances the charge mobility and suppresses the electron-hole recombination in AC-TiO₂ composite, which enhances the photocatalytic activity of the composite. The hybrid material AC-TiO₂ composite displayed a higher photocatalytic activity against Reactive Red 120 and ofloxacin. The stability of the AC-TiO₂ was tested against RR 120 dye degradation with multiple runs. GC-MS analyzed the degradation intermediates, and a suitable degradation pathway was also proposed. These results demonstrate that AC-TiO₂ composite could be effectively used as an ecofriendly, cost-effective, stable, and highly efficient photocatalyst.

Production and characterization of bamboo-based activated carbon through single-step H3PO4 activation for CO2 capture

Bamboo is the fastest-growing plant and is abundant in Malaysia. It is employed as a starting material for activated carbon production and evaluated for its potential in CO₂ capture. A single-stage phosphoric acid (H₃PO₄) activation is adopted by varying the concentrations of H₃PO₄ between 50 and 70 wt.% at a constant temperature and holding time of 500°C and 120 min, respectively. The bamboo-based activated carbons are characterized in terms of product yield, surface area, and porosity, as well as surface chemistry properties. Referring to the experimental findings, the prepared activated carbons have BET surface area of >1000 m² g^-1, which implies the effectiveness of the single-stage H₃PO₄ activation. Furthermore, the prepared activated carbon via 50 wt.% H₃PO₄ activation shows the highest BET surface area and carbon dioxide (CO₂) adsorption capacity of 1.45 mmol g^-1 at 25°C/1 bar and 9.0 mmol g^-1 at 25°C/30 bar. With respect to both the characterization analysis and CO₂ adsorption performance, it is concluded that bamboo waste conversion to activated carbon through H₃PO₄ activation method is indeed promising.