High surface area porous carbon from cotton stalk agro-residue for CO2 adsorption and study of techno-economic viability of commercial production

Capturing CO2 through High Surface Area Activated Carbon Derived from Seed Shells of Balanites Aegyptiaca

Activated carbon is an attractive adsorbent for capturing various environmental pollutants, including CO2. Herein, an optimal synthesis and impressive performance of activated carbon made from Balanites aegyptiaca (Desert date) seed shells is reported, which is an abundant agricultural waste in the Middle East and Africa. The synthesis route involved pretreating the biomass with KOH and heating it under a suitable temperature profile. An optimal KOH-to-biomass ratio and multi-stage carbonization yielded activated carbon with a surface area above 3000 m2/g and an average pore size of nearly 4.1 nm. At 0 °C, this activated carbon exhibited CO2 uptake of 11.3 mmol g-1 that surpassed the uptake capacity of previously reported activated carbons. The selectivity towards CO2 was also found to be significantly higher compared to other gases. Thus, the present approach demonstrates an efficient conversion of agricultural waste to activated carbon for capturing CO2 and other environmental contaminants.

The Resource Utilization of Poplar Leaves for CO2 Adsorption

Every late autumn, fluttering poplar leaves scatter throughout the campus and city streets. In this work, poplar leaves were used as the raw material, while H3PO4 and KOH were used as activators and urea was used as the nitrogen source to prepare biomass based-activated carbons (ACs) to capture CO2. The pore structures, functional groups and morphology, and desorption performance of the prepared ACs were characterized; the CO2 adsorption, regeneration, and kinetics were also evaluated. The results showed that H3PO4 and urea obviously promoted the development of pore structures and pyrrole nitrogen (N-5), while KOH and urea were more conductive to the formation of hydroxyl (-OH) and ether (C-O) functional groups. At optimal operating conditions, the CO2 adsorption capacity of H3PO4- and KOH-activated poplar leaves after urea treatment reached 4.07 and 3.85 mmol/g, respectively, at room temperature; both showed stable regenerative behaviour after ten adsorption-desorption cycles.

Sustainable production of activated carbon from indigenous Acacia etbaica tree branches employing microwave induced and low temperature activation

Growing demand for activated carbon as an efficient and cost effective means of treating environmental pollution necessitates the economical production of good quality activated carbon. It is possible if it is done using low cost precursor materials and economical production methods. In the present study, two types of activated carbon were produced from Acacia etbaica tree branches while employing phosphoric acid as an activating agent. The first sample underwent carbonization by microwave irradiation (AC-MWI), while the second sample was carbonised in a furnace (AC-CA). Characterization of the formed activated carbon samples was executed by proximate and ultimate analysis adopting standard ASTM procedures. In addition to the elemental analysis, hardness, bulk density, pH, moisture and ash content, surface morphology, BET specific surface area, pore volume, volatile matter, fixed carbon, and iodine number were determined. Characteristics of both activated carbon samples were compared with the characteristics of activated carbon available in the literature and activated carbon available commercially in the market. The comparison revealed that the characteristics of the produced activated carbon samples was well comparable with the activated carbons produced from other species of Acacia tree and activated carbon available commercially. Results showed that the produced activated carbon demonstrated high activation efficiency of 39.8% and 48.7% for AC-CA and AC-MWI, respectively. Furthermore, AC-MWI has a BET specific surface area higher than that of AC-CA (1065 m2/g and 773 m2/g respectively). It was found that the BET specific surface area and pore volume of AC-MWI was higher by 37.7% and 12.7%, respectively, as compared to the values acquired for AC-CA. Additionally, activated carbon could be produced by microwave irradiation in about 48% less time as compared to traditional low temperature heating. The adsorption study of produced the activated carbon was performed utilising methylene blue (MB) as a contaminant, and the data was fitted to Langmuir, Freundlich, as well as Harkins-Jura isotherm showing comparable correlation. However, Freundlich isotherm was found to be the best to elaborate the MB adsorption on the produced activated carbon. The results confirmed the viability of microwave irradiation in producing good quality activated carbon from Acacia etbaica tree branches, which demonstrated comparable characteristics with commercially available activated carbon. The strategy could be beneficial for the country in order to produce high quality activated carbon and strengthen its self-reliance.

Development of Low-Cost Porous Carbons through Alkali Activation of Crop Waste for CO2 Capture

To achieve the "double carbon" (carbon peak and carbon neutrality) target, low-cost CO₂ capture at large CO₂ emission points is of great importance, during which the development of low-cost CO₂ sorbents will play a key role. Here, we chose peanut shells (P) from crop waste as the raw material and KOH and K₂CO₃ as activators to prepare porous carbons by a simple one-step activation method. Interestingly, the porous carbon showed a good adsorption capacity of 2.41 mmol/g for 15% CO₂ when the mass ratio of K₂CO₃ to P and the activation time were only 0.5 and 0.5 h, respectively, and the adsorption capacity remained at 98.76% after 10 adsorption-desorption cycle regenerations. The characterization results suggested that the activated peanut shell-based porous carbons were mainly microporous and partly mesoporous, and hydroxyl (O-H), ether (C-O), and pyrrolic nitrogen (N-5) functional groups that promoted CO₂ adsorption were formed during activation. In conclusion, KOH- and K₂CO₃-activated P, especially K₂CO₃-activated P, showed good CO₂ adsorption and regeneration performance. In addition, not only the use of a small amount of the activator but also the raw material of crop waste reduces the sorbent preparation costs and CO₂ capture costs.

The Capture and Transformation of Carbon Dioxide in Concrete: A Review

Concrete is one of the most commonly used engineering materials in the world. Carbonation of cement-based materials balances the CO2 emissions from the cement industry, which means that carbon neutrality in the cement industry can be achieved by the carbon sequestration ability of cement-based materials. Carbon dioxide is a symmetrical molecule and is difficult to separate. This work introduces the important significance of CO2 absorption by using cement-based materials, and summarizes the basic characteristics of carbonation of concrete, including the affected factors, mathematical modeling carbonization, and the method for detecting carbonation. From the perspective of carbon sequestration, it mainly goes through carbon capture and carbon storage. As the first stage of carbon sequestration, carbon capture is the premise of carbon sequestration and determines the maximum amount of carbon sequestration. Carbon sequestration with carbonization reaction as the main way has been studied a lot, but there is little attention to carbon capture performance. As an effective way to enhance the carbon sequestration capacity of cement-based materials, increasing the total amount of carbon sequestration can become a considerably important research direction.

Valorization of orange peel waste to tunable heteroatom-doped hydrochar-derived microporous carbons for selective CO2 adsorption and separation

Constrained by the extortionately expensive carbon sources, low carbon yields, inadequate adsorption capacities, and corrosive chemical activating agents, the commercialization of carbonaceous CO₂ adsorbents remains a challenging task. Herein, potassium oxalate (K₂C₂O₄), an activating agent with less corrosive properties, was used for the synthesis of activated carbons from inexhaustibly available "orange peel biowaste." For the first time, a comprehensive report is presented on the effect of hydrothermal treatment, hydrochar/K₂C₂O₄ ratio, activation temperature, and melamine modification in tailoring the porosity and surface functionalization of activated carbons. The optimized sample, OPMK-900, exhibited large specific surface area ~2130 m²/g; micropore volume ~1.1166 cm³/g, and a high pyrrolic nitrogen content (~ 46.1 %). Notably, melamine played the dual role as a promoter to K₂C₂O₄ porosity generation and a nitrogen dopant, which synergistically led to an efficient CO₂ uptake of ~6.67 mmol/g at 273 K/ 1 bar via micropore-filling mechanism and Lewis acid-base interactions. Moreover, remarkably high IAST CO₂/N₂ selectivity (105 at 273 K and 96 at 298 K) surpasses most of the biomass-derived carbons. Furthermore, the moderately high isosteric heat of adsorption (∆H_ads ~ 38.9 kJ/mol) revealed the physisorption mechanism of adsorption with a limited energy requirement for the regeneration of the spent adsorbents.

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.

From polyvinyl chloride waste to activated carbons: the role of occurring additives on porosity development and gas adsorption properties

Conversion of waste plastic to carbon materials has been considered as a potential approach for plastic recycling. In this study, polyvinyl chloride (PVC) plastic, one of the most widely used polymers, was used as a single precursor to prepare porous carbons via chemical activation process. The results showed that KOH activation followed by acid washing was an effective strategy to recover all calcium- and up to 92% of titanium-based compounds, the main metal additives in PVC, in the form of soluble salt. Those metal additives in PVC acted as a type of hard template, which benefit the development of microporosity and carbon dioxide (CO₂) adsorption. Textural characterization demonstrated that the prepared carbons possessed high surface area and pore volume of up to 2507 m²/g and 1.11 cm³/g, respectively. At 0 °C and 100 kPa, the PVC-derived carbon, PH_73, which has highest ultra-micropore volume among all samples, exhibited excellent CO₂ adsorption capacity of 6.90 mmol/g and high CO₂/N₂ selectivity. Converting the non-degradable PVC into high-quality porous carbon materials could be considered as a potential strategy for plastic waste recycling.

High-pressure carbon dioxide-hydrothermal enhance yield and methylene blue adsorption performance of banana pseudo-stem activated carbon

In order to reduce environmental risks and fungus disease spread of banana waste, the high-pressure CO₂-hydrothermal treatment was developed to produce hydrochar as a precursor of activated carbon from banana pseudo-stem(BP). SEM, BET, XRD, Raman and FTIR was used to investigate the influence mechanism of the high-pressure CO₂-hydrothermal pretreatment on the yield and methylene blue(MB) adsorption capacities of the activated carbon. The results show that although the adsorption capacities of BP after high-pressure CO₂-hydrothermal pretreatment(BPx) is decrease due to decrease of oxygen-containing functional group and flatter spatial structure, that of BPx after KOH activation(BPx-A) significantly increase and is higher than that of BP by direct KOH activation(BP-A). Because BP-A presents honeycomb porous microstructures and has a higher mesoporous structure(138-472 m²/g), plentiful active sites and rich the abundant influential adsorption group of MB adsorption. In addition, compared to BP-A(0.68%), the total yield of BPx-A(2.42-9.11%) is 356-1340%.

Chemical Activation of Lignocellulosic Precursors and Residues: What Else to Consider?

This paper provides the basis for understanding the preparation and properties of an old, but advanced material: activated carbon. The activated carbons discussed herein are obtained from "green" precursors: biomass residues. Accordingly, the present study starts analyzing the components of biomass residues, such as cellulose, hemicellulose, and lignin, and the features that make them suitable raw materials for preparing activated carbons. The physicochemical transformations of these components during their heat treatment that lead to the development of a carbonized material, a biochar, are also considered. The influence of the chemical activation experimental conditions on the yield and porosity development of the final activated carbons are revised as well, and compared with those for physical activation, highlighting the physicochemical interactions between the activating agents and the lignocellulosic components. This review incorporates a comprehensive discussion about the surface chemistry that can be developed as a result of chemical activation and compiles some results related to the mechanical properties and conformation of activated carbons, scarcely analyzed in most published papers. Finally, economic, and environmental issues involved in the large-scale preparation of activated carbons by chemical activation of lignocellulosic precursors are commented on as well.

Optimizing the Properties of Hybrids Based on Graphene Oxide for Carbon Dioxide Capture

The reduction of CO2 emissions and its elimination from the atmosphere has become one of the major problems worldwide, since CO2 is the main cause of the greenhouse effect and climate change. In recent years, a great number of carbonaceous materials that can be used as CO2 adsorbents have been synthesized. The strategy is usually to synthesize the materials and determine their adsorption capacity without studying previously the factors that influence this capacity. In this work, different properties of the adsorbents are analyzed to study their influence on the CO2 adsorption capacity. For this purpose, 10 adsorbents have been synthesized using different strategies and characterized with X-ray photoelectron spectroscopy, X-ray diffraction, and micro-Raman spectroscopy. The percentage of sp2 carbons, the position of the D + D' peak of the second-order Raman spectrum, the micropore volume, and the grain size of the C sp2 domains have been related to the amount of CO2 adsorbed by the adsorbents. The results confirm a linear relationship between the volume of the micropores and the CO2 uptake and it proves that CO2 retention is favored in those materials that, in addition to having a high volume of micropores, also have low grain size of C.

The development of activated carbon from corncob for CO2 capture

The accumulation and incineration of crop waste pollutes the environment and releases a large amount of CO2.

A review on application of activated carbons for carbon dioxide capture: present performance, preparation, and surface modification for further improvement

The atmosphere security and regulation of climate change are being continuously highlighted as a pressing issue. The crisis of climate change owing to the anthropogenic carbon dioxide emission has led many governments at federal and provincial levels to promulgate policies to address this concern. Among them is regulating the carbon dioxide emission from major industrial sources such as power plants, petrochemical industries, cement plants, and other industries that depend on the combustion of fossil fuels for energy to operate. In view of this, various CO2 capture and sequestration technologies have been investigated and presented. From this review, adsorption of CO2 on porous solid materials has been gaining increasing attention due to its cost-effectiveness, ease of application, and comparably low energy demand. Despite the myriad of advanced materials such as zeolites, carbons-based, metal-organic frameworks, mesoporous silicas, and polymers being researched, research on activated carbons (ACs) continue to be in the mainstream. Therefore, this review is endeavored to elucidate the adsorption properties of CO2 on activated carbons derived from different sources. Selective adsorption based on pore size/shape and surface chemistry is investigated. Accordingly, the effect of surface modifications of the ACs with NH3, amines, and metal oxides on adsorption performance toward CO2 is evaluated. The adsorption performance of the activated carbons under humid conditions is also reviewed. Finally, activated carbon-based composite has been surveyed and recommended as a feasible strategy to improve AC adsorption properties toward CO2. The activated carbon surface in the graphical abstract is nitrogen rich modified using ammonia through thermal treatment. The values of CO2 emissions by sources are taken from (Yoro and Daramola 2020).