Microporous carbon nanoflakes derived from biomass cork waste for CO2 capture

Conversion of waste cork to N-doped porous carbons by urea-assisted hydrothermal method for enhanced VOC capture

Converting waste resources into porous carbon for pollutants capture is an effective strategy to achieve the environmental goal of "treating waste with waste". Cork is an ideal precursor of porous carbons due to its ordered honeycomb-like cell structure and layered composition distribution. Herein, N-doped porous carbons (PCs) were prepared via two steps of urea-assisted hydrothermal carbonization and chemical activation to mitigate volatile organic compounds (VOCs) pollution. Results indicated that the obtained PC4-800 exhibited remarkable features for adsorption including high total pore volume (0.97 cm3/g) and specific surface area (1864.89 m2/g), as well as abundant N-containing functional groups. The excellent pore structure was primarily owing to the corrosion of the carbon matrix by the gas produced from the reaction of K2CO3 and N-containing functional groups. The adsorption results showed that the PC4-800 have an outstanding toluene adsorption capacity (867.03 mg/g) that outperforming majority of adsorbents previously reported. There are substantial pores in N-doped PCs with a pore width of 1.71-2.28 nm, which is 3 to 4 times the molecular dynamic diameter of toluene, and plays a crucial role in the absorption process. Moreover, the promotional influence of N-functional groups on the toluene adsorption process was verified through DFT calculation by Gaussian imitating, where N-6 generated π-electron enrichment sites on the surface of N-doped PCs, facilitating π-π dispersion with the benzene ring in toluene. This study provides a new strategy to convert waste cork into high-performance adsorbents for VOCs removal.

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.

Synthesis and applications of biomass-derived porous carbon materials in energy utilization and environmental remediation

Renewable biomass and its waste are considered among the most promising applications materials owing to the depletion of fossil fuel and concerns about environmental pollution. Notably, advanced porous carbon materials derived from carbon-rich biomass precursors exhibit controllable pore structures, large surface areas, natural microstructures, and abundant functional groups. In addition, these three-dimensional structures provide sufficient reaction sites and fascinating physicochemical properties that are conducive to heteroatom doping and functional modification. This review systematically summarizes the design methods and related mechanisms of biomass-derived porous carbon materials (BDPCMs), discusses how the synthesis conditions influence the structure and performance of the carbon material, and emphasizes the importance of its use in energy utilization and environmental remediation applications. Current BDPCMs challenges and future development strategies are finally discussed to provide systematic information for further synthesis and performance optimization, which are expected to lead to novel ideas for the future development of bio-based carbon materials.

Investigation of CO2 Adsorption on Avocado Stone-Derived Activated Carbon Obtained through NaOH Treatment

Activated carbons were prepared from avocado stone through NaOH activation and subsequent carbonization. The following textural parameters were achieved: specific surface area: 817-1172 m²/g, total pore volume: 0.538-0.691 cm³/g, micropore volume 0.259-0.375 cm³/g. The well-developed microporosity resulted in a good CO₂ adsorption value of 5.9 mmol/g at a temperature of 0 °C and 1 bar and selectivity over nitrogen for flue gas simulation. The activated carbons were investigated using nitrogen sorption at -196 °C, CO₂ sorption, X-ray diffraction, and SEM. It was found that the adsorption data were more in line with the Sips model. The isosteric heat of adsorption for the best sorbent was calculated. It was found that the isosteric heat of adsorption changed in the range of 25 to 40 kJ/mol depending on the surface coverage. The novelty of the work is the production of highly microporous activated carbons from avocado stones with high CO₂ adsorption. Before now, the activation of avocado stones using NaOH had never been described.

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.

Critical assessment of the performance of next-generation carbon-based adsorbents for CO2 capture focused on their structural properties

Carbon dioxide emissions and their sharply rising effect on global warming have encouraged research efforts to develop efficient technologies and materials for CO₂ capture. Post-combustion CO₂ capture by adsorption using solid materials is considered an attractive technology to achieve this goal. Templated materials, such as Zeolite Templated-Carbons and MOF-Derived Carbons, are considered as the next-generation carbon adsorbent materials, owing to their outstanding textural properties (high surface areas of ca. 4000 m² g^-1 and micropore volumes of ca. 1.7 cm³ g^-1) and their versatility for surface functionalization. These materials have demonstrated remarkable CO₂ adsorption capacities and CO₂/N₂ selectivities up to ca. 5 mmol g^-1 and 100, respectively, at 298 K and 1 bar, and low isosteric heat of adsorption at zero coverage of ca. 12 kJ mol^-1. Herein, a review of the advances in preparation of ZTCs and MDCs for CO₂ capture is presented, followed by a critical analysis of the effects of textural properties and surface functionality on CO₂ adsorption, including CO₂ uptake, CO₂/N₂ selectivity, and isosteric heat of adsorption. This analysis led to the introduction of a V_microx N-content factor to evaluate the interplay between N-content and textural properties to maximize the CO₂ uptake. Despite their promising performance in CO₂ uptake, further testing using mixtures and impurities, and studies on adsorbent regeneration, and cyclic operation are desirable to demonstrate the stability of the MDCs and ZTCs for large scale processes. In addition, advances in scale-up syntheses and their economics are needed.

Carbon Dioxide Capture through Physical and Chemical Adsorption Using Porous Carbon Materials: A Review

Due to rapid industrialization and urban development across the globe, the emission of carbon dioxide (CO2) has been significantly increased, resulting in adverse effects on the climate and ecosystems. In this regard, carbon capture and storage (CCS) is considered to be a promising technology in reducing atmospheric CO2 concentration. Among the CO2 capture technologies, adsorption has grabbed significant attention owing to its advantageous characteristics discovered in recent years. Porous carbon-based materials have emerged as one of the most versatile CO2 adsorbents. Numerous research activities have been conducted by synthesizing carbon-based adsorbents using different precursors to investigate their performances towards CCS. Additionally, amine-functionalized carbon-based adsorbents have exhibited remarkable potential for selective capturing of CO2 in the presence of other gases and humidity conditions. The present review describes the CO2 emission sources, health, and environmental impacts of CO2 towards the human beings, options for CCS, and different CO2 separation technologies. Apart from the above, different synthesis routes of carbon-based adsorbents using various precursors have been elucidated. The CO2 adsorption selectivity, capacity, and reusability of the current and applied carbon materials have also been summarized. Furthermore, the critical factors controlling the adsorption performance (e.g., the effect of textural and functional properties) are comprehensively discussed. Finally, the current challenges and future research directions have also been summarized.

Honeycomb-like activated carbon with microporous nanosheets structure prepared from waste biomass cork for highly efficient dye wastewater treatment

Cork, a porous biomass material, is consist of thin-walled hollow prismatic cells arranged into a compact and orderly honeycomb-like structure and could be applied as an adsorption material. Here, cork-activated carbons (CACs) with a fluffy honeycomb-like structure were synthesized by two-step pyrolysis with solid KOH chemical activation to rapidly and efficiently adsorb methylene blue (MB) (maximum wavelength: 664 nm). The structure, morphology and surface functional groups of the CACs were characterized using BET, SEM, and FTIR analysis. The results show that the CACs have a well-developed hierarchical porous structure and an ultra-high specific surface area of 2864.9 m²/g, which would facilitate the efficient diffusion and adsorption of MB molecules onto CACs. MB adsorption performance results show that the CACs have an outstanding maximum MB adsorption capacity (1103.68 mg/g) and fast adsorption kinetics (800 mg/L, 99.8% in 10 min), indicating that CACs possess significant advantages compared with most other adsorbents previously reported. The adsorption mechanism was studied by various kinetic models, isothermal models and thermodynamic models. Langmuir model is the most adapted to describe the adsorption process, indicating that the MB molecules are uniformly adsorbed on CAC's surface in a single layer. Moreover, MB adsorption by the CACs was an endothermic, spontaneous and randomly increasing adsorption. The regeneration test showed that the uptake of MB onto CACs can still reached 580 mg/g after three adsorption-desorption cycles, demonstrating the excellent reusability of CACs. The continuous adsorption performance of MB onto CACs was evaluated by a packed column test, which further confirmed its potential as an adsorbent for dye wastewater purification.

In-situ pyrolysis of Taihu blue algae biomass as appealing porous carbon adsorbent for CO2 capture: Role of the intrinsic N

An environment-friendly, cost-effective, and facile N self-doping porous carbon (NC) were prepared through in-situ pyrolysis of nitrogen abundant Taihu blue algae biomass for CO₂ uptake. It was found that the CO₂ sorption capacity of porous carbon prepared through carbonization at 800 °C with KOH activation (N-C-800) exhibit higher CO₂ uptake capacity of 4.88 (1 bar and 0 °C) and 2.76 mmol/g (1 bar and 25 °C) respectively, with the CO₂/N₂ selectivity of N-C-800 attaining 39.3. Besides, the adsorption capacity of N-C-800 remained stable even after 7 repeated cycles, with a slight loss of nearly 6%. Moreover, total graphitic N (N_tg) sources from the intrinsic N in N-C-800 is not only higher than other agro-sourced porous carbon materials, but the graphitic N performed a sound correlation with the CO₂ uptake capacity. Combining experiments with Density Functional Theory (DFT) calculations, higher adsorption energy of N-C-800 (-13.6 kJ/mol, comparing with -6.9 kJ/mol of N-free carbon framework) would render the efficient adsorption of CO₂ molecular onto the graphitic N site. The current study not only provides a new option for the reclamation of Taihu blue algae biomass as N self-doping material, but a proof-of-concept investigation employing NC materials as an appealing candidate for CO₂ capture.

From typical silicon-rich biomass to porous carbon-zeolite composite: A sustainable approach for efficient adsorption of CO2

Focusing on the high-valued utilization of the widespread silicon-rich waste biomass, a sustainable route by simultaneous utilization of carbon and silicon from silicon-rich rice husk was proposed in this work. Specifically, porous carbon-zeolite composite with hierarchical porous structure of micro/meso pores (carbon) and ultra-microporous pores (Na-X zeolite) was in situ prepared by a facile one-pot method. The obtained porous carbon-zeolite composite (PC₂-Z) had a higher yield of 67.66% compared to the porous carbon without silicon (PC₂) of 43.33%. Moreover, due to the high ultra-micropore volume of the PC₂-Z sample (up to 0.181 cm³/g), it exhibited high dynamic CO₂ adsorption capacity of 1.81 mmol/g and CO₂/N₂ selectivity of 9.80 (1 bar), which were higher than 1.67 mmol/g and 7.01 (1 bar) for PC₂, respectively. PC₂-Z also showed good regeneration efficiency above 99% after ten cycles. Furthermore, the economic and energy consumption assessment of this utilization route was conducted. Overall, a facile one-pot route was developed to prepare highly efficient composite absorbents from silicon-rich biomass, which can be widely used in different environmental applications.