Nitrogen/Oxygen Co-Doped Porous Carbon Derived from Biomass for Low-Pressure CO2 Capture

Leveraging experimental and computational tools for advancing carbon capture adsorbents research

CO2 emissions have been steadily increasing and have been a major contributor for climate change compelling nations to take decisive action fast. The average global temperature could reach 1.5 °C by 2035 which could cause a significant impact on the environment, if the emissions are left unchecked. Several strategies have been explored of which carbon capture is considered the most suitable for faster deployment. Among different carbon capture solutions, adsorption is considered both practical and sustainable for scale-up. But the development of adsorbents that can exhibit satisfactory performance is typically done through the experimental approach. This hit and trial method is costly and time consuming and often success is not guaranteed. Machine learning (ML) and other computational tools offer an alternate to this approach and is accessible to everyone. Often, the research towards materials focuses on maximizing its performance under simulated conditions. The aim of this study is to present a holistic view on progress in material research for carbon capture and the various tools available in this regard. Thus, in this review, we first present a context on the workflow for carbon capture material development before providing various machine learning and computational tools available to support researchers at each stage of the process. The most popular application of ML models is for predicting material performance and recommends that ML approaches can be utilized wherever possible so that experimentations can be focused on the later stages of the research and development.

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.

Conversion mechanism of selenium on activated carbon surface: Experimental and density functional theory study

The mechanism of SeO2 capture by activated carbon (AC) was explored via combining experiments with density functional theory (DFT). Adsorption experiments confirmed that after mass loss coefficient correction of AC, the selenium capture capacity of AC reached 7.76 mg/g at 350 °C. AC reached a saturated selenium removal capacity of 9.93 mg/g at 50 min. The weight loss curve recorded the temperature window of selenium desorption on AC surface at about 305 °C. The XPS spectrum revealed that the decomposition and reduction behavior of SeO2 on the AC surface promoted the existence of selenium in the form of Se0. DFT calculations showed that SeO2 was chemically adsorbed on the typical Armchair and Zigzag surfaces of AC, and the adsorption energies of the most stable structures were - 89.77 and - 235.12 kcal/mol, respectively. The effect of temperature on selenium capture via AC was studied by thermodynamic and kinetic analysis. Temperature increase promoted the decomposition and reduction of SeO2 on the AC surface. Kinetic analysis further confirmed that the transformation of Se4+→Se0 was more dominated by decomposition behavior. A part of SeO2 in the gas phase was reduced to Se0 by CO and enriched on AC as elemental selenium.

Biomass-based adsorbents for post-combustion CO2 capture: Preparation, performances, modeling, and assessment

The adsorbents are critical carriers in the process of adsorption-based post-combustion CO₂ capture. Biomass-based adsorbents (BAs) are considered to have great potential because of their high efficiency, low cost, and good sustainability. To understand the methods, theories, and technologies of BAs-based CO₂ capture, this work analyzes their preparation and activation/modification, influencing factors, mechanisms, thermodynamics/kinetics, regeneration and cycle performances, and the pathway to application. It is found that BAs prepared by pyrolysis, chemical activation, and modification with dual heteroatoms are more conducive to improving adsorption sites. CO₂ adsorption capacity positively correlates with elemental C and fixed carbon of feedstocks, but negatively with moisture. The BAs prepared at 550-600 °C have high performance. The specific surface area (SSA) increases as the preparation time increases by 9.4%-93.4%. The adsorption capacity is positively correlated to the SSA (R = 0.880) and microporous volume (R = 0.773). Moreover, it decreases linearly with increasing operating temperature with the slope of -0.6 mmol/(g·°C) but increases exponentially with increasing operating pressure and CO₂ concentration with the power of 0.824. The adsorption process includes physical and/or physicochemical adsorption. Freundlich isotherm equation and pseudo-second-order model characterize the adsorption thermodynamics and kinetics more effectively with R² = 0.985-1.000 and R² = 0.894-1.000. The quantum chemistry indicates that most BAs modified with non-metallic belong to physisorption. The regeneration of BAs has low energy consumption (<3.44 MJ/kg CO₂) and loss rate (<8%). Furthermore, the technical pathway is proposed for application. Finally, the challenges are also presented to facilitate the development of BAs-CO₂ capture.

Oxygen and nitrogen enriched pectin-derived micro-meso porous carbon for CO2 uptake

Oxygen and nitrogen enriched micro-meso porous carbon powders have been prepared from pectin and melamine as oxygen and nitrogen containing organic precursors, respectively. The synthesis process has been performed following a solvothermal approach in an alkaline solution during which Pluronic F127 was added to the solution as the soft template. Following the solvothermal treatment, the carbonization process has been performed at 700, 850 and 950 °C. The synthesized porous carbons have been characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms and Fourier transform infrared spectroscopy (FTIR). The surface area of 499.5 m2 g-1, total pore volume of 0.35 cm3 g-1, and a high nitrogen and oxygen content of 9.3 and 29.1 wt% are displayed for the fine sample. The optimal porous carbon had CO2 adsorption of up to 3.1 mmol g-1 at 273 K at 1 bar owing to abundant basic nitrogen-containing functionalities and the valuable micro-meso porous structure. Despite the absence of any reagent and also having a relatively moderate specific surface area, compared to similar materials, a very high ratio of adsorption capacity to specific surface area (6.2 μmol m-2) was observed. The Elovich kinetic model was found to be the best and the physisorption process was reported.

Adsorption of Hg(II) in an Aqueous Solution by Activated Carbon Prepared from Rice Husk Using KOH Activation

With the development of industry, the discharge of wastewater containing mercury ions posed a serious threat to human health. Using biomass waste as an adsorbent to treat wastewater containing mercury ions was a better way due to its positive impacts on the environment and resource saving. In this research, activated carbon (AC) was prepared from rice husk (RH) by the KOH chemical activation method. The characterization results of scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) showed that rice husk-activated carbon (RHAC) had good pore structure and oxygen-containing functional groups. The influences of contact time, initial concentration of Hg(II), adsorbent dosage, pH, and ionic strength on mercury ion removal were investigated. The Langmuir model was most suitable for the adsorption isotherm of RHAC, and its maximum adsorption capacity for Hg(II) was 55.87 mg/g. RHAC still had a high removal capacity for Hg(II) after five regeneration cycles. RHAC had excellent removal efficiency for mercury ion wastewater. At the same time, RH could be used as a nonpolluting and outstanding characteristic adsorbent material.