Exploring a New Method to Study the Effects of Surface Functional Groups on Adsorption of CO₂ and CH₄ on Activated Carbons

Abstract

The commercial coconut shell-activated carbon was modified to change the number of oxygen-containing functional groups. N2 adsorption/desorption isotherms, Fourier transform infrared (FT-IR), and Boehm titration were adopted to describe the physical and chemical properties of the samples. The adsorption isotherms of CO2 and CH4 on both the unmodified and modified samples were measured. To better understand the effects of surface oxygen-containing functional groups on adsorption of CO2 and CH4, the overall adsorption could be considered as the result of adsorption within the pores and adsorption onto the oxygen-containing functional groups. Thus, a new way to understand different adsorption mechanisms by calculation was proposed. On the basis of the results, there is a significant correlation between the saturation adsorption capacity of CO2 and the number of oxygen-containing functional groups, especially carboxyl and hydroxyl. According to the values of enthalpy (−12.2 to −20 kJ/mol), it can be known that the adsorption caused by oxygen-containing functional groups is exothermic and belongs to physisorption. A semiempirical relationship between the variation of the surface oxygen-functional groups and the variation of the adsorbed amount was established. The method proposed in this paper provides a new way to study the effects of surface functional groups on the adsorption of CO2 and CH4 and can be even promoted in studying the adsorption mechanism of other adsorbates.

Preparation and characterization of activated carbon modified by potassium for carbon dioxide/methane adsorption and separation

“…Meanwhile, that of methane on 55‐KAC decreases by 0.17 mmol g −1 . This result proves that the adsorption capacity of carbon dioxide is influenced by both pore structure and surface chemical properties again [15, 33].…”

“…Meanwhile, that of methane on 55-KAC decreases by 0.17 mmol g À 1 . This result proves that the adsorption capacity of carbon dioxide is influenced by both pore structure and surface chemical properties again [15,33]. The separation of carbon dioxide/methane mixture on the modified samples also raises with the increasing modification temperature, Figure 4.…”

“…However, that of methane on 0.1 K‐AC is almost the same with that on R‐AC, Table 2. This is due to that the adsorption capacity of carbon dioxide is not only related to the pore structure of the adsorbent but also the chemical properties of the adsorbent surface, while that of methane is mainly relevant to the pore structure [33].…”

Research and application of tongue and face diagnosis based on deep learning

“…The difference between the images captured by mobile and the images captured by standard tongue diagnostic devices lies in noise and picture resolution, and the images captured by mobile in the tongue image processing method require algorithms to exclude the influence of light and background. Song et al 11 applied the algorithm of LBP (Local Binary Patterns) combined with Adaboost in a cell phone terminal to achieve near real-time tongue image detection, and the accuracy of image analysis was achieved by deep learning algorithm through a residual network without setting the scene. In order to construct a color correction function model for tongue images based on cell phone terminals, Wang et al 12 compared tongue images taken by different models of cell phones with those taken by the TDA-1 micro-tongue diagnostic instrument, and analyzed more than 300 cases of tongue images for standard color card L*a*b color value acquisition; with the optimized back propagation (BP) neural network as the model, the constructed network can correct tongue color and moss color.…”

Interplay between oxygen doping and ultra-microporosity improves the CO2/N2 separation performance of carbons derived from aromatic polycarboxylates

“…It also has been suggested that the surface chemistry, rather than the textural properties, governs the CO 2 capture performance at lower pressures, while the textural properties become more important at higher CO 2 pressures, when the adsorption process becomes controlled by the micropore filling mechanism [41,42]. Carboxyls and hydroxyls have been suggested as the most effective oxygenated functionalities for selective adsorption of CO 2 , due to their high polarity, compared to carbonyls and ethers [43,44]. A recent work reported that oxygen can actually be detrimental to the capture performance, although in this case the focus was on the external surface functionalisation [45].…”