Effect of Calcination Temperature and Chemical Composition of PAN-Derived Carbon Microfibers on N2, CO2, and CH4 Adsorption

Abstract

This work investigates the interplay of carbonization temperature and the chemical composition of carbon microfibers (CMFs), and their impact on the equilibration time and adsorption of three molecules (N2, CO2, and CH4). PAN derived CMFs were synthesized by electrospinning and calcined at three distinct temperatures (600, 700 and 800 °C), which led to samples with different textural and chemical properties assessed by FTIR, TGA/DTA, XRD, Raman, TEM, XPS, and N2 adsorption. We examine why samples calcined at low/moderate temperatures (600 and 700 °C) show an open hysteresis loop in nitrogen adsorption/desorption isotherms at −196.15 °C. The equilibrium time in adsorption measurements is nearly the same for these samples, despite their distinct chemical compositions. Increasing the equilibrium time did not allow for the closure of the hysteresis loop, but by rising the analysis temperature this was achieved. By means of the isosteric enthalpy of adsorption measurements and ab initio calculations, adsorbent/adsorbate interactions for CO2, CH4 and N2 were found to be inversely proportional to the temperature of carbonization of the samples (CMF-600 > CMF-700 > CMF-800). The enhancement of adsorbent/adsorbate interaction at lower carbonization temperatures is directly related to the presence of nitrogen and oxygen functional groups on the surface of CMFs. Nonetheless, a higher concentration of heteroatoms also causes: (i) a reduction in the adsorption capacity of CO2 and CH4 and (ii) open hysteresis loops in N2 adsorption at cryogenic temperatures. Therefore, the calcination of PAN derived microfibers at temperatures above 800 °C is recommended, which results in materials with suitable micropore volume and a low content of surface heteroatoms, leading to high CO2 uptake while keeping acceptable selectivity with regards to CH4 and moderate adsorption enthalpies.

Biochar/Clay Composite Particle Immobilized Compound Bacteria: Preparation, Collaborative Degradation Performance and Environmental Tolerance

“…In the formula, C oil represents the concentration of oil in the water sample, mg L −1 ; Q represents the concentration of oil in the n-hexane extract obtained from the standard curve, mg L −1 ; V 1 represents the volume of n-hexane extraction solvent, mL; and V 2 represents the volume of the sample, mL. The control of the preparation formula (biochar dosage, Na 2 SiO 3 dosage and NaHCO 3 dosage) could change the surface structure of biochar to a certain extent and affect its adsorption performance for NH 4 + -N [15]. Therefore, in this study, the orthogonal experiment method was used to investigate the effect of the BCCP preparation formula on NH 4 + -N adsorption (Table 3).…”

Immobilization of Ochrobactrum sp. on Biochar/Clay Composite Particle: Optimization of Preparation and Performance for Nitrogen Removal

“…The same phenomenon existed in the research of Chen et al (2018) who found that the surface area and pore volume of bentonite increased to 56.09 and 0.0611 cm 3 g −1 when the calcined temperature was 400 • C, respectively, but sharply declined to 30.53 and 0.051 cm 3 g −1 at 800 • C. Yan et al (2018) prepared a kind of porous diatomite microsphere by spray drying method and the methylene blue adsorption capacity and removal efficiency demonstrated the maximum values when the calcined temperature was 600 • C, and decreased when the temperature rose. Ojeda-López et al (2021) found that adsorbent/adsorbate interactions for CO 2 , CH 4 , and N 2 were inversely proportional to calcined temperature (CMF-600 > CMF-700 > CMF-800) by the mean of the isosteric enthalpy of adsorption measurements.…”

Effect of pre-carbonization temperature on the porous structure and electrochemical properties of activated carbon fibers derived from kapok for supercapacitor applications

“…(ii) Trapped nitrogen could not be released because of its affinity for the heterogeneous surface of ACFs. (iii) The nearsolid state condensation of the adsorbate occurred at the entryway of pores [36,37]. The specific surface area of ACFs was calculated using the Brunauer-Emmett-Teller (BET) method utilizing the adsorption data in the P/P0 range of 0.05 to 0.30.…”