TY  - JOUR
VL  - 294
JF  - Microporous and Mesoporous Materials
A1  - Mukhtar, A.
A1  - Mellon, N.
A1  - Saqib, S.
A1  - Khawar, A.
A1  - Rafiq, S.
A1  - Ullah, S.
A1  - Al-Sehemi, A.G.
A1  - Babar, M.
A1  - Bustam, M.A.
A1  - Khan, W.A.
A1  - Tahir, M.S.
UR  - https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075373765&doi=10.1016%2fj.micromeso.2019.109883&partnerID=40&md5=46820ea590a9e056e9330bfdaf692264
PB  - Elsevier B.V.
SN  - 13871811
Y1  - 2020///
ID  - scholars13443
TI  - CO2/CH4 adsorption over functionalized multi-walled carbon nanotubes; an experimental study, isotherms analysis, mechanism, and thermodynamics
KW  - Air purification; Carbon dioxide; Gas adsorption; Isotherms; Mass transfer; Methane; Molecules; Nanotubes; Natural gas; Oxygen; Physisorption; Pore structure; Surface roughness; Temperature; Thermodynamic stability
KW  -  CO2 adsorption; Functionalized multi-walled carbon nanotubes; Impact of temperatures; Mass transfer characteristics; Surface functional groups; Surface functionalities; Thermal instabilities; Thermodynamic behaviors
KW  -  Multiwalled carbon nanotubes (MWCN)
N2  - Understanding of the interactions of the CO2 molecules with pore structure and surface functionalities during natural gas purification provides significant knowledge about potential adsorbent materials. This study reports the oxygen-rich surface functional groups attachment on MWCNTs followed by characterization, low-pressure selective CO2/CH4 adsorption behavior, the impact of temperature, isotherms analysis, mechanism study, thermodynamic behavior, turnover frequency, and turnover number analysis. The FESEM and TEM analysis revealed some negligible defect on MWCNTs surface. The MWCNTs surface roughness was observed after ultra-sonication with the attachment of oxygen functionalities without opening ends of MWCNTs. Structural sustainability and thermal instability were observed due to the early decomposition of (-COOH) groups at < 225 °C. Functionalization results BET surface area loss indicating the pore filling by acid molecules with existence of transport pores demonstrating excellent mass transfer characteristics. The functionalities exhibited enhancement in CO2 uptake capacity from 0.0874 to 0.3274 mmol/g. The temperature influences indicated that the adsorption is thermodynamically controlled. CO2/CH4 selectivity reduced at elevated pressure directing the pressure-driven pore-filling mechanism. Isotherms analysis revealed that the low temperature favors high affinity. The separation factor was found less than unity indicating the process favorability. Additionally, isotherms analysis revealed heterogeneity of MWCNTs with multi-layer formation. Furthermore, D-R model fitting showed adsorption energy values within the range of 3.462â??8.087 kJ/mol indicating the adsorption is physisorption leading to combination of physisorption and chemisorption at elevated temperatures. Finally, thermodynamic exhibited positive Î?G°, and negative Î?H° and Î?S° attributing the energy requirement for process startup, exothermic, and reduction in the randomness. The TON and TOF values were found to be within the specified range of MWNCTs. © 2019 Elsevier Inc.
N1  - cited By 45
AV  - none
ER  -