Linear free energy relationships for the adsorption of volatile organic compounds onto multiwalled carbon nanotubes at different relative humidities: comparison with organoclays and activated carbon.
Accurate prediction of the sorption coefficients of volatile organic compounds (VOCs) on carbon nanotubes (CNTs) is of major importance for developing an effective VOC removal process and risk assessment of released nanomaterial-carrying contaminants. The linear free energy relationship (LFER) approach was applied to investigate the adsorption mechanisms of VOCs on multiwalled CNTs (MWCNTs). The gas-solid partition coefficients (log Kd) of 17 VOCs were determined at 0%, 55%, and 90% relative humidity (RH). The cavity/dispersion interaction is generally the most influential adsorption mechanism for all RH cases. The hydrogen-accepting interactions declined but with constant hydrogen-donating interactions during the increase of RH, suggesting that the acidity of VOC was important in forming sorptive interaction with the MWCNT surface. Moreover, the comparison of log Kdof VOCs on MWCNTs and other sorbents revealed that the sorption performance of MWCNTs is much more stable over a wider range of RHs due to better site availability and site quality. Furthermore, for all 6 adsorbents in all RHs, the positive contribution of hydrogen bonding ability was found as compared to the negative one found for sorbents completely in water, indicating that the hydrogen-bond donor and acceptor on the sorbent surface contribute to the sorption in the gas phase. In conclusion, the LFER-derived coefficients can be useful in predicting the performance of VOC adsorption on adsorbents and in facilitating the design of efficient VOC removal systems.
Department of Agricultural Chemistry, National Taiwan University, Taipei 106, Taiwan. yhs@ntu.edu.tw.
Mei-Syue
MS
Li
Department of Agricultural Chemistry, National Taiwan University, Taipei 106, Taiwan. yhs@ntu.edu.tw.
Reuben
R
Wang
Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong, China. dave.kuo@cityu.edu.hk and City University of Hong Kong, Shenzhen Research Institute, Shenzhen, China.
Dave Ta
DT
Fu Kuo
Department of Agricultural Chemistry, National Taiwan University, Taipei 106, Taiwan. yhs@ntu.edu.tw.
Yang-Hsin
http://orcid.org/0000-0002-1326-0720
YH
Shih
D000327:Adsorption; D000393:Air Pollutants / Q000737:chemistry*; D000538:Aluminum Silicates / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry; D002606:Charcoal / Q000737:chemistry*; D000077215:Clay; D006813:Humidity; D006860:Hydrogen Bonding; D008956:Models, Chemical; D037742:Nanotubes, Carbon / Q000737:chemistry*; D013499:Surface Properties; D055549:Volatile Organic Compounds / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D000393:Air Pollutants; D000538:Aluminum Silicates; D037742:Nanotubes, Carbon; D055549:Volatile Organic Compounds; D014867:Water; D001546:Bentonite; D002606:Charcoal; D000077215:Clay