Selective Adsorption of VOCs/Water Vapor on Activated Carbon: The Role of Adsorbent and VOC Molecular Polarity
The presence of abundant water vapor in industrial organic waste gases greatly reduces the selective adsorption of volatile organic pollutants (VOCs). The polarity of the adsorbent and VOC molecules plays an important role in the adsorption process, especially in the presence of water vapor. In this...
Saved in:
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-04-01
|
| Series: | Separations |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2297-8739/12/4/86 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1849714058768416768 |
|---|---|
| author | Wenlin Hang Jiaxing Sun Ronghang Zhao Heng Chen Jinjin Li |
| author_facet | Wenlin Hang Jiaxing Sun Ronghang Zhao Heng Chen Jinjin Li |
| author_sort | Wenlin Hang |
| collection | DOAJ |
| description | The presence of abundant water vapor in industrial organic waste gases greatly reduces the selective adsorption of volatile organic pollutants (VOCs). The polarity of the adsorbent and VOC molecules plays an important role in the adsorption process, especially in the presence of water vapor. In this paper, commercial coconut shell activated carbon (CSC) was modified by a thermal reduction treatment to obtain heat-treated coconut shell activated carbon (HCSC). CSC and HCSC exhibited similar pore structure characteristics but differed significantly in surface oxygen content (10.97% and 7.55%, respectively). Dynamic adsorption breakthrough experiments were conducted to determine the dynamic adsorption capacities of toluene on both adsorbents under varying relative humidity levels. HCSC demonstrated superior toluene/water vapor adsorption selectivity. Further analyses of toluene adsorption kinetics, activation energy, and water vapor adsorption isotherms revealed that the lower surface oxygen functional group content of HCSC resulted in a weaker surface polarity, facilitating the adsorption of weakly polar toluene. This was attributed to stronger toluene–HCSC interactions and weaker water–HCSC interactions. The dynamic adsorption capacities of three VOCs with varying polarities were also tested on HCSC. The observed VOC/water vapor adsorption selectivity had the following order: toluene > n-heptane > 1,2-dichloroethane. Grand Canonical Monte Carlo (GCMC) simulations were employed to quantify the relationship between the adsorption selectivity of eight VOCs with varying polarities and their molecular polarity. The results indicated a decrease in adsorption selectivity with increasing VOC polarity. A mechanistic analysis suggests that more polar VOCs prefer to adsorb polar oxygen-containing functional groups, competing with water molecules for adsorption sites. Under high humidity, hydrogen bonding leads to the formation of water clusters, exacerbating this competition. This research holds significant implications for the efficient selective adsorption of VOCs with varying polarities in humid industrial conditions. |
| format | Article |
| id | doaj-art-e13638e95041407f903e5cc90ae5c618 |
| institution | DOAJ |
| issn | 2297-8739 |
| language | English |
| publishDate | 2025-04-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Separations |
| spelling | doaj-art-e13638e95041407f903e5cc90ae5c6182025-08-20T03:13:48ZengMDPI AGSeparations2297-87392025-04-011248610.3390/separations12040086Selective Adsorption of VOCs/Water Vapor on Activated Carbon: The Role of Adsorbent and VOC Molecular PolarityWenlin Hang0Jiaxing Sun1Ronghang Zhao2Heng Chen3Jinjin Li4Jiangsu Guoxin Yangzhou Power Generation LLCO, Yangzhou 225131, ChinaJiangsu Guoxin Yangzhou Power Generation LLCO, Yangzhou 225131, ChinaJiangsu Guoxin Yangzhou Power Generation LLCO, Yangzhou 225131, ChinaSchool of Mechatronics and Energy Engineering, Ningbo Tech University, Ningbo 315200, ChinaCollege of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037, ChinaThe presence of abundant water vapor in industrial organic waste gases greatly reduces the selective adsorption of volatile organic pollutants (VOCs). The polarity of the adsorbent and VOC molecules plays an important role in the adsorption process, especially in the presence of water vapor. In this paper, commercial coconut shell activated carbon (CSC) was modified by a thermal reduction treatment to obtain heat-treated coconut shell activated carbon (HCSC). CSC and HCSC exhibited similar pore structure characteristics but differed significantly in surface oxygen content (10.97% and 7.55%, respectively). Dynamic adsorption breakthrough experiments were conducted to determine the dynamic adsorption capacities of toluene on both adsorbents under varying relative humidity levels. HCSC demonstrated superior toluene/water vapor adsorption selectivity. Further analyses of toluene adsorption kinetics, activation energy, and water vapor adsorption isotherms revealed that the lower surface oxygen functional group content of HCSC resulted in a weaker surface polarity, facilitating the adsorption of weakly polar toluene. This was attributed to stronger toluene–HCSC interactions and weaker water–HCSC interactions. The dynamic adsorption capacities of three VOCs with varying polarities were also tested on HCSC. The observed VOC/water vapor adsorption selectivity had the following order: toluene > n-heptane > 1,2-dichloroethane. Grand Canonical Monte Carlo (GCMC) simulations were employed to quantify the relationship between the adsorption selectivity of eight VOCs with varying polarities and their molecular polarity. The results indicated a decrease in adsorption selectivity with increasing VOC polarity. A mechanistic analysis suggests that more polar VOCs prefer to adsorb polar oxygen-containing functional groups, competing with water molecules for adsorption sites. Under high humidity, hydrogen bonding leads to the formation of water clusters, exacerbating this competition. This research holds significant implications for the efficient selective adsorption of VOCs with varying polarities in humid industrial conditions.https://www.mdpi.com/2297-8739/12/4/86adsorption selectivitymolecular polarityadsorbentactivated carbonwater vapor |
| spellingShingle | Wenlin Hang Jiaxing Sun Ronghang Zhao Heng Chen Jinjin Li Selective Adsorption of VOCs/Water Vapor on Activated Carbon: The Role of Adsorbent and VOC Molecular Polarity Separations adsorption selectivity molecular polarity adsorbent activated carbon water vapor |
| title | Selective Adsorption of VOCs/Water Vapor on Activated Carbon: The Role of Adsorbent and VOC Molecular Polarity |
| title_full | Selective Adsorption of VOCs/Water Vapor on Activated Carbon: The Role of Adsorbent and VOC Molecular Polarity |
| title_fullStr | Selective Adsorption of VOCs/Water Vapor on Activated Carbon: The Role of Adsorbent and VOC Molecular Polarity |
| title_full_unstemmed | Selective Adsorption of VOCs/Water Vapor on Activated Carbon: The Role of Adsorbent and VOC Molecular Polarity |
| title_short | Selective Adsorption of VOCs/Water Vapor on Activated Carbon: The Role of Adsorbent and VOC Molecular Polarity |
| title_sort | selective adsorption of vocs water vapor on activated carbon the role of adsorbent and voc molecular polarity |
| topic | adsorption selectivity molecular polarity adsorbent activated carbon water vapor |
| url | https://www.mdpi.com/2297-8739/12/4/86 |
| work_keys_str_mv | AT wenlinhang selectiveadsorptionofvocswatervaporonactivatedcarbontheroleofadsorbentandvocmolecularpolarity AT jiaxingsun selectiveadsorptionofvocswatervaporonactivatedcarbontheroleofadsorbentandvocmolecularpolarity AT ronghangzhao selectiveadsorptionofvocswatervaporonactivatedcarbontheroleofadsorbentandvocmolecularpolarity AT hengchen selectiveadsorptionofvocswatervaporonactivatedcarbontheroleofadsorbentandvocmolecularpolarity AT jinjinli selectiveadsorptionofvocswatervaporonactivatedcarbontheroleofadsorbentandvocmolecularpolarity |