Effect of thin hydrophobic films for toluene adsorption and desorption behavior on activated carbon fiber under dry and humid conditions

The toluene adsorption and desorption behavior of bare activated carbon fibers (ACFs) and those with a thin hydrophobic coating were studied. ACF surfaces were made hydrophobic by evaporating polydimethylsiloxane (PDMS) on AFCs under atmospheric pressure condition. In the breakthrough curve of bare-ACF for toluene under humid air condition, the roll-up phenomenon towards toluene adsorption was observed. This was attributed to the substitution of the adsorbed toluene by water on ACF, leading to a rise of outlet concentration above the inlet concentration with a decrease in the amount of adsorbed toluene. Compared to bare-ACF, a superior selectivity and adsorption capacity for toluene was observed on the ACFs coated with PDMS. It is suggested that the PDMS-coating can increase the removal efficiency of ACF for toluene under humid air condition.

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► Provision of hydrophobicity to ACF by PDMS coating.
► Toluene adsorption and desorption behavior on bare-ACF and PDMS/ACFs.
► Superior selectivity of toluene adsorption on PDMS-coated ACF under humid air condition.
► Enhancement of adsorption capacity for toluene in the presence of humidity.