Novel activated carbon fiber cloth filter with functionalized silica nanoparticles for adsorption of toxic industrial chemicals

Abstract

Toxic industrial chemicals (TICs) are used for various civilian and military operations but can be hazardous to humans. There is interest in developing filters that can remove a wide range of airborne TICs (e.g., basic, acidic, organophosphate, and aromatic compounds) to reduce exposure in the work place and from terrorist attacks. A regenerable TIC air filter is particularly desirable because it removes the need for costly filter disposal and replacement. This study evaluates commercially available activated carbon fiber cloth (ACFC) and ACFC that has been modified with functionalized nanoparticles for their abilities to adsorb select TICs and for the regenerability of the adsorbents. The unmodified and modified ACFC samples were tested here for their ability to adsorb anhydrous ammonia (NH₃), hydrogen cyanide (HCN), and dimethyl methylphosphonate (DMMP) in dry and humid gas streams as representative basic, acidic, and organophosphate compounds, respectively. The unmodified ACFC was not an effective adsorbent for NH₃ (i.e., 2 and 3.1 mg NH₃/g ACFC at 1000 ppm_v NH₃ in dry and humid air respectively) or HCN (no detectable adsorption), but successfully adsorbed 840 mg DMMP/g ACFC at 100 ppm_v DMMP. The modified ACFC showed significant improvements for NH₃ and HCN adsorption in dried air (i.e., 19.5 mg NH₃/g ACFC at 1000 ppm_v NH₃ and 4.7 mg HCN/g ACFC at 150 ppm_v HCN, respectively) and in humid air (i.e., 41.4 mg NH₃/g ACFC at 1000 ppm_v NH₃ and 1.6 mg HCN/g ACFC at 50 ppm_v HCN, respectively) when compared to the unmodified sample. The modified ACFC also showed 2–5 % degradation of its initial dry mass after regeneration and then showed no detectable degradation. The modified ACFC also had similar electrical resistance to that of unmodified ACFC (i.e., within 1 %), indicating that it can be regenerated using electrothermal heating.