Selective removal of formaldehyde based on Hantzsch reaction using acetylacetone/ammonia-modified mixed matrix absorbent as a novel absorber

Abstract

Selective removal of formaldehyde (HCHO) was evaluated using acetylacetone/ammonia-modified mixed matrix absorbents (MMAs) as new absorber. For this purpose MMAs were synthesized using activated multi-walled carbon nanotubes as inorganic phase (filler), poly ester resin as organic phase, silica power as disperser and cobalt as hardener. The synthesized MMAs were then activated at 400°C in air for ∼4h and modified with acetylacetone/ammonia. After drying the modified MMAs under sun light for ∼12h, they were packed into a column for selective removal of HCHO. Optimized values for effective parameters having influence on the HCHO removal included acetylacetone (acac) mole fraction (Xacac)=0.56, XNH3=0.44 as well as 1:2 (V/W) for volume to weight ratio of acac/NH3:MMAs. In this system standard HCHO solutions were generated using air as solvent and thermally generated HCHO using an MQ-138 sensor. The standard HCHO solutions were then introduced to the absorber using segmented flow injection analysis. Under optimized conditions the efficiencies of HCHO removal for each pure and modified MMAs were estimated to 10% and 90% respectively. The absorber was also stable up to ∼12.0atm. pressure. The synthesized absorber was also regenerated by purging air with pressure between 12.0 and 16.0atm. at room temperature for ∼30.0min. The reproducibility of the synthesized MMAs was also evaluated to ∼3.1%, during four replicate removals. No interference was observed due to the selective reaction between HCHO and acac/NH3. Finally the system was adopted for removal of HCHO from some petrochemical air samples.