Selective and Efficient Removal of Volatile Organic Compounds by Channel-type Gamma-Cyclodextrin. Assembly through Inclusion Complexation

Abstract

Cyclodextrins (CD), produced from enzymatic degradation of starch, are a form of biorenewable cyclic oligosaccharide which has an outstanding capability to form inclusion complexes with a Variety of molecules including pollutants due to their toroid-shaped molecular structure. In this study, by a simple reprecipitation method, we obtained channel-type packing from gamma-CD where CD molecules are stacked on top of each other to form long cylindrical channels. The gamma-CD channel-type crystals have shown very effective removal of organic volatile compounds (VOCs;: aniline and toluene) from the surroundings, whereas cage-type gamma-CD could not entrap VOCs froth the same environment. Encapsulation capability of channel-type gamma-CD is at a,2:1 and molar ratio for aniline/CD and toluene/CD, respectively. Thus, channel-type gamma-CD crystals have shown higher removal efficiency for aniline compared to toluene. Channel-type gamma-CD is also able to remove aniline selectively from surroundings. Additionally, computational modeling studies suggested that single gamma-CD cavity Can hest two, molecules of aniline or toluene for the complexation, yet, aniline is more insistent to make a complex with the gamma-CD cavity when compared to toluene. We show that channekype gamma-CID can remove VOCs molecules (aniline and toluene) as efficiently as activated carbon. Hence; being a starch based biorenewable cyclic oligosaccharide in the form of white powder, the use of channel-type gamma-CD crystals could be a competitive alternative to activated carbon as an adsorbent for the VOC removal/filtering.