Removal of aromatic hydrocarbon compounds by hydroxypropyl-cyclodextrin

Activated carbon has been used for the recovery and removal of benzene, tol uene, and xylenes in air and water for a long time. However, removal of ben zene, toluene, and xylenes from soil is very difficult. They can be removed by an increase in the apparent solubility of organic compounds in soil. Th e apparent solubilities of benzene, toluene, and xylene were investigated t o estimate their inclusion behavior into natural cyclodextrins (CDs) and hy droxypropyl-cyclodextrins (HP-CDs) in the liquid phase. The apparent solubi lities of benzene, toluene, and xylenes did not increase by adding natural CDs but did increase when HP-CDs were added. Benzene, toluene, and xylenes in a HP-CD solution depended on the relationship between the molecular diam eter of benzene, toluene, and xylenes, the CD cavity size, and the l-octano l-water partition coefficient. That of p-xylene was larger than that of o-x ylene and m-xylene because of the smallest steric hindrance of p-xylene. (C ) 1999 Academic Press.