Cyclodextrins for desorption and solubilization of 2,4,6-trinitrotoluene and its metabolites from soil

Heptakis-2,6-di-O-methyl-beta-cyclodextrin (DM beta CD) and hydroxypropyl-b eta-cyclodextrin (HP beta CD) (1% w/w solutions) were investigated for thei r ability to desorb 2,4,6-trinitrotoluene (TNT), 4-amino-2,6-dinitrotoluene (4-ADNT), and 2,4-diamino-4-nitrotoluene (2,4-DANT) from two artificially contaminated soils (an organic rich topsoil and an illite shale). The DM be ta CD (which is highly surface active) was more effective than HP beta CD ( negligible surface activity) for desorption of the three nitroaromatic comp ounds (NACs) from the two soils. The efficiency of both CDs for NAC removal from topsoil decreased with increasing amino substitution (i.e. TNT > 4-AD NT > 2,4-DANT), whereas for illite the efficiency generally decreased with increasing nitro substitution (i.e. TNT < 4-ADNT. 2,4-DANT). In general, th e NAC removal efficiency increased with decreases in the sorption capacity constant (K-d). The two CDs were also assessed for their ability to remove TNT from a highly contaminated topsoil (5265 mg/kg) obtained from a former manufacturing facility that had been aged for 10-40 yr. The estimated assoc iation constants (K-S) were comparable to those obtained for solubilization of pure TNT into aqueous solution. This study demonstrates the effectivene ss of CDs in decontaminating a variety of soils containing both high and lo w levels of TNT and some of its associated metabolites.