Solid-state 13C NMR studies of the interaction of acetone, carbon tetrachloride and trichloroethylene with soil components

Solid-state 13C NMR has been applied to investigate the interaction of soil components with isotopically-enriched (13C) organic pollutants — acetone, trichloroethylene and carbon tetrachloride. Acetone was studied when adsorbed onto bentonite, kaolinite and humic acid. Trichloroethylene was adsorbed onto kaolinite and bentonite. Carbon tetrachloride was adsorbed onto kaolinite, bentonite, humic acid and a whole soil. The 13C NMR results show no evidence of covalent bond formation between these compounds and soil components under the conditions studied. Substantial chemical shift differences of acetone adsorbed onto these various soil materials are related to the strengths of hydrogen bonds between the carbonyl group of acetone and hydroxyl protons presents in the clay or humic structures. For acetone adsorbed onto humic acid, the wide carbonyl peak shows evidence of a broad distribution of chemical and magnetic environments, e.g. with a distribution of proton-donor hydrogen-bonding sites of the humic structure. The 13C NMR signal observed for the carbonyl group of acetone adsorbed onto bentonite consists of narrow and broad components, which might be related to the previously reported multiphase nature of bentonite.