TNB (Temple-Northeastern-Birmingham) Model of Humic Acid
Figure 1 - Molecular structure of TNB humic acid monomer, show chiral centers of
lowest energy structure, as determined by both molecular mechanics (MM3) and semi-empirical
quantum mechanics (AM1, PM3). Rings (or proto-rings) are labelled alphabetically.
Figure 2 - Hexamer of Humic Acid, optimized by MM3, showing condensed saccharide
(in this case, alginic acid),
projecting to the left. Notice the central, oval-shaped cavity to the right. Carbon atoms are cyan, oxygen atoms are red,
and nitrogen atoms are dark blue. Hydrogen atoms have been omitted for clarity.
Why are We Interested in Humic Acid?
Humic acid holds onto many metals very strongly. Some of these metals
are Hg
(mercury), Cd (cadmium), and Pb (lead), which are all toxic, and found in polluted
soil and streams. Humic acid can be used to de-contaminate these.
Humic acid can also be used to eliminate the danger from organic compounds,
such at TCE (trichloroethylene - the chemical involved in the film
"A Civil Action"), and GB (Sarin - a deadly nerve gas). After 9/11, the importance of being
able to decontaminate such poisons has only increased. Extensive experimentation
has been conducted here at Temple University with these two chemicals.
Figure 3 - Molecular structure of Sarin (GB).
Figure 4 - Proposed mechanism for reductive dehalogenation of TCE
(trichloroethylene) by humic acid.
Figure 5 - Proposed mechanism for reductive dehalogenation of TCE
(trichloroethylene) by humic acid, showing the crucial role played by catalytic oxidation of chloride ion.
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© 2003-2012 by Lawrence T. Sein. All rights reserved.
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