SREL Reprint #1836

In situ measurements of tetraphenylboron degradation kinetics on clay mineral surfaces by IR

Douglas B. Hunter and Paul M. Bertsch

Division of Biogeochemistry, University of Georgia, Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29802

Abstract: An attenuated total reflectance Fourier transform infrared (ATR-IR) spectroscopic method has been developed to quantitatively measure, in situ, the surface-facilitated degradation of tetraphenylboron (TPB) in fully aquated clay pastes. Two pathways for degradation of TPB could be studied both independently and simultaneously. Surface-facilitated oxidation of TPB to diphenylboric acid (DPBA) at Lewis acid sites on clay mineral surfaces was investigated on three members of the smectite family of clays. No degradation of TPB occurred on hectorite, which contains no structural Fe. TPB degraded to DPBA on montmorillonite and nontronite. A color change in nontronite indicated the production of mixed valance Fe3+-O-Fe2+ states and clearly demonstrates the reduction of structural iron during the course of the reaction. The degradation of TPB to triphenylboron (TriPB) at Bronsted acid sites could also be measured on aluminum-saturated clays either independently on hectorite or simultaneously to the Lewis acid reaction on montmorillinite by the ATR-IR method. First-order rate models are developed for both reactions and describe the data well.

SREL Reprint #1836

Hunter, D.B. and P.M. Bertsch. 1994. In situ measurements of tetraphenylboron degradation kinetics on clay mineral surfaces by IR. Environmental Science and Technology 28:686-691. 

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).