IN-SITU MEASUREMENTS OF TETRAPHENYLBORON DEGRADATION KINETICS ON CLAYMINERAL SURFACES BY IR

An attenuated total reflectance Fourier transform infrared (ATR-IR) sp ectroscopic method has been developed to quantitatively measure, in si tu, the surface-facilitated degradation of tetraphenylboron (TPB) in f ully aquated clay pastes. Two pathways for degradation of TPB could be studied both independently and simultaneously. Surface-facilitated ox idation of TPB to diphenylboric acid (DPBA) at Lewis acid sites on cla y mineral surfaces was investigated on three members of the smectite f amily of clays. No degradation of TPB occurred on hectorite, which con tains no structural Fe. TPB degraded to DPBA on montmorillonite and no ntronite. A color change in nontronite indicated the production of mix ed valance Fe3+-O-Fe2+ states and clearly demonstrates the reduction o f structural iron during the course of the reaction. The degradation o f TPB to triphenylboron (TriPB) at Bronsted acid sites could also be m easured 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 reactio ns and describe the data well.