A large spill of 4-methyl cyclohexane methanol (MCHM) and propylene glycol phenyl ether (PPh) into the Elk River near Charleston, West Virginia, led to serious water contamination and concern about the human health consequences and appropriate remediation. The time-resolved and steady-state radiolysis methods were employed to determine reaction kinetics and mechanisms of hydroxyl radical with MCHM and PPh. The bimolecular rate constants for hydroxyl radical with MCHM and PPh are 5.04 ± 0.09 × 109 M-1 s-1 and 9.15 ± 0.08 × 109 M-1 s-1, respectively, using the time-resolved competition kinetics with thiocyanate (SCN-). The formation of the hydroxycyclohexadienyl radical resulting from hydroxyl radical addition to the aromatic ring in PPh was measured using transient absorption spectroscopy (250 ~ 380 nm) with a maximum absorption at 330 nm. The rate constant for the specific addition of hydroxyl radical to the aromatic ring in PPh is 8.98 ± 0.26 × 109 M-1 s-1, indicating hydroxyl radical reacts primarily by addition to the aromatic ring. Detailed product studies using LC-QTOF/MS for PPh indicates hydroxyl radical attack to benzene ring results in two isomeric products assigned to ortho and para isomers based on the enhanced reactivity of these positions. SPME-GC/MS analysis of MCHM indicates hydroxyl radical mediated oxidation of MCHM primarily involves H-abstraction followed by radical oxidation pathways. The fundamental kinetic parameters and detailed product studies using pulse and gamma radiolysis provide fundamental mechanistic understanding of hydroxyl radical initiated reactions, essential to assessing the remediation of these problematic pollutants in drinking water by AOPs and anticipating the biological and environmental fate of MCHM and PPh.

Radiolysis studies on the degradation of cyclohexane methanol (MCHM)

251st National Meeting (2016)

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