Photochemical reaction kinetics and mechanism of bisphenol A with K₂S₂O₈ in aqueous solution: a laser flash photolysis study

Abstract

The photochemical reaction kinetics and mechanism of bisphenol A (BPA) with potassium persulfate (K2S2O8) were investigated by using 266 nm laser flash photolysis and gas chromatography mass spectrum (GC-MS) technique. Sulfate radical (SO4•–), generated upon K2S2O8 photolysis, reacted with BPA with the overall rate constant of (1.61±0.15)×109 L mol-1 s-1, and two main reaction mechanisms were involved. One was addition channel to generate BPA–SO4•– adduct with a specific second-order rate constant of (1.09±0.15)×109 L mol-1s-1. Molecular oxygen was involved in the decay of the BPA–SO4•– adduct with a rate constant of (1.28±0.14)×108 L mol-1 s-1. Another channel was the formation of BPA’s phenoxyl radical, likely derived from a deprotonation of the cation radical (BPA•+) generated from single electron transfer reactions. The specific rate constant of BPA’s phenoxyl radical formation was determined to be (6.16±0.08)×108 L mol-1 s-1. The overall rate constant was in line with the sum of aforementioned two specific rate constants for two main reaction channels. By comparing these rate constants, it was indicated that SO4•– addition channel accounted for ~65% (1.09/1.61) to the overall reaction, and phenoxyl radical formation accounted for only ~35% (0.62/1.61). The transformation products of BPA were identified by using GC-MS including 4-isopropylphenol, 4-isopropenylphenol, and 2, 4-di-tert-butylphenol, and the reaction mechanism was proposed. These results may provide microscopic kinetics and mechanism information on BPA degradation using SO4•–-based advanced oxidation processes (AOPs).

Direct Determination of Absolute Radical Quantum Yields in Hydroxyl and Sulfate Radical-Based Treatment Processes

“…The detection of normalSO 4 • − was achieved by direct monitoring at its feature wavelength, 450 nm ( ε = 1650 M –1 cm –1 ), and N ( normalSO 4 • − ) 0 was derived from the maximum absorbance. Figure c (red line) showed that after the excitation, the maximal absorbance can increase to 0.044, and the initial concentration of produced normalSO 4 • − was then determined to be 26.6 μM (Figure c, inset red line).…”

Carrageenan as a Sacrificial Binder for 5 V LiNi0.5Mn1.5O4 Cathodes in Lithium‐Ion Batteries

“…In the pristine state, no specific signal was observed for the composite films of all three binders. After the first charging process, however, the peak near 300 nm, ascribed [ 32 ] to the sulfate‐derived radical, was observed only for the CRN‐based composite film (Figure S22a, Supporting Information), unlike its ALG‐ and PVDF‐based counterparts (Figure S22b,c, Supporting Information). This sulfate‐derived radical reacts with the Lewis acidic PF 5 decomposed from the anion of the lithium salt (Figure S21a, Supporting Information) to form the LiSO 4 PF 5 − intermediate ( m / z = 228.93) as detected by ToF‐SIMS (Figure S23a, Supporting Information).…”