The Aqueous Degradation of Butylated Hydroxyanisole by UV/S₂O₈^2-: Study of Reaction Mechanisms via Dimerization and Mineralization

Abstract

Three distinctive phases of BHA reactivity toward UV/ S2O8(2-) at acidic, neutral, and basic pH range were examined, where 80-100% mineralization has been observed within an hour of irradiation under 254 nm. A reduction in solution pH during the reaction was observed mainly due to the complete conversion of S2O8(2-) to sulfate ion together with proton generation. Seven measurable intermediates were found via an oxidation and dimerization process at all tested pH levels. The BHA decay mechanisms are quite different in acidic condition and at other pH levels. There are three unique intermediates that are only detectable at pH 3 via two additional pathways. This is due to the generation of weaker oxidants or radicals which results in a slower degradation of the BHA, and therefore, the accumulation of these intermediates to detectable levels. The rate of BHA decay generally increases from low to high pH levels; however, the corresponding mineralization at higher pH is retarded due to the futile process of recombining radicals and involvement of intermediates. Therefore, neutral pH was suggested to be the optimum condition in terms of mineralization and moderate efficiency in removing BHA.

Degradation of polyvinyl alcohol in aqueous solutions using UV-365 nm/S2O8 2− process

“…These observations implied that UV-365 nm/S 2 O 8 2-process was associated with a higher degradation efficiency of PVA owing to the following mechanism (Hori et al 2005(Hori et al , 2007Lau et al 2007;Salari et al 2009;Criquet and Leitner 2009;Lin et al 2011). and it can directly degrade PVA in aqueous solutions (Eq.…”

“…Therefore, UV/S 2 O 8 2-process has been confirmed to be effective in degrading organic contaminants (Hori et al 2005(Hori et al , 2007Lau et al 2007;Salari et al 2009;Criquet and Leitner 2009;Lin et al 2011). For example, Lin et al (2011) found that phenol (0.5 mM) can be completely degraded within 20 min using UV/S 2 O 8 2-process with a UV wavelength of 254 nm and an S 2 O 8 2-concentration of 84 mM.…”

Application of central composite design for the optimization of photo-destruction of a textile dye using UV/S2O8 2- process

“…S 2 O 8 2-is normally available as a salt associated with ammonium, sodium, or potassium. The comparative performance of K 2 S 2 O 8 (KPS) and (NH 4 ) 2 S 2 O 8 (APS) as the oxidant under the irradiation of UV light for removal of butylated hydroxyanisole 9 and a textile dye (Basic yellow 2)…”

“…The USEPA has listed it under the secondary drinking water standards with a maximum concentration of 250 mg/l (1.43 mmol/ l), based on aesthetic reasons 9,12 . The main objective of the optimization in this work is to determine the optimum values of variables for photooxidative decolorization using UV/S 2 O 8 2-process, from the CCD model obtained using the experimental data.…”

Photochemical oxidation of methyldiethanolamine (MDEA) in aqueous solution by UV/K2S2O8 process

“…It has also been reported to be effective for degrading organic matters in hazardous wastewaters in acidic or basic media through direct chemical oxidation, where peroxydisulfate is used as a sacrificial reagent [17][18][19]. However, since the reactions of peroxydisulfate are generally slow at normal temperature.…”