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This study proposes a novel disinfection process by sequential application of peracetic acid (PAA) and ultra-violet light (UV), on the basis of elucidation of disinfection mechanisms under UV/PAA. Results show that hydroxyl radicals, generated by UV-activated PAA, contribute to the enhanced inactivation of Escherichia coli under UV/PAA compared to PAA alone or UV alone. Furthermore, the location of hydroxyl radical generation is a critical factor. Unlike UV/H2O2, which generates hydroxyl radicals mainly in the bulk solution, the hydroxyl radicals under UV/PAA are produced close to or inside E. coli cells, due to PAA diffusion. Therefore, hydroxyl radicals exert significantly strongermore »
Oxidation of Amino Acids by Peracetic Acid: Reaction Kinetics, Pathways and Theoretical CalculationsPeracetic acid (PAA) is a sanitizer with increasing use in food, medical and water treatment industries. Amino acids are important components in targeted foods for PAA treatment and ubiquitous in natural waterbodies and wastewater effluents as the primary form of dissolved organic nitrogen. To better understand the possible reactions, this work investigated the reaction kinetics and transformation pathways of selected amino acids towards PAA. Experimental results demonstrated that most amino acids showed sluggish reactivity to PAA except cysteine (CYS), methionine (MET), and histidine (HIS). CYS showed the highest reactivity with a very rapid reaction rate. Reactions of MET and HISmore »
Peracetic acid (PAA) is a widely used disinfectant, and combined UV light with PAA (i.e. UV/PAA) can be a novel advanced oxidation process for elimination of water contaminants. This study is among the first to evaluate the photolysis of PAA under UV irradiation (254 nm) and degradation of pharmaceuticals by UV/PAA. PAA exhibited high quantum yields (Φ254nm = 1.20 and 2.09 mol·Einstein−1 for the neutral (PAA0) and anionic (PAA-) species, respectively) and also showed scavenging effects on hydroxyl radicals (k•OH/PAA0 = (9.33±0.3)×108 M−1·s−1 and k•OH/PAA- = (9.97±2.3)×109 M−1·s−1). The pharmaceuticals were persistent with PAA alone but degraded rapidly by UV/PAA.more »
Oxidation of β-Lactam Antibiotics by Peracetic Acid: Reaction Kinetics, Product and Pathway EvaluationPeracetic acid (PAA) is a disinfection oxidant used in many industries including wastewater treatment. β-Lactams, a group of widely prescribed antibiotics, are frequently detected in wastewater effluent and in the natural aquatic environment. The reaction kinetics and transformation of seven β-lactams (cefalexin (CFX), cefadroxil (CFR), cefapirin (CFP), cephalothin (CFT), ampicillin (AMP), amoxicillin (AMX) and penicillin G (PG)) toward PAA were investigated to elucidate the behavior of β-lactams during PAA oxidation processes. The reaction follows second-order kinetics and is much faster at pH 5 and 7 than at pH 9 due to speciation of PAA. Reactivity to PAA follows the ordermore »