Chemical transformation of short chain saturated carboxylic acids under UV irradiation in aqueous solutions.
Item
-
Title
-
Chemical transformation of short chain saturated carboxylic acids under UV irradiation in aqueous solutions.
-
Identifier
-
AAI3103177
-
identifier
-
3103177
-
Creator
-
Talu, Gonca F.
-
Contributor
-
Adviser: Vasil Diyamandoglu
-
Date
-
2003
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Engineering, Environmental
-
Abstract
-
Low molecular weight carboxylic acids are likely to be encountered in water supplies, and decompose during UV disinfection of water. The photodecomposition kinetics of five short chain saturated carboxylic acids (formic, oxalic, glycolic, glyoxalic and pyruvic acids) and some selected mixtures have been studied under UV irradiation at 253.7 nm. The irradiation experiments were performed in a 5-L glass reactor equipped with eight low-pressure quartz immersion lamps. The effects of UV light intensity (Ia) (1.38 x 10-6 to 5.27 x 10-6 E/Ls), temperature (T) (15--35°C), initial concentration (C0) (0.2--5.2 mg C/L), initial pH (pH0) (5.0--9.0) and alkalinity (0--50 mgL-1 NaHCO3 as CaCO3) on the photodecomposition of acid solutions were investigated. Total carbon (TC) and non-purgable organic carbon (NPOC) profiles were also determined during some of the photodecomposition experiments to quantify the dissolved organic carbon remaining in solution. All studied acids decayed following split rate reaction. Formate and oxalate readily decayed at different rates without any observed intermediates while they were both consistent intermediates of glyoxalate decomposition. Glycolate irradiation produced glyoxalate that further decayed to form formate and oxalate during the decomposition reaction. Glycolate and oxalate were observed as product of pyruvate along with two unidentified anionic reaction products. Oxalate was the common intermediate product of decomposition of glyoxalate, glycolate and pyruvate and decayed after the decay of all other observed intermediates. Formate, glyoxalate and glycolate decay followed pseudo-zero order kinetics while pseudo-first order kinetic was observed for oxalate and pyruvate decay. NPOC and TC data revealed that all carbon in formate and oxalate is eventually converted to CO2, while decay of either glyoxalate, glycolate and pyruvate may result in the formation of volatile products. The reaction pH profile for formate and oxalate photodecomposition without prior pH0 adjustment was predicted using closed system equilibrium analysis. The kinetic data clearly showed time dependent variation in the composition of the irradiated water. It is, therefore, to be expected that the disinfection by-product formation potential (DBPFP) of any water subjected to UV irradiation will be a function of the combined effect of absorbed photon flux and the process contact time.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
