Degradation of Organic Contaminants in Water by Solar Radiation: Examining the Photochemical Transformation Pathways of 2,4-Dimethylphenol in the Presence of Dissolved Organic Matter
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. School of Earth Sciences Honors Theses; 2010
Produced water is the greatest source of waste by product associated with oil and natural gas operations. This study, examined the potential for solar radiation to effectively degrade toxic organic compounds commonly found in produced water, specifically 2,4-dimethylphenol (DMP). Treatment of these contaminants by solar irradiance is an attractive treatment alternative, as harnessing the sun’s light energy is a "green" approach that could be an economical and effective means to remediate produced water. Direct and indirect photolysis experiments were conducted at concentrations found in “treated” produced water, using pH adjusted reaction solutions with respect to environmental fresh water systems (pH≈8). Further the effect of dissolved organic matter (DOM) as a "photosensitizer" (catalyst) was investigated. Analysis of direct and indirect photolysis experiments by high-pressure liquid chromatography (HPLC) with detection by UV absorption at 272nm revealed photodegradation that obeyed first order kinetics. Indirect photolysis experiments in the presence of DOM utilized Suwannee River Fulvic Acid (SRFA), a terrestrially derived DOM and Pony Lake, Antarctica Fulvic Acid (PLFA) a DOM derived from algal precursors. Reactions solutions were prepared at environmentally relative total organic carbon concentrations (TOC≈3-5mg/L). Both DOM mediated DMP photolysis occurred at increased rates relative to direct photolysis, but was significantly faster in reactions involving SRFA. To determine the indirect pathways of degradation, molecular probes were used as competitive scavengers that reacted with specific reactive phototransients e.g. radicals, reactive oxygen species, etc. It was concluded that DMP degrades by reaction with photo-excited triplet DOM (3DOM). Overall, it has been shown that the organic contaminant DMP photodegrades significantly in the presence of DOM and sunlight.
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