| Summary: | 碩士 === 國立屏東科技大學 === 環境工程與科學系所 === 105 === In recent years, Saccharin (SAC), one of widely used artificial sweeteners is regarded as one of emerging contaminants in environment, due to its potential adverse effects on environment and human health. In this study, we explored the electrochemical degradation of SAC under different operating parameters (current density, temperature, Na2SO4 electrolyte concentration, anode area, cathode area, and real water matrix (river water and food processing wasterwater treatment plant effluent)) in undivided and divided cells. LC-MS/MS, HPLC, and IC analyses were performed to determine the intermediates (products) and pathways of SAC electro-degradation. Moreover, UV, fluorescence excitation-emission matrix (EEM), and Microtox® toxicity tests were conducted to evaluate the characteristics of water matrices during SAC electro-degradation.
The results showed that no SAC oxidation peak was observed on the BDD electrode. In the divided cells, the SAC degradation and TOC removal increased with an increasing current density, Na2SO4 concentration, or anode area but the SAC degradation and TOC removal were lowered when increasing temperature. A similar trend was found in the undivided cell; however, the SAC degradation and TOC removal increased when the cathode area decreased. The better SAC degradation and TOC removal in divided cell were obtained at 0.25 A/cm2, 25oC, Na2SO4 concentration = 0.4 M, and anode area = 4 cm2. This is also true in undivided cell, but the current density and cathode area were 0.75 A/cm2, and 0.2 cm2, respectively。In both cells, the electro-degradation efficiencies of SAC reached 100 % in different SAC spiked water matrices, although the TOC removal and mineralization current efficiencies were better in the divided cell than in the undivided one. For 30 min electrolysis the SUVA254 of all SAC spiked water matrices increased, while those of 0.4 M Na2SO4 and riverwater D decreased to ND at 60 and 120 min, respectively. However, the variation of SUVA254 in wastewater A before biotreatment (BBT) or B BBT was consistent with that of TOC removal. Without spiking SAC and 0.4 M Na2SO4, the main EEM peaks of riverwater D, wastewater A BBT, wastewater B BBT were in Tryptophan and soluble microbial by-product-like regions while , these fluorescence peaks had lower intensities or disappeared after SAC addition. After 120 min electrolysis, the SAC EEM peaks disappeared but some peaks with very low intensities still existed. This phenomenon is attributed the slight presence of original dissolved organic matter which was harder to be degraded than SAC in the water matrices. In both cells, the SAC was initially hydrolyzed into saccharide anions, and then it was degraded to the intermediates of acetamide-N-sulfonate, benzamide, phenol, succinic acid, hexane-2, 5-dione, maleic acid, oxalic acid, oxalic acid, formic acid, ammonium, and nitrite before the mineralization; however, acetic acid was not detected in the undivided cell. Without spiking SAC, the all water matrices did not show any Microtox® toxicity response. After spiking SAC, the Microtox® toxicity effect values increased and then decreased in all real water matrices during 120 min electrolysis.
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