| dc.description.abstract | The objective of this study was to investigate the degradation of anthraquinone dyes in aqueous solution by ozonation using a semi-batch reactor. The effects of various operating parameters, such as initial dye concentrations, ozone feed rates and initial pH, on performance of color, dye, and TOC removal were evaluated. Also, possible dye degradation products were identified to investigate degradation pathways. Finally, the biodegradability enhancement of dye solution by ozonation was assessed.
The experimental results showed that Reactive Blue 19 (RB-19) could be degraded by ozonation. The color and dye removal were more rapid and complete than TOC removal in all ozonation tests. However, increasing the initial RB-19 concentration had significant effect on decreasing the elimination of RB-19. In addition, increasing ozone feed rates had all positive effects on color, dye and TOC removal, particularly on TOC diminution. Also, the rate constant and efficiency of color removal were highest at initial acidic pH condition, but dye and TOC removal were more effective at the basic pH value likely due to more powerful and non-selective hydroxyl radical oxidation.
The results of UV/VIS and FTIR spectra showed that the anthraquinone structures, nitrogen linkages and amino groups of RB-19 were destroyed under direct ozone reaction. The identification by LC-MS and GC-MS analyses indicated that some organic acids (e.g., phthalic acids) and 1,3-indanone could be the primary degradation products, respectively. Thus, the possible degradation pathways, which count on the initial destruction of either amino groups or C–N–Aromatic linkages, were proposed
Basically, ozonation was confirmed to have potential to increase BOD5/COD ratio of RB-19 solution. On the other hand, ozonation also decreased Microtox toxicity and increased SOUR of RB-19 solution. The enhanced biodegradability was validated by screen tests, which revealed an improved DOC removal by biodegradation.
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