Photo-catalytic oxidation of dyes using EDTA-Fe

• Main Authors: Ssu-Ying Chiang, 江思瑩
• Other Authors: Shyi-Tien Chen
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/45099137456088315868

碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程研究所 === 101 === The composition of dyes become rather complicate nowadays due to the desire of colors and the improvement in making them. This in turns makes the treatment of dyeing wastewater a challenge. Conventionally chemical oxidation is considered as the most efficient mean in treating dyeing wastewater, which use oxidant along with catalyst to deprive the electron(s) of dyes to meet the regulatory standard on chemical oxygen demand (COD). Photochemical oxidation is a similar way as chemical oxidation, yet in which the light is used for electron transfer of dyes. In previous study in our group we found that by treating crystal violet (CV) for 2 hours using a photo-catalytic oxidation by peroxide and EDTA-Fe, the degradation of CV reached 90 and 100% at with light and no-light condition, respectively. When TiO2 was used to replace peroxide, the degradation of CV at 30 and 50% was determined at with light and no light conditions. Both results confirmed that the light enhanced the degradability of CV. Thus in current research 5 factors, including H2O2, TiO2, EDTA-Fe, ferrous oxalate and Fe2+, were screened to examine their importance in terms the degradability of the three dyes, namely Acid Red-114 ( AR-114), Reactive Black-5 (RB-5) and Disperse Black EX-SF (DB-EX-SF). The main objectives include: (1) to construct a dye degrading system using light, (2) to optimize the operational conditions of the dye degrading system, and (3) to explore the possible mechanism of dye oxidation. At first a dye degrading system was to be defined to ensure the comparability of test results and the stability of the results collected. Furthermore the most important factors were to be screened by factorial and fractional factorial experiments followed by using the grid design to determene the optimal treatment dosages of the selected factors. Finally the dye degradation over time was to be determined and model fitted as a tool to compare the rates of dye degradation at different treatment conditions. For dye analysis, the AR-114 and RB-5 were analyzed by UV spectrophotometer, any DB-EX-SF by high-performance liquid chromatography (HPLC) due to its particle-like feature that may obstacle the pathway of light. Use of a transparent glass bottle filled with 30 mL of dye-containing wastewater was considered adequate to serve as a reactive system for various dye oxidizing experiments. The resulted statistic analysis showed a value of % error at 0.9~4.9% (n=3), indicating its accuracy in terms of the repeat runs. The results of screening runs depicted the less significance of ferrous iron and ferrous oxalate so that the H2O2, TiO2 and EDTA-Fe were considered as the most important factors in terms of dye degradation. The results of the grid design showed that the optimal dosages of H2O2, TiO2 and EDTA-Fe for AR-114 degradation were 0.04 g in 30 mL, 0.68 and 0.18 mM, respectively and the % degradation reached 88.3%; for the RB-5 degradation, the dosags were 0.01 g in 30 mL, 0.26 and 0.09 mM and the % degradation was 85.9%