Tekstil Boyar Maddelerinin İleri Oksidasyon Yöntemleri (Uv, Uv/H2o2, Uv/Ozon,Uv/H2o2-Ozon) İle Muamele Edilmesi
Özet
Waste waters that belong to textile industry have typical characteristics like high organic contamination and including intensive color. Approximately 70% of textile dyes are reactive dyes that contain azo chromophore groups. It is really hard to remove this dye stuff because of their complex chemical structure and high molecular weight. Additionally, including dye stuff of textile waste water can be toxic, carcinogenic and even mutagenic.
Advanced oxidation processes are effective in degrading of pollutants in the wastewater by the presence of both oxidizing (hydroxyl) and reducing (hydrated electrons) which may be present in the final environment. Reactive Black 5 (RB5) is widely used in textile industry and it is studied to degrade structure of RB5 in aqueous solution at different conditions. UV-irradiation, UV/H2O2, ozone and UV/O3 prosesses were used as AOP’s to degrade the structure of RB5 dye.
The concentration of RB5 are selected as 6 mgL-1 and 50 mgL-1. 6 mgL-1 and 50 mgL-1 RB5 solutions are irradiated with UV lamp ( which has maximum emission at 254 nm wavelength and 16 W power) in the absence and presence of (0.3-2.4 mM) H2O2 during (30,60,120,180 minutes) irradiation times. To degrade the intermediates obtained and RB5 completely in water, H2O2 and O3 are used to increase the possibility of the formation of oxidative hydroxyl radicals in addition to UV irradiation.
Different ozonation times (10-180 seconds) and different UV irradiation times (0-180 minutes) were studied to investigate the effect of ozonation time and UV-irradiation times on RB5 degradation in water. The minumum conditions for 50 mgL-1 RB5 were 60 second ozonation and 120 minutes UV-irradiation. The degradation of RB5 in water was followed as a function of UV-irradiation or ozonation time and the remaining RB5 as undegraded were determined by using the UV-GB spectrophotometer. Formation of formaldehyde in RB5 solutions was investigated as a function of irradiation time in the presence of H2O2. Dissolved oxygen (DO) and pH values were detrmined in the presence and absence of H2O2 and O3. To detect and analyze intermediate species, Thermo trace 1300 Gas Chromatography Mass Spectrometers (GC-MS) and Agilent Technologies 6224 TOF LC/MS Spectrometer were used. Ion Chromatography was used for analyzing of aliphatic acid and anions.
When 50 mgL-1 aqueous solution of RB5 was irradiated by UV llight during 180 minutes maximum degradation for RB5 in water was 27.92 %. The irradiation time required for higher degradation of RB5 was reduced in the presence of hydrogen peroxide. In the presence of 0.3 mM H2O2 and 180 minutes UV-light irradiation, RB5’s degradation in water is 95.07 %. If we think using with only H2O2, RB5 degradation is 5.34 % . So, H2O2 is not effective on degradation of RB5 by itself. When H2O2 is used with UV-light, there is much more degradation of RB5 with the strong oxidant effect of radicals. In other words, percent rate of degradation depend on UV-light time and peroxide concentration.
For 6 mgL-1 RB5 solution, minimum conditions for UV/ H2O2 process were 0.3 mM H2O2 and 60 minute UV-irradiation and degradation percent was determined as 100 %. Degradation of RB5 in water was 0.50 % using with only H2O2 by itself. It was studied with 0-180 second ozonation and different UV-irradiation times for concentradations of RB5 (6 mgL-1 and 50 mgL-1). UV/O3 process produce more .OH radicals than UV/H2O2 process. UV/O3 process is much more effective method. If Ozonation was used only for 50 mgL-1 RB5 aqueous solution during 60 second, degradation percent would be 85.75 %. The degradation percent of RB5 in water increased by 100 % in 120 minute UV-irradiation to 60 second ozonation 50 mgL-1. 6 mgL-1 RB5 solution was exposured to 10 second ozonation, degradation percent was 65.67 %. To have degradation 100 %, 60 second ozonation and 120 minutes UV-irradiation were required. To compare all these processes, it has been decided only O3 and UV/O3 methods are effectual methods.
Key words: Degradation of Reactive Black 5 (RB5), Advanced Oxidation Processes (AOP’s), UV, UV/H2O2, O3, UV/O3.
