Environmental regulations have imposed limitations on a wide variety of organic and
inorganic pollutants in industrial textile wastewaters. There are several degradation
methods used in literature studies. Among these methods ozonation is one of the
most considered way to degrade refractory chemicals in textile wastewaters. In
recent years, catalytic ozonation as being one of the advanced oxidation processes
(AOPs), is applied to reduce the ozone consumption and to increase the Chemical
Oxygen Demand (COD) and Total Organic Carbon (TOC) removals.
Ozonation and catalytic ozonation of single and mixed dye solutions have been
examined both in a semi-batch reactor and also in a three phase fluidized bed reactor.
The dyes that are used in this study are Basic Blue 41 (BB-41), Basic Yellow 28
(BY-28) and Basic Red 18.1 (BR-18.1), these dyes are obtained from AKSA A.S.
(Yalova, Istanbul) textile plant. In order to measure the concentration of each dye in
the mixed dye solution, &ldquo / absorbance vs. concentration&rdquo / calibration correlations were
developed. The effect of inlet dye concentration, inlet gas and liquid flow rates, pH,
catalyst type [perflorooctyl alumina (PFOA) and alumina] and catalyst dosage were
determined experimentally. Catalyst characterization analyses were done in order to
determine the maximum number of times that the catalyst can be used and it was
found to be 3 times. Gas washing bottle experiments are conducted to find the
v
amount of ozone required to oxidize one mole of each dye used in the study.
Oxidation of BB-41, BR-18.1 and BY-28 dyes were investigated in a semi-batch
reactor as single dye solutions by sole and catalytic ozonation with alumina and
PFOA catalyst particles. The highest TOC and COD removals being 58.3% and
62.9%, respectively, were obtained at pH of 10 for BB-41 and 55.2% and 58.8%,
respectively, for BR-18.1 with alumina catalyst. On the other hand, for BY-28 PFOA
catalyst yielded highest TOC and COD reductions being 61.3% and 66.9%,
respectively, at pH of 4.
Minimum fluidization velocity (uL,min), the hold-up values of gas, liquid and solid
phases, the dispersion coefficients (DL), and volumetric ozone-water mass transfer
coefficients (kLa) were estimated at various gas and liquid flow rates in order to
observe the effect of liquid mixing in the reactor on ozonation process. While PFOA
catalyst was found to be effective in oxidizing BY-28 in acidic conditions (pH=4),
BR-18.1 and BB-41 are degraded in alkaline medium (pH=10) with alumina catalyst
better compared to acidic conditions. For catalytic ozonation reactions in fluidized
bed reactor, the highest dye removals in mixed dye solution were observed for BY-
28 being 99.29% for gas flow rate (QG) of 340 L/h, liquid flow rate (QL) of 150 L/h
and pH=4, initial dye concentration being 30 mg/L of each dye with PFOA catalyst,
while for BR-18.1 and BB-41 being 95.39% and 97.95% respectively for QG = 340
L/h, QL = 150 L/h and pH=10, initial dye concentration being 30 mg/L of each dye
with alumina catalyst. The highest TOC and COD reductions, 25.2% and 32.4%,
respectively, were achieved in the catalytic ozonation of the mixed dye using PFOA
as the catalyst at a pH of 4 and at a gas to liquid flow rate ratio of 2.26 (QG = 340
L/h, QL = 150 L/h). Highest dye removals were obtained at the same gas and liquid
flow rates as those of the highest TOC and COD reductions in the experiments.
Empirical TOC removal equations were obtained as a function of inlet TOC
concentration, solution pH, gas and liquid flow rates.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12613794/index.pdf |
| Date | 01 October 2011 |
| Creators | Balci, Ayse Irem |
| Contributors | Ozbelge, Ayse Tulay |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for METU campus |
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