Date of Award

9-2003

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Dr. Al aa Eldin Salem .

Second Advisor

Dr. Ibrahim Salem

Third Advisor

Dr. Ihsan Shehada

Abstract

Dyes have become a very important part to countless modem applications. As a result of this huge consumption of dyes in manufacturing processes, huge amounts of wastewater contaminated with dyes are released into different natural dumps like rivers and seas. These dyes contaminated wastes have dangerous impacts on the environment and toxic affects. Two problems are facing scientists concerned about this environmental task. First, dyes vary in their chemical and physical natures and different waste treatments are needed which sometime are not available. Second, getting rid of these pollutants from its sources is costly, that many manufactures can not afford. As a result, solving these two problems is a hot area for environmental researches.

Different approaches to deal with dyes pollutants have been applied. One of these approaches is the chemical treatment of dyes using the bleaching and oxidation power of hydrogen peroxide. H2O2 was used to degrade many organic dyes especially in the presence of some metal ions like Fe+2 or Cu+2. This method is effective, has safe clearance outcomes and economically cheap in addition to the availability of its primary materials worldwide.

In this work, two commonly used dyes by many manufacturers haves been chosen for investigation. These are the thionine and methyl violet dyes. The aim of this study was to study the kinetics and mechanisms of catalyzed and noncatalyzed degradation of the two dyes using H2O2. Degradation products were identified using different analytical techniques like C, H, N analysis, IR, and HPLC. Cu+2 ion was used as catalyst. Due to the difficulty in identifying degradation products by analytical techniques, a computational approach to calculate the potential energy for each fragment was carried out. In the following, a brief description for each chapter of the thesis:

1. Chapter I, introduction, includes a general and updated literature survey on dyes degradation kinetics and mechanisms. Different treatment approaches were also described. An updated survey on thionine and methyl violet dyes was also given.

2. Chapter II, experimental, include a description of experimental procedures, instrumentation used, materials and reagents, preparation of the various standard and buffer solutions and finally a brief description of the computational approach used.

3. Chapter III, result and discussions. In this part the following themes have been studied and discussed.

1. Kinetics of thionine and methyl violet dyes degradation by H2O2 were investigated. Oxidation in presence and absence of catalysts was also studied.

2. The oxidation rate for the uncatalyzed reaction was found to increase when concentration of H2O2 increases until it reaches a maximum value at high concentrations of H2O2. In catalyzed reaction, the rate reached maximum at the beginning and started to declines with increasing concentrations of H2O2.

3. The oxidation rate for both uncatalyzed and catalyzed reactions is increased by increasing concentrations of methyl violet dye until high concentrations of dye and then it decreased.

4. The oxidation rates for both uncatalyzed and catalyzed reactions for both dyes increased by increasing concentrations of Cu+2. Strong acceleration by adding Cu+2 to the reaction medium is attributed to the induction of free radicals which are highly active in attacking the organic dyes.

5. The oxidation rate for both uncatalyzed and catalyzed reactions is increased by increasing pH values and reaches maximum in pH range of 9.0 - 11.0.

6. The oxidation rate for both uncatalyzed and catalyzed reactions is increased by increasing the ionic strength of the reaction medium.

7. The oxidation rate for both uncatalyzed and catalyzed reactions was found to decrease by increasing the concentration of sodium dodecyl sulphate, SDS, even before reaching the critical micelles concentration, CMC value.

Different analytical methods have been used to identify the degradation products of the two dyes. Elemental analysis, IR, and HPLC analyses were used to identify the degradation products. But due to the difficulties of separating these products, a computerized approach to predict these compounds by predicting the most energetically favorable compounds and reaction rout have been done. The two dyes were found to possibly produce up to four products through different cracking pathways.

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