Date of Award

2007

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Dr. Salman Ashraf

Second Advisor

Dr. Oya Sipahioglu

Third Advisor

Dr.Tareek Yousoof

Abstract

Synthetic dyes are a major part of our life. Products ranging from clothes to leather

Accessories to furniture all depend on extensive use of organic dyes.

There are numerous classes of these dyes. However, azo, anthraquinonoid,

Triarylmethane, diarylmethane, acridine, quinine, xanthane and nitro represent the major

Classes and are most commonly used dyes.

An unfortunate side effect of their widespread use is the fact that up to 12% of these dyes are

Wasted during the dyeing process, and that approximately 20% of this waste enters the environment (mostly in water supply). The effluents from these industries cause the water bodies to not only become colored, but also cause an environmental damage to the living organisms by stopping the re-oxygenation capacity of water as well as blocking sunlight. Furthermore, many of these dyes are potentially carcinogenic and can enter our drinking water supply. In fact, results from animal studies show that exposure to some can lead to cancerous and precancerous liver conditions.

Therefore, there is a need to find economical and bio-friendly methods to degrade dyes in

Industrial waste effluents. A number of different approaches (such as adsorption, coagulation etc.) have been developed to remove dyes from aqueous solution. However, all these methods are either costly, inefficient or result in the production of secondary waste products.

Recently a set of new approaches called advanced oxidation processes (AOP) have been developed to efficiently degrade these dye pollutants. Among the most promising of these AOP include generation of hydroxyl radicals from H202 using either:

1. UV radiation (Photolysis),

2. Fe2 ions (Fenton's reagents),

3. Combination of UV and Fe2+ (Photo Fenton) or

4. Using Ti02 (Ti02 photo catalysis).

In comparison with other AOPs, such as Fenton, ozone, UV/03, UV/Ti02, etc., the photolysis of

hydrogen peroxide has the advantages such as the complete miscibility of H202 with water, the stability and commercial availability of hydrogen peroxide, no phase transfer problems, no sludge formation, simplicity of operation and lower Investment costs.

Extensive work has been carried out on the use of one specific AOP a given dye. However, the

Efficiency of a given AOP on the different classes of dyes is not widely published. In this study,

UV- H202 (UV Photolysis) was used to study the kinetics of oxidation and subsequent degradation of eight of the major dye classes. It was found that the degradation process seems to occur according to a similar mechanism for all the selected dyes and follow an apparent first order kinetics. The dye degradation was dependent on the amount of the hydrogen peroxide used and inversely proportional to the dye concentration. The optimum concentration of the UV/H202 reagent and dye concentration was different for each dye. Furthermore, it was found that depending on the class of dye, common ions and salts that are normally part of the wastewater stream had dramatic effects on the degradation rates.

This study has shed light on whether the different classes of dyes are degraded equally well by

Specific AOP approach. Also, we studied the effect of salts (that are normally present in textile

Waste streams) on the photolytic degradation of these dyes.

Lastly, an attempt was made to identify the final degradation products of these dyes and propose degradation scheme.

A comparative analysis was done by using the data from the study. The results indicated that

Different classes of dyes most efficiently degraded (like diarylmethane) than other classes (like a thraquinone).

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