State-of-the-Art Catalysis

**75**

**Chapter 5**

**Abstract**

discussed.

carcinogenic dyes

**1. Introduction**

Detoxification of Carcinogenic

Dyes by Noble Metal (Ag,

Photocatalysts

Au, Pt) Impregnated Titania

*Sivakumar Thiripuranthagan and Valentine Rupa*

Textile industries produce large quantities of waste water which is notoriously known to contain strong colour, suspended solids and COD. Although several treatment processes, such as filtration, coagulation, oxidation, ozonation, reverse osmosis, etc., have been practiced for many decades, they all have inherent limitations. They transfer the harmful pollutants from one phase to another and do not address detoxification. Semiconductor photocatalysis is a promising technique for photodegradation of hazardous chemicals found in waste waters. Among various semiconductors, TiO2 has been studied widely. However, the main drawbacks associated with TiO2 are (i) large band gap (Eg > 3.2 eV) (only UV active) and (ii) recombination of excitons. Dye sensitisation, coupling of semiconductors, and transitional metal doping are some of the methods reported to shift its optical response to visible region. Herein, nanoparticles of different noble metals such as Ag, Au and Pt were deposited on synthesised TiO2, characterized by XRD, TEM, FT-IR, BET, UV-Vis and AAS and were subjected to the degradation of some textile dyes namely Tartrazine (TAZ), Reactive Yellow-17 (RY-17) and Reactive Black-5 (RB-5) under both UV and visible irradiations. The reaction conditions such as catalyst concentration, dye concentration, pH, irradiation time, light intensity, and additives were optimized for complete decolourisation and

**Keywords:** photocatalyst, gold impregnated titania, textile effluent, detoxification,

Dyeing and finishing processes are the two important steps in textile industries. Large number of synthetic dyes are used extensively in the textile dyeing process and these industries produce large quantities of waste water containing carcinogenic dyes. When ground water mixes with such waste water it gets polluted and cause allergy, damage of eye, brain, liver and reproductive organs and deformities in babies during pregnant period. Thus, water pollution is a major concern in the developing nations. Though dyes are aesthetic pollutants by nature of their colour,
