**Table 7.**

*Percentage decolourisation of the different dyes (TAZ, RY-17 and RB-5) using different catalysts.*

The degradation percentage of the dyes (TAZ, RY-17 and RB-5) using different catalysts at the time period of 8 h are given in **Table 8**.

The photocatalytic studies carried out under UV and visible irradiations leads to the following observations:


The higher activity of M/TiO2 catalysts under visible region is explained below:


#### **Figure 12.**

*Degradation of (A) TAZ, (B) RY-17 and (C) RB-5 using different TiO2 catalysts under UV (D,E and F) visible irradiations. (reaction conditions: Dye concentration: TAZ = 1 × 10<sup>−</sup><sup>4</sup> M, both RY-17 & RB-5 = 1 × 10<sup>−</sup><sup>5</sup> M, weight of catalyst = 1.5 g, volume of dye solution = 250 mL and pH = neutral).*


#### **Table 8.**

*Percentage degradation of the dyes (TAZ, RY-17 and RB-5) using different catalysts.*

### **3.6 Effluent studies**

## *3.6.1 Photocatalytic activity of M/TiO2 with the actual effluent sample*

The photocatalytic activity of the synthesised M/TiO2 catalysts (M = Ag, Au and Pt) was tested with the real effluent samples collected from a textile industry (M/s Ramkay, Erode, Tamil Nadu, India).

The industrial effluent (1 L) sample was first filtered to remove any insoluble matter (carbonates, hydroxides, etc.). As the initial pH was in weakly acidic, it was increased to 7 by adding dil. NH4OH and the pH adjusted effluent was then subjected to photocatalytic treatment by adding 6 g of the M/TiO2 (M = Ag, Au and Pt) catalyst. Before the lamp was switched on, the effluent was equilibrated for few minutes with continuous stirring. The effluent was then irradiated using visible light source. Aliquots of the sample were withdrawn at regular time intervals and the extent of decolourisation was monitored using UV-Vis spectrophotometer (Hitachi U 2000). The degradation of the dyes was also determined by using total

**95**

*Detoxification of Carcinogenic Dyes by Noble Metal (Ag, Au, Pt) Impregnated Titania…*

organic carbon analyser (TOC). The decolourisation and degradation results

*(A) Decolourisation and (B) degradation of textile effluent using M/TiO2 catalysts. (reaction conditions:* 

The effluent studies show that, all the M/TiO2 catalysts decolourise and degrade the effluent samples significantly. However, these catalysts decolourise the effluent to the extent of only 65–75% and degrade to the extent of 25–30% that too after longer time of irradiation (12 h). The lesser percentages of decolourisation and degradation may be due to the presence of infinite number of dyes, salts etc. in the

The optimised reactions parameters for the degradation of TAT, RY-17 and RB-5

complete decolourisation (TAZ: 5 ½ h (UV) 6 ½ h (visible), RY-17: 5 h (UV) 6 h (visible), RB-5: 6 h (UV) 7 h (visible). Decolourisation and degradation were comparatively faster under UV than under visible. Inhibitors such as sodium chloride, sodium carbonate and ethanol decreased the degradation rate and electron acceptors such as H2O2 and potassium per sulphate showed beneficial effect. As far as the photocatalytic efficiency of the catalysts are concerned, the following order was

Au/TiO2 > Ag/TiO2~Pt/TiO2 > Synthesised TiO2 > TiO2 (P − 25 Degussa)

Among the noble metals, Au/TiO2 catalyst was found to be the most active catalyst. This may be attributed to the small band gap value of Au/TiO2 leading to

All the M/TiO2 catalysts were found to be more active towards the decolourisation of all the dyes even under visible irradiation. The enhanced photocatalytic activity of the M/TiO2 under visible light irradiation may be due to the presence of impregnated metals, which act as electron traps and by this way they prevent electron hole recombination. The synthesised M/TiO2 catalysts were found to be very active towards the decolourisation and degradation of textile dye effluent collected

M), catalyst weight (1.5 g/L), pH (7) and the time taken for

M and for both RY-17 and

*DOI: http://dx.doi.org/10.5772/intechopen.80467*

obtained are shown in **Figure 13**.

The initial dye concentration (TAZ = 1 × 10<sup>−</sup><sup>4</sup>

*weight of catalyst = 6 g, volume of effluent = 1 L and pH = neutral).*

observed under both UV and visible irradiations,

better visible light absorption.

from an industry as well.

effluent.

**Figure 13.**

**4. Conclusions**

were found to be:

RB-5 = 1 × 10<sup>−</sup><sup>5</sup>

*Detoxification of Carcinogenic Dyes by Noble Metal (Ag, Au, Pt) Impregnated Titania… DOI: http://dx.doi.org/10.5772/intechopen.80467*

**Figure 13.**

*Gold Nanoparticles - Reaching New Heights*

**94**

**3.6 Effluent studies**

**Table 8.**

**Figure 12.**

*RB-5 = 1 × 10<sup>−</sup><sup>5</sup>*

**Dyes Degradation (%)**

**TiO2 (P-25 Degussa)**

(M/s Ramkay, Erode, Tamil Nadu, India).

*3.6.1 Photocatalytic activity of M/TiO2 with the actual effluent sample*

*Percentage degradation of the dyes (TAZ, RY-17 and RB-5) using different catalysts.*

*Degradation of (A) TAZ, (B) RY-17 and (C) RB-5 using different TiO2 catalysts under UV (D,E* 

 *M, weight of catalyst = 1.5 g, volume of dye solution = 250 mL and pH = neutral).*

TAZ 38 29 53 43 83 88 84 90 84 90 RY-17 40 31 63 49 84 96 85 96 85 96 RB-5 35 23 51 41 80 82 81 93 81 94

**UV Visible UV Visible UV Visible UV Visible UV Visible**

 *M, both RY-17 &* 

**Pt/TiO2 Ag/TiO2 Au/TiO2**

*and F) visible irradiations. (reaction conditions: Dye concentration: TAZ = 1 × 10<sup>−</sup><sup>4</sup>*

**Synthesised TiO2**

The photocatalytic activity of the synthesised M/TiO2 catalysts (M = Ag, Au and Pt) was tested with the real effluent samples collected from a textile industry

The industrial effluent (1 L) sample was first filtered to remove any insoluble matter (carbonates, hydroxides, etc.). As the initial pH was in weakly acidic, it was increased to 7 by adding dil. NH4OH and the pH adjusted effluent was then subjected to photocatalytic treatment by adding 6 g of the M/TiO2 (M = Ag, Au and Pt) catalyst. Before the lamp was switched on, the effluent was equilibrated for few minutes with continuous stirring. The effluent was then irradiated using visible light source. Aliquots of the sample were withdrawn at regular time intervals and the extent of decolourisation was monitored using UV-Vis spectrophotometer (Hitachi U 2000). The degradation of the dyes was also determined by using total

*(A) Decolourisation and (B) degradation of textile effluent using M/TiO2 catalysts. (reaction conditions: weight of catalyst = 6 g, volume of effluent = 1 L and pH = neutral).*

organic carbon analyser (TOC). The decolourisation and degradation results obtained are shown in **Figure 13**.

The effluent studies show that, all the M/TiO2 catalysts decolourise and degrade the effluent samples significantly. However, these catalysts decolourise the effluent to the extent of only 65–75% and degrade to the extent of 25–30% that too after longer time of irradiation (12 h). The lesser percentages of decolourisation and degradation may be due to the presence of infinite number of dyes, salts etc. in the effluent.
