**2.2 Deposition of TiO2 coating on zinc by spray pyrolysis**

Spray pyrolysis technique used in this work is a tubular reactor type as it is given in **Figure 1**. The precursor solution is pumped through a 100 kHz ultrasonic atomizer (Lechler Inc.) to the heated substrate held within a tubular quartz reactor (5 cm in i.d. and 30 cm in length). On the graphite sample holder, the zinc metal substrate was placed and heated by quartz heating bulbs located on top and below the tube. The temperature of the substrate was controlled by a thermocouple type K connected to the temperature controller display. The solution was pumped into the atomizer once the temperature controller indicated the desired temperature, and the atomized droplets of the precursor were dispersed and transported using nitrogen (N2) and oxygen (O2) as the carrier gases towards the substrate to the reaction chamber. The aerosol droplets were decomposed and transformed to very tiny

**193**

**Figure 2.**

*Treatment of Textile Dyeing Waste Water Using TiO2/Zn Electrode by Spray Pyrolysis…*

particles of oxide compounds upon meeting the hot surface of the zinc substrate. The usual spray time for one time deposition of a 50 ml solution batch was around 30–45 min depending on the spray conditions. The sample was then cooled down by 5–10°C/min from the deposition temperature slowly to room temperature. The electrodes were prepared with dimensions of 9 cm × 3.2 cm × .5 cm. **Figure 1** shows the photograph of the pretreated zinc plate, coating on zinc in spray pyrolysis and

*(a) Photograph of the pretreated zinc plate, (b) Coating on zinc in spray pyrolysis, (c) TiO2/Zn.*

Disperse dye was obtained from one of the textile industry in Coimbatore, Tamil Nadu. (Commercial name; Coralene Navy RDRLSR, Coralene Red 3G, Rubru RD GLFI) The simulated wastewater was prepared by dissolving a 150 ppm of disperse dyes in distilled water. The experimental device is schematically shown in **Figure 2**. The EC unit consists of an electrochemical reactor which is a glass beaker with magnetic stirring, a D.C power supply and two sets of EC process were run with TiO2/Zn – TiO2/Zn and Zn – Zn. (Hereafter these electrodes will be

represented as 'A' (TiO2/Zn – TiO2/Zn) and 'B' (Zn – Zn)).

*Schematic representation of EC process (Source: http://pubs.sciepub.com).*

*DOI: http://dx.doi.org/10.5772/intechopen.95325*

the TiO2/Zn plate.

**Figure 1.**

**2.3 Electrocoagulation process**

*Treatment of Textile Dyeing Waste Water Using TiO2/Zn Electrode by Spray Pyrolysis… DOI: http://dx.doi.org/10.5772/intechopen.95325*

**Figure 1.**

*Dyes and Pigments - Novel Applications and Waste Treatment*

terization of the electrode. (SEM, XRD, EDS)

textile waste water using TiO2/Zn in EC process.

phases to address the issues mentioned in the objectives.

**2.1 Preparation of TiO2/Zn electrode by spray pyrolysis**

(15 ml) was added maintaining the temperature 5 to 10o

**2.2 Deposition of TiO2 coating on zinc by spray pyrolysis**

with reduction in electrolysis time and applied current.

• To prepare TiO2/Zn from TiCl3 by Spray pyrolysis method and surface charac-

• To investigate the influence of operational parameters in the removal of dye in

• To identify the strategy for improvement of the color removal efficiency (CRE)

The detailed methodology of the present study, which was carried out in two

• Removal of disperse dye (Coralene Navy RDRLSR, Coralene Red 3G, Rubru RD GLFI) from synthetic wastewater using TiO2/Zn Electrode in electroco-

In general the experimental procedure recommended by Beck and Co-workers was adopted for the preparation of TiO2/Zn electrode by spray pyrolysis of TiCl3 by the following procedure [26]. The TiO2 coating was done on zinc substrate which was cleaned well and sand blasted to make the surface adherent for the coating. Etching was done for the same purpose using etchants (5% Oxalic acid in water)

C for 1 hour. The surface was then washed properly with water, rinsed using

C.

Then it was coated with the precursor solution TiCl3 (0.05 N) 4 ml, 1:1 HNO3 water (2.5 ml). The precursor solution was cooled to 5°C to which isopropyl alcohol

Spray pyrolysis technique used in this work is a tubular reactor type as it is given in **Figure 1**. The precursor solution is pumped through a 100 kHz ultrasonic atomizer (Lechler Inc.) to the heated substrate held within a tubular quartz reactor (5 cm in i.d. and 30 cm in length). On the graphite sample holder, the zinc metal substrate was placed and heated by quartz heating bulbs located on top and below the tube. The temperature of the substrate was controlled by a thermocouple type K connected to the temperature controller display. The solution was pumped into the atomizer once the temperature controller indicated the desired temperature, and the atomized droplets of the precursor were dispersed and transported using nitrogen (N2) and oxygen (O2) as the carrier gases towards the substrate to the reaction chamber. The aerosol droplets were decomposed and transformed to very tiny

• Preparation of TiO2/Zn Electrode by spray pyrolysis method using the

**1.8 Objectives of the study**

• Sludge characterization.

**2. Materials/methods**

precursor TiCl3

agulation process.

**192**

at 60o

triple distilled water.

*(a) Photograph of the pretreated zinc plate, (b) Coating on zinc in spray pyrolysis, (c) TiO2/Zn.*

particles of oxide compounds upon meeting the hot surface of the zinc substrate. The usual spray time for one time deposition of a 50 ml solution batch was around 30–45 min depending on the spray conditions. The sample was then cooled down by 5–10°C/min from the deposition temperature slowly to room temperature. The electrodes were prepared with dimensions of 9 cm × 3.2 cm × .5 cm. **Figure 1** shows the photograph of the pretreated zinc plate, coating on zinc in spray pyrolysis and the TiO2/Zn plate.

## **2.3 Electrocoagulation process**

Disperse dye was obtained from one of the textile industry in Coimbatore, Tamil Nadu. (Commercial name; Coralene Navy RDRLSR, Coralene Red 3G, Rubru RD GLFI) The simulated wastewater was prepared by dissolving a 150 ppm of disperse dyes in distilled water. The experimental device is schematically shown in **Figure 2**. The EC unit consists of an electrochemical reactor which is a glass beaker with magnetic stirring, a D.C power supply and two sets of EC process were run with TiO2/Zn – TiO2/Zn and Zn – Zn. (Hereafter these electrodes will be represented as 'A' (TiO2/Zn – TiO2/Zn) and 'B' (Zn – Zn)).

#### **Figure 2.**

*Schematic representation of EC process (Source: http://pubs.sciepub.com).*

The electrodes were used with dimensions of 9 cm × 3.2 cm × .5 cm. The total effective electrode area was 28.16 cm2 and the spacing between electrodes was 1 cm. The electrodes were connected to a digital dc power supply (var tech) providing a current ranging from 0.05 to 0.3A. 500 ml electro coagulation cell that contained the 250 ml test solution and a magnetic stirrer was used to stir the solution, thereby enhancing the efficiency. The applied current was adjusted to a desired value and the coagulation was started. In each run, 250 ml of dye solution was placed into the electrolytic cell. Before each run, electrodes were washed with water and dipped in 15% hydrochloric acid in order to remove dust from the electrode plates and thus weigh the electrodes after drying. The electrode plates are washed with water at the end of each run, dried and weighed at last. Whattman filter paper was used to filter the subsequent treated sample and filtrate was used for the analysis. The individual effects of electrolysis time and applied current on colour removal efficiency were quantified in this analysis (CRE). The pH was adjusted by adding 0.5 M HCl or 0.5 M NaOH. The conductivity of solutions was raised and adjusted to different values by the addition of NaCl. All experiments were carried out at constant temperature of 25°C. Two sets of EC process were carried out with 'A' and 'B' electrodes with operating parameters like pH, EC time, dye concentration, addition of electrolyte NaCl and applied current for optimization to achieve higher Color Removal Efficiency (CRE%). On the basis of the initial experiments, other parameter rates were considered constant. The experimental set up in EC process, after the experiment, the coagulated dye solution getting separated as sludge settling and floating are given in **Figure 3**.
