**2.2. EC rotating anode reactor**

**Figure 1** illustrates the new EC reactor employed in the current study. The reactor (10 L working volume) was made from Perspex and has a cylindrical form stirred tank setting (total length = 500 mm; inner diameter = 174 mm; external diameter = 180 mm). To keep the impeller structure and sustain the rotation of the electrode, a 32-mm-diameter rotating shaft was attached to a regulating speed motor. The motor is a DC electrical type and offers a number of steady-state speeds in the range of 0–1000 rpm. The electrodes were produced from the aluminum substance; the rotating anode comprises ten impellers. All the impellers have four rods (diameter = 12 mm, length = 30 mm) each and ten rings, which were employed as the cathode. Every one of the ring (thickness = 12 mm, internal diameter = 134 mm, diameter = 172 mm) was serially organized, maintaining 30 mm distance of apart. The entire active surface area is 500 cm<sup>2</sup> ; the reactor comprises three equally spaced baffles to establish the cathode rings by terminating the rotation and tangential flow arrangements of the mass fluid. The endorsed surface area-to-volume ratio ranges from 5 to 45 m<sup>2</sup> /m<sup>3</sup> [8]. In the current model, the ratio was minimized (to 5 m<sup>2</sup> /m<sup>3</sup> ) with the aid of a small area of the electrode for treatment of a great wastewater volume. The patent novelty filing was performed with application number PI 2015702202.


**Table 1.** Characteristics of textile wastewater.

#### **2.3. Experimental procedure**

interact to generate insoluble OH<sup>−</sup>

112 Wastewater and Water Quality

**2. Materials and methods**

**2.1. Wastewater characteristics**

**2.2. EC rotating anode reactor**

area-to-volume ratio ranges from 5 to 45 m<sup>2</sup>

/m<sup>3</sup>

500 cm<sup>2</sup>

mized (to 5 m<sup>2</sup>

ions. The generated insoluble hydroxides adsorb the con-

taminants from the solution either by electrostatic attraction or complexation before the coagulation [3, 4]. Lessening of the electrodes' internal resistance drop (IR-drop) is one of the most essentials toward reducing the total cost of EC operation to enhance the current performance by enhancing the state of turbulence. Both oxygen and hydrogen gas emerged near the cathode and anode as soon as each gas bubble nucleates. The bubbles are like insulating spherical figures, generating a film that fouls oxide over the electrode surface (passivation effects). This issue increases the total electrical resistance of the cell, thereby needing a superior quantity of electrical energy to attain the optimal removal [5]. To moderate the bubble accumulation, the electrolyte flow around the electrodes must be augmented for the bubbles to be pushed out [6]. To proffer solution to these, the current EC reactor with rotating anode was conducted to enhance the reactors' overall efficiency [7]. Additionally, the leading objective of the present work is to study the treatment of textile wastewater using a novel EC reactor under optimum operating conditions and to compare the performance with that of conventional EC reactor.

The wastewater used for the present study was obtained from one of the foremost textile industries in Babylon (Iraq). For dyeing of fabrics, the industry employs Imperon Violet KB (CAS #: 6358-46-9). **Table 1** presents the major characteristics of the textile wastewater, while

**Figure 1** illustrates the new EC reactor employed in the current study. The reactor (10 L working volume) was made from Perspex and has a cylindrical form stirred tank setting (total length = 500 mm; inner diameter = 174 mm; external diameter = 180 mm). To keep the impeller structure and sustain the rotation of the electrode, a 32-mm-diameter rotating shaft was attached to a regulating speed motor. The motor is a DC electrical type and offers a number of steady-state speeds in the range of 0–1000 rpm. The electrodes were produced from the aluminum substance; the rotating anode comprises ten impellers. All the impellers have four rods (diameter = 12 mm, length = 30 mm) each and ten rings, which were employed as the cathode. Every one of the ring (thickness = 12 mm, internal diameter = 134 mm, diameter = 172 mm) was serially organized, maintaining 30 mm distance of apart. The entire active surface area is

; the reactor comprises three equally spaced baffles to establish the cathode rings by terminating the rotation and tangential flow arrangements of the mass fluid. The endorsed surface

) with the aid of a small area of the electrode for treatment of a great wastewa-

[8]. In the current model, the ratio was mini-

/m<sup>3</sup>

ter volume. The patent novelty filing was performed with application number PI 2015702202.

**Table 2** shows the properties of the employed Imperon Violet KB.

The performance of EC process was determined based on color removal, TSS and COD. The experiment was initially performed by investigating the influence of CD and the anode rotation speed. The overall competence of the reactor was investigated using three major variables: overall rotation speed of the anode, CD and processing time. The value of RT of 10–30 min was maintained. Three values of CD (4, 6 and 8 mA/cm<sup>2</sup> ) with different steady-state anode rotation speed (75, 150 and 250 rpm) were observed at room temperature (25–27°C). The selection of the current densities was based on some initial studies, which show an insignificant change in the total removal efficiency when the value of CD exceeds 8 mA/cm<sup>2</sup> . For all the runs, a 10 L sample was used for the EC process, and nine different batches of EC runs were performed. Upon concluding each run, a primary sample was removed, and the cells were washed with a 5% HCl solution for 10 min and subsequently washed using a sponge. The anode and cathode were linked to the positive and negative parts of DC power supply (YIZHAN, 0–6 A; 0-40 V, China). 30 V was used as the main voltage was for each experiment. For voltage measurement, a voltmeter was attached to the cell in parallel. For each run, the current was kept constant by using a variable resistance and monitored using an ammeter. For each iteration, the samples were left to settle for 30 min and subsequently filtered. About 100 ml of supernatant sample was collected for examination and analysis in replicates. The same parameters were examined for the entire replicated sample.

**Table 2.** Properties of Imperon violet KB.

The experiment was performed using four different sets of operating conditions to obtain best parameters. The influence of pH on the EC system was investigated at varying pH values (5–10 by addition of 0.5 M NaOH). Some secondary electrolytes like Na<sup>2</sup> SO<sup>4</sup> and NaCl (0.0, 0.02, 0.05 and 0.10 kg/m<sup>3</sup> ) were added to the wastewater toward investigating the effect of electrolyte support on the removal efficiency. The influence of temperature was studied, ranging from 25 to 45°C using water circulation to sustain the temperature as the EC process proceeds. The IED between the cathode rings and anode impellers were attained for various distance (1, 1.5 and 2 cm). At the end of experimentation, the best operating condition was determined again in triplicate to confirm the accuracy of the EC operation and repeatability for treatment of textile wastewater pollutants. For comparison study using same textile wastewater, the results of the conventional model with parallel electrodes in two phases have been observed by our previous works using EC alone by aluminum plates [9] and on enhancing of EC process by combining with electro-oxidation (EO) using titanium plates [10].

The passivation and adsorption phenomenon was also investigated using the electrochemical impedance spectroscopy. The experiment was performed using AC signal potential amplitude maintained at 10 mV, and the observed frequency range was 0.01–105 Hz. A potentiostat was employed to carry out the electrochemical impedance assays. The impedance experiments were performed in a single-partition, three-electrode system, consisting of an Al electrode

rings and (iv) top view of cathode rings and impeller anode.

**Figure 1.** (a) Illustration of EC rotating anode setup. (b) Representation of the EC rotating anode system: (1) motor variable speed, (2) stainless steel shaft (D = 32 mm), (3) Teflon flange cover (upper) (H = 100 mm, D = 280 mm), (4) impeller anode aluminum rod (D = 12 mm, L = 30 mm, no = 4), (5) aluminum ring cathode (T = 12 mm, d.In = 132 mm, D.Out =1 72 mm, no = 10), (6) Perspex reactor (L = 500 mm, d.In = 174 cm, D.Out = 180 mm), (7) upper ports (D = 10 mm, no = 3), (8) ball bearing, (9) thrust bearing, (10) lower port (D = 10 mm), (11) zoom couping and (12) Teflon flange cover (lower) (D = 280 mm, H = 100 mm). (c) Electrode configurations: (i) cathode and anode, (ii) anode impellers, (iii) cathode

Treatment of Textile Wastewater Using a Novel Electrocoagulation Reactor Design

http://dx.doi.org/10.5772/intechopen.76876

115

Treatment of Textile Wastewater Using a Novel Electrocoagulation Reactor Design http://dx.doi.org/10.5772/intechopen.76876 115

**Figure 1.** (a) Illustration of EC rotating anode setup. (b) Representation of the EC rotating anode system: (1) motor variable speed, (2) stainless steel shaft (D = 32 mm), (3) Teflon flange cover (upper) (H = 100 mm, D = 280 mm), (4) impeller anode aluminum rod (D = 12 mm, L = 30 mm, no = 4), (5) aluminum ring cathode (T = 12 mm, d.In = 132 mm, D.Out =1 72 mm, no = 10), (6) Perspex reactor (L = 500 mm, d.In = 174 cm, D.Out = 180 mm), (7) upper ports (D = 10 mm, no = 3), (8) ball bearing, (9) thrust bearing, (10) lower port (D = 10 mm), (11) zoom couping and (12) Teflon flange cover (lower) (D = 280 mm, H = 100 mm). (c) Electrode configurations: (i) cathode and anode, (ii) anode impellers, (iii) cathode rings and (iv) top view of cathode rings and impeller anode.

The experiment was performed using four different sets of operating conditions to obtain best parameters. The influence of pH on the EC system was investigated at varying pH val-

O5

of electrolyte support on the removal efficiency. The influence of temperature was studied, ranging from 25 to 45°C using water circulation to sustain the temperature as the EC process proceeds. The IED between the cathode rings and anode impellers were attained for various distance (1, 1.5 and 2 cm). At the end of experimentation, the best operating condition was determined again in triplicate to confirm the accuracy of the EC operation and repeatability for treatment of textile wastewater pollutants. For comparison study using same textile wastewater, the results of the conventional model with parallel electrodes in two phases have been observed by our previous works using EC alone by aluminum plates [9] and on enhancing of

) were added to the wastewater toward investigating the effect

SO<sup>4</sup>

and NaCl

ues (5–10 by addition of 0.5 M NaOH). Some secondary electrolytes like Na<sup>2</sup>

EC process by combining with electro-oxidation (EO) using titanium plates [10].

(0.0, 0.02, 0.05 and 0.10 kg/m<sup>3</sup>

**Table 2.** Properties of Imperon violet KB.

\*Absorbance of 0.34 at 533.

Chemical formula C32H26N<sup>4</sup>

The molecular weight (g/mol) 546.57 λmax (nm)\* 533

**Color Imperon Violet KB**

Chemical structure

114 Wastewater and Water Quality

The passivation and adsorption phenomenon was also investigated using the electrochemical impedance spectroscopy. The experiment was performed using AC signal potential amplitude maintained at 10 mV, and the observed frequency range was 0.01–105 Hz. A potentiostat was employed to carry out the electrochemical impedance assays. The impedance experiments were performed in a single-partition, three-electrode system, consisting of an Al electrode (1:25 of the original size) as the working electrode, a platinum wire as a counter electrode and Ag/AgCl (3 M KCl) electrode as a reference electrode.

where m<sup>1</sup>

process and m3

and m2

sludge after 30 min (mL/L).

**2.6. Economic analysis**

computed using [3].

sludge per m3

energy and (Cenergy)S

30 min of settling [11]. The SVI is defined as.

Celectrode = intake of electrode for treatment of 1 m<sup>3</sup>

of wastewater (kg/m<sup>3</sup>

Cenergy (kWh/m3) <sup>=</sup> (Cenergy)<sup>S</sup>

are the mass of the cup (with the membrane) after and before the filtration

Treatment of Textile Wastewater Using a Novel Electrocoagulation Reactor Design

http://dx.doi.org/10.5772/intechopen.76876

117

 is the mass of the same cup after the drying for 24 h at 100°C. A sludge volume index (SVI) was implemented to decide the settling properties of the sludge suspensions. The SVI (mL/g) is the volume (in mm) used by 1 g of a suspension subject to

SVI = VD<sup>30</sup> /TSS (3)

where TSS is the concentration of suspended solids (g/L) and VD30 is the volume of settled

The total operating costs for treatment of wastewater process include electricity, equipment, chemical usage, labor, maintenance and sludge disposal. For EC process, the major costs of operation include the cost of electricity and electrode material. In this study, the cost of chemical supplements and sludge disposal was added as well. The total cost of operation (TCO) was

TCO = *a* Cenergy + *b* Celectrode + *d* Csludge + *e* Cchemicals (4)

Cenergy = UIRT/*V* (5)

Celectrode = M<sup>w</sup> I RT/ZF*V* (6)

where Cenergy = denotes intake of energy per cubic meter of wastewater (kWh/m<sup>3</sup>

electricity (about 0.075US\$/kWh); *b* = cost of iron or aluminum (2.5US\$/kg); *d* = sludge disposal cost excluding the drying and including transportation (0.06US\$/kg); *e* = cost of chemi-

kg) and NaCl (0.06US\$/kg); U = voltage; I = intensity of the current; RT = EC electrolysis time; *V* = textile wastewater working volume; M<sup>w</sup> = molar mass of the iron (55.84 g/mol) or aluminum (26.98 g/mol); Z = quantity of electrons moved (3); F = Faraday constant (96,500 C/mol). The operating expense was computed according to the Iraqi market prices for the year 2017. For EC rotating anode, the total consumption of electrical energy was estimated as follows:

where (Cenergy)M signifies the rate at which the DC motor anode rotation consumed electrical

cals that can be added: LPM 3135 polymer (3.0US\$/kg), NaOH (0.5US\$/kg), Na<sup>2</sup>

of wastewater (kg/m<sup>3</sup>

<sup>+</sup> (Cenergy)<sup>M</sup>

signifies the amount of electrical energy consumed by the reacting system

); Cchemical = amount of chemicals (kg/m<sup>3</sup>

);

); Csludge = quantity of

SO<sup>4</sup>

).; *a* = total cost of

(0.25US\$/

(7)
