COMPARISON OF FE AND AL ELECTRODES IN THE TREATMENT OF BLUE CA DYE EFFLUENT USING ELECTRO COAGULATION PROCESS.

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1 COMPARISON OF FE AND AL ELECTRODES IN THE TREATMENT OF BLUE CA DYE EFFLUENT USING ELECTRO COAGULATION PROCESS. VINODHA S, DIEGO CARMEREGO, JEGATHAMBAL P School of Civil Engineering Karunya University (Karunya Institute of Technology and Sciences) (Declared as Deemed-to-be-under Sec-3 of the UGC Act, 1956) Karunya Nagar, Coimbatore INDIA Abstract In this work a comparison between Fe and Al electrodes, for electrocoagulation process was conducted with Blue CA dye. As there is no standard method to measure the colour intensity, a UV-Vis spectrophotometer was used to quantify the absorbance initially before the treatment and after the treatment of the dye solution. Removal efficiencies on the Blue CA were obtained by measuring absorbance of a sample at 588 nm. The percentage of Colour Removal Efficiency (CRE (%)) reached in a maximum of 92.45% for iron and 40.35% for aluminium. Removal was found highly dependent upon important parameters such as NaCl concentration, current density, time of treatment and initial ph. The obtained results showed that the colour removal optimal conditions are the following: initial ph of about 7.5, current density of 120 ma, 40 minutes of -electrolysis time, and 3% of concentration of NaCl, for 0.04% of dye with Fe. With iron electrode the CRE was high, about 93% for the optimized set, and for aluminium electrode the CRE was low about 40% for the same conditions that of iron electrode Keywords : Decolourisation, Textile wastewater, Electro-coagulation 1. Introduction The textile industry, particularly in India, nowadays is an important sector of its economy, such as one of the major contributors to the total output of the fast growing Indian industrial sector which is at present revolving around 14%. These textile dyeing industries consumes large quantities of water and produces large volumes of wastewater. Therefore, with this perspective of growth, more wastewater is expected, i.e., more industries will throw its wastewater in the environment. [5] Furthermore, one of the major challenges facing mankind today is to provide clean water to a vast majority of population around the world. There is an urgent need to develop innovative, more effective and inexpensive technique for treatment of wastewater. [3] Therefore, it is necessary to treat dye effluents prior to their discharge to the receiving water stream in order to meet the environmental regulations. [2] The discharge of such dyes in the ecosystem is considered as a major environmental concern. Dye effluents, are not only aesthetic pollutants by nature of their colour, but may interfere light penetration in water, thereby disturbing biological activities of aquatic life. [2] The technique used in this experiment is electro coagulation, which has been a practice for most of the 20 th century with limited success and popularity earlier. Electrocoagulation (EC) has been used for different types of treatment, for example, industrial wastewater containing metals, it has been used for treating wastewater from pulp and paper industries, and at times only for primary treatment. The studies about EC are increasing due to its good efficiency a low cost on treatment of water. Therefore, development of this technology is pertinent for industries and for the environment. ISSN : Vol. 4 No.05 May

2 This process has the potential to extensively eliminate the disadvantages of the classical treatment techniques. Moreover, the mechanisms of EC are yet to be clearly understood and there has been very little consideration of the factors that influence the effective removal of ionic species, particularly metal ions, from wastewater by this technique. [3] Basically, this report aims to show the efficiency of electrocoagulation for treatment of textile wastewater with Blue CA and compare the results between Fe electrode and Aluminium electrode for a same optimum condition. 2. Materials and Methods 2.1 Experimental setup The EC unit consists of an electrochemical which is a glass beaker with magnetic stirring, a D.C., power supply and two electrodes. Figure 1 shows a schematic diagram of the experimental setup, where: 1, DC power supply; 2, Electrode pair; 3, Electrolytic cell; 4, Magnetic stirrer. Both electrodes (Iron and Aluminium) having an effective area 23.04cm 2 and the submerged surface area of the each electrode plate was approximately 45cm 2. They were placed vertically and dipped in 250 ml aqueous dye solutions. Fig 1- Scheme of the experimental arrangement Electrodes were connected to a DC power supply, while the magnetic stirrer was to continuously mix the solution. 2.2 Procedure Blue CA dye powder was used to make solutions with deionised water and Sodium Chloride (NaCl), and then was diluted according to the desired concentration. The concentrations of dye were as 0.01%, 0.02%, 0.03%, 0.04%, and, 0.05%. Different currents were maintained as 60, 90, 120, and 150 ma. The first run of EC was done for 20 minutes electrolysis time with various concentrations of dye, and then the solution was left for 30 minutes at stirring. After settling for about an hour the samples were filtered and checked for ph, conductivity, and absorbance. Dye concentration was measured using UV/vis Spectrophotometer at a wavelength corresponding to the maximum absorbance of dye. The calculation of colour removal efficiency (CRE (%)) before and after electrocoagulation treatment was performed using this formula: (1) Where, Abs 0 and Abs 1 are respectively absorbance of dye before and after electrocoagulation. As a next step the dye concentration was fixed and the variable is the electrolysis time. EC was tested with 10, 20, 30, 40, and, 50 minutes, afterwards the tests was with different initial ph (5.5, 6.5, 7.5, and, 8.5) and, then different concentration of NaCl (1%, 2%, 3%, 4%, and, 5%). ISSN : Vol. 4 No.05 May

3 3. Analysis of data and results In this section the analysis and the effects of all parameters involved in the experiments conducted, using the iron electrode and aluminium electrode has been discussed. 3.1 Iron electrode Due to the generation of OH - on cathode surfaces, the ph in the system is expected to increase with treatment time. When the ph increases to a certain level, coagulant will begin to accumulate in the solution. A portion of the colorant will be decomposed by the formation of Fe 2+ and/or Fe 3+ from the anode. The majority of colour was removed by adsorption. Below is shown the parameters that effect electrocoagulation process with Iron electrode Effect of initial concentration of dye on the colour removal efficiency In practice, the textile plant s wastewaters to be treated are currently varying in dye concentration. So it is crucial to investigate the effect of dye initial concentration on the electrocoagulation process. Therefore, different dye concentrations, in the range of % of 1 litre, were tested under with different and constant current intensity, as shown on Table 1. According to the Figure 2, it may be seen that increasing initial dye concentration results in decreasing removal efficiency. In fact, when the initial concentration varied from 0.01 to 0.02% of 1 L, the removal percentage was, for example, 51.6% and 28.44% respectively, for 60mA current density. It is clear that lower is the dye concentration better is the CRE. Table 1- Effect of current on varied concentrations, for Fe electrode Curre nt CRE (ma) 0.01% 0.02% 0.03% 0.04% 0.05% % 28.44% 43.1% 6.7% 1.5% % 82.17% 67.8% 51.6% 34.8% % 90.60% 79.7% 40.7% 40.9% % 93.81% 88.3% 78.3% 40.1% For optimum set 0.04% of dye concentration was chosen, that is a not high concentration and not low. In other words, good results are obtained at low concentrations and not quite bad for high concentration. Fig 2- Effect of current on varied concentrations ISSN : Vol. 4 No.05 May

4 3.1.2 Effect of current density on the colour removal efficiency It has been established that current density determines the coagulant production rate which influences the pollutant treatment by the electrocoagulation process [2]. To study the effect of current density on the colour removal efficiency, different current densities were chosen from 60 to 150mA (at intervals of 30mA). As seen in Figure 3, increasing current density results in increasing removal efficiency. Fig 3- Effect of current density Beyond 150mA current density no significant improvement in removal efficiency is observed. Therefore considering the excess of electrical energy consumption at higher densities, and no much difference between CRE, 120mA is considered as optimal in the present work Effect of time of electrolysis on the colour removal efficiency Reaction time influences the treatment efficiency of the electrolytic process. During electrolysis, anodic electrodissolution led to the release of coagulating species. The dye removal efficiency depends directly on the concentration of metal ions produced on the electrodes. When the electrolysis time is increased, the concentration of metal ions and their hydroxide flocs increase [2]. The effect of time of electrolysis was studied at constant current density of 120mA (for optimum current density found before), As shown in Figure 3, for 0.04% of concentration of dye, there is a comparison with different electrolysis time. An increase in the time of electrolysis from 10 to 50 min yields an increase in the dye removal efficiency from 7.38% to 98.45%. Fig 4- Effect of time of electrolysis Effect of initial ph on the colour removal efficiency Literature reports that ph plays a key role on the performance of EC [2]. In order to investigate the effect of the ph of the solution on dye removal a series of experiments were performed by adjusting the initial ph in the interval from 5.5 to 8.5 (intervals of 1.0). The effect of ph on electrocoagulation is illustrated in Figure 3. The results showed that when ph of the dye solutions was between 6.5 and 8.5, dye removal efficiency was optimal with a maximum at ph 8.5 with 82.35%. For the acidic and the basic zones, corresponding to ph less than 5 and ph greater than 9 respectively, a significant drop in dye removal efficiency was observed. ISSN : Vol. 4 No.05 May

5 Fig 5- Effect of initial ph Effect of concentration of NaCl on the colour removal efficiency In real dyebaths various types of salts are present to be used as dye auxiliaries. For example, NaCl enhances dye diffusion and adsorption onto the fiber, whereas Na 2 CO 3 increases the dye bath ph and enables dye fixation through the formation of covalent bonds [2]. It was tested with different concentrations of NaCl. Runs were performed at initial ph 7.5, current density of 120mA, for 40 min. At 5% it gets a really poor CRE, but for 4%, the highest CRE, is 80.12%. Fig 6- Effect of concentration of NaCl 3.2 Aluminium electrode The results of the works show that aluminium electrode was not good for colour removal efficiency, for Blue CA. The procedure and analysis for aluminium electrode was proceeded in the same way as that of the iron electrode Effect of initial concentration of dye on the colour removal efficiency With the same procedure as that of iron, for aluminium electrode 5 samples (different dye concentration) each sample was subjected at different current densities and the results are presented in Table 2. ISSN : Vol. 4 No.05 May

6 Table 2- Effect of current on varied concentrations, for Al electrode Current (ma) CRE 0.01% 0.02% 0.03% 0.04% 0.05% % 29.16% 40.35% 2.48% -5.60% % 34.25% 15.61% 2.83% -5.27% % 36.44% 21.01% 1.04% -5.43% % 36.73% 23.06% 0.28% -7.67% The higher is dye concentration, lesser is CRE, for some samples the same thing happened with current density, that the CRE is growing down, as show at Table 2. For 0.04% and 0.05% the CRE is found to be decreasing accordingly to the current density increase. The results were found to be poor compared to Iron electrode Fig 7- Effect of initial concentration of dye Effect of current density on the colour removal efficiency For aluminium electrode the same optimised condition were used. The dye concentration was fixed as 0.04%, and tested with different current densities, as shown in Figure 7. The effect of current density for aluminium electrode and for 0.04% of dye, had good CRE for 90mA, and decreased when the current was boosted Effect of time of electrolysis on the colour removal efficiency Using 120mA effect of electrolysis time for colour removal efficiency was tested which is shown in Figure 9. As seen more the time of electrolysis, the CRE is more efficient. Fig 8- Effect of time of electrolysis The CRE at 50 min, was about 29.83% and for 40min was 13.90% ISSN : Vol. 4 No.05 May

7 Effect of initial ph on the colour removal efficiency Nevertheless, the electrolysis time was fixed 40 min, as was used for Fe electrode. For aluminium electrode, the ph made a representative difference at CRE; it is shown at Figure 10. Fig 9- Effect of initial ph The highest CRE was at 5.5 ph, about 10.58%, after that 7.5 ph, with 9.75% of CRE Effect of concentration of NaCl on the colour removal efficiency The optimum condition was 120mA current density, 40min of electrolysis time, 7.5pH, and these conditions were used to take the results for concentration of NaCl. The Figure 11 shows the results obtained. Fig 10- Effect of concentration of NaCl For 5% of NaCl obtained 16.79% CRE was obtained, and also have 2% of NaCl with a good CRE, about 14.76% Comparison of Fe and Al electrodes This comparison is between Fe and Al in the same conditions, however, it could be optimized for each different material, in other words, the Al electrode could be optimized with a different set of parameters in comparison to the Fe electrode. In this study the efficiency of Al and Fe electrode used in the elctrocoagulation process for Blue CA dye, in the same conditions is compared. In Figure Current Vs CRE with Al and Fe electrodes, is shown under same operating condition. ISSN : Vol. 4 No.05 May

8 Fig 11- Effect of current density Fig 12- Effect of electrolysis time Fig 13- Effect of ph Fig 14- Effect of concentration of NaCl ISSN : Vol. 4 No.05 May

9 4. Conclusions The experiments were conducted with Blue CA and two types of electrodes were used for a comparative study. For iron the set was optimized, as 120mA; 40min of electrolysis time; 7.5pH and 4% of NaCl, and, consequently good results were found for CRE, more than 90% of colour removal. Using Aluminium electrode and the same optimised condition the CRE was poor compared to that of iron, Hence a different optimized condition can be found to work with aluminium electrode. Hence, the results showed that Fe and Al cannot work properly with the same conditions, and, even if was optimized a set for aluminium electrode, this set would need to boost the number of the parameters. Recommendations For future works and experiments about Electrocoagulation would be useful compare Fe and Al in the best conditions for both, otherwise, some of it will get a low colour removal, considering that each material works at different conditions for a high colour removal. Therefore, the optimum conditions for Fe and Al could be a better way to compare these different materials. 5. References [1] Chen-lu Yang, Jared McGarrahan, Electrochemical coagulation for textile effluent decolorization, Journal of Hazardous Materials B127 (2005) [2] S. Aoudj, A. Khelifa, N. Drouiche; M. Hecini, H. Hamitouche, Electrocoagulation process applied to wastewater containing dyes from textile industry, Chemical Engineering and Processing 49 (2010) [3] M. Yousuf A. Mollah, Robert Schennach, Jose R. Parga, David L. Cocke, Electrocoagulation (EC) science and applications, Journal of Hazardous Materials B84 (2001) [4] Inoussa Zongo, Amadou Hama Maiga, Joseph Wéthé, Gérard Valentin, Jean-Pierre Leclerc, Gérard Paternotte, François Lapicque, Electrocoagulation for the treatment of textile wastewater with Al or Fe electrodes: Compared variations of COD levels, turbidity and absorbance, Journal of Hazardous Materials 169 (2009) [5] B. Ramesh Babu, A. K. Parande, and T. Prem Kumar, Cotton Textile Processing: Waste Generation and Effluent Treatment, The Journal of Cotton Science 11: (2007). [6] M. G. Arroyo, V. Pérez-Herranz, M. T. Montañes, J. García-Antón, J. L. Guiñón, Effect of ph chloride concentration on the removal of hexavalent chromium in a batch electrocoagulation reactor, Journal of Hazardous Materials 169 (2009) ISSN : Vol. 4 No.05 May