- Open Access
Electrochemical degradation of scarlet red dye from aqueous environment by titanium-based dimensionally stable anodes with SS electrodes
Applied Biological Chemistry volume 61, pages289–293(2018)
Textile effluents are toxic and carcinogenic materials that exist in the aquatic environment. In this study, the degradation efficiency of commercially available scarlet red dye investigated on TSA-SS Electro Fenton process (EFP) was reported. It is of great interest in the field of environmental engineering to remove dyes from aquatic environment. The influence of operating parameters such as pH (2–9), current density (0.1–0.5 mA/cm2), concentration of dye (0.1–0.5 g/L), H2O2 (0.1–0.5 g/L) concentration and Fe2+ concentration (0.01–0.03 g/L) were analyzed by batch system. The optimum degradation conditions were determined as pH—3, current density—0.4 mA/cm2, concentration of dye—0.4 g/L, H2O2 concentration—0.5 g/L and Fe2+ concentration—0.025 g/L. These results indicated that the degradation efficiency of scarlet red dye by EFP depends on solution pH and Fenton reagent concentration and a low pH value was favorable for the dye degradation. It has been demonstrated that more than 94% dye removal was obtained at 50 min. Electro Fenton process was also investigated by cyclic voltammetry technologies.
The pot ability of water is affected by various factors which include wastewater from industries. Various industries such as textiles, rubber, plastics, paper, cosmetics and tanneries use various dyeing process. They release waste water which contains dye effluents in a major proportion. Among them, textile industries generate large volume of effluents which contains organic dye effluents. Various processes were adopted to treat wastewater containing organic contaminants, particularly electrocoagulation, ultra-filtration, reverse osmosis (RO) and activated carbon adsorption. These treatment processes were not much effective to improve the quality of water with tolerable levels of effluents. To attain this objective, a treatment method is applied which entail the application of advanced oxidation process (AOP) [1, 2]. This method is recommended when wastewaters have high chemical stability, low biodegradability and this produces the complete mineralization of pollutants to CO2, H2O and inorganic compounds . This AOP is attained when EFP is carried out. This EFP could be applied for various types of contaminants especially organic substances . In EFP, H2O2 serves as the source of OH˚ radicals. So, with increase in H2O2 concentration degradation takes place effectively. These hydroxyl radicals act as redox agent with high redox potential. But if H2O2 concentration exceeds the limit, it will affect the process by production of per hydroxyl radicals  as shown in Eq. (1).
Also Fe2+ concentration helps in increase in efficiency by production of OH° radicals from H2O2. But after a particular concentration Fe2+ ions will have scavenging effect on OH° radicals  as shown in Eq. (2).
This will reduce the efficiency of the process. So an optimum of Fe2+ concentration had to be maintained for effective degradation of the solution. The pH was considered to be one of the important factors which help in effective degradation . At higher pH, complex formation of Fe2+ ions will take place thereby reducing the process efficiency. In this study, the influence of various parameters had studied.
Materials and methods
In this work, commercially used dye scarlet red was purchased from Erode textile industry and the properties of scarlet red dye are given in Table 1. All chemicals like FeCl3, H2O2, HCl and KCl of analytical grade purchased from merck. To test the removal efficiency UV–Vis spectroscopy (Model No. 3250, Agilent Technologies) is used for determination of dye concentration. The solution pH was measured with (Hanna instruments) pH meter.
Electrolysis was performed in a 1000-ml capacity cylindrical beaker with two electrodes. Titanium-based dimensionally stable anodes (DSA) and stainless steel (SS) were used as electrodes for anode and cathode, respectively. Area of each electrode was 50 cm2 . The synthetic dye solution of various concentrations was taken, and the pH was adjusted by adding 0.1 mM HCl solution. After that, various proportions of Fenton’s reagents were added. The electrodes were partially immersed in a beaker that contains the synthetic solution 0.1 mM KCl chosen as the supporting electrolyte to maintain the current density . The required electric power during the electrolysis process was provided by a laboratory DC power supply (Aplab 0.32 V, 0–10 A). The electrolytic cell was constantly stirred with a magnetic stirrer in order to avoid the concentration gradient.
Cyclic voltammetry (CV) measurements were carried out using a potentiostat/galvanostat EG&G Model 263A and a frequency response detector FRD 100 of Princeton Applied Research. The working electrode was the glassy carbon, the counter electrode was a platinum, and a reference electrode was silver electrode. All the experiments were carried out at room temperature.
Results and discussion
Influence of pH
In this process, pH is an important parameter and it affects the hydroxyl radical mechanism of EFP. The pH was varied within the range of 2–9. The maximum degradation efficiency was obtained at pH 3 as illustrated in Fig. 1. Therefore, acidic pH favors the degradation when compared to the basic pH levels . Because when the pH is increased Fe2+ ions form insoluble complexes which cannot activate H2O2 to produce OH˚ radicals. They finally precipitate as Fe (OH)3 which cannot act as catalyst . So degradation efficiency decreases with increase in pH. The previous results obtained  were well matched with the current data.
Influence of Fe2+ concentration
Fe2+ ions added as catalyst play an important role in EFP process in which degradation takes place efficiently. Figure 2 illustrates the effect of Fe2+ concentration on degradation of dye during EFP process. These ions help in the activation of H2O2 and in turn help in the production of OH˚ radicals leading to the degradation efficiency improvement as shown in Eq. (3) . The Fe2+ concentration was varied between 0.01 and 0.03 g/L in the interval of 0.05 g/L.
The optimum Fe2+ dosage with maximum degradation efficiency was found to be 0.025 g/L. After that point degradation efficiency starts to decrease. This was because of the scavenging effect of Fe2+ ions which convert OH˚ radicals to OH− ions .
Influence of H2O2 concentration
H2O2 reagent provides the hydroxyl radicals for carrying out the mineralization mechanism that produces the sludge [8, 15]. The concentration of hydroxyl radicals was dependent on the addition of H2O2 concentration , and it influences the decomposition of complex organic compounds by Fenton’s reaction. Due to the high cost of H2O2 selection of an optimum H2O2 concentration by Fenton’s reagent is important for dye degradation . The degradation increases with increase in H2O2 concentration varied at a range of 0.1–0.5 g/L and was the maximum efficiency obtained at 0.5 g/L illustrated in Fig. 3. However, the increase of H2O2 further results in the decrease in dye removal process because surplus H2O2 molecules act as a scavenger of hydroxyl radical to formation of perhydroxyl radical with low oxidation potential .
Influence of dye concentration
Dye concentration was varied over the range of 0.1–0.5 g/L. The optimum dye concentration was found to be 0.4 g/L for which maximum degradation was obtained. Figure 4 illustrates the influence of dye concentration in EFP process at lower concentration, the lesser degradation of dye was related to the low frequency of effective collisions between molecules and surplus Fe2+ molecules causing scavenging effect . But also with higher concentration of dye, efficiency of the process decreases due to the intermediate components that react with hydroxyl radicals instead of dye components . Also, the reactive species produced was not enough for effective degradation of dyes at higher concentration. So when the concentration of dye increases, the amount of Fenton’s reagent added to the solution had to be increased. Figure 4 illustrates the variation of degradation efficiency on the basis of dye concentration.
Influence of current density
In all oxidation mechanism of electrochemical method current density was considered to be the important parameter. The influence of current density had been examined in the range of 0.1–0.5 mA/cm2 optimum of 0.4 mA/cm2, and the results are illustrated in Fig. 5. The data from the graph show that there is a gradual increase in the degradation rate with increase in current. The increase in current density enhances the oxidation power which in turn helps in the greater production of H2O2 and leads to the generation of more amounts of hydroxyl radicals from Fenton’s reagent . At higher current density, the degradation efficiency was attained almost constant due to the formation of intermediates as complexes of Fe2+ with carboxylic acids that were more difficult to destroy during electrolysis .
Mechanism of degradation of azo dyes
In EFP the degradation of o’scarlet red dye was investigated in acidic pH of 3. Fe2+ ions were used as catalyst, and H2O2 acts as a reagent. As the current density was intensified the degradation of dye also progressed gradually. The hydroxyl radicals produced by H2O2 help in this process. As the color loss becomes visible it could be explained by reaction of OH˚ radicals with azo bonds (–N=N–) . They break the azo bond which causes the decolorization due to change in absorption properties. From the removal efficiency curves, we can infer that color intensity decreases as time increases during the reaction. The reaction between hydroxyl radicals and azo bonds produces hydroxylated derivatives . The scarlet dye compound disappeared by producing intermediates like hydroxyl derivatives and other iron complexes.
Figure 6 illustrates the cyclic voltammetry (CV) scan 0.4 g/L dye solution at pH 3.0; scan rate was 30 mV/s. It was clearly visible that the Oxygen Reduction Reaction (ORR) currents at the cathode potential higher than − 0.9 V. As the operating cathode potential of H2O2-producing dye solution was changed from − 0.9 to − 0.7 V and cathode potentials appeared almost the same over the whole testing period, it was concluded that the presence of scarlet red dye had a slight impact on the ORR process occurring on the surface of the TSA-SS Electro Fenton process.
Electro Fenton processes have been proved to be a feasible technology for the treatment of dyes from synthetic solutions. In this study, the degradation of scarlet red dye was investigated by EFP using TSA-SS electrodes. The influence of operating parameters such as pH (2–9), current density (0.1–0.5 mA/cm2), concentration of dye (0.1–0.5 g/L), concentration of H2O2 (0.1–0.5 g/L) and concentration of Fe2+ (0.01–0.03 g/L) was analyzed in a batch system. The optimum solution pH for EFP for the scarlet red dye was obtained at 3. The optimum concentration of H2O2, Fe2+ and dye concentration was 0.5, 0.025 and 0.4 g/L with the current density of 0.4 mA/cm2, respectively. At the optimal conditions, 94% of scarlet red was degraded from the solution at 50 min. The conducted cyclic voltammetry studies confirm that, an impact was occurred over the surface of TSA-SS Electro Fenton process by the presence of scarlet red dye.
Oller I, Malato S, Sánchez-Pérez JA (2011) Combination of advanced oxidation processes and biological treatments for wastewater decontamination: a review. J Sci Total Environ 409:4141–4166
Matilainen A, Sillanpää M (2010) Removal of natural organic matter from drinking water by advanced oxidation processes. Chemos J 80:351–365
Reddy PM, Raju BR, Karuppiah J, Reddy EL, Subrahmanyam C (2013) Degradation and mineralization of methylene blue by dielectric barrier discharge non-thermal plasma reactor. Chem Eng J 217:41–47
Gua L, Nie JY, Zhua N, Wangc L, Yuana HP, Shoua Z (2012) Enhanced Fenton’s degradation of real naphthalene dye intermediate wastewater containing 6-nitro-1-diazo-2-naphthol-4-sulfonic acid: a pilot scale study. Chem Eng J 189–190:108–116
Panda N, Sahoo H, Mohapatra S (2011) Decolourization of methyl orange using fenton-like mesoporous Fe2O3–SiO2 composite. J Hazard Mater 185:359–365
Whebi DJ, Hafez HM, El Masri MH, El Jamal MM (2010) Influence of certain inorganic ions and ligands on degradation of methyl red by Fenton’s reagent. J Univ Chem Technol Metall 45(3):303–312
Cruz-González K, Torres-López O, García-León A, Guzmán-Mar JL, Reyes LH, Hernández-Ramírez A, Peralta-Hernández JM (2010) Determination of optimum operating parameters for Acid Yellow 36 decolorization by electro-Fenton process using BDD cathode. Chem Eng J 160:199–206
Rahmani AR, Nematollahi D, Azarian G, Godini K, Berizi Z (2015) Activated sludge treatment by electro-Fenton process: parameter optimization and degradation mechanism. Korean J Chem Eng 32(8):1570–1577
Samarghandi MR, Shabanloo A, Shamsi K, Mehralipour J, Poureshgh Y (2014) Performance of Electrofenton process to remove cyanide from aquatic environments in presence of interfering humic acids. J Health 4(4):293–303
Panizza M, Mehmet A, Oturan (2011) Degradation of Alizarin Red by electro-Fenton process using a graphite-felt cathode. Electrochim Acta 56(20):7084–7087
Babuponnusami A, Muthukumar K (2012) Removal of phenol by heterogenous photo electro Fenton-like process using nano-zero valent iron. J Sep Purif Technol 98:130–135
Rosales E, Pazos M, Sanromán MA (2012) Advances in the electro-Fenton process for remediation of recalcitrant organic compounds. J Chem Eng Technol 35(4):609–617
Zhen GY, Lu XQ, Wang BY, Zhao YC, Chai XL, Niu DJ, Zhao TT (2014) Enhanced dewatering characteristics of waste activated sludge with Fenton pretreatment: effectiveness and statistical optimization. Front Environ Sci Eng 8(2):267–276
Zhou L, Zhongxin H, Zhang C, Bi Z, Jin T, Zhou M (2013) Electro generation of hydrogen peroxide for electro-Fenton system by oxygen reduction using chemically modified graphite felt cathode. J Sep Purif Technol 111:131–136
Moussavi G, Bagheri A, Khavanin A (2012) The investigation of degradation and mineralization of high concentrations of formaldehyde in an electro-Fenton process combined with the biodegradation. J Hazard Mater 237–238:147–152
Sevimli MF, Deliktaş E, Şahinkaya S, Güçlü D (2014) A comparative study for treatment of white liquor by different applications of Fenton process. Arab J Chem 7(6):1116–1123
Moussavi G, Aqanaghad M (2015) Performance evaluation of electro-Fenton process for pretreatment and biodegradability improvement of a pesticide manufacturing plant effluent. J Sustain Environ Res 25:249–254
Isarain-Cha`vez E, Garrido JA, Rodriguez RM, Centellas F, Arias C, Cabot PL, Brillas E (2011) Mineralization of metoprolol by electro-Fenton and photoelectro-Fenton processes. J Phys Chem 115:1234–1242
Azizi A, Moghaddam MRA, Maknoon R, Kowsari E (2016) Investigation of enhanced Fenton process (EFP) in color and COD removal of wastewater containing Acid Red 18 by response surface methodology: evaluation of EFP as post treatment. J Desalination Water Treat 57:14083–14092
Ibhadon AO, Fitzpatrick P (2013) Heterogeneous photocatalysis: recent advances and applications. J Catal. 3:189–218
Ghosh P, Thakur LK, Samanta AN, Ray S (2012) Electro-Fenton treatment of synthetic organic dyes: influence of operational parameters and kinetic study. Korean J Chem Eng 29(9):1203–1210
De Luna MD, Veciana ML, Su CC, Lu MC (2012) Acetaminophen degradation by electro-Fenton and photo electro-Fenton using a double cathode electrochemical cell. J Hazard Mater. 217–218:200–207
Xu X-R, Li X-Z (2010) Degradation of azo dye Orange G in aqueous solutions by persulfate with ferrous ion. J Sep Purif Technol 72(1):105–111
About this article
Cite this article
Gomathi, E., Balraj, B. & Kumaraguru, K. Electrochemical degradation of scarlet red dye from aqueous environment by titanium-based dimensionally stable anodes with SS electrodes. Appl Biol Chem 61, 289–293 (2018). https://doi.org/10.1007/s13765-018-0357-5
- Electro Fenton process
- Dye degradation
- TSA-SS electrode