INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 1, No 6, 2011 © 2011 Ganesan.R et al., licensee IPA- Open access - Distributed under Creative Commons Attribution License 2.0 Research article

ISSN 0976 – 4402

Decolourisation of textile dyeing Wastewater by modified solar Photo-Fenton Oxidation

Ganesan.R1, Thanasekaran.K2 1. Research Scholar, Centre for Environmental Studies, Anna University, Chennai-600025 2. Professor of Environmental Engineering, Centre for Environmental Studies, Anna University, Chennai-600 025 [email protected] doi:10.6088/ijes.00106020011 ABSTRACT In a laboratory study, decolourisation of real textile dyeing wastewater by modified solar photo-Fenton (Steel scrap/ H2O2 ) process under irradiation with sunlight was examined. Batch experiments were conducted to determine optimal operating conditions .The optimal doses of H2O2 and steel scrap were 15 mL/L and 1 g/L, respectively at pH 3.Colour removal of 89% was obtained under optimum conditions. These results suggest that, the modified solar photo-Fenton process proved to be efficient for decolourisation of the real textile dyeing wastewater. A simplified mechanism of hydroxyl radical production in the presence of steel scrap as a catalyst has been proposed. The morphologic analysis and mapping of the elementary composition of Steel scrap used as a catalyst was determined by scanning electronic microscopy. Keywords: Textile dyeing wastewater, Steel scrap, Decolourisation, Solar light, Hydrogen peroxide, Modified solar photo-Fenton process. 1. Introduction More than 10,000 dyes are used in the textile industry and 280,000 tonnes of textile dyes are discharged every year world wide ( Hsueh et al., 2005), Textile dyeing and finishing processes produce large quantities of wastewater that is highly coloured and contains large concentration of organic matter( Mass et al.,2005),which is difficult to treat via classical methods. Apart from the aesthetic problems created when coloured effluents reach the natural water currents, dyes strongly absorb sunlight, thus impeding the photosynthetic activity of aquatic plants and seriously threatening the whole ecosystem (Slokar et al.,1998), The advanced oxidation processes (AOPs), are currently considered to be a potential treatment method for the removal of colour which are characterized by production of the hydroxyl radical (OH·) as a primary oxidant. Among the various AOPs, the use of Fenton reagent (H2O2/Fe2+) is one of the most effective methods of organic pollutant oxidation. The Fenton reagent has been found to be effective in treating various industrial wastewater components including aromatic amines (Casero et al., 1997), and a wide variety of dyes [Kuo et al., 1992; Nam et al., 2001), as well as many other substances, eg. Pesticide (Huston et al., 1999; Barbusinski et al., 2001), and surfactants (Lin et al., 1999), Therefore, the Fenton reagent has been applied to treat a variety of wastes such as those associated with the textile and chemical industries. The advantage of the Fenton reagent is that no energy input is necessary to activate hydrogen peroxide (Barbusinski et al., 2003), Therefore, this method offers a cost effective source of

Received on February, 2011 Published on March 2011

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Decolourisation Of Textile Dyeing Wastewater By Modified Solar Photo-Fenton Oxidation

hydroxyl radicals, using easy to handle reagents. However, disadvantages in using the Fenton reagent include the production of a substantial amount of Fe (OH)3 precipitate (Barbusinski, 2005), and additional water pollution caused by the homogeneous catalyst that is added as an iron salt, cannot be retained in the process ( Malik et al., 2003),To solve these problems, the application of alternative iron sources as catalyst containing organic contaminants has been studied extensively. A number of researchers have investigated the application of iron oxide such as hematite, ferrihydrite and crystalline goethite (Kavitha et al., 2004; Montserra et al., 2002; Juan Mataias Chacon et al, 2006; Patricia et al., 2007), They generally have observed a greatly accelerated decomposition of hydrogen peroxide but variable amounts of contaminant were lost. Another group of investigations consisted in the application of iron powder in the H2O2 /Fe0 system. Zero-valent iron metal (Fe0) is a very promising reactive medium due to its low cost, effectiveness, ability to degrade contaminants and its accessibility (Nilesh Tantak et al., 2006; Meric et al., 2004). It was found that iron powder could be used to replace iron salts as a catalyst for the Fenton reaction (Jian-Hui Sun et al., 2010). In this study a modified solar photo-Fenton process using heterogeneous catalyst (Steel scrap) was developed and applied to catalyze the oxidation reaction of textile dyeing wastewater. A batch process was conducted to demonstrate the feasibility of colour removal from textile dyeing wastewater by the newly developed oxidation technology. 2. Materials and Methods 2.1 Chemicals H2O2 (30w/w) (Merck), The double distilled water was used to prepare experimental solution. The pH of the reaction solutions was adjusted using 1N H2SO4 and NaOH solutions.

Figure 1: Schematic diagram of lab-scale Modified Solar Photo-Fenton reactor

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2.2. Modified Solar Photo-Fenton Reactor and Decolourisation Procedure All modified solar photo-Fenton experiments were carried out at Anna University campus in Chennai (13°00.57’’N; 80°14.12’’E), Tamilnadu, India, using multiple borosilicate glass trays as reactor as shown in Fig.1. The experiments were conducted using solar light in the month of March 2010 (UV intensity 22±2 W/m2). Glass stirrer was used for mixing of wastewater with H2O2.The obtained solution was pumped with the help of a peristaltic pump to the reactor filled with a steel scrap as a catalyst. The experiments were conducted on 500mL wastewater samples (in duplicate).The time duration of experiments was 30 minutes Samples were collected at every 5 minutes interval, NaOH solution was used to quench the oxidation by rising the pH to 7.At this pH further generation of hydroxyl radical is prevented then centrifuged at 3000 rpm in 3 min and were analysed for colour. 2.3Analytical methods The textile dyeing Wastewater samples were taken in polyethylene bottles from an industry at Tirupur, Tamilnadu, India. Samples taken were preserved in the refrigerator at 4° C in accordance with the standard methods for the Examination of Water and Wastewater (APHA, 2002). Textile wastewater samples were characterized in terms of the pH value as well as of BOD3, COD, TDS, TSS, Chlorides and Sulphate Concentrations (APHA, 2002). .All solutions were prepared with double distilled water. The pH of the solutions was measured using Elico LI 120 equipped with combined glass-calomel electrode. A Heracus-sepatech Labofuge 200 centrifuge was used for the centrifuging of the samples at 3000 rpm for 3 minutes duration for removing turbidity before colour measurement. The detection of the colour value was determined using a Spekol UV-Vis Spectrophotometer according to Method 2120C in standard methods (APHA, 2002). The initial value of colour was 0.433 [absorbance at wavelength (λmax)=600nm, number of selected ordinates =10]. A Scanning Electron Microscopy instrument (HITACHI Model-S3400) was used for SEM-EDX analysis for finding the chemical composition of the steel scrap used as a catalyst, and the Lux meter was used for measurement of solar irradiation. 2.4. Mechanism of the Modified Solar photo -Fenton Process In an aqueous solution, under acidic conditions, Fe2+ ions are released to the solution by the steel scrap. The steel scrap acts as a heterogeneous catalyst for the activation of hydrogen peroxide. When Steel scrap is used as a solid catalyst, Fe ions are leached from the solid material. Then, the iron ions act as homogeneous catalyst for the activation of H2O2 to generate hydroxyl radicals according to the Fenton reaction. ( Barbusinski.,2005), Because the Steel scraps release Fe2+ ions to the solution under acidic conditions, iron dissolution is an initial step for the oxidation of contaminants by the H2O2/Steel scrap process. When textile dyeing wastewater oxidation occurs, the initial Fe2+ions are consumed, and then the oxidation rate will depend on the dissolution rate of Fe2+. This mechanism has three stages: 1st stage dissolution of scrap and release of Fe2+ions, 2nd stage-the solar photo- Fenton reaction including formation of hydroxyl radicals OH● and 3rd stage-oxidation of textile dyeing wastewater 3. Results and Discussion 3.1 Chemical Composition and Morphologic Analysis of Steel Scrap

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The steel scrap is produced during metal sawing was washed and dried at 103°C. The heated Steel scrap was cooled and separated by a sieve to get uniform size. The particle size of steel scrap used in the study was in the range of 0.5-2 mm. The chemical composition of the Steel scrap used as a catalyst is shown in Table 1. The morphologic analysis of steel scrap used as a catalyst is shown in Fig.2. The solids present an irregular surface and the small particle aggregates are observed. The (Energy Dispersive X-Ray) EDX analysis showed presence of very high amount of Fe, C and O as shown in Figure 3. Table 1: Chemical composition of the scrap used as a catalyst in percentage by weight C O 41.39 8.77

Fe Si 45.91 1.20

Mn Ca 0.46 0.50

Mo 0.35

Al 0.31

Trace Elements 1.11

Figure 2: Morphologic analysis of Steel scrap used as catalyst

Figure 3: EDX analysis of the Steel scrap used as catalyst

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3.2 Characterization of textile dyeing wastewater The textile wastewater was obtained from a textile industry at Tirupur, Tamilnadu, India, during March 2010. Samples taken were preserved in the refrigerator at 4°C in accordance with the standard methods for the Examination of Water and Wastewater (APHA., 2002). The characterization of the raw effluent has been done by collecting raw effluent samples from equalization tank in the industry. The wastewater samples were characterized in terms of the pH value as well as of BOD3, COD, TDS, TSS, Chlorides and Sulphate Concentrations (APHA., 2002).The characteristics of raw effluent are listed in Table 2. Table 2: Characteristics of the raw textile effluent Sl.No 1 2 3 4 5 6 7 8

Characteristics Colour,Absorbance in nm COD, mg/L pH Chlorides, mg/L BOD3, mg/L Sulphate, mg/L Total suspended solids, mg/L Total dissolved solids, mg/L

Value 0.433 1706 8.8 396 420 450 50 3460

3.4 Effect of initial pH variation The aqueous pH has a major effect on the efficiency of modified solar photo-Fenton reaction. Fig 4 demonstrates the effect of pH on the decolourisation of the textile dyeing wastewater. The reactor was run for 30 min under controlled pH condition (3,4,5,6&7)with a constant dose of Steel scrap of 1 mg/L and H2O2 of 20 mL/L. It is apparent from the figure that the percentage decolorisation decreases with increase in pH, at pH 3 it is 89% .The observed decolourisation of 89% at pH 3 is also supported by previous studies., Kuo (Kuo.,1992) observed 93% of decolourisation of dye in 30 min. Malik and Saha (Malik et al., 2003), reported that the optimum pH was 3 for the decolourisation of dyes. Meric et al., showed that more than 99% of colour removal was possible in the pH range of 3-3.5.

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Figure 4: Effect of pH on decolourisation (catalyst=1g/L and H2O2=20mL/L) Ganesan.R, Thanasekaran.K International Journal of Environmental Sciences Volume 1 No.6, 2011

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3.5. Effect of Initial concentration of H2O2

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The effect of concentration of H2O2 on the rate of decolourisation was carried out for duration of 30min with real textile dyeing wastewater. The reaction was done at pH 3 with the constant dose of steel scrap 1mg/L.The concentration of H2O2 was varied from 5 to 20 mL/L. From the data shown in Fig.5 it can be seen that the maximum efficiency of decolourisation was observed at 15 mL/L. The efficiency increased with the increased quantity of H2O2.The lower rate of H2O2 did not give significant reduction in colour removal. It may be due to that higher rate of reaction may not compensate the large amount of oxidants (Montserrat Perez et al., 2002).The decolourisation of textile dyeing wastewater was increased by increasing the concentration of H2O2.This can be explained by the effect of the additionally produced hydroxyl radicals. The decolourisation above certain ranges improvement was not obvious. This may be due to the recombination of hydroxyl radicals and also hydroxyl radicals reaction with H2O2 contributing to the hydroxyl radical scavenging capacity (Modirshala et al., 2006).

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Figure 5: Effect of H2O2 on decolourisation (pH =3 and catalyst concentration =1g/L) 3.6 Effect of initial catalyst (scrap) dosage The effect of dosage of catalyst (Steel scrap) on the rate of decolourisation was studied in the range of 0.5 to 2 g/L. The time vs percentage decolourization was plotted for all dosage of Steel scrap as shown in Fig. 6 In the study, maximum efficiency of decolourization of 89% was obtained at 1g/L. The decolourisation was decreased with increased quantity of steel scrap. The use of large quantities of Steel scrap in solution has a negative effect on decolourisation. An increase in the concentration of Steel scrap did not improve the oxidation process and Steel scrap acts only as a catalyst. In the presence of UV/Solar light, the concentration of Fe2+ increased which is available for hydroxyl radical generation (Kavitha et al., 2004). Ferrous ion regeneration can be stopped since the organic matter can be a hydroxyl radical scavenger and hence can cause the interruption of the radical chain reaction (Bertanza et al., 2003).

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% Decolourisation

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Figure 6: Effect of catalyst dosage on decolourisation (pH =3 and H2O2=15mL/L) 4. Conclusions The results confirm that steel scrap can be used as a source of Fe ions (catalyst) in the solar photo- Fenton process. It was observed that Steel scrap acted as a heterogeneous catalyst for the activation of hydrogen peroxide. The modified solar photo-Fenton process was found to be very efficient for decolourisation of real textile dyeing wastewater. The optimal doses of H2O2 and Steel scrap were 15 mL/L and 1 g/L, respectively at pH 3.These results suggest that, compared with both the classical solar photo-Fenton reaction and solar photo-Fenton reaction with alternative iron sources, the new modified solar photo-Fenton process (H2O2/Steel scrap) has clear advantages. This process is relatively economical because the Steel scrap can be used as a discard material, e.g from machining. The Modified Solar photo-Fenton process is easy to operate, allowing it to retain the catalyst in the process and thus the catalyst (steel scrap) can be used repeatedly. The Modified Solar photo-Fenton reaction with the use of steel scrap offers greater possibilities for practical application of solar photo-Fenton reagent. 5. References 1. APHA,2002, Standard methods for the examination of water and wastewater, 20th edn., “American Public Health Association”, Washington, DC, 2. Barbusinski K and Filipek K.,2001, Use of Fenton’s reagent for removal of pesticides from industrial wastewater, “Polish .J. Environ. Stud”, 10 (4), pp 207. 3. Barbusinski K and Majewski J.,2003, Discoloration of Azo Dye acid Red18 by Fenton Reagent in the Presence of Iron Powder, “Polish.J.Environ.Stud”,12 (2), pp 151-155. 4. Barbusinski K.,2005, The Modified Fenton Process for Decolorization of Dye Wastewater, “Polish.J.Environ.Stud”, 14(3),pp 281-285. 5. Bertanza G, Collivignarelli C, Collivignarelliand Zenaboni S,2003, Treatment of industrial wastewater by means of hydrogen peroxide AOPs: Effects of process

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parameters, “3rd International Conference on oxidation technologies for water and wastewater treatment”,57, pp 392-397. 6. Casero I , Sicilia D , Rubio S and Perez-Bendito D ,1997, Chemical degradation of aromatic amines by Fenton’s reagents, “Water Res”,31, pp1985. 7. Hsueh C L, Huang Y H , Wang C C and Chen S,2005, Degradation of azo dyes using low iron concentration of Fenton and Fenton-like system, “Chemosphere”, 58 ,pp 1409-14. 8. Huston P L and Pignatello J J.,1999, Degradation of selected pesticide active ingredients and commercial formulations in water by the photo-assisted Fenton reaction, “Water Res”, 33, pp1238. 9. Juan Mataias Chacon, Ma.TeresaLeal, ManuelSanchez and Erick Bandala R.,2006, Solar photocatalytic degradation of azo-dyes by photo-Fenton process, “Dyes and Pigments”,69, pp 144-150. 10. Jian-Hui Sun and Shao-Hui Shi,2010, Fenton oxidative decolourization of the azo dye Direct Blue15 in aqueous solution, “Chemical Engineering Journal”, 155, pp 680-683. 11. Kavitha V and Palanivelu K.,2004, The role of ferrous ion in Fenton and photoFenton processes for the degradation of Phenol, “Chemosphere”, 55,pp 1235-1243. 12. Kuo W.G.,1992, Decolourizing dye wastewater with Fenton’s reagent, “Water Res”, 26, pp 881-886. 13. Lin S H , Lin C M and Leu H G.,1999, Operating characteristics of kinetic studies of surfactant wastewater treatment by Fenton oxidation, “Water Res”,33 pp 1735. 14. Mass.R., and Chaudhari S.,2005, Adsorption and biological decolourization of azo dye reactive Red-2 in semi continuous anaerobic reactors, “Process Biochem”,40,pp 699-705. 15. Malik P K and Saha S K.,2003, Oxidation of direct dyes with hydrogen peroxide using ferrous ion as catalyst, “Sep. Purif. Technol”,31 pp 241-250. 16. Meric S , Kaptan D and Olmez T., 2004,Color and COD removal from wastewater containing Reactive Black 5 using Fenton’s oxidation process, “Chemosphere”, 54 (3), pp 435-441. 17. Modirshala N.,Behnajady M.A, and Ghanbary F.,2006, Decolourisation and mineralization of C.I. Acid Yellow 23 by Fenton and photo-Fenton processes, “Dyes and pigments”, Article in press. 18. Montserrat Perez, Francesco Torrades, Xavier Domenech, and Jose Peral,2002, Fenton and photo-Fenton oxidation of textiles effluents, “Water Research” , 36, pp 2703-2710. 19. Nam S , Renganathan V and Tratnyek P G.,2001, Substituent effects on azo dye oxidation by Fe3+ EDTA, H2O2 system, “Chemosphere”, 45, pp 59.

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20. Nilesh Tantak P and Sanjeev Chaudhari, 2006, Degradation of azo dyes by sequential Fenton’s oxidation and aerobic biological treatment, “Journal of Hazardous Materials B” 136,pp 698-705. 21. Patricia A.Carneiro et al.,2007, Homogeneous photo degradation of C.I. Reactive Blue 4 using a photo-Fenton process under artificial and solar irradiation, “ Dyes and Pigments”,74, pp 127-132. 22. Slokar.Y., M and MajcenLeMarechala.A.,1998, Methods for decolourisation of textile wastewaters. “Dyes and Pigments”, 37 (4), pp 335-356.

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