The study proposes a simple, novel and green alternative for the efficient reduction of azo dyes by the standard method, EN 14362-1:2012 (Annex. F) for detection of harmful aromatic amines in colorants, by incorporating microwave heating in place of convective heating. Basic dye response to reduction methods was explored by UV-visible spectroscopy and the results were confirmed through GC-MS and HPLC-DAD. Four azo dyes namely Acid red 1 (AR-1), Direct blue 15 (DB-15), Direct red 28 (DR-28) and Direct red 7 (DR-7) were reduced with sodium dithionite at 70 °C for 30 min in a buffered solution at pH 6.0, serving as a reference method. The decline in dye absorbance after their reduction was explored by UV-visible spectroscopy with carefully chosen bands of maximum absorbance from 300 to 700 nm. The alternative method exposed dye solutions to short microwave heating (10 s) and immediate cooling, in cycles till the desired duration of microwave heating was achieved. Results obtained from reference method were used for comparison with MAR (experimental method 1). Most prominent results of MAR were observed in the case of DR-28 dye. Hence DR-28 was further subjected to the conditions of experimental method 2, which was simply EN 14362-1:2012 (F) method modified with MAR. For standard method and experimental method 2, amines were analysed by GC-MS and HPLC-DAD. MAR methods were compared with reference and standard reduction methods for efficiencies. The total saving with MAR in terms of time and energy was ~70% and ~92% respectively.
Government of Canada. Aromatic azo and benzidine-based substance grouping, Certain azo acid dyes. Environment and Climate Change Canada HC 2016.
IUC Commission, IULTCS. ISO/DIS 17234-1 (IUC 20-1). Chemical tests for the determination of certain azo colorants in dyed leathers Part 1: Determination of certain aromatic amines derived from azo colorants: International organization of standards. Geneva: ISO; 2012.
British Standards Institution. BS EN 14362-1. Textiles – Methods for determination of certain aromatic amines derived from azo colorants Part 1: Detection of the use of certain azo colorants accessible with and without extracting the fibers. Brussels: BSI; 2012.
Kocaokutgen H, Heren Z. Thermal behaviour of some azo dyes containing sterically hindered and water-soluble groups. Turkish Journal of Chemistry 1998; 22(4): 403-8.
Blus K. Photo-stability of acid dyes, derivatives of 1-phenyl-3-methylpyrazol-5-one in polyamide fibers. Fibres & Textiles in Eastern Europe 2005; 13(6): 54.
Waheed S, Ashraf CM. Stability of reactive dyes in sunlight changes in their colour coordinates. Jour Chem Soc Pak Vol 2003; 25(2).
Rao CV, Giri AS, Goud VV, Golder AK. Studies on pH-dependent color variation and decomposition mechanism of Brilliant Green dye in Fenton reaction. International Journal of Industrial Chemistry 2016; 7(1): 71-80. https://doi.org/10.1007/s40090-015-0060-x
Guardia MdL, Garrigues S. Handbook of green analytical chemistry: Wiley Online Library 2012.
Razzaq T, Kappe CO. On the energy efficiency of Microwave‐assisted organic reactions. ChemSusChem 2008; 1(1‐2): 123-32. https://doi.org/10.1002/cssc.200700036
McGowan CB, Leadbeater NE. Clean, fast organic chemistry: microwave-assisted laboratory experiments 2006.
Bi X, Wang P, Jiao C, Cao H. Degradation of remazol golden yellow dye wastewater in microwave enhanced ClO2 catalytic oxidation process. Journal of Hazardous Materials 2009; 168(2): 895-900. https://doi.org/10.1016/j.jhazmat.2009.02.108
Riaz U, Ashraf S, Aqib M. Microwave-assisted degradation of acid orange using a conjugated polymer, polyaniline, as catalyst. Arabian Journal of Chemistry 2014; 7(1): 79-86. https://doi.org/10.1016/j.arabjc.2013.07.001
Park SH, Kim S-J, Seo S-G, Jung S-C. Assessment of microwave/UV/O3 in the photo-catalytic degradation of bromothymol blue in aqueous nano TiO2 particles dispersions. Nanoscale research letters 2010; 5(10): 1627. https://doi.org/10.1007/s11671-010-9686-y
Ferrari C, Longo I, Tombari E, Bramanti E. A novel microwave photochemical reactor for the oxidative decomposition of Acid orange 7 azo dye by MW/UV/H2O2 process. Journal of Photochemistry and Photobiology A: Chemistry 2009; 204(2): 115-21. https://doi.org/10.1016/j.jphotochem.2009.03.001
Parolin F, Nascimento UM, Azevedo EB. Microwave-enhanced UV/H2O2 degradation of an azo dye (tartrazine): optimization, colour removal, mineralization and ecotoxicity. Environmental Technology 2013; 34(10): 1247-53. https://doi.org/10.1080/09593330.2012.744431
Bose AK, Ganguly SN, Manhas MS, He W, Speck J. Cold microwave chemistry: synthesis using pre-cooled reagents. Tetrahedron Letters 2006; 47(19): 3213-5. https://doi.org/10.1016/j.tetlet.2006.03.059
Chen P-K, Rosana MR, Dudley GB, Stiegman A. Parameters affecting the microwave-specific acceleration of a chemical reaction. The Journal of Organic Chemistry 2014; 79(16): 7425-36. https://doi.org/10.1021/jo5011526
Kappe C, Dallinger D, Murphree S. Practical microwave synthesis for organic chemists 2009. Wiley-VCH: Weinheim, Germany.
Gemeay AH. Kinetics and mechanism of the reduction of some azo-dyes by inorganic oxysulfur compounds. Dyes and Pigments 2002; 54(3): 201-12. https://doi.org/10.1016/S0143-7208(02)00040-2
Vellanki BP, Batchelor B, Abdel-Wahab A. Advanced reduction processes: a new class of treatment processes. Environmental Engineering Science 2013; 30(5): 264-71. https://doi.org/10.1089/ees.2012.0273
Land E, Shallow A, Mendham J, Denney R, Barnes J, Thomas M. Vogel's Quantitative Chemical Analysis: Prentice Hall 2000.
Tierney J, Lidström P. Microwave assisted organic synthesis: John Wiley & Sons 2009.
Rosana MR, Hunt J, Ferrari A, Southworth TA, Tao Y, Stiegman AE, et al. Microwave-specific acceleration of a Friedel–Crafts reaction: evidence for selective heating in homogeneous solution. The Journal of Organic Chemistry 2014; 79(16): 7437-50. https://doi.org/10.1021/jo501153r
Gedye RN, Rank W, Westaway KC. The rapid synthesis of organic compounds in microwave ovens. II. Canadian Journal of Chemistry 1991; 69(4): 706-11. https://doi.org/10.1139/v91-106
Painagoni KM, Patil HD. Estimation of ground and excited state dipole moments of some laser dyes. Int Journal of Engineering Research and Application 2013; 3(5): 641-7.
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.