Effect of Fenton's treatment on the biodegradability of chromium-complex azo dyes.
Pretreatment of an acid dyebath effluent bearing a new generation chromium complex azo dyestuff (C0 = 350 mg/L) with Fenton's reagent was investigated. Preliminary optimisation (baseline) experiments were conducted to determine the Fe2+, H2O2 concentrations and pH required to the highest possible COD and colour removals. Kinetic studies were carried out at varying temperatures (20 degrees C < T < 70 degrees C) to establish a relationship between COD abatement and H2O2 consumption. The activation energy found for catalytic H2O2 decomposition (Ea = 9.8 kJ/mol) appeared to be significantly less than that of fermentative (Ea = 23 kJ/mol) and of thermal (Ea = 76 kJ/mol) H2O2 decomposition, implying that H2O2 decomposition during the Fenton's reaction occurs more spontaneously. The experimental studies indicated that approximately 30% COD and complete colour removal could be achieved under optimised Fenton pretreatment conditions (Fe2+ = 2 mM; H2O2 = 30 mM; pH = 3; at T = 60 degrees C). Long-term activated sludge experiments revealed that although the raw and pretreated acid dyebath effluent contained practically the same amount of "readily biodegradable" COD (inert COD fraction < or = 10%), biodegradation of the chemically pretreated acid dye effluent proceeded appreciably faster than that of the untreated acid dyebath effluent.
Istanbul Technical University, Faculty of Civil Engineering, Department of Environmental Engineering, 34469 Maslak, Istanbul, Turkey.
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Arslan-Alaton
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Kabdaşli
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Teksoy
D001391:Azo Compounds / Q000737:chemistry* / Q000378:metabolism*; D019149:Bioreactors; D002374:Catalase / Q000378:metabolism; D002857:Chromium / Q000737:chemistry*; D003116:Color; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008837:Micrococcus / Q000201:enzymology; D013696:Temperature
D001391:Azo Compounds; C045076:Fenton's reagent; D002857:Chromium; D006861:Hydrogen Peroxide; D007501:Iron; D002374:Catalase