Ɇɟɠɞɭɧɚрɨɞɧɚ ɧɚɭɱɧɚ кɨɧɮɟрɟɧɰия “ɍɇИɌЕХ’05” – Гɚɛрɨɜɨ II-383 ‘ 05 INTERNATIONAL SCIENTIFIC CONFERENCE 24 – 25 November 2005, GABROVO CATALYTIC WET HYDROGEN PEROXIDE OXIDATION OF REACTIVE PROCION MARINE H-EXL DYE SOLUTIONS Carmen Zaharia, Mariana Neamţu, Ayfer Yediler 1 , Mioara Surpăţeanu and Matei Macoveanu Department of Environmental Engineering and Management, Faculty of Chemical Engineering “Gh.Asachi” Technical University, D.Mangeron Blvd., no.71A, 700050 - Iasi, Romania 1 GSF-National Research Centre, Institute for Ecological Chemistry, Neuherberg-Münich, Germany Abstract The decomposition of reactive Procion Marine H-EXL azo dye solutions using a catalytic wet hydrogen peroxide oxidation (CWHPO) was studied. The catalyst currently named Fe-exchanged Y zeolite (FeY 5 ) was prepared by ion-exchange, using a commercially ultra stable Y-zeolite. All experiments were performed on a laboratory scale set-up at pH range of 3-7, catalyst amount of 0.5-1.25 g/L and respectively, hydrogen peroxide concentration of 10-20 mmol/L. The effects of different variables as pH, catalyst and hydrogen peroxide concentrations on wet hydrogen peroxide dye oxidation have been assessed. The dye decomposition rates were expressed through dye or color and COD removal (treatment degrees). The results indicate that after only 10 minutes at t=50°C, 20 mmol/L H 2 O 2 and 1g/L FeY 5 , the color removal was 94.91 % at pH=3 and 34.93 % at pH=5. The operational conditions corresponding to a pH=5, temperature of 50°C, 20 mmol/L H 2 O 2 and 1g/L FeY 5 but 60 minutes of wet oxidation lead to more than 97.84 % dye removal which corresponds to 64.23 % COD removal (treatment degree). A preliminary study of catalytic wet hydrogen peroxide oxidation of a synthetic textile wastewater containing the Procion Marine H-EXL dye was also performed. The catalyst allows almost total dye elimination and a significant COD removal without significant leaching of Fe ions. With this type of catalyst, it is possible to extend the range of pH values for which Fenton-type oxidation can not occur and no iron hydroxide sludge is forming. Keywords: catalytic wet hydrogen peroxide oxidation, Fe-exchanged ultra stable Y zeolite (FeY 5 ), Procion Marine H-EXL dye. INTRODUCTION Some textile wastewaters are strongly coloured and are found to be toxic and carcinogenic to the aquatic environments. Azo dyes constitute one of the most important classes of commercial dyes. These dyes comprise about one half of all dyes used today and currently presented into the textile wastewaters [1]. Among many methods of wastewater treatment, a promising approach is the advanced oxidation process (AOP). This method implies generation and subsequent reaction of hydroxyl radicals, which are the most powerful oxidizing species after fluorine [2]. The Fenton processes have been used as a powerful source of hydroxyl radicals from H 2 O 2 in the presence of transition metal cations. So, these systems offer an effective source of hydroxyl radicals but also two major disadvantages that limit the industrial application of this technology: (i) the tight range of pH in which the reaction proceeds and (ii) the need for recovering of precipitated catalyst after the dye treatment. The resulted sludge may contain organic substances as well as heavy metals and has to be further treated, increasing thus the overall costs. A solution of this problem could be the use of heterogeneous solid Fenton catalysts, such as zeolites [2-7]. Some catalysts based on zeolites with ferrous iron in composition together with hydrogen peroxide can be efficiently used into the dye decomposition process. The oxidation mechanism is based on reaction between iron (II) and hydrogen peroxide with OH• generation. The hydroxyl radicals have a very high oxidation potential (2.80 V). The mechanism is similar with the action of “Feroxide process” [8]. The decomposition compounds after the catalytic wet hydrogen peroxide dye oxidation were intermediate compounds as amines, organic acids and inorganic compounds as oxalates, carbonates, nitrates, sulphates etc. [9]. The target of this paper is assessing the catalytic performances of the Fe-exchanged ultra