Current Research Papers Enhancement of photodegradation of mordant dyes by iron powder and H 2 O 2 in presence of UV light KEYWORDS Mordant dyes; Eriochrome red B; H 2 O 2 /UV; Photo-fenton; Iron powder. ABSTRACT In this study different treatment methods such as H 2 O 2 /UV, Fenton and photo-Fenton (Fe +n /H 2 O 2 /UV) treatments, have been used to investigate the removal of the Mordant red 7 (MR7) azo dye from aqueous solution. In photo-Fenton treatment, iron (Fe) powder was used as a cheap source of Fe 2+ ions. Complete decolorization of MR7 using H 2 O 2 /UV process, achieved in less than 60 min. The photodegradation process was mainly effected by different parameters such as initial dye concentrations, [H 2 O 2 ], pH value and presence of different inorganic salts such as carbonate, nitrate and chloride ions. The decrease in the degradation percent was in the order of Carbonate > chloride > nitrate ions. In comparison, the photo-Fenton treat- ment, using Fe powder as a source of Fe 2+ ions, was more efficient in the decolorization of MR7. It was found that complete decolorization of MR 7 obtained in about 30 min. Furthermore, mineralization of MR 7 was investi- gated using chemical oxygen demand (COD) experiment. The results indi- cated that, 66.67% of the MR7 dye was mineralized using H 2 O 2 /UV process in a 3.0 h photoperiod. While photo-Fenton treatment (in presence of Fe 0 powder), was more efficient and resulted in complete mineralization of MR7 dye in about 2.0 h of photoperiod.  2010 Trade Science Inc. - INDIA INTRODUCTION Advanced oxidation technologies (AOTs) are those processes which involve powerful oxidizing agents such as hydroxyl free radicals (OH) to efficiently oxidize a wide range of organic pollutants in wastewater at ambient temperature and pressure [1-4] . The chemical reactions involved in AOTs are faster than oxidation that takes place in the environment. Hydroxyl radical (OH) has strong oxidizing potential (E = +1.8 V at neutral pH to +2.7V in acidic solutions), that lead to effective degradation of a wide variety of aqueous contaminants including azo dyes [5-7] . Presence of pollutants such as azo dyes in wastewater is of particular environmental concern since they can originate toxic by-products in the environment [8,9] . Mordant dyes are one class of azo-dyes characterized by the presence of a hydroxyl group ortho to the azo-group and are M.Taha Elmorsi 1,2 *, Yasser M.Riyad 2 , Zeinhom H.Mohamed 2 , Sawsan A.Mahmoud 3 , Hassan M.Abd El Bary 2 1 Chemistry Department, Faculty of Science, Jazan University, Jazan, 706, (KSA) 2 Chemistry Department, Faculty of Science, Al-Azhar University, 11884, Cairo, (EGYPT) 3 Egyptian Petroleum Research Institute, Cairo, (EGYPT) E-mail : taha_elmorsi@yahoo.com Received: 6 th April, 2010 ; Accepted: 16 th April, 2010 Environmental Science An Indian Journal Trade Science Inc. Volume 5 Issue 3 ESAIJ, 5(3), 2010 [215-222] June 2010 Environmental Science ISSN : 0974 - 7451