Photochemistry and Photobiology, 20**, **: *–* Rapid Communication The Effect of Loading Palladium on Zinc Oxide on the Photocatalytic Degradation of Methyl tert-Butyl Ether (MTBE) in Water Zaki S. Seddigi 1 , Saleh A. Ahmed* 1 , Shahid P. Ansari 1 , Naeema H. Yarkandi 1 , Ekram Danish 2 , Abdullah Abu Alkibash 3 , Mohammed D. Y. Oteef 4 and Shakeel Ahmed 5 1 Chemistry Department, College of Applied Sciences, Umm Al-Qura University, Makkah, Saudi Arabia 2 Chemistry Department, College of Sciences, King Abdulaziz University, Jeddah, Saudi Arabia 3 Chemistry Department, College of Sciences, King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia 4 Chemistry Department, College of Science, King Khalid University, Abha, Saudi Arabia 5 Center for Refining & Petrochemicals, Research Institute, King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia Received 26 July 2013, accepted 14 January 2014, DOI: 10.1111/php.12242 ABSTRACT A series of heterogeneous catalysts was prepared by doping zinc oxide with different palladium loadings in the range of 0.5%–1.5%. The prepared catalysts were characterized by SEM, TEM and XRD. These catalysts were applied to study the degradation of Methyl tert-Butyl Ether (MTBE). An amount of 100 mg of each of these catalysts was added to an aqueous solution of 100 ppm of MTBE. The resulting mix- tures were irradiated with UV light for a period of 5 h. A 99.7% removal of MTBE was achieved in the case of the zinc oxide photocatalyst particles doped with 1% Pd. The photo- reaction was found to be a first-order one. INTRODUCTION Fuel oxygenates are special types of organic compounds blended with gasoline to improve its quality (1). These com- pounds provide enough oxygen which enhances the combustion process to come to completion which will in turn increase the octane rating of the fuel. As a result, the harmful vehicular emissions are reduced (2). The compounds that are used as fuel oxygenates include methyl tert-butyl ether (MTBE), ethyl tert- butyl ether, tert-amyl methyl ether, ethanol and methanol (3). MTBE is generally used because of its unique properties such as its significant blending properties and the low cost of its pro- duction (4,5). However, as a result of accidental spills, the underground leakage of pipelines and the problems associated with the storage tanks, MTBE has started to appear in the water bodies. MTBE is stable chemically as well as biologically and its adsorption on soil is insignificant. It is also hydrophilic (~50 gL 1 ), thus it dissolves in water/moisture and moves rap- idly through soil and accumulates in water bodies (6). Increased concentrations of MTBE in drinking water render this water unsafe for human consumption. Skin eruption, diarrhea, respira- tory problem are the general symptoms noted on exposure to water contaminated with MTBE (7). The United States Environ- mental Protection Agency (USEPA) has considered the presence of MTBE in water as a potential human carcinogen and has issued a ban on its usage as an additive in the fuel (8). Many traditional techniques like aerobic/anaerobic degradation, air- stripping, activated carbon treatments were not successful to remove MTBE from water. This can be attributed to the resis- tance of MTBE to biodegradation and to the Henry’s law con- stant (5.5 9 10 4 atm m 3 mol 1 at 25°C) (9). Recently, heterogeneous photocatalysis have been used to degrade the environmental remediation where the toxic and non- biodegradable organic molecules are subjected to degradation. Photocatalysis is initiated by irradiating a suitable catalyst with an electromagnetic light of suitable wavelength having an energy that is higher than or equal to that of the band gap of the catalyst material (10,11). This irradiation forces an electron from the valance band to conduction band, thus creating a hole (h + ). These photogenerated electrons and holes will act as reducing and oxidizing agents during the photocatalytic reac- tions. ZnO as a photocatalyst has been reported to give good results when applied using various practical conditions (13–17). The increasing interest in ZnO as a photocatalyst can be attrib- uted to its distinct photochemical and catalytic properties and the possible mechanism of the photocatalysis may be given as below: (12). ZnO þ hv ! e  þ h þ ð1Þ ðO 2 Þads: þ e  ! O  2  ð2Þ H 2 O ! OH  þ H þ ð3Þ O  2  þ H þ ! HOO  ð4Þ HOO  þ e  !HOO  ð5Þ HOO  þ H þ ! H 2 O 2 ð6Þ H 2 O 2 þ e  ! 2  OH ð7Þ *Corresponding author e-mail: saleh_63@hotmail.com (Saleh A. Ahmed) © 2014 The American Society of Photobiology 1