In: Water Purification ISBN 978-1-60741-599-2 Editors: N. Gertsen and L. Sønderby, pp. © 2009 Nova Science Publishers, Inc. Chapter 6 PHOTO-DEGRADATION OF METHYL ORANGE WITH DIRECT SOLAR LIGHT USING ZnO AND ACTIVATED CARBON-SUPPORTED ZnO Hikmat S. Hilal * , Ghazi Y. M. Nour and Ahed Zyoud Department of Chemistry, An-Najah N. University, P.O. Box 7, Nablus, West bank, Palestine ABSTRACT ZnO is a wide band gap (3.2 eV) semiconductor, with limited photo-catalytic applications to shorter wavelengths only. However, it is suitable to use in solar light photo-degradation of different contaminants, due to a number of reasons, taking into account that the reaching-in solar radiation contains only a tail in the near UV region. The high absorptivity of ZnO makes it efficient photo-catalyst under direct solar light. Moreover, it is relatively safe, abundant and non costly. In this chapter, ZnO has been investigated as a potential catalyst for photo-degradation of methyl orange (a known dye) in aqueous solutions with direct natural solar light under different conditions. The major aim was to assess the efficiency and stability of ZnO under photo-electrochemical (PEC) conditions, and to suggest techniques to enhance such features. This will shed light on the future applicability of ZnO as a candidate for economic and friendly processes in water purification. Recovery of ZnO particles, after reaction completion, has been facilitated by supporting ZnO onto activated carbon, to yield AC/ZnO system. The AC/ZnO was used as catalyst for contaminant photo-degradation in water solutions under direct solar light. Both catalytic systems, naked ZnO and AC/ZnO, were highly efficient in degrading both contaminants, reaching complete removal in reasonable times. The latter system showed higher efficiency. In both systems, the reaction goes faster with higher catalyst loading, until a maximum efficiency is reached at a certain concentration, after which the catalyst concentration did not show a systematic effect. * Fax: 00-970-9-2387982; E-mail: hikmathilal@yahoo.com