Accepted Article This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/wej.12522 This article is protected by copyright. All rights reserved. DR MAHA ABDELBASET TONY (Orcid ID : 0000-0003-3670-503X) Article type : Full length original research paper Synthesis of nano-sized amorphous and nanocrystalline TiO 2 for photochemical oxidation of methomyl insecticide in aqueous media Maha A. Tony 1,2* , Shehab A. Mansour 2 1 Civil and Environmental Engineering, West Virginia University, Morgantown, WV 26506- 6103. USA 2 Advanced Materials/Solar Energy and Environmental Sustainability (AMSEES) Laboratory, Basic Engineering Science Department, Faculty of Engineering, Menoufia University, Shebin El-Kom, Egypt ------------------------------------------------------------------------------------ *Corresponding author, Tel: +2 0482221549, Fax: +2 0482235695; E-mail: dr.maha.tony@gmail.com, ORCID: 0000-0003-3670-503X Abstract Aqueous solution loaded with methomyl insecticide is photo-catalytically treated upon UV radiation and TiO 2 in a green sustainable oxidation technique. TiO 2 is a highly promising photocatalytic oxidation method, whereas, the main findings is increasing the surface area for maximizing the treatment efficiency. Herein, TiO 2 was synthesized via sonochemical hydrolysis technique and amorphous TiO 2 (TM100) was obtained. Further, annealing of amorphous TiO 2 at 500 ºC resulting in anatase-phase TiO 2 (TN500). The phase structure of the both samples was confirmed by high-resolution transmission electron microscope (HR- TEM). The results revealed that the materials exhibited high methomyl removal efficiency due to its nanostructure nature. The optimum TM100 and TN500 for the treatment were 40 and 20 mg/L and resulted in 99.5 % and 100 % methomyl removal, respectively. Furthermore, pH and H 2 O 2 effect were studied. Additionally, high correlation was attained between empirical and modeled values with a second order kinetic model for the two processes. Keywords: amorphous; anatase; methomyl aqueous solution; oxidation; TiO 2 ; ultraviolet light