Process Safety and Environmental Protection 102 (2016) 294–302 Contents lists available at ScienceDirect Process Safety and Environmental Protection journal homepage: www.elsevier.com/locate/psep Preparation of phthalocyanine/TiO 2 nanocomposites for photocatalytic removal of toxic Cr(VI) ions Rıza Bayrak a , Cansu Albay b , Melek Koc ¸ b , ˙ Ilknur Altın b , ˙ Ismail De ˘ girmencio ˘ glu b,** , Münevver Sökmen b,* a Sinop University, Vocational School of Health Services, Department of Medical Laboratory Techniques, 57000 Sinop, Turkey b Karadeniz Technical University, Faculty of Science, Department of Chemistry, 61080 Trabzon, Turkey article info Article history: Received 7 July 2015 Received in revised form 1 February 2016 Accepted 31 March 2016 Available online 7 April 2016 Keywords: Photocatalysis Azomethine-bridged phenolic phthalocyanine Phthalocyanine/TiO 2 composites Dye sensitization Cr(VI) reduction Photocatalytic removal abstract In this study, a group of novel metal free azomethine-bridged phenolic phthalocyanines (H 2 Pc) was synthesized. These derivatives are completely new and first time reported. Four derivatives at peripheral or non-peripheral substitution on macro cyclic ring were synthe- sized and characterized employing various spectroscopic methods. H 2 Pc derivatives (defined as H 2 Pc-1, H 2 Pc-2, H 2 Pc-3, H 2 Pc-4) were immobilized on TiO 2 nanoparticles to obtain pho- toactive nanocomposites (H 2 Pc/TiO 2 , 1% of the mass of TiO 2 ). H 2 Pc derivatives were used as photosensitizer to improve the near visible-light photocatalytic efficiency of TiO 2 catalyst in wastewater treatment. Photocatalytic abilities nanocomposites were tested for photocat- alytic reduction of chromium (VI) ions (10mg/L) and compared with neat TiO 2 . A near UV light source (365 nm) was used for illumination in a batch reactor and Cr(VI) concentration was monitored during 150 min treatment period. It is clear that H 2 Pc sensitized photocat- alyst is effective for the reduction of chromium ions. Removal percentages were between 83.70 and 99.75% indicating almost total reduction of toxic Cr(VI) ions. Neat TiO 2 was able to reduce only 55.43% of initial Cr(VI) ions. All phthalocyanine containing TiO 2 composites are significantly more effective and reduce more Cr(VI) ions than TiO 2 itself. Photocatalytic action of the catalysts is decreased in the following order H 2 Pc-4/TiO 2 >H 2 Pc-2/TiO 2 >H 2 Pc- 1/TiO 2 >H 2 Pc-3/TiO 2 . © 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction Phthalocyanines (Pc), a blue-green-colored aromatic macro- cyclic compounds, have a great deal of attention from scientists in diverse fields such as catalysis, solar energy con- version, photodynamic therapy of cancer, non-linear optics, gas sensors and laser dyes due to their highly delocalized elec- tronic structure (Akc ¸ay et al., 2013; Topuz et al., 2013; Przybyl and Janczak, 2015; Bilgic ¸li et al., 2015). Major problem of Pc ∗ Corresponding author. Tel.: +90 462 3772532; fax: +90 4623253196. ∗∗ Corresponding author. Tel.: +90 462 3773321; fax: +90 4623253196. E-mail addresses: ismail61@ktu.edu.tr ( ˙ I. De ˘ girmencio ˘ glu), msokmen@ktu.edu.tr (M. Sökmen). molecule is its insolubility in water and this can be enhanced by substitution on its peripheral or non-peripheral positions. Peripheral means substitution of functional group to nitrile carbon at  position and non-peripheral at  position (López Zeballosa et al., 2015). Photocatalysis is an advanced oxidation technology (AOT) for removal of pollutants in water that usually involves anatase type titanium dioxide (TiO 2 ) in the presence of light. Because of its partially large band gap energy (e.g., 3.2 eV) http://dx.doi.org/10.1016/j.psep.2016.03.023 0957-5820/© 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.