DE GRUYTER Journal of Advanced Oxidation Technologies. 2017; 20160176 V. Sydorchuk 1 / S. Khalameida 1 / B. Charmas 2 / J. Skubiszewska-Zięba 2 / V. Zazhigalov 1 / L. Davydenko 3 Catalytic Degradation of Safranin T in Aqueous Medium Using Non-conventional Processes 1 Institute for Sorption and Problems of Endoecology, NAS of Ukraine Naumova Street 13, 03164 Kyiv, Ukraine, E-mail: svkhal@ukr.net 2 The Department of Chromatographic Methods, Maria Curie Skłodowska University M.C. Skłodowska Square 3, 20-031 Lublin, Poland 3 O.O.Chuiko Institute of Surface Chemistry, NAS of Ukraine Naumova Street 17, 03164 Kyiv, Ukraine Abstract: Eleven TiO 2 powders as catalysts have been studied in process of safranin T degradation in aqueous medium using mechanochemical, microwave and ultrasonic techniques. The degree of degradation has been controlled by means of spectrophotometric analysis of safranin T solutions before and after treatment and total organic carbon measurements. XRD, DTA-TG and BET analysis, FTIR spectroscopy and mass spectrometry of initial and spent catalysts have been carried out for explanation of obtained results. It has been established that the catalytic activity of TiO 2 under mechanochemical treatment depends on phase composition and dispersity (spe- cific surface area). Particularly, catalytic activity of mono-phase titanias inversely depends on specific surface area of initial catalyst. Sono- and microwave catalytic degradation were less effective. Keywords: mono- and bi-phase titania, mechanochemical, microwave, sonochemical techniques, crystal struc- ture, dyes degradation DOI: 10.1515/jaots-2016-0176 Received: July 5, 2016; Revised: October 7, 2016; Accepted: October 13, 2016 1 Introduction Photocatalytic degradation of pollutants in wastewaters using semiconductor catalysts (mostly titanium and zinc oxides) under UV irradiation is considered as advantageous, clean and the most effective technology [1–3]. However, photocatalytic processes using oxides possess several disadvantages: (i) UV light is screened by cat- alyst particles; (ii) shallow penetration of UV light in turbid wastewaters; (iii) high recombination rate among electron/hole pairs; (iv) poor adsorption of organic pollutants on the hydrophilic oxide surface. As a result, rel- atively low efficiency of many photocatalytic transformations is observed. Besides, there are well-known that UV irradiation is only about 4 % in the sunlight. Therefore, some new methods for water purification from haz- ardous chemicals are required and have been developed recently. Among them, advanced oxidation processes (AOPs) [4, 5] which often use different ways of energy supply in the wastewaters containing a heterogeneous catalyst. Ball milling, microwave and ultrasound irradiation (mechano-, microwave and sonocatalysis, respec- tively) are the approaches to achieve “green” chemistry goals [4, 6–13]. Particularly, ball milling is used for synthesis or activation of titanium dioxide as well as titanates and others niobates for the purposes of photo- catalysis [13–18]. It is important that these techniques, unlike the other AOPs, do not require the introduction of oxidiz- ing agents in the reaction mixture. Nonetheless, all mentioned above types of impact on the aqueous reaction medium (mechanochemical, microwave, sonochemical) cause formation of highly reactive species including hydroxyl, hydrogen, and hydroperoxyl radicals, as well as hydrogen peroxide both in solution and on the cat- alyst surface. Microwaves are a form of non-ionizing electromagnetic energy corresponding to the frequencies between 100 and 5,000 MHz [10]. Microwave treatment (MWT) is an attractive dielectric heating method which may have a unique ability to influence on chemical processes [6, 10]. From the viewpoint of catalysis, it is important that semiconductor catalysts absorb microwave energy. Meantime, thermal and specific non-thermal effects on the solid surface, which originate from absorption of microwave radiation, are usually observed [10, 19]. At the same time, only microwave radiation has no effect or has a minor effect on pollutant degradation processes [10, 11, 19]. At least, such a conclusion can be drawn for the processes for which a temperature of purified solution during the microwave treatment equals 100–180 °C [10, 19]. V. Sydorchuk is the corresponding author. © 2017 by Walter De Gruyter GmbH. Brought to you by | New York University Authenticated Download Date | 2/21/17 10:41 AM