Technetium removal from the aqueous solution using zeolites A and Y containing transition metal ions Co 2+ and Zn 2+ Radmila V. Hercigonja 1 • Sanja D. Vranjes ˇ-Djuric ´ 2 • Marija D. Mirkovic ´ 2 • Bojana M. Markovic ´ 3 • Danijela D. Maksin 2 • Bojana N. Markovic ´ 4 • Aleksandra B. Nastasovic ´ 3 Received: 16 January 2018 Ó Akade ´miai Kiado ´, Budapest, Hungary 2018 Abstract The adsorption properties of two zeolite types, faujasite (NaY, ZnY, CoY) and LTA-4A zeolite (NaA, ZnA, CoA), towards technetium were studied in batch static experiments. The Si/Al ratio, acidity, dealumination, chargebalance cations of zeolite, contact time and temperature determined the adsorption efficiency. The maximum removal efficiency of 98.8% and K d value (2.06 9 10 -4 cm 3 g -1 ) was achieved using CoY (zeolite type Y). The kinetics of technetium adsorption followed the pseudo-second order model. The TcO 2 adsorption is mainly due to the hydrogen bonds between protons of the zeolitic structural OH groups (Bronsted acid center) and oxygen from the TcO 2 - . Keywords Technetium Á Zeolite Á Adsorption Á Kinetics Introduction The improper discharges from nuclear processing plants, fallout from nuclear weapons tests and other sources such as nuclear power plants and medicinal use of metastable 99m Tc cause the release of substantial amount of technetium-99 ( 99 Tc) into the environment [1]. In energetic nuclear reactors, 99 Tc is formed in the thermal neutron fission of 235 U with high yield 6.13%. 99 Tc has become an increasingly important since it is a long-lived radionuclide (b-emitter) with a half-life of 2.13 9 10 5 years, while 99m Tc is short lived (with a half-life of 6.0072 h) and rapidly decays to 99 Tc [2]. Thus, technetium is considered to be one of the important hazardous elements in high-level radioactive waste. When it is released into the environ- ment, a number of plants and animals take up 99 Tc to an appreciable extent and the biomagnifications of 99 Tc in the food chain is an obvious concern. The control of environ- ment pollution by 99 Tc is therefore considered a primary task. It is essential to develop reliable and cost-effective methods to remove 99 Tc from a variety of vehicles, ranging from high-level liquid waste to low levels of radioactivity in groundwater. Many researchers have examined the immobilization of 99 Tc, as well as its adsorption from contaminated groundwaters using various adsorbent mate- rials [3–5]. Technetium solubility and adsorption behavior is strongly dependent on its valence state. In oxygenated and suboxygenated environments this radionuclide is in the predominant chemically stable Tc(VII) valent state in the form of pertechnetate anion (TcO 4 - ). Under reducing or anoxic conditions Tc(IV) is stable as TcO 2 ÁnH 2 O[6]. Faujasite (FAU) (zeolite type Y) and LTA-4A (zeolite type A) zeolites have a cubic crystal structure. Their three- dimensional structure is built by silicate [SiO 4 ] 4- and aluminate [AlO 4 ] 5- tetrahedral framework which are linked by oxygen atom at the corners. When one of the Si atoms is substituted by Al, the framework becomes nega- tively charged. This is compensated by the presence of a positively charged cations. & Aleksandra B. Nastasovic ´ anastasovic@yahoo.com; anastaso@chem.bg.ac.rs 1 Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade, Republic of Serbia 2 Vinc ˇa Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, Belgrade, Republic of Serbia 3 Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Njegos ˇeva 12, Belgrade, Republic of Serbia 4 Faculty of Biology, University of Belgrade, Studentski trg 16, Belgrade, Republic of Serbia 123 Journal of Radioanalytical and Nuclear Chemistry https://doi.org/10.1007/s10967-018-5893-2