Biosorption of radiostrontium by alginate beads: application of isotherm models and thermodynamic studies Cem Gok • Udo Gerstmann • Sule Aytas Received: 28 April 2012 / Published online: 24 May 2012 Ó Akade ´miai Kiado ´, Budapest, Hungary 2012 Abstract Radioactive strontium is one of the major radioactive contaminant and its contamination is a very serious concern. Therefore, there is a need for economic, effective, non-toxic, readily available and abundant adsorbent or biosorbent to remove strontium from solu- tions. In this study, biosorption of 85 Sr as a surrogate for 90 Sr onto alginate beads was investigated in a batch system. Alginate beads were prepared from Na-alginate via cross- linking with divalent calcium ions according to the egg box model. The effect of several parameters such as pH, initial strontium concentration, contact time, dosage of alginate beads and temperature were investigated. In order to optimize the design of biosorption system for the removal of strontium, it is important to establish the most appro- priate correlation for equilibrium curves. The experimental isotherm data were described by 6 different biosorption isotherm models, namely Langmuir, Freundlich, Dubinin– Radushkevich, Temkin, Flory–Huggins and Brunauer, Emmer and Teller, with constants obtained from linear and non-linear regression methods. The thermodynamic parameters (DH°, DS° and DG°) for strontium biosorption were also determined. The results indicate that these algi- nate beads have a good potential for the biosorption of strontium from solutions. Keywords Strontium  Biosorption  Alginate beads  Modelling  Thermodynamic Introduction Strontium has two important radioactive isotopes, 90 Sr which emits b radiation with a half-life 28.78 years and 85 Sr which is a c emitter with a half-life of 64.84 days. 90 Sr can be found in nuclear wastes and 85 Sr is used in industry and medicine. 90 Sr is one of the most hazardous radio- nuclides, posing a long term radiation hazard [1] because of its long half-life and high mobility [2]. Once released into the environment, strontium can enter the food chain and consequently be absorbed into the human body. As a chemical and physiological equivalent of calcium it is absorbed from the gastrointestinal tract after intake of contaminated foodstuffs and deposited primarily in the skeleton. Ingestion of strontium radionuclides through contaminated foodstuff and drinking water may lead to a significant internal radiation exposure of the population [3, 4]. Strontium has been taken part in many sorption and removal studies because of its radiation toxicity. Bascetin and Atun [5] investigated strontium adsorption behavior on montmorillonite and kaolinite using 90 Sr as a tracer by batch method. Sorption–desorption experiments of C. Gok  U. Gerstmann Helmholtz-Zentrum Mu ¨nchen, German Research Center for Environmental Health, Institute of Radiation Protection, Ingolsta ¨dter Landstr. 1, 85764 Neuherberg, Germany C. Gok  S. Aytas Institute of Nuclear Sciences, Ege University, 35100 Bornova, Izmir, Turkey Present Address: C. Gok (&) Faculty of Science and Letters, Department of Physics, Pamukkale University, Kınıklı, 20020 Denizli, Turkey e-mail: cemgok2005@gmail.com; cemgok@pau.edu.tr Present Address: U. Gerstmann German Federal Office for Radiation Protection, Ingolsta ¨dter Landstr. 1, 85764 Neuherberg, Germany 123 J Radioanal Nucl Chem (2013) 295:777–788 DOI 10.1007/s10967-012-1838-3