Journal of Hazardous Materials B116 (2004) 125–134 Biosorption of cesium by native and chemically modified biomass of marine algae: introduce the new biosorbents for biotechnology applications R. Jalali-Rad a,∗ , H. Ghafourian a , Y. Asef a , S.T. Dalir a , M.H. Sahafipour a , B.M. Gharanjik b a Department of Biotechnology, Nuclear Research Center, Atomic Energy Organization of Iran, Tehran, Iran b Offshore Fisheries Research Center, Chabahar, Iran Received 1 February 2004; received in revised form 17 June 2004; accepted 10 August 2004 Available online 28 October 2004 Abstract Biosorption batch experiments were conducted to determine the cesium binding ability of native biomass and chemically modified biosor- bents derived from marine algae, namely ferrocyanide algal sorbents type 1 and type 2 (FASs1 and FASs2). The applicability of the Langmuir and Freundlich isotherms for representation of the experimental data was investigated. The cesium sorption performances of the various types of sorbents were compared using the maximum capacities (q max values) obtained from fitting the Langmuir isotherm to the values calculated from the sorption experiments, which FASs type 1 and type 2 showed better sorption performances for cesium. FASs1 and FASs2 derived from formaldehyde and glutaraldehyde crosslinked Padina australis exhibited lower sorption capacities than those prepared from the non-crosslinked one. Most of the cesium ions were bound to FASs1, derived from Sargassum glaucescens and P. australis, in <2 min and equilibrium reached within the first 30min of contact. Biosorption of cesium by FASs1 derived from P. australis and Cystoseria indica was constantly occurred at a wide range of pH, between 1 and 10, and the highest removal took place at pH 4. The presence of sodium and potassium at 0.5 and 1 mM did not inhibit cesium biosorption by algae biomass. The maximum cesium uptake was acquired using the large particles of FAS2 originated from S. glaucescens (2–4 mm). Desorption of cesium from the metal-laden FASs1 (from P. australis, S. glaucescens and Dictyota indica) was completely achieved applying 0.5 and 1 M NaOH and KOH, although the cesium sorption capacity of the biosorbents (from C. indica and S. glaucescens) decreased by 46–51% after 9 sorption–desorption cycles. © 2004 Published by Elsevier B.V. Keywords: Cesium biosorption; Desorption; Marine algae; Ferrocyanide algal sorbents; Crosslinked biomass 1. Introduction Stable cesium ( 133 Cs), that is the rarest of the alkali met- als, has little economic value and no essential biological role. However, nuclear technology has resulted in the large amount release of radioactive Cs isotopes into the environment. 137 Cs has been a matter of serious concern because of its long half- life of 30 years and high water solubility. Thus, hazardous quantities of 137 Cs will remain in the environment for cen- ∗ Corresponding author. Tel.: +98 21 61383438; fax: +98 21 8021412. E-mail addresses: rjalali@aeoi.org.ir, rjalalirad@yahoo.com (R. Jalali-Rad). turies and living organisms easily absorb 137 Cs mistaking it for harmless potassium [1–7]. Alternative technologies for removal of other heavy metals and radionuclides, such as metal precipitation and chelating agents, have been ineffective for Cs removal [2]. To date, the removal of Cs radioisotopes from radioactive waste ef- fluents has relied largely on ion-exchange methods. Natural and synthetic zeolites (e.g. mordenite, clinoptilolite, erion- ite, chazabite and aluminosilicates) have been used for large- scale separation of 137 Cs from low- and intermediate-level radioactive waste effluents [2]. However, one disadvantage of the application of zeolites relates to the competitive inter- actions of other monovalent cations, in particular Na + and K + 0304-3894/$ – see front matter © 2004 Published by Elsevier B.V. doi:10.1016/j.jhazmat.2004.08.022