Process Biochemistry 46 (2011) 736–744 View metadata, citation and similar papers at core.ac.uk brought to you by CORE Contents lists available at ScienceDirect provided by Elsevier - Publisher Connector Process Biochemistry journal homepage: www.elsevier.com/locate/procbio Samarium(III) and praseodymium(III) biosorption on Sargassum sp.: Batch study Robson C. Oliveira a,∗, Claire Jouannin b, Eric Guibal b, Oswaldo Garcia Jr. a a Departamento de Bioquímica e Tecnologia Química, Instituto de Química, UNESP – Univ Estadual Paulista, Rua Prof. Francisco Degni, s/n, C. P. 14800-900, Araraquara, SP, Brazil b Laboratoire Génie de l’Environnement Industriel, Ecole des Mines d’Alès (EMA), 6, avenue de Clavières, F-30319 Alès Cedex, France article info abstract Article history: This work evaluates the potential of a Sargassum biomass for the biosorption of Sm(III) and Pr(III) using Received 24 September 2010 synthetic solutions. Under selected experimental conditions (excess of sorbent), the biosorption kinetics Received in revised form 9 November 2010 were fast: 30–40 min were sufficient for the complete recovery of the metals. The kinetic profiles were Accepted 25 November 2010 modeled using the pseudo-second order rate equation. The second objective of this study was to evaluate the possibility to separate these metals. Biosorption isotherms and uptake kinetics for the two metals (in Keywords: binary component solutions) were almost overlapped. The biomass did not show significant selectivity Sargassum sp. for any of these two metals, in batch reactor. Biosorption Physicochemical modeling © 2010 Elsevier Ltd. Open access under the Elsevier OA license. Samarium Praseodymium Selectivity 1. Introduction boxyl, amino, sulfate, etc.) present on the cell wall [12]. Dead biomass is generally preferred since it limits the toxicity effects The recovery of heavy metals removal from dilute aqueous of heavy metals (which may accumulate at the surface of cell walls systems has required the development of new technologies for and/or in the cytoplasm) and the necessity to provide nutrients their concentration and separation [1,2]. Biosorption is a promis- [2,13,14]. Alternatively, other biomaterials can be used for these ing biotechnological alternative to conventional physicochemical purposes as biopolymers, activated sludge, agriculture wastes, etc. processes such as: chemical precipitation, electrochemical sepa- [15]. ration, membrane separation, reverse osmosis, ion-exchange or The mechanisms involved in metal accumulation on biosorp- adsorption resins [3–6]. Conventional methods involve either cap- tion sites are numerous and their interpretation is made difficult ital or high operational costs. They can also be associated to the complexity of the biologic systems (presence of various reac- production of secondary residues that may cause environmental tive groups, interactions between the compounds, etc.). However, hazards or complexity in treatment or valorization [6,7]. The ini- in most cases, metal binding proceeds through electrostatic interac- tial incentives for biosorption development in industrial process tion, surface complexation, ion-exchange, and precipitation, which are the low cost of biosorbents, their high efficiency for metal can occur individually or combined [5,16]. removal (especially in low-concentration solutions), the biosor- Sargassum sp. biomass used in this work belongs to Phaeophyta bent regeneration (and the potential metal recovery), the fast group (brown seaweed). This alga is very abundant on the coasts kinetics of adsorption and desorption, and the non-generation of of Brazil, Cuba, Australia, USA, and Asian Southeast [17]. Generally secondary residues (or at least their limited environmental impact) the cellular walls of Phaeophyta are constituted of a fibrillar skeleton [8]. and an amorphous matrix. The outer layer is an amorphous matrix Biosorption is a term that describes metal removal by passive that is linked to the fibrillar skeleton (mainly cellulose) via hydro- binding in living and dead biomass from aqueous solutions in a gen bonding. The amorphous matrix is predominately formed by mechanism that is not controlled by metabolic steps. The metal alginate, besides little amounts of fucoidan have been identified linkage is based on the chemical properties of the cellular enve- [18]. The alginate contributes to cellular wall resistance and flexibil- lope without requiring biologic activity [9–11]. The process occurs ity [18,19]. Alginate carboxyl groups are the most abundant acidic through interactions between metal species and actives sites (car- groups (involved in metal binding): they represent approximately 70% of the titrated sites. The biosorption uptake is directly asso- ciated to the presence of carboxyl groups in the alginate polymer. ∗ The second functional group of the brown seaweed is constituted Corresponding author. E-mail addresses: [email protected], [email protected] (R.C. Oliveira), of sulfonic acid, present in the fucoidan: these groups may also con- [email protected] (E. Guibal). tribute to biosorption [18]. Numerous studies have recently focused 1359-5113 © 2010 Elsevier Ltd. Open access under the Elsevier OA license. doi:10.1016/j.procbio.2010.11.021 R.C. Oliveira et al. / Process Biochemistry 46 (2011) 736–744 737 on the use of Sargassum biomass for the binding of several metals 50 ◦C. The slightly acidic washing contributes to stabilize the biomass and prevent including Ni(II) [20], Cu(II) [21,22], and Zn(II) [23]. further leaching of organic compounds. In addition, this stabilization contributes to The group of rare earth metals (REs) comprises scandium, reduce pH variation that may occur during metal sorption. Strong pH variations may cause difficulties in the comparison of experimental results when different amounts yttrium, and lanthanide series. The RE application fields are exten- of sorbent (which may interact with the solution through proton binding or proton sive, as a consequence of their peculiar spectroscopic and magnetic release) are used. The conditions for acidic pre-treatment are soft enough to prevent properties [23]. REs are of major interest for the development of a degradation of the biosorbent. several disciplines: coordination chemistry, organometallic com- pounds, luminescent compounds, catalysis, solid state chemistry, 2.2. Rare earth solutions analytical and environmental chemistry, industrial applications, RE stock solutions were prepared from Sm(III) and Pr(III,IV) oxides (both Aldrich biology, and medicine. These metals are essential for man- Chemical Company 99.9%). The metal oxides were burned off at 900 ◦C for 3 h. ufacturing products such as lasers, superconductors, cracking They were subsequently dissolved in small amounts of concentrated HCl under catalysts for petroleum, miniaturized equipments, fluorescents heating before being diluted with demineralized water until final concentration of ∼5.0gL−1. For these solutions, the RE concentrations were standardized by tripli- lamps, satellites, phosphorus, ultraviolet radiation absorbers, per- cate analysis using the complexometric titration with a standard solution of EDTA. manent magnets, and electronic information storages [24,25]. The titration was carried out in buffer solution of acetate/acetic acid at pH 6.0 ± 0.2 Although REs are very abundant in the Nature, they present high using xylenol orange as the titration indicator (prepared in ethanol/water solution). market values due to expensive and complex processes for their For metal biosorption experiments, the solutions used were prepared from dilu- ± separation and purification from mixtures because of their chem- tions of stock solutions and pH adjustment to 5.0 0.1 with diluted HCl or NaOH solutions. The metal concentrations in both initial and withdrawn samples were ical similarities. These processes involve several steps of solvent determined by an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP- extraction and/or ion-exchange resins, both with high costs [12,17]. AES JY 2000, Jobin-Yvon, Longjumeau, France). The ICP calibration was done utilizing The RE chemical similarities result from their electronic configura- RE standard solutions with three different concentrations and emission lines at tions: the trivalent state is the more stable thermodynamically in 359.260 and 414.311 nm for Sm(III) and Pr(III), respectively. aqueous solution. Each lanthanide element has in its electronic con- 2.3. Batch experiments figuration an inner shell with electrons in the 4fn orbital shielded 2 6 1–10 by an outer shell composed of electrons in orbitals 5s ,5p ,5d , The biosorption experiments in batch systems were carried out in flasks contain- and 6s2. The differences among lanthanides elements are caused by ing 0.100 ± 0.020 g of biomass and 50 mL of RE solution for kinetics and isotherm, electrostatic effect associated with the increase of shielded nuclear and 0.220 ± 0.040 g of biomass and 100 mL of RE solution for acid–base characteri- zation. The flasks were maintained under agitation at 150 rpm and temperature of charge through electrons partial supply of 4f orbital (which results ◦ ◦ 20 C (kinetics and isotherms) or 30 C (acid–base characterization). All batch exper- on lanthanide contraction of atomic and ionic radius along lan- iments were performed at least in triplicates. The calculation of the biosorption thanide series). This contraction is responsible for low differences uptake (q) is given by the mass balance equation, Eq.