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Adsorption isotherms for Cr (VI) by two immobilized marine cyanobacteria

Adsorption isotherms for Cr (VI) by two immobilized marine cyanobacteria Ann Microbiol (2012) 62:241–246 DOI 10.1007/s13213-011-0252-3 ORIGINAL ARTICLE Adsorption isotherms for Cr (VI) by two immobilized marine cyanobacteria Kamaraj Rajeshwari & Muthukannan Satheesh Kumar & Nooruddin Thajuddin Received: 20 December 2010 /Accepted: 14 March 2011 /Published online: 1 April 2011 Springer-Verlag and the University of Milan 2011 Abstract Immobilized forms of two marine cyanobacteria, paint, and electroplating industries and the waste water of Oscillatoria sp. NTMS01 and Phormidium sp. NTMS02, tanneries (Leusch et al. 1995; Viraraghavan and Yan 2001). were selected for the removal of chromium (VI) ions from Conventional methods for removing metal ions from an aqueous solution. Biosorption was studied as a function aqueous solutions include chemical precipitation, filtration, of pH (1–6), contact time (5–180 min) and initial chromium ion exchange, electrochemical treatment, and reverse concentration (1–3 mg/L) to compare the maximum osmosis, but these are expensive and ineffective when capacity of two immobilized marine cyanobacteria. These metal ions in the aqueous solution are in the range of 1– organisms were found to be efficient sorbents for the 100 mg/L (Leusch et al. 1995; Volesky 2001; Viraraghavan removal of chromium (VI) ions in lower concentrations. and Yan 2001). Biological approaches are now being Biosorption equilibrium was established in about 30 min. considered as an alternative for the removal of heavy metal Maximum adsorption was observed at pH 3. The biosorp- contamination. Biosorption and/or bioaccumulation have tion was performed as described in terms of Langmuir and emerged as cost effective and efficient alternative methods. Freundlich isotherms. These organisms were found to fit Biosorption is the passive process of adsorbing metal ions better by the Freundlich isotherm, which indicated hetero- by metabolically inactive biomass, and is dependent on the geneity of the algal surface. affinity between the metallic species or its ionic forms and the binding sites on the molecular structure of the cellular . . Keywords Biosorption Chromium Marine wall (Manriquez et al. 1997; Pardo et al. 2003). Micro- . . cyanobacteria Immobilized cell Adsorption isotherm organisms including algae, bacteria, yeasts, fungi and plants can be used as biosorbents for metal removal (Wang and Chen 2006). Cyanobacteria are the largest group of Introduction photosynthetic prokaryotes, existing in various environ- ments where moisture and sunlight are available. Cyano- Heavy metal pollution in aquatic systems has become a bacteria are suggested to have some advantages over other serious threat today and is of great environmental concern microorganisms because of their large surface area, greater as these contaminants are non-biodegradable and thus mucilage volume with high binding affinity, simple nutrient persistent. Metals are mobilized and carried into the food requirements (Roy et al. 1993), and ubiquitous nature, and chain and thus become a risk factor for human health have been shown to serve as an efficient biosorbent for (Paknikar et al. 2003). Chromium (Cr) is a common removing heavy metal in lower concentrations (1–100 contaminant from the steel, textile, aluminium, ink, dye, mg/L). Immobilization of the biomass in solid structures creates a material with the right size, mechanical strength, : : K. Rajeshwari M. S. Kumar N. Thajuddin (*) rigidity and porosity necessary for maximum efficiency Department of Microbiology, School of Life Sciences, (Veglio and Beolchini 1997). Earlier, the hypersaline Bharathidasan University, cyanobacterium Phormidium tenue was screened for deg- Palkalai perur, radation of naphthalene and anthracene (Kumar et al. Tiruchirappalli 620 024 Tamilnadu, India 2009). In industrial operations, immobilized microbial cells e-mail: nthaju2002@yahoo.com 242 Ann Microbiol (2012) 62:241–246 could also provide additional advantages over freely double distilled water, and working standards were suspended cells, e.g., ease of regeneration and reuse of obtained by further dilution. the biomass, easier solid–liquid separation, and minimal clogging in continuous flow systems (Awasthi and Rai Determination of concentrations of Cr (VI) ion 2004; Katircioglu et al. 2008). In the present study, marine cyanobacteria are used for biosorption studies. It is already The concentration of Cr (VI) of the sample was determined known that cyanobacteria isolated from metal-contaminated by spectrophotometry (Optizen 3220 UV) at 540 nm using sites exhibit higher efficiency in removing metals but, in 1,5 diphenyl carbazide reagent in acid solution as a this study, marine cyanobacteria from unpolluted environ- complexing agent for Cr (VI) (Clesceri et al. 1996). ments were selected to test their efficiency in removing metals at lower concentrations. Biosorption studies Chromium (VI) removal capacities of the two biosorbents Materials and methods were studied in batches under varying pH (1–6), initial metal ion concentration (1–3 mg/L), contact time (5– Isolation of cyanobacteria and preparation of biosorbents 180 min) at 26°C. The pH of the metal solution was varied by the addition of 0.1 M HCl or NaOH. The experiments Two axenic cultures of cyanobacterial strains, Oscillatoria were carried out in 250 mL Erlenmeyer flasks containing sp. NTMS01 and Phormidium sp. NTMS02, were obtained 100 mL metal ion solution and 50 immobilized cyanobac- from the Culture Collection Centre of the Department of terial beads. The flasks were agitated for 3 h at 120 rpm. Microbiology, Bharathidasan University, Tiruchirappalli, Aliquots of 1 mL metal ion solution were taken from the India. Pure cultures were grown on MN medium, which triplicate reactions at regular intervals and centrifuged at was composed of the following: NaNO (0.75 g), K HPO 4,000 rpm for 25 min. Cr (VI) ions in the supernatants were 3 2 4 (0.02 g), MgSO ·7H O (0.04 g), CaCl ·2H O (0.02 g), determined spectrophotometrically, using the 1,5 diphenyl 4 2 2 2 NaCO (0.02 g), citric acid (0.003 g), ferric ammonium carbazide method. For each treatment, blanks were also run citrate (0.003 g), EDTA (0.0005 g) and trace elements without cyanobacteria to account for adsorption by the solution (1 mL) in 1,000 mL water (750 mL sea water and alginate. 250 mL distilled water). Trace elements solution (1 mL) containing H BO (2.86 g), MnCl ·4H O (1.81 g), Statistical analysis 3 3 2 2 ZnSO ·7H O (0.222 g), NaMoO ·2H O (0.39 g), 4 2 4 2 Experiments were performed in triplicate, and the results CuSO ·5H O (0.079 g), Co(NO ) ·6H O (0.0494 g) in 4 2 3 2 2 1,000 mL distilled water. The pH of the medium was presented are those of a representative experiment wherein adjusted to 7.0. The cells were grown in sterile flasks all Cr (VI) determinations were performed in triplicate. containing 100 mL MN medium. Experimental cultures Data were analyzed statistically and the results are were incubated at 25±2°C, under a 14/10 h light/dark expressed as the mean (±SE) of three independent −2 −1 cycle, with illumination of 27 μRm s under cool white replicates. SE is represented by bars in the figures. The fluorescent lamps. The cultures were gently shaken by hand removal of Cr (VI) was influenced greatly by the variation on alternate days. of pH, initial metal ion concentration and contact time. For immobilization of cyanobacterial cells, sodium Metal ion removal was explained in terms of Langmuir alginate (5.5%) was mixed with 50 mL concentrated and Freundlich isotherms. The data of Langmuir and suspension of cyanobacterium and dropped through a Freundlich isotherms were analyzed statistically using syringe into 0.1 M CaCl . The beads, approximately 3– linear regression analysis employing the SPSS package 4 mm in diameter, were cured in the solution for about 1 h, (http://www.spss.com). and then washed three times with 150 mL sterile distilled water. The cured beads were then stored in 5 mM CaCl solution at 4°C until use. The dry weight of the prepared Results and discussion biomass was determined after drying the alginate beads overnight in an oven at 50°C (Katircioglu et al. 2008). Effect of pH on Cr (VI) biosorption Preparation of Cr (VI) solution Metal ion biosorption onto two biosorbents from an aqueous solutions is dependent on the pH of solution, as A synthetic stock solution of Cr (VI) was prepared by it affects biosorbent surface charge, degree of ionization, solution chemistry of the metals, activity of the functional dissolving a calculated quantity of K Cr O (AR Grade) in 2 2 7 Ann Microbiol (2012) 62:241–246 243 groups in the biomass, and competition of metallic ions (Tsezos and Volesky 1982a, b; Friis and Myers-Keith 1986; Galun et al. 1987; Ramelow et al. 1992; Katircioglu et al. 2008). The pH of aqueous metal solution (2 mg/L) was found to influence biosorption of Cr (VI) by the two marine species (Fig. 1). Percentage adsorption of Cr (VI) from the solution increased at pH 3. Up to 85% removal of Cr (VI) was achieved by using Oscillatoria sp. NTMS01 while Phormidium sp. NTMS02 had an efficiency of 75%. Under acidic conditions, the predominant species of Cr (VI) are 2− − 2− 2− [Cr O ] , [HCrO ] , [Cr O ] , and [Cr O ] , and the 2 7 4 4 13 3 10 surface of the sorbent becomes protonated and attracts anionic species of Cr (VI) (Ozer and Ozer 2003; Selvaraj et al. 2003). The optimum biosorptive removal of Cr (VI) at acidic pH has been reported for biosorbents of Synecho- coccus (Li et al. 2007), Dunaliella sp. (Donmez and Aksu 2002), Bacillus sp. (Nurba et al. 2002) and Rhizopus Fig. 2 Effect of agitation time on equilibrium Cr (VI) sorption nigricans (Sudha and Abraham 2001). A similar experi- capacity of two immobilized marine cyanobacterial strains (initial Cr concentration 2 mg/L, pH 3, and temperature 26°C) ment was conducted using control beads (beads without cyanobacteria) and 30% removal was observed. Effect of contact time the cells, which is substantially related to the composi- tion of proteins and carbohydrate and the charge density Chromium (VI) adsorption by two biosorbents as a function of the cell surface (Li et al. 2007). Groups with higher of time is depicted in Fig. 2. The rate of adsorption was affinities are freshly occupied so removal was high and fast high and very fast during the first 5–10 min, with during the initial contact time. Similar experiments were conducted with controls, and 25% removal was observed in Oscillatoria sp. NTMS01 and Phormidium sp. NTMS02 showing 85% and 75% removal, respectively. Equilibrium 120–180 min. was attained after 25 min. The fastest stage of biosorption could be dependent principally on the surface nature of Effect of initial Cr (VI) concentration According to the Bureau of Indian Standards (BIS), the permissible discharge level of Cr (VI) in industrial effluent is 0.1 mg/L (Congeevaram et al. 2007). It is necessary to remove chromium from aqueous solution in lower concen- trations. In present study, the effect of the initial concen- tration of Cr (VI), in the range of 1–3 mg/L, on its uptake by the immobilized biomass of the two species at optimized pH and contact time was also studied and is depicted in Fig. 3. These organisms showed that maximum percentage removal of Cr (VI) was at 2 mg/L. Nostoc calcicola HH-12 and Chroococcus sp. H-11 isolated from metal-contaminated sites has shown minimum percent removal of Cr less than 10 mg/L (Anjana et al. 2007). The ability of algae to bind metals may be attributed to the presence of effective groups, such as hydroxyl-phosphate, amino, and carboxyl groups, on the surface of the biomass that can capture metals (Khummongkol et al. 1982; Xue and Sigg 1990). The cyanobacterial envelope consists mainly of polysac- charides that are negatively charged and rich in uronic acids; thus they exhibit high metal-binding capacity Fig. 1 Effect of pH on equilibrium Cr (VI) sorption capacity of two (Manzini et al. 1984;Subramanian andUma 1996; Volesky strains of marine cyanobacteria in immobilized form (initial Cr concentration 2 mg/L, contact time 30 min, temperature 26°C) 1994). The maximum Cr (VI) biosorption capacity of 244 Ann Microbiol (2012) 62:241–246 sites; the model is described by the following linear equation (Crist et al. 1981): C =q ¼ 1=q C þ K =q e e d e m m where C is the equilibrium chromium concentration (mg/ L), q the metal adsorbed on the adsorbent (mg/g dry wt), q the maximal biosorption capacity, K is the Langmuir m d constant of the system. In this model, C /q is related e e linearly to q . However, the chances that a molecule adsorbed onto the surface may make it more or less difficult for another molecule to become attached to a neighboring site on the biosorbent, and this might lead to a deviation from the Langmuir biosorption equation. Under such a situation, the Freundlich isotherm may be more suitable, which can be expressed by the linear equation in Fig. 3 Effect of initial Cr (VI) concentration on equilibrium Cr (VI) logarithmic form as: sorption capacity of two immobilized cyanobacterial strains (contact time 30 min, pH 3, temperature 26°C) log q ¼ log K þ 1=n log C f e immobilized Oscillatoria sp. NTMS01 was found to be Where K is the Freundlich constant indicating adsor- bent capacity (mg/g dry wt), and n is the Freundlich 10% higher than that of immobilized Phormidium sp. NTMS02. This is probably due to the larger surface area of exponent known as adsorbent intensity (Freundlich and Oscillatoria sp. NTMS01. Helle 1939). This model shows that log q is linearly related to log C Adsorption isotherms The modeling results of the Langmuir and Freundlich models for Oscillatoria sp. NTMS01 and Phormidium sp. We next investigated Langmuir and Freundlich sorption NTMS02 immobilized species are shown in Fig. 4; the results indicate that the biosorption of Cr (VI) obeys only isotherms. The Langmuir model assumes monolayer bio- sorption onto a surface with a finite number of identical the Freundlich model. These figures show that the Fig. 4 a–d Modelling of Cr (VI) biosorption isotherm by Langmuir (a, c) vs Freundlich (b, d) sorption isotherms for Oscillatoria sp. NTMS01 and Phormidium sp. NTMS02 Ann Microbiol (2012) 62:241–246 245 Crist HR, Oberholser K, Shank N (1981) Nature of bonding between Freundlich isotherm had a higher correlation coefficient (r) metallic ions and algal cellwalls. Environ Sci Technol 15:1212– in the two selected organisms than that of the Langmuir isotherm. Therefore, in this study, the mechanisms involved Donmez G, Aksu Z (2002) Removal of chromium (VI) from saline in Cr (VI) removal by the two organisms were based on wastewaters by Dunaliella species. Process Biochem 38(5):751–762 Freundlich H, Helle WJ (1939) Rubber die adsorption in Lusungen. J Freundlich parameters. Freundlich’s model constants, K Am Chem Soc 61:2–28 and n were calculated and the values obtained for Friis N, Myers-Keith P (1986) Biosorption of uranium and lead by Oscillatoria sp. NTMS01 were, K =23.4 and n=1.42, Streptomyces longwoodensis. Biotechnol Bioeng 28:21–28 whereas in the case of Phormidium sp. NTMS02, K = Galun M, Galun E, Siegel BZ, Keller PE, Lehr H, Siegel SM (1987) Removal of metal ions from aqueous solutions by Penicillum 17.54 and n=1.64. biomass: kinetic and uptake parameters. Water Air Soil Pollut Freundlich parameters indicated a significant increase in 33:359–371 Cr (VI) uptake by immobilization of Oscillatoria sp. Katircioglu H, Aslim B, Turker AR, Atici T, Beyatli Y (2008) Removal of NTMS01 in sodium alginate beads. Biosorption in the cadmium (II) ion from aqueous system by dry biomass, immobilized live and heat-inactivated Oscillatoria sp. H1 isolated from two selected organisms fits better to the Freundlich freshwater (Mogan Lake). Bioresour Technol 99:4185–4191 isotherm, indicating heterogenicity of the algal surface or Khummongkol D, Canterford GS, Freyer C (1982) Accumulation of surfaces supporting sites of varied affinities. heavy metals in unicellular algae. Biotechnol Bioeng 12:2643– Kumar MS, Muralitharan G, Thajuddin N (2009) Screening of a hypersaline cyanobacterium, Phormidium tenue, for the degrada- Conclusion tion of aromatic hydrocarbons: naphthalene and anthracene. Biotechnol letters 31(12):1863–1866 In the present work, Cr (VI) adsorption by the two Leusch A, Holan ZR, Volesky B (1995) Biosorption of heavy metals (Cd, Cu, Ni, Pb, and Zn) by chemically-reinforced biomass of marine cyanobacteria, Oscillatoria sp. NTMS01 and marine algae. J Chem Technol Biotechnol 62:279–288 Phormidium sp. NTMS02, were compared and studied at Li S, Jin-lan X, Hua HE, Zhen-Yuan N, Guan-zhou Q (2007) varying pH, contact time and Cr (VI) concentration. Biosorption mechanism of Cr (VI) onto cells of Synechococcus Biosorption capacities for Cr (VI) were found to be sp. J Cent South Uni Technol, 02-0157-06 Manriquez RA, Magana PI, Lopez V, Guzman R (1997) Biosorption strongly dependent on the pH of the solution, and of Cu by Thiobacillus ferrooxidans. Bioprocess Eng 18:113–118 maximum capacities were obtained at pH 3 with a contact Manzini G, Ceesaro A, Delbin F, Paoletti S, Reisenhofer E (1984) time of 30 min. The equilibrium was described by Copper (II) binding by natural ionic polysaccharides. Part I, Langmuir and Freundlich adsorption isotherms. Adsorp- potentiometeric and spectroscopic data. Bioelectrochem Bioeng 12:443–454 tion of Cr (VI) by the two selected organisms fit better to Nurba M, Nourbakshsh S, Kilicarslan S (2002) Biosorption of Cr6+, the Freundlich isotherm than the Langmuir model. Higher Pb2+ and Cu2+ ions in industrial waste water on Bacillus sp. J K and correlation coefficient values were obtained in the Chem Eng 85(2/3):351–355 case of Oscillatoria sp. NTMS01. Thus, these organisms Ozer A, Ozer D (2003) Comparative study of the biosorption of Pb (II), Ni (II) and Cr (VI) ions onto S. cerevisiae: Determination of hold great promise in helping to mitigate heavy metal biosorption heats J. J Hazard Mater 100(1/3):219–229 pollution. Paknikar KM, Pethkar AV, Puranik PR (2003) Bioremediation of metalliferous wastes and products using inactivated microbial Acknowledgments This investigation was supported by the Minis- biomass. Indian J Biotechnol 2:426–443 try of Earth Sciences (MoES), Government of India. M.S. acknowl- Pardo R, Herguedas M, Barrado E, Vega M (2003) Biosorption of edges the award of UGC–Rajiv Gandhi National Fellowship (RGNF). cadmium, copper, lead and zinc by inactive biomass of P. putida. Anal Bioanal Chem 376:26–32 Ramelow GJ, Fralick D, Zhao Y (1992) Factors affecting the uptake of aqueous metal ions by dried seaweed biomass. Microbiology References 72:81–93 Roy D, Greenlaw PN, Shane BS (1993) Adsorption of heavy metals Anjana K, Kaushik A, Kiran B, Nisha R (2007) Biosorption of Cr (VI) by green algae and ground rice hulls. J Environ Sci Health by immobilized biomass of two indigenous strains of cyanobac- 28:37–50 teria isolated from metal contaminated soil. J Hazard Mater Selvaraj K, Manonmani S, Pattabi S (2003) Removal of hexavalent 148:383–386 chromium using distillery sludge. Bioresour Technol 89:207–211 Awasthi M, Rai LC (2004) Adsorption of nickel, zinc and cadmium Subramanian G, Uma L (1996) Cyanobacteria in pollution control. J by immobilized green algae and cyanobacteria: a comparative Sci Ind Res 55:685–692 study. Ann Microbiol 54(3):257–267 Sudha SR, Abraham TE (2001) Biosorption of Cr (VI) from Clesceri LS, Greenberg AE, Trussell RR (1996) Standard methods for aqueous solution by Rhizopus nigricans J. Bioresour Technol the examination of water and wastewater. APHA, AWWA and 79(1):73–81 WPCF, Washington DC Tsezos M, Volesky B (1982a) The Mechanism of uranium biosorption Congeevaram S, Dhanarani S, Park J, Dexilin M, Thamaraiselvi K by Rhizopus arrhizus. Biotechnol Bioeng 24:385–401 (2007) Biosorption of Chromium and Nickel by heavy metal Tsezos M, Volesky B (1982b) The Mechanism of thorium resistant fungal and bacterial isolates. J Hazard Mater 146:270– biosorption by Rhizopus arrhizus. Biotechnol Bioeng 24:955– 969 246 Ann Microbiol (2012) 62:241–246 Veglio F, Beolchini F (1997) Removal of metals by biosorption: a Volesky B (2001) Detoxification of metal-bearing effluents: biosorp- review. Hydrometallurgy 44:301–316 tion for the next century. Hydrometallurgy 59:203–216 Viraraghavan T, Yan GY (2001) Heavy metal removal in a biosorption Wang JL, Chen C (2006) Biosorption of heavy metals by column by immobilized M. rouxii biomass. Bioresour Technol Saccharomyces cerevisiae; a review. Biotechnol Adv 24:427– 78:243–249 451 Volesky B (1994) Advances in biosorption of metals: Selection of Xue HB, Sigg L (1990) The binding of heavy metals to algal surfaces. biomasss types. FEMS Microbiol Rev 14:291–302 Water Res 22:917–926 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Annals of Microbiology Springer Journals

Adsorption isotherms for Cr (VI) by two immobilized marine cyanobacteria

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Springer Journals
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Copyright © 2011 by Springer-Verlag and the University of Milan
Subject
Life Sciences; Microbiology; Microbial Genetics and Genomics; Microbial Ecology; Mycology; Medical Microbiology; Applied Microbiology
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DOI
10.1007/s13213-011-0252-3
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Abstract

Ann Microbiol (2012) 62:241–246 DOI 10.1007/s13213-011-0252-3 ORIGINAL ARTICLE Adsorption isotherms for Cr (VI) by two immobilized marine cyanobacteria Kamaraj Rajeshwari & Muthukannan Satheesh Kumar & Nooruddin Thajuddin Received: 20 December 2010 /Accepted: 14 March 2011 /Published online: 1 April 2011 Springer-Verlag and the University of Milan 2011 Abstract Immobilized forms of two marine cyanobacteria, paint, and electroplating industries and the waste water of Oscillatoria sp. NTMS01 and Phormidium sp. NTMS02, tanneries (Leusch et al. 1995; Viraraghavan and Yan 2001). were selected for the removal of chromium (VI) ions from Conventional methods for removing metal ions from an aqueous solution. Biosorption was studied as a function aqueous solutions include chemical precipitation, filtration, of pH (1–6), contact time (5–180 min) and initial chromium ion exchange, electrochemical treatment, and reverse concentration (1–3 mg/L) to compare the maximum osmosis, but these are expensive and ineffective when capacity of two immobilized marine cyanobacteria. These metal ions in the aqueous solution are in the range of 1– organisms were found to be efficient sorbents for the 100 mg/L (Leusch et al. 1995; Volesky 2001; Viraraghavan removal of chromium (VI) ions in lower concentrations. and Yan 2001). Biological approaches are now being Biosorption equilibrium was established in about 30 min. considered as an alternative for the removal of heavy metal Maximum adsorption was observed at pH 3. The biosorp- contamination. Biosorption and/or bioaccumulation have tion was performed as described in terms of Langmuir and emerged as cost effective and efficient alternative methods. Freundlich isotherms. These organisms were found to fit Biosorption is the passive process of adsorbing metal ions better by the Freundlich isotherm, which indicated hetero- by metabolically inactive biomass, and is dependent on the geneity of the algal surface. affinity between the metallic species or its ionic forms and the binding sites on the molecular structure of the cellular . . Keywords Biosorption Chromium Marine wall (Manriquez et al. 1997; Pardo et al. 2003). Micro- . . cyanobacteria Immobilized cell Adsorption isotherm organisms including algae, bacteria, yeasts, fungi and plants can be used as biosorbents for metal removal (Wang and Chen 2006). Cyanobacteria are the largest group of Introduction photosynthetic prokaryotes, existing in various environ- ments where moisture and sunlight are available. Cyano- Heavy metal pollution in aquatic systems has become a bacteria are suggested to have some advantages over other serious threat today and is of great environmental concern microorganisms because of their large surface area, greater as these contaminants are non-biodegradable and thus mucilage volume with high binding affinity, simple nutrient persistent. Metals are mobilized and carried into the food requirements (Roy et al. 1993), and ubiquitous nature, and chain and thus become a risk factor for human health have been shown to serve as an efficient biosorbent for (Paknikar et al. 2003). Chromium (Cr) is a common removing heavy metal in lower concentrations (1–100 contaminant from the steel, textile, aluminium, ink, dye, mg/L). Immobilization of the biomass in solid structures creates a material with the right size, mechanical strength, : : K. Rajeshwari M. S. Kumar N. Thajuddin (*) rigidity and porosity necessary for maximum efficiency Department of Microbiology, School of Life Sciences, (Veglio and Beolchini 1997). Earlier, the hypersaline Bharathidasan University, cyanobacterium Phormidium tenue was screened for deg- Palkalai perur, radation of naphthalene and anthracene (Kumar et al. Tiruchirappalli 620 024 Tamilnadu, India 2009). In industrial operations, immobilized microbial cells e-mail: nthaju2002@yahoo.com 242 Ann Microbiol (2012) 62:241–246 could also provide additional advantages over freely double distilled water, and working standards were suspended cells, e.g., ease of regeneration and reuse of obtained by further dilution. the biomass, easier solid–liquid separation, and minimal clogging in continuous flow systems (Awasthi and Rai Determination of concentrations of Cr (VI) ion 2004; Katircioglu et al. 2008). In the present study, marine cyanobacteria are used for biosorption studies. It is already The concentration of Cr (VI) of the sample was determined known that cyanobacteria isolated from metal-contaminated by spectrophotometry (Optizen 3220 UV) at 540 nm using sites exhibit higher efficiency in removing metals but, in 1,5 diphenyl carbazide reagent in acid solution as a this study, marine cyanobacteria from unpolluted environ- complexing agent for Cr (VI) (Clesceri et al. 1996). ments were selected to test their efficiency in removing metals at lower concentrations. Biosorption studies Chromium (VI) removal capacities of the two biosorbents Materials and methods were studied in batches under varying pH (1–6), initial metal ion concentration (1–3 mg/L), contact time (5– Isolation of cyanobacteria and preparation of biosorbents 180 min) at 26°C. The pH of the metal solution was varied by the addition of 0.1 M HCl or NaOH. The experiments Two axenic cultures of cyanobacterial strains, Oscillatoria were carried out in 250 mL Erlenmeyer flasks containing sp. NTMS01 and Phormidium sp. NTMS02, were obtained 100 mL metal ion solution and 50 immobilized cyanobac- from the Culture Collection Centre of the Department of terial beads. The flasks were agitated for 3 h at 120 rpm. Microbiology, Bharathidasan University, Tiruchirappalli, Aliquots of 1 mL metal ion solution were taken from the India. Pure cultures were grown on MN medium, which triplicate reactions at regular intervals and centrifuged at was composed of the following: NaNO (0.75 g), K HPO 4,000 rpm for 25 min. Cr (VI) ions in the supernatants were 3 2 4 (0.02 g), MgSO ·7H O (0.04 g), CaCl ·2H O (0.02 g), determined spectrophotometrically, using the 1,5 diphenyl 4 2 2 2 NaCO (0.02 g), citric acid (0.003 g), ferric ammonium carbazide method. For each treatment, blanks were also run citrate (0.003 g), EDTA (0.0005 g) and trace elements without cyanobacteria to account for adsorption by the solution (1 mL) in 1,000 mL water (750 mL sea water and alginate. 250 mL distilled water). Trace elements solution (1 mL) containing H BO (2.86 g), MnCl ·4H O (1.81 g), Statistical analysis 3 3 2 2 ZnSO ·7H O (0.222 g), NaMoO ·2H O (0.39 g), 4 2 4 2 Experiments were performed in triplicate, and the results CuSO ·5H O (0.079 g), Co(NO ) ·6H O (0.0494 g) in 4 2 3 2 2 1,000 mL distilled water. The pH of the medium was presented are those of a representative experiment wherein adjusted to 7.0. The cells were grown in sterile flasks all Cr (VI) determinations were performed in triplicate. containing 100 mL MN medium. Experimental cultures Data were analyzed statistically and the results are were incubated at 25±2°C, under a 14/10 h light/dark expressed as the mean (±SE) of three independent −2 −1 cycle, with illumination of 27 μRm s under cool white replicates. SE is represented by bars in the figures. The fluorescent lamps. The cultures were gently shaken by hand removal of Cr (VI) was influenced greatly by the variation on alternate days. of pH, initial metal ion concentration and contact time. For immobilization of cyanobacterial cells, sodium Metal ion removal was explained in terms of Langmuir alginate (5.5%) was mixed with 50 mL concentrated and Freundlich isotherms. The data of Langmuir and suspension of cyanobacterium and dropped through a Freundlich isotherms were analyzed statistically using syringe into 0.1 M CaCl . The beads, approximately 3– linear regression analysis employing the SPSS package 4 mm in diameter, were cured in the solution for about 1 h, (http://www.spss.com). and then washed three times with 150 mL sterile distilled water. The cured beads were then stored in 5 mM CaCl solution at 4°C until use. The dry weight of the prepared Results and discussion biomass was determined after drying the alginate beads overnight in an oven at 50°C (Katircioglu et al. 2008). Effect of pH on Cr (VI) biosorption Preparation of Cr (VI) solution Metal ion biosorption onto two biosorbents from an aqueous solutions is dependent on the pH of solution, as A synthetic stock solution of Cr (VI) was prepared by it affects biosorbent surface charge, degree of ionization, solution chemistry of the metals, activity of the functional dissolving a calculated quantity of K Cr O (AR Grade) in 2 2 7 Ann Microbiol (2012) 62:241–246 243 groups in the biomass, and competition of metallic ions (Tsezos and Volesky 1982a, b; Friis and Myers-Keith 1986; Galun et al. 1987; Ramelow et al. 1992; Katircioglu et al. 2008). The pH of aqueous metal solution (2 mg/L) was found to influence biosorption of Cr (VI) by the two marine species (Fig. 1). Percentage adsorption of Cr (VI) from the solution increased at pH 3. Up to 85% removal of Cr (VI) was achieved by using Oscillatoria sp. NTMS01 while Phormidium sp. NTMS02 had an efficiency of 75%. Under acidic conditions, the predominant species of Cr (VI) are 2− − 2− 2− [Cr O ] , [HCrO ] , [Cr O ] , and [Cr O ] , and the 2 7 4 4 13 3 10 surface of the sorbent becomes protonated and attracts anionic species of Cr (VI) (Ozer and Ozer 2003; Selvaraj et al. 2003). The optimum biosorptive removal of Cr (VI) at acidic pH has been reported for biosorbents of Synecho- coccus (Li et al. 2007), Dunaliella sp. (Donmez and Aksu 2002), Bacillus sp. (Nurba et al. 2002) and Rhizopus Fig. 2 Effect of agitation time on equilibrium Cr (VI) sorption nigricans (Sudha and Abraham 2001). A similar experi- capacity of two immobilized marine cyanobacterial strains (initial Cr concentration 2 mg/L, pH 3, and temperature 26°C) ment was conducted using control beads (beads without cyanobacteria) and 30% removal was observed. Effect of contact time the cells, which is substantially related to the composi- tion of proteins and carbohydrate and the charge density Chromium (VI) adsorption by two biosorbents as a function of the cell surface (Li et al. 2007). Groups with higher of time is depicted in Fig. 2. The rate of adsorption was affinities are freshly occupied so removal was high and fast high and very fast during the first 5–10 min, with during the initial contact time. Similar experiments were conducted with controls, and 25% removal was observed in Oscillatoria sp. NTMS01 and Phormidium sp. NTMS02 showing 85% and 75% removal, respectively. Equilibrium 120–180 min. was attained after 25 min. The fastest stage of biosorption could be dependent principally on the surface nature of Effect of initial Cr (VI) concentration According to the Bureau of Indian Standards (BIS), the permissible discharge level of Cr (VI) in industrial effluent is 0.1 mg/L (Congeevaram et al. 2007). It is necessary to remove chromium from aqueous solution in lower concen- trations. In present study, the effect of the initial concen- tration of Cr (VI), in the range of 1–3 mg/L, on its uptake by the immobilized biomass of the two species at optimized pH and contact time was also studied and is depicted in Fig. 3. These organisms showed that maximum percentage removal of Cr (VI) was at 2 mg/L. Nostoc calcicola HH-12 and Chroococcus sp. H-11 isolated from metal-contaminated sites has shown minimum percent removal of Cr less than 10 mg/L (Anjana et al. 2007). The ability of algae to bind metals may be attributed to the presence of effective groups, such as hydroxyl-phosphate, amino, and carboxyl groups, on the surface of the biomass that can capture metals (Khummongkol et al. 1982; Xue and Sigg 1990). The cyanobacterial envelope consists mainly of polysac- charides that are negatively charged and rich in uronic acids; thus they exhibit high metal-binding capacity Fig. 1 Effect of pH on equilibrium Cr (VI) sorption capacity of two (Manzini et al. 1984;Subramanian andUma 1996; Volesky strains of marine cyanobacteria in immobilized form (initial Cr concentration 2 mg/L, contact time 30 min, temperature 26°C) 1994). The maximum Cr (VI) biosorption capacity of 244 Ann Microbiol (2012) 62:241–246 sites; the model is described by the following linear equation (Crist et al. 1981): C =q ¼ 1=q C þ K =q e e d e m m where C is the equilibrium chromium concentration (mg/ L), q the metal adsorbed on the adsorbent (mg/g dry wt), q the maximal biosorption capacity, K is the Langmuir m d constant of the system. In this model, C /q is related e e linearly to q . However, the chances that a molecule adsorbed onto the surface may make it more or less difficult for another molecule to become attached to a neighboring site on the biosorbent, and this might lead to a deviation from the Langmuir biosorption equation. Under such a situation, the Freundlich isotherm may be more suitable, which can be expressed by the linear equation in Fig. 3 Effect of initial Cr (VI) concentration on equilibrium Cr (VI) logarithmic form as: sorption capacity of two immobilized cyanobacterial strains (contact time 30 min, pH 3, temperature 26°C) log q ¼ log K þ 1=n log C f e immobilized Oscillatoria sp. NTMS01 was found to be Where K is the Freundlich constant indicating adsor- bent capacity (mg/g dry wt), and n is the Freundlich 10% higher than that of immobilized Phormidium sp. NTMS02. This is probably due to the larger surface area of exponent known as adsorbent intensity (Freundlich and Oscillatoria sp. NTMS01. Helle 1939). This model shows that log q is linearly related to log C Adsorption isotherms The modeling results of the Langmuir and Freundlich models for Oscillatoria sp. NTMS01 and Phormidium sp. We next investigated Langmuir and Freundlich sorption NTMS02 immobilized species are shown in Fig. 4; the results indicate that the biosorption of Cr (VI) obeys only isotherms. The Langmuir model assumes monolayer bio- sorption onto a surface with a finite number of identical the Freundlich model. These figures show that the Fig. 4 a–d Modelling of Cr (VI) biosorption isotherm by Langmuir (a, c) vs Freundlich (b, d) sorption isotherms for Oscillatoria sp. NTMS01 and Phormidium sp. NTMS02 Ann Microbiol (2012) 62:241–246 245 Crist HR, Oberholser K, Shank N (1981) Nature of bonding between Freundlich isotherm had a higher correlation coefficient (r) metallic ions and algal cellwalls. Environ Sci Technol 15:1212– in the two selected organisms than that of the Langmuir isotherm. Therefore, in this study, the mechanisms involved Donmez G, Aksu Z (2002) Removal of chromium (VI) from saline in Cr (VI) removal by the two organisms were based on wastewaters by Dunaliella species. Process Biochem 38(5):751–762 Freundlich H, Helle WJ (1939) Rubber die adsorption in Lusungen. J Freundlich parameters. Freundlich’s model constants, K Am Chem Soc 61:2–28 and n were calculated and the values obtained for Friis N, Myers-Keith P (1986) Biosorption of uranium and lead by Oscillatoria sp. NTMS01 were, K =23.4 and n=1.42, Streptomyces longwoodensis. Biotechnol Bioeng 28:21–28 whereas in the case of Phormidium sp. NTMS02, K = Galun M, Galun E, Siegel BZ, Keller PE, Lehr H, Siegel SM (1987) Removal of metal ions from aqueous solutions by Penicillum 17.54 and n=1.64. biomass: kinetic and uptake parameters. Water Air Soil Pollut Freundlich parameters indicated a significant increase in 33:359–371 Cr (VI) uptake by immobilization of Oscillatoria sp. Katircioglu H, Aslim B, Turker AR, Atici T, Beyatli Y (2008) Removal of NTMS01 in sodium alginate beads. Biosorption in the cadmium (II) ion from aqueous system by dry biomass, immobilized live and heat-inactivated Oscillatoria sp. H1 isolated from two selected organisms fits better to the Freundlich freshwater (Mogan Lake). Bioresour Technol 99:4185–4191 isotherm, indicating heterogenicity of the algal surface or Khummongkol D, Canterford GS, Freyer C (1982) Accumulation of surfaces supporting sites of varied affinities. heavy metals in unicellular algae. Biotechnol Bioeng 12:2643– Kumar MS, Muralitharan G, Thajuddin N (2009) Screening of a hypersaline cyanobacterium, Phormidium tenue, for the degrada- Conclusion tion of aromatic hydrocarbons: naphthalene and anthracene. Biotechnol letters 31(12):1863–1866 In the present work, Cr (VI) adsorption by the two Leusch A, Holan ZR, Volesky B (1995) Biosorption of heavy metals (Cd, Cu, Ni, Pb, and Zn) by chemically-reinforced biomass of marine cyanobacteria, Oscillatoria sp. NTMS01 and marine algae. J Chem Technol Biotechnol 62:279–288 Phormidium sp. NTMS02, were compared and studied at Li S, Jin-lan X, Hua HE, Zhen-Yuan N, Guan-zhou Q (2007) varying pH, contact time and Cr (VI) concentration. Biosorption mechanism of Cr (VI) onto cells of Synechococcus Biosorption capacities for Cr (VI) were found to be sp. J Cent South Uni Technol, 02-0157-06 Manriquez RA, Magana PI, Lopez V, Guzman R (1997) Biosorption strongly dependent on the pH of the solution, and of Cu by Thiobacillus ferrooxidans. Bioprocess Eng 18:113–118 maximum capacities were obtained at pH 3 with a contact Manzini G, Ceesaro A, Delbin F, Paoletti S, Reisenhofer E (1984) time of 30 min. 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Published: Apr 1, 2011

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