title: Biosorption of Cr(VI) by free and immobilized Pediastrum boryanum biomass: equilibrium, kinetic, and thermodynamic studies.
abstract: OBJECTIVE
  The biosorption of Cr(VI) from aqueous solution has been studied using free and immobilized Pediastrum boryanum cells in a batch system. The algal cells were immobilized in alginate and alginate-gelatin beads via entrapment, and their algal cell free counterparts were used as control systems during biosorption studies of Cr(VI).
  
  
  METHODS
  The changes in the functional groups of the biosorbents formulations were confirmed by Fourier transform infrared spectra. The effect of pH, equilibrium time, initial concentration of metal ions, and temperature on the biosorption of Cr(VI) ion was investigated.
  
  
  RESULTS
  The maximum Cr(VI) biosorption capacities were found to be 17.3, 6.73, 14.0, 23.8, and 29.6 mg/g for the free algal cells, and alginate, alginate-gelatin, alginate-cells, and alginate-gelatin-cells at pH 2.0, which are corresponding to an initial Cr(VI) concentration of 400 mg/L. The biosorption of Cr(VI) on all the tested biosorbents (P. boryanum cells, alginate, alginate-gelatin, and alginate-cells, alginate-gelatin-cells) followed Langmuir adsorption isotherm model.
  
  
  CONCLUSIONS
  The thermodynamic studies indicated that the biosorption process was spontaneous and endothermic in nature under studied conditions. For all the tested biosorbents, biosorption kinetic was best described by the pseudo-second-order model.
authors.affiliation: Department of Biology, Faculty of Arts and Science, Ahi Evran University, Kırsehir, Turkey.
authors.forename: T Baykal
authors.initials: TB
authors.lastname: Ozer
authors.forename: I Acıkgoz
authors.initials: IA
authors.lastname: Erkaya
authors.forename: Abel U
authors.initials: AU
authors.lastname: Udoh
authors.forename: D Yalcın
authors.initials: DY
authors.lastname: Duygu
authors.forename: Aydın
authors.initials: A
authors.lastname: Akbulut
authors.forename: Gulay
authors.initials: G
authors.lastname: Bayramoglu
authors.forename: M Yakup
authors.initials: MY
authors.lastname: Arica
mesh_terms: D000327:Adsorption; D000464:Alginates / Q000737:chemistry; D001673:Biodegradation, Environmental; D002857:Chromium / Q000737:chemistry / Q000378:metabolism*; D005780:Gelatin / Q000737:chemistry; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D007700:Kinetics; D019216:Metals, Heavy / Q000737:chemistry / Q000378:metabolism; D058086:Microalgae / Q000378:metabolism* / Q000648:ultrastructure; D013499:Surface Properties; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism*; D018508:Water Purification
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D019216:Metals, Heavy; D014874:Water Pollutants, Chemical; D002857:Chromium; D020723:Glucuronic Acid; D005780:Gelatin