title: Sequestration of chromium by exopolysaccharides of Nostoc and Gloeocapsa from dilute aqueous solutions.
abstract: This article reports the chromium removal potential of exopolysaccharides (EPS) of two indigenously isolated cyanobacterial strains, Gloeocapsa calcarea and Nostoc punctiforme. The biosorption was studied by varying pH from 2 to 6 and initial chromium concentration from 5 to 20mg/L to find out the optimized conditions for maximum chromium removal by EPS. Two equilibrium models, Langmuir and Freundlich, were used to explain these results. The Freundlich model was found to be better applicable to the experimental data as compared to Langmuir as inferred from high value of coefficient of determination whereas the optimal conditions were found to be same for the two (pH 2 and initial chromium concentration 20 mg/L). EPS production by the two strains was also studied which was found to be higher for Gloeocapsa. On the basis of experimental results and model parameters, it can be inferred that the EPS extracted from Nostoc has comparatively high biosorption capacity and can be utilized for the removal of chromium from dilute aqueous solution. Adsorption of chromium on EPS was further confirmed by surface morphology observed in scanning electron micrographs.
authors.affiliation: Department of Environmental Science and Engineering, Guru Jambheshwar University of Science & Technology, Hisar, India.
authors.forename: Mona
authors.initials: M
authors.lastname: Sharma
authors.forename: Anubha
authors.initials: A
authors.lastname: Kaushik
authors.lastname: Somvir
authors.forename: Kiran
authors.initials: K
authors.lastname: Bala
authors.forename: Anjana
authors.initials: A
authors.lastname: Kamra
mesh_terms: D000327:Adsorption; D002857:Chromium / Q000737:chemistry / Q000302:isolation & purification*; D000458:Cyanobacteria / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D046937:Nostoc / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
chemical_list: D011134:Polysaccharides; D012996:Solutions; D014874:Water Pollutants, Chemical; D002857:Chromium