Chromium (VI) Biosorption from Aqueous Solutions by Free and Immobilized Biomass of Oscillatoria sp. H1 Isolated from Freshwater

The Oscillatoria sp. H1 (Cyanobacteria) isolated from Mogan Lake was researched for the removal of chromium (VI) ions from aqueous solutions and were used free (dry biomass), immobilized (in Ca-alginate) live and immobilized heat-inactivated biomass as biosorbents. Particularly, the effects of physico-chemical parameters like pH, the temperature change, initial concentration, biosorption time and biosorbent dosages on the biosorption of Cr (VI) ions were investigated. The biosorption of Cr (VI) ions for all biosorbents was determined as a highest value at pH 6.0. The temperatures which changed between 20 and 40°C did not affect the biosorption capacity. The biosorption of Cr (VI) ions on both free (dry) and immobilized (live and heat-inactivated) Oscillatoria sp. H1 biomass (mg/g) increased as the initial concentration of Cr (VI) ions was increased in the medium. Biosorption equilibrium was established in about 60 min. The retention of Cr (VI) increased with increasing the amount of the adsorbent up to 0.04 g and 30 bead. The results show that immobilized inactive cells (13.83 mg/g) and dry biomass (15.81 mg/g) had less biosorption capacity than that of the immobilized live form (20.82 mg/g). The Langmuir and Freundlich isotherm models were used to fit the equilibrium biosorption data. The biosorbent systems could be regenerated by washing with a solution of 10 mM HCl. The percent desorption achieved was as high as 98%. The biosorbents were reused in three biosorption-desorption cycles without significant loss of their initial biosorption capacity. The results indicated that the immobilized live Oscillatoria sp. H1 could be suitable for development of an efficient biosorbent for the removal of chromium (VI) from wastewater from some industrial processes and other ones.