Biosorption of chromium and nickel by dried biomass of cyanobacterium Oscillatoria laete-virens

The use of nonliving microorganisms seems to be a preferred option to the use of living cells for the removal of heavy metal ions from wastewater. Biosorption experiments were carried out using dried biomass powder of cyanobacteria Oscillatoria laete-virens, collected from a wastewater canal. Adsorption of both Cr (VI) and Ni (II) by the biosorbent is optimum at pH 5.0 suggesting that the adsorption is controlled by ionic attraction. Cr (VI) and Ni (II) adsorption was fast at initial stage of the contact period and maximum adsorption took place within the first 60–75 min. Initial metal ion concentration plays an important role in determining the adsorption capacity. The maximum adsorption capacity (q_max) of Cr (VI) and Ni (II) by the cyanobacterial biomass was 103.09 and 84.75 mg g⁻¹ respectively. The high degree of correlation for the linearized Langmuir relationship suggests a single surface reaction with constant activation energy is the predominant sorption step and possibly the predominant rate-controlling step. Adsorption strongly supports to the pseudo second-order kinetics which further suggests that biosorption is the rate-controlling step. This study shows that dried biomass of Oscillatoria laete-virens has the potential to remove heavy metals like Cr (VI) and Ni (II) in polluted water.