Biosorption of cobalt and its effect on growth and metabolites of Synechocystis pevalekii and Scenedesmus bernardii: Isothermal analysis

Because of their toxic potential, industrial effluents that contain cobalt ions have become a severe environmental problem, unless properly treated. This research tends to study the removal of cobalt from aqueous solution by Synechocystis pevalekii and Scenedesmus bernardii, grown at different concentrations of Co2+ ions, and to study its impacts on growth and metabolism. With increased concentrations of Co2+ ions, chlorophyll a, dry weight, and total lipids decreased. The highest CAT and LOX activity was observed in both tested algae at concentrations of 0.5 and 0.2 mgl(-1) of Co2+. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich sorption isotherms were obtained by Sy. pevalekii and Sc. bernardii, for the quantitative description of Co2+ uptake. All models studied are well suited to describe the Co2+ isotherm biosorption equilibrium by Sy. pevalekii than by Sc. bernardii. Dubinin-Radushkevich isotherm suggesting that the adsorption mechanism was physical in nature. Sy pevalekii was an efficient to remove Co2+ ions than Sc. bernardii. Nevertheless, affinity constant of Co2+ for Sc. bernardii was higher than that of Sy. pevalekii, revealing that Sc. bernardii is more sensitive to Co2+ ion toxicity than Sy. pevalekii. FTIR study of algae before and after biosorption showed the presence of groups of amide, alkyl, hydroxyl, carbonyl and carboxyl responsible for Co2+ ions biosorption. This indicates that Sy. pevalekii and Sc. bernardii can be used as a biosorbent for removing heavy metals from various contaminated sites. (c) 2020 Elsevier B.V. All rights reserved.