In this present study, biosorption of Zn(II) from aqueous solution by cyanobacterium Fischerella ambigua was investigated in batch experiments. The effects of pH, bacterial dosage, initial Zn(II) concentration, contact time and temperature were studied. Removal process was influenced significantly by the variation of pH, biosorbent concentration, initial Zn(II) ion concentration, temperature and contact time. Optimum biosorption conditions were found to be initial pH of 5, bacterial dosage of 0.2 g/l and initial Zn(II) ion concentration of 175 mg/l at room temperature and contact time of 90 min. The maximum uptake capacity of F. ambigua for Zn(II) ions was found to be 98.03 mg/g at optimum conditions. The correlation coefficient for the second-order kinetic model was 0.995. The Freundlich isotherm model showed better fit to the equilibrium of the system, compared with the Langmuir model. Fourier transform infrared analysis of bacterial biomass revealed the presence of carboxyl, hydroxyl, sulfite and amino groups, which are likely responsible for the biosorption of Zn(II). The negative values of Gibbs free energy, ΔG, confirm the spontaneous nature of the biosorption process. Finally, F. ambigua adsorption capacity was compared with other biosorbents. Results showed that F. ambigua was an efficient biosorbent in the removal of Zn(II) ions from an aqueous solution
