Biosorption of iron(III) from aqueous solution by dried biomass of Synechocystis sp. PCC 6803

Abstract

In this study, the dried biomass of Synechocystis sp. PCC 6803 was used as biosorbent for removing Fe(III)) ions from aqueous solution. The effects of exposure time, the initial metal concentration, biosorbent dose, and solution pH on the biosorption efficiency of Fe(III) from synthetic solutions were investigated. The Fe(III) adsorption was relatively fast and the equilibrium time was 60 min with the maximum biosorption capacity (qm) of 10.98 mg Fe(III) g−1 biosorbent (85%) at pH 3.5, 10 g L−1 biomass dosage, and 30 °C. Among four biosorption isotherms, the Redlich-Peterson and the Langmuir isotherm models described better the adsorption of Fe(III) onto dried biomass than did the Freundlich and the Temkin isotherm models. The biosorption of Fe(III) using dried biomass of Synechocystis sp. PCC 6803 followed the second-order kinetics. Thermodynamic studies established the biosorption process to be energetically favorable with negative free energy change. FTIR and SEM-EDX analyses revealed the presence of functional groups of negative valences on the biosorbent surface responsible for the Fe(III) binding. Desorption of Fe(III) was attained up to 79% using 0.1 M HNO3; however, the capacity of biomass as biosorbent was decreased after the first adsorption-desorption cycle. Moreover, the biosorption efficiency of the algal biosorbent for the removal of Fe(III) from groundwater was 65%. Overall, this finding suggested an eco-friendly strategy for remediation of Fe(III)-polluted wastewater by biosorption onto the Synechocystis sp. PCC 6803 biomass.