Equilibrium and Kinetics of Adsorption of Mn²⁺ by Haloarchaeon Halobacterium sp. GUSF (MTCC3265)

Abstract

The coastal waters of countries bordering on an ocean show increases in manganese pollution due to runoff from mining activity and from industries dealing with production of ferroalloys, steel, iron, petrochemicals, and fertilizers. One gram of dried cells of haloarchaeon Halobacterium sp. GUSF (MTCC3265) adsorbed 99% Mn²⁺ in 60 min at pH 6.8 and 30ºC on contact with 109.54 mg Mn²⁺ per liter in saline solution. Adsorbed Mn²⁺ was quantified by atomic absorption spectrometry and demonstrated on the cell surface by SEM-EDX. Mn²⁺ adsorbed to functional groups of the adsorbent was studied by FTIR. The adsorption process of Mn²⁺ showed saturation and followed pseudo–second-order kinetics; was consistent with the homogeneity of the Langmuir model (R² of 0.99); exhibited a Q_max of 62.5 mg g⁻¹ and a binding energy of 0.018 L mg⁻¹. The Mn²⁺adsorption was also consistent with the heterogeneity of the Freundlich model by exhibiting a K_f of 1.0 mg g⁻¹ with an n value of 1.1. Adsorption efficiency of 99% was retained even after a third adsorption-desorption cycle. This is the first report on metal ion adsorption, using Mn²⁺ as an example, by the haloarchaeon Halobacterium sp. GUSF (MTCC3265) in the domain Archaea.

Keywords:

• Halobacterium sp. GUSF (MTCC3265)
• Mn²⁺
• adsorption isotherm
• kinetics

Acknowledgments

I.F. acknowledges Dr. M. Shyamprasad and Mr.V. Khedekar, National Institute of Oceanography, Goa, India for helping with the use of the SEM-EDX facility.

Additional information

Funding

I.F is grateful for the award of Junior Research fellowship to S.N. under the in-house project of OASTC, Goa University, Goa, funded by Ministry of Earth Sciences, New Delhi, India. S.N. is also indebted to Goa University for the Research studentship.