Sorption of Methylene Blue by an Oscillatoria sp.–Dominated Cyanobacterial Mat

ABSTRACT

The ability of an Oscillatoria sp.–dominated cyanobacterial mat in sorbing methylene blue (MB), a cationic dye, was investigated using the batch contact method. The sorption of MB onto the powdered biomass was not significantly influenced by initial pH (2–10) and temperature (5–45°C) of the solution. MB sorption occurred slowly, requiring 1–8 h for the establishment of equilibrium. A slow attainment of equilibrium seems to be related with the large size of MB ions. The isotherm data of MB sorption by the mat biomass could effectively fit to Langmuir and Freundlich models. The maximum MB sorption capacity (q _max) of the test biomass was 78.43 mg g⁻¹, which changed little with variation in biomass concentration. Moreover, the test biomass could efficiently sorb MB from solution in presence of Na⁺, K⁺, and Ca²⁺, which usually occur at high concentrations in natural waters, and also in presence of Cd²⁺. These particular characteristics together with pH and temperature independence of the sorption process make the mat biomass an ideal MB sorbent.

KEYWORDS:

• biosorption
• cyanobacterial mat
• methylene blue
• Oscillatoria
• sorption isotherms

ACKNOWLEDGMENTS

We thank the Coordinator, Industrial Microbiology, and Head, Department of Botany, Banaras Hindu University, for facilities. D.K. thanks the Council of Scientific and Industrial Research, New Delhi, for financial support in the form of a Senior Research Fellowship. L.K.P. is grateful to University Grant Commission, New Delhi, for the Meritorious Student Junior Research Fellowship in Science.