Synergistic effect of a spinel ferrite on the adsorption capacity of nano bio-silica for the removal of methylene blue

ABSTRACT

The synergistic effect of CoFe₂O₄ on the capacity of bio-silica extracted from rice husk for the removal of methylene blue (MB) was investigated. The novel composite of cobalt ferrite/nano bio-silica was prepared by dispersing cobalt and iron salt in ratio 1:2 in a solution containing bio-silica, calcined at 700°C and characterized. The adsorption capacity of the composite (253.6 mg g⁻¹) was higher than that of bio-silica (52.6 mg g⁻¹), and the process was exothermic and spontaneous. Langmuir and Freundlich models were applicable to explain the adsorption isotherm, while pseudo-second-order and Elovich are best applicable for the kinetics mechanism. The amount of MB that was removed, increased with an increase in ionic strength due to dimerization of MB. Regeneration and reusability of the adsorbents showed that they are economically viable. Energy-filtered transmission electron microscopy (EFTEM) and Fourier transformed infrared (FTIR) analysis of MB-loaded adsorbent confirmed the adsorption of MB.

GRAPHICAL ABSTRACT

KEYWORDS:

• Bio-silica
• methylene blue
• cobalt ferrite
• adsorption
• specific surface area

Acknowledgements

The authors would like to thank the UFMG-Microscopy Center for the structural support.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Sunday J. Olusegun http://orcid.org/0000-0002-2479-0540

Erico T. F. Freitas http://orcid.org/0000-0002-8509-8662

Luciano R. S. Lara http://orcid.org/0000-0002-1264-4239

Nelcy D. S. Mohallem http://orcid.org/0000-0002-9094-4536

Additional information

Funding

This study was supported by the FAPEMIG, CNPq and TWAS.