Biosorption mechanisms of cationic and anionic dyes in a low-cost residue from brewer’s spent grain

ABSTRACT

The brewer's spent grain (BSG) is a byproduct of the brewing industry produced in large quantities and with few ecological disposal options. The use of this low-cost residue was investigated for the removal of methylene blue (MB) and tartrazine yellow (TY) dyes. The BSG has been extensively characterized to obtain its physicochemical characteristics. Batch experiments were conducted to investigate the effects of biosorption parameters: initial pH, kinetics, equilibrium isotherms and adsorption thermodynamics. The characterization showed high carbon content and heterogeneous morphology with the presence of meso and macropores. The best experimental conditions were obtained as pH 11 for MB and pH 2 for TY. Kinetics resulted in an equilibrium time of 240 min for MB and 300 min for TY and was best represented by the pseudo-second order model. Different interaction mechanisms were suggested, such as electrostatic interactions, electron donors and electron acceptors, hydrogen bonds, π–π dispersion interactions and the dye molecules aggregation. Equilibrium data were better represented by Langmuir isotherm. The maximum adsorbed amount of MB and TY was 284.75 and 26.18 mg/g, respectively, in each better experimental condition. Through the thermodynamic analysis, it was observed that the adsorption of the dyes was spontaneous and favourable. MB is preferentially retained through chemisorption, whereas TY followed a physical process. Considering the characteristics and results found compared to the recent literature, it was verified that BSG can be used as an effective and innovative biosorbent for removal purposes of dyeing effluent.

GRAPHICAL ABSTRACT

KEYWORDS:

• Brewer's spent grain
• Biosorption
• Kinetics
• Mechanism
• Dyes removal

Acknowledgements

The authors wish to thank the National Council for Scientific and Technological Development – CNPq for financial support and the Laboratory of X-Ray Diffraction (LARX), State University of Londrina, for the XRD analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

ORCID

Fernanda de Oliveira Tavares http://orcid.org/0000-0002-3713-1413

Maria Angélica S. D. Barros http://orcid.org/0000-0001-9696-5218

Additional information

Funding

This work was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico [grant number 134100/2018-2].