Preparation, characterization and application of sorbent envelopes with Carica papaya seeds and Citrus grandis rind for cationic dyes removal

ABSTRACT

The sorption of cationic dyes was studied using sorbents derived from pulverized papaya seeds and pomelo rind. A convenient fixed sorbent envelope protocol with methods for quality check on the readiness of sorbent material for subsequent sorption was developed. Sorbents based on papaya seeds had higher affinity for methylene blue and brilliant green dyes than pomelo rind. Amongst Langmuir, Freundlich and Temkin isotherms, the sorption of both cationic dyes fitted the Langmuir isotherm best. The multi-step linearity behavior on the intra-particle diffusion model with a positive intercept indicated that intra-particle diffusion was not the sole sorption rate-determining factor. The utility of the envelope protocol as a convenient evaluation method for sorbent characteristics and effectiveness was also demonstrated. Magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy was explored and found to differentiate between the two fruit wastes and had the potential for elucidating sorbent–sorbate interactions.

GRAPHICAL ABSTRACT

KEYWORDS:

• Sorption
• sorbent
• cationic dyes
• papaya seeds
• Citrus grandis rind

Acknowledgements

The authors thank Dr Ji’En Wu and Mdm Yan Hui Han for the MAS NMR scans.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

M. Q. Ho appreciates her mother’s support in the harvest of fruit waste samples for her research project.May Quan Ho has been a part-time graduate research student at the Department of Chemistry, National University of Singapore. She is now working in product stewardship and regulatory affairs at a chemical multinational company.

S. F. Y. Li is a faculty member at the Department of Chemistry, National University of Singapore. He received his B.Sc., Ph.D. and DSc degrees from Imperial College, UK. His research interests include biosensors, capillary electrophoresis, metabolomics, environmental science and technology, photocatalysis, microbial fuel cells and nanomaterials. He has authored/co-authored 359 publications in international peer review journals. He serves/served on editorial advisory boards of several international scientific journals, including Electrophoresis, Analytical Sciences and Journal of Chromatographic Science.

ORCID

S. F. Y. Li http://orcid.org/0000-0002-2092-9226

Additional information

Funding

We acknowledge financial support from the Ministry of Education [grant numbers R-143-000-A14-114 and R-143-00-A14-133].