Effective adsorption of polycyclic aromatic Congo red dye by modified garlic peel

Abstract

To evaluate the competence of garlic peel (GP) as a low-cost bio-adsorbent, GP was chemically modified with sodium carbonate (Na₂CO₃) and hydrochloric acid, and used to adsorb Congo red (CR). The surface morphology, chemical characterization and structural information of the adsorbents were studied by scanning electron microscopy, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy. The impact of different adsorption settings on the removal effectiveness of CR by sodium carbonate-treated garlic peel (Na₂CO₃-GP) was also studied. The optimum conditions for effective adsorption of CR by Na₂CO₃-GP is found to be pH of 7, 90 minutes of equilibrium contact duration, 50 mg/L of initial CR concentration, 200 revolutions per minute of stirring (RPM), 0.10 g/mL of adsorbent dosage, and temperature of 298 K. As indicated by Langmuir isotherm, monolayer adsorption occurs at a maximum capacity of 52.6 mg/g for Na₂CO₃-GP. Adsorption kinetic studies suggest chemisorption, the process follows a pseudo-second-order model and thermodynamics of adsorption specifies that the process is spontaneous. The results explicitly show that Na₂CO₃-GP can be an effective bio-adsorbent for the removal of CR.

Graphical Abstract

Keywords:

• Garlic peel
• adsorption
• chemical modification
• bio-adsorbent
• dye removal

Author contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by N.L. and J.A. A.K.P, N.L. and J.A. contributed to the writing of first draft. All authors read and approved the final manuscript.

Disclosure statement

The authors report there are no competing interests to declare.

Data availability

Data will be made available on request.

Acknowledgements

Sophisticated Analytical Instrument Facility (SAIF), Indian Institute of Technology Bombay is acknowledged for providing FTIR and EDX results. The authors are grateful to Dr. Jackson Gurung, Mr. Karthik Nair, Mr. Rana Pratap and Mr. Vinay Kr Shakyawar for their support. The support received from National Institute of Technology Mizoram is gratefully acknowledged.

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.