Removal of Acid blue 93 dye from aqueous media using an agro-industrial waste as bioadsorbent: An OPAT and DoE Approach

ABSTRACT

The current article reports an effective and low-cost removal of Acid blue 93 dye using synthesised peanut (Arachis hypogaea) shells. In first step, the adsorbents were examined using pH_pzc, TG-DTG, FTIR and SEM characterisation techniques. In the second phase, the parameters such as contact time (CT), pH, adsorbent dosage (AD) and initial concentration of dye (ICD) were assessed using one parameter at a time adsorption study (OPAT). Selecting the same parameters an effort was also made using design of experiment (DoE). It was found that, for maximum removal both the studies, OPAT and DoE delivered similar optimum conditions as CT 60 min, pH 7, AD 7 g l⁻¹ and ICD 50 mg l⁻¹. In addition, DoE added an edifying output in terms of percentage of contribution: ICD (36.35%) > AD (31.39%) > CT (27.03%)> pH (5.24%). In accordance with the above studies, kinetics, isotherm and thermodynamic analysis were also performed followed by error analysis. In kinetics, pseudo-second-order model was superior; in isotherm study, Langmuir model was dominant with a $q_m$ value of 23.36 mg g⁻¹. Thermodynamic parameters such as$\mathrm{\Delta }{G}^{\circ }$,$\mathrm{\Delta }{H}^{\circ }$ and$\mathrm{\Delta }{S}^{\circ }$ stated the adsorption endothermic and spontaneous. The novelty of this work is in the development of the pre-treated peanut (A. hypogaea) shells for efficient and low-cost removal of Acid blue 93 dye from aqueous media.

KEYWORDS:

• Acid blue 93
• adsorption
• characterisation
• error analysis
• peanut shells
• Taguchi

Acknowledgments

I would like to thank NIT Silchar for providing TEQIP - III funds for this research. In addition, I would also like to acknowledge the Centre for Energy - IIT Guwahati, Sophisticated Analytical Instrument Facility - IIT Bombay and Department of Materials Sciences and Engineering - IIT Kanpur for accessing analytical instrumentation services.

Disclosure of potential conflicts of interest

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

Additional information

Funding

This work was supported by the National Institute of Technology Silchar, Assam, India.