Assessment of the biosorption characteristics of lychee (Litchi chinensis) peel waste for the removal of Acid Blue 25 dye from water

Abstract

The aim of this study was to examine the adsorption potential of lychee (Litchi chinensis) peel waste for the removal of Acid Blue 25 dye from aqueous solutions. The adsorption was studied as a function of contact time, initial dye concentration and temperature by batch method. Equilibrium sorption isotherms showed that the lychee peel adsorbent possessed a high affinity and sorption capacity for Acid Blue 25, with a monolayer sorption capacity of ca. 200 mg g⁻¹. The equilibrium adsorption data were well described by the Langmuir model. Kinetic studies revealed that the present system of dye adsorption on lychee peel adsorbent could be described more favourably by the pseudo‐second‐order kinetic model. The thermodynamic parameters, namely free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) changes, were determined for the process. The results of the present study suggest that lychee peel waste can be used beneficially as an adsorbent in treating industrial effluents containing dyes.

Keywords:

• Acid Blue 25 dye
• lychee (Litchi chinensis)
• peel waste
• adsorbent
• equilibrium isotherms
• kinetic modelling

Acknowledgement

The authors are thankful to the Council of Scientific and Industrial Research (CSIR), New Delhi, India, for financial support and to The Director, CBRI, Roorkee, for his kind permission to conduct and publish this work. We also wish to thank the anonymous reviewers whose willingness to share their expertise has been of enormous benefit.