Utilizing tea waste for methylene blue removal: Insights from batch and fixed-bed adsorption studies

Abstract

This study explores the potential of tea waste as a cost-effective and eco-friendly biosorbent for the removal of hazardous Methylene Blue (MB) dye from aqueous solutions. The tea waste-based adsorbent has been synthesised and characterised using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) to examine its functional groups, crystallinity, and surface morphology. Batch adsorption experiments evaluated the impact of initial dye concentration, contact time, and adsorbent dosage. Isotherm analysis revealed Langmuir model compatibility with a high monolayer capacity (qₘₐₓ = 454.54 mg/g), indicating effective surface interaction. Kinetic modeling showed excellent fit with the pseudo-second-order model (R² = 1.000), suggesting chemisorption as the primary mechanism.A fixed-bed column study assessed the effects of flow rate, bed height, and column diameter on breakthrough behaviour. Optimal conditions 4 mL/min flow rate, 2 cm bed height, and 1.5 cm column diameter achieved a 105 min. breakthrough time. Process optimization via Box–Behnken response surface methodology confirmed the model's predictive strength. The results demonstrate that tea waste is a promising low-cost biosorbent for the efficient removal of MB dye, with potential application in wastewater treatment systems.