Tea Factory Waste Used as an Adsorbent for Efficient Removal of Acid Yellow 25 Dye from Water: Modelling and Kinetics Study for Batch and Fixed Bed Adsorption Column

Abstract

There is a need for extensive environmental protection measures because dye pollution in water has become a major problem. The current study addresses the crucial problem of dye pollution in water by developing a novel adsorbent from industrial tea waste for use in a batch adsorption, as well as a fixed-bed column to remove acid yellow 25 dye (AY25) from aqueous solutions. The developed adsorbent's chemical composition and surface characteristics have been identified using FTIR, XPS, BET and FESEM-EDX analysis. The adsorption processes are consistent with the Langmuir isotherm model and pseudo second order (PSO) kinetics, according to isotherm and kinetic model investigations for batch adsorption of AY25 dye onto the produced tea waste adsorbent. The excellent capacity for adsorption has been found to be 27.93 mg g⁻¹ for Langmuir models and 35.24 mg g⁻¹ for pseudo-second-order kinetics. The produced adsorbent was eventually studied by employing it as stationary phase in fixed bed adsorption columns (FBAC), which also exhibited excellent removal efficiencies for AY25. The FBAC study was carried out to remove AY25 dye at three different concentrations of 50, 100, and 150 mg L⁻¹ and three different bed heights of 18.5, 20.5 and 22.5 cm, with a constant flow rate of 3 ml min⁻¹ and ambient temperature. The column's saturation adsorption capacity would improve as the influent AY25 concentration and bed depth increased. Furthermore, the fixed-bed column filled with produced adsorbent for removing AY25 fit the Yan and Thomas models well, with its maximum adsorption capacity of 70.38 mg g⁻¹ and 121.69 mg g⁻¹ respectively. The produced adsorbent was examined for reusability and found to be effective at adsorption for three cycles. These findings show that the generated tea waste adsorbent is a very good adsorbent for removing dyes, which makes it a viable option for environmentally friendly wastewater treatment applications.