SYNTHESIS OF BLACK TEA STALK BASED ACTIVATED CARBON VIA CHEMICAL ACTIVATION FOR SCAVENGING ZN(II) IONS IN AQUEOUS SOLUTION

Abstract

Activated carbon (AC) synthesized from biomass is an environmentally friendly water purification method, as it provides a green solution that harnesses renewable resources to efficiently adsorb pollutants. Zinc ions (Zn(II)) are common pollutant found in wastewater, posing a risk to the ecosystem. Consequently, the objective of this research is to manufacture AC from black tea stalks (TSAC) to adsorb Zn(II) ions. The TSAC was prepared through chemical activation method using potassium hydroxide (KOH) at a ratio of 1:1. Characterization of the pore structure gave BET surface area of 892.56 m²/g and a total pore volume of 0.31 cm³/g. These properties provide a large surface area and pore volume to trap the Zn(II) ions. Scanning electron microscopy (SEM) analysis of the precursor displayed a dense surface and lack of pore structure. Conversely, the TSAC revealed a surface that was notably porous. The equilibrium study examined the effects of initial Zn(II) concentration (5 to 30 mg/L), contact time (1-8 hours), and solution temperature (30, 45 and 60 °C), with a fixed TSAC dosage of 0.20g. The results reveal that as the Zn(II) concentration increases, there is an increase in adsorption uptake while the corresponding percentage removal decreases. The optimal Zn(II) uptake by TSAC occurs at a solution temperature of 60 °C. Isotherm studies indicate that the Zn(II)-TSAC adsorption system adheres to the Freundlich model, with maximum monolayer adsorption capacity (Q_m) of 28.74 mg/g. In kinetic studies, the pseudo-first-order (PFO) model is the most suitable for describing the Zn(II)-TSAC adsorption system. Boyd plot analysis indicates that the controlling factor is film diffusion. The application of KOH chemical treatment has resulted in the formation of well-defined pores, thereby improving the TSAC ability to adsorb Zn(II) ions.