NANO-ZnO IMMOBILIZED ON BIO-ACTIVATED CARBON FROM ROBUSTA COFFEE HUSK FOR PHOTOCATALYTIC DEGRADATION OF FLUORESCENT DYE

Abstract

ZnO's photocatalytic properties make it a widely used semiconductor, while bio-activated carbon (BAC) from agricultural waste is emerging as a sustainable and cost-effective photocatalyst substrate. This study explores the preparation and characterization of a nano ZnO/BAC composite from coffee husks for efficient degradation of Rhodamine B (RhB) under simulated sunlight. BAC was produced by carbonizing coffee husks at 900°C in argon and activating with HCl. ZnO nanoparticles (20–100 nm) were deposited on BAC, confirmed by SEM images. UV-Vis DRS analysis indicated strong ZnO absorption below 400 nm, enhancing photocatalytic performance. RhB degradation followed pseudo-first-order kinetics (k₁ = 0.0206 min^-1, R² = 0.9894), achieving 91.46% removal in 120 minutes, particularly rapid in the first 40 minutes. The composite showed good reusability, retaining over 88% efficiency after seven cycles. These results highlight ZnO/BAC as a promising sustainable photocatalyst for dye removal in wastewater treatment.