Preliminary study of doxycycline adsorption from aqueous solution on alkaline modified biochar derived from banana peel

Abstract

This study explores the adsorption of doxycycline (DOX) from aqueous solutions onto biochar derived from banana peel, which was prepared using a potassium hydroxide activation method (KOH-BPB). The biochar properties were characterized based on morphology, surface area (SBET of 710.241 m² g^-1), functional groups, and surface charge (pHPZC = 7.7). Parameters, including initial pH, DOX concentration, and ionic strength, that influenced the DOX adsorption capacity of KOH-BPB were examined. Adsorption equilibrium of DOX on KOH-BPB was assessed through four isothermal models: the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models. The obtained data were most compatible with the Langmuir model (R² = 0.9879). KOH-BPB has a maximum DOX absorption capacity of 121.95 mg g^-1 which exceeds that of many comparable absorbents. The maximum DOX removal was 96.7% at pH 6, a DOX concentration of 20 mg L^-1, and a KOH-BPB dose of 1.0 g L^-1. These findings reveal that biochar from banana peel effectively removes antibiotic residues from water. This study provides a potential, low-cost, and environmentally friendly adsorbent.