Study on the caffeine adsorption capacity of coffee husk biochar activated by K2CO3

Abstract

    Pyrolyzed and activated coffee husks create an efficient caffeine-adsorbing material, serving as an alternative to imported activated carbon and solvents for caffeine removal from water. This new adsorbent material can also capture caffeine, heavy metals, pesticides, chemicals, and pharmaceuticals, contributing to environmental applications. Additionally, it enhances the value of coffee production and promotes a green model in the coffee and food industries. Biochar derived from the pyrolysis of coffee husks (BC) and activated carbon (BC-K₂CO₃) adsorbed caffeine from green coffee extract containing caffeine are measured and analyzed for caffeine adsorption efficiency. Accordingly, BC and BC-K₂CO₃ at 400°C were analyzed for their microstructure evaluation by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR). Adsorption performance, caffeine removal capacity, and factors influencing the adsorption process were also evaluated. The optimal adsorption conditions were an initial caffeine concentration of ≤ 0.025 g/mL, a biochar dosage of 0.1 g/mL, and a contact time of 120 minutes. The caffeine adsorption process of both BC and BC-K₂CO₃ followed the Freundlich adsorption isotherm model (R² > 0.992). The maximum adsorption capacity (Qm) of BC-K₂CO₃ was 33.74 mg/g, which was higher than that of non-activated BC, which had a Qm of 13.99 mg/g.