Synthesis of Nitrogen-Doped Sago Bark Biochar (Metroxylon sago) via Hydrothermal Method as a Congo Red Adsorbent

Abstrak

Sago bark biochar (Metroxylon sagu) is a promising adsorbent for dye removal from wastewater, although its performance may require surface modification. This study aimed to modify sago bark biochar (BC) with urea through hydrothermal treatment at 200 °C for 12–48 h to obtain nitrogen-doped biochar (BC-NH) and assess its performance in Congo red adsorption. Urea was selected as the nitrogen precursor because nitrogen-containing functionalities can be introduced onto the biochar surface, potentially strengthening adsorbent–adsorbate interactions. The BC-NH samples were characterized by ATR-FTIR spectroscopy and Brunauer–Emmett–Teller (BET) analysis to examine surface functional groups and textural properties. The ATR-FTIR spectra showed bands at 1553 and 1016 cm⁻¹, assigned to C=N and C–N-related vibrations, respectively. The specific surface area decreased from 59.90 m2/g for pristine biochar to 19.69, 24.00, and 37.57 m²/g for BC-NH12, BC-NH24, and BC-NH48, respectively, but increased with longer hydrothermal treatment. The adsorption data were better fitted by the Langmuir model than by the Freundlich model, and the selected optimum contact time was 40 min. BC-NH48, prepared with a 48-h hydrothermal treatment, showed the highest maximum adsorption capacity (2.38 mg/g) for Congo red. These findings suggest that BC-NH48 may be a potential adsorbent for Congo red removal.

Kata kunci

• Adsorption
• N-doping
• Sago bark biochar
• congo red
• hydrothermal