Preparation of nitrogen-doped bagasse-derived biochar with outstanding methylene blue adsorption performance

Biochar is a promising adsorbent for wastewater treatment; however, effective modification techniques are required to optimize its adsorption efficiency. In this study, nitrogen-doped modified bagasse biochar was prepared from bagasse biomass using a synchronous pyrolysis and activation process with urea (CH 4 N 2 O) as the N source and sodium bicarbonate (NaHCO 3 ) as the chemical activator. Adsorption experiments of the modified sugarcane bagasse biochar for removing methylene blue (MB) in aqueous solution were carried out to investigate the effects of different biochar dosages, solution pH, and adsorption time on the adsorption performance. Adsorption optimization experiments reveal that the adsorption capacity of 50 mg modified biochar added to a 30 mg/L MB solution at 40 °C and pH 11.0 is ∼20 times that of unmodified biochar at the same dose after 120 min (84.2 and 4.45 mg/g, respectively). The isothermal adsorption behavior of MB with the biochar conforms to the Langmuir model and the adsorption kinetics follows the quasi-second-order kinetic equation, indicating that chemical adsorption dominates such adsorption. The adsorption performance of the biochar before and after modification were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and elemental analysis to explore the adsorption mechanism. This study increases the scope for the disposal and utilization of bagasse agricultural waste and has important practical significance for the development of low-cost environmentally-friendly adsorbent materials. • N-doped bagasse biochar was prepared by simultaneous pyrolysis and activation. • Modification increased the adsorption capacity of the biochar by a factor of 20. • The adsorption fitted the Langmuir model and quasi-second-order kinetic equation. • The MB adsorption mechanism of the biochar was dominated by chemical adsorption. • N-doped bagasse-derived biochar is a good candidate for adsorbent materials.