Prussian blue-impregnated waste pomelo peels-derived biochar for enhanced adsorption of NH3

Ammonia (NH3) is the main odor-causing substance in composting off-gases and one of the key factors leading to PM2.5. Herein, a novel Prussian blue-impregnated waste pomelo peels-derived biochar (PB/NBCs) was developed to capture the NH3 in composting gases. Pomelo peels-derived biochar (PP-500) was obtained by pyrolysis carbonization at 500 °C. Acidification treatment (the mass ratio of HNO3 to PP-500 of 4) and the impregnation of Prussian blue (PB) provided more acidic functional groups (AFGs) and exposure of active adsorption sites on the PB/NBCs surface. Therefore, the as-fabricated PB/NBC-500-4-4 had a rich N (23.58 at.%) and O (10.87 at.%) content as well as abundant mesoporous structure (an average pore size of 3.82 nm), delivered an excellent NH3 adsorption capability of 152.8 mg g−1 at 298 K and 100 kPa and showed a fast adsorption kinetics (circa 95% of balance capacity after 30 min), moderate heat of adsorption (24–26 kJ/mol) and tolerable recyclability (circa 50.5 mg g−1 after 8 cycles). The adsorption mechanism on the PB/NBC-500-4-4 was proposed to be a coupled process of combining physical and chemical adsorption. These results highlight the great potential of the PB/NBC-500-4-4 as an adsorbent for capturing NH3. In addition, this work also offers new insights into a relatively simple and readily scalable production of biochar for treating waste with waste.