Silver-Modified Biochar: Investigating NO2 Adsorption and Reduction Efficiency at Different Temperatures

This study investigates the adsorption and reduction of NO2 on biochar (BCC) and silver-modified biochar (Ag-BCC) in a continuous flow. Ag-BCC showed a higher NO2 adsorption capacity (11.78 mg/g) than BCC (11.04 mg/g) at 200 °C, despite its lower surface area (345 vs. 402 m2/g). While neither material decomposed NO2 at 22 °C, Ag-BCC achieved a NO/NO2 ratio of 20% (vs. 9% for BCC) at 200 °C, highlighting the catalytic role of silver in NO2 conversion. Breakthrough curve modeling identified the Dose–Response model as optimal, accurately describing adsorption kinetics at all temperatures (22–200 °C). Adsorption rate constants decreased with increasing temperature, confirming exothermicity. Overall, the results highlight the enhanced performance of Ag-BCC for NO2 capture and conversion, underlining the potential of surface-modified biochars in the sustainable mitigation of air pollution.