Effect of process parameters influencing the chemical modification of activated carbon fiber for carbon dioxide removal

Climate change issues and acid rain episodes have triggered new research directions and the conceptualization of new preventive approaches to reduce toxic gases from entering the environment. The reduction of carbon dioxide (CO2) levels in the indoor environment are also one of the challenging human safety issues during emergency incidents and rescues; for instance, a building fire. The use of an activated carbon fiber (ACF) based mask is not only effective to filter CO2 but it is also practically easy to use during such demanding situations. Such modified adsorbents will have high adsorption volume, fast adsorption rates and good thermal, acid and alkaline resistance properties. For the emergency mode considering fires, the major task is atmospheric recovery. Thus, CO2 concentration in the post-fire smoke could be high. The smoke in the room causes suffocations and unconsciousness leading to fatal injuries. In this study, ACF was modified using copper nitrate trihydrate [Cu (NO3)2.3H2O] by impregnation and carbonization (450 °C), followed by its characterization. The modified ACF (Cu-ACF-12) showed large surface area (1147 m2 g−1), high micropore volume (0.45 cm3 g−1) and an average pore size of 1.57 nm. CO2 removal tests were carried out in a lab scale fixed bed adsorption column using the modified ACF. The process parameters were optimized based on a Box-Behnken Design (BBD) and tested in the following ranges: gas flow rate - 150-250 ml min−1, moisture content - 0-40% and modification of the ACF impregnated with copper (Cu) - 4-12 wt.%. The experimental results were statistically interpreted to elucidate the main and interaction effects. The modification of ACF showed positive effects on CO2 removal, while gas flow rate and moisture content decreased the CO2 removal. Under the optimal conditions, (gas flow rate - 150 ml min−1, moisture content - 0% and modification of the ACF - 8%), CO2 removal capacity of 2.31 mmol of CO2 g−1 Cu-ACF was obtained.