Effects of various cold plasma atmospheres and external influencing factors on the adsorption of formaldehyde gas by bamboo-based carbon microfibers

Abstract

To effectively enhance the adsorption performance of gaseous formaldehyde (HCHO) by bamboo-based carbon microfibers (BCMFs), the active oxygen (O) and nitrogen (N)-containing functional groups were rapidly introduced by cold plasma. The effects of plasma time, plasma atmospheres including oxygen (O2), nitrogen (N2), air, and argon (Ar) as well as ambient temperature, flow rate, and initial concentration of gaseous HCHO on the adsorption performance of BCMFs were comprehensively investigated. The typical kinetic, isothermal, and thermodynamic models were also evaluated. The O2-plasma activated BCMFs showed the most serious etching effects among four atmospheres. The adsorption capacities were ranked as BCMF-800-N-10 (203.87 mg g−1) > BCMF-800-Ar-10 (166.26 mg g−1) > BCMF-800-Air-10 (151.28 mg g−1) > BCMF-800-O-10 (144.21 mg g−1), which were 112.99%, 73.69%, 58.04%, and 50.66% higher than the control, respectively. The O–CO and pyrrolic N groups were more easily formed onto BCMF-800-N-10. The Langmuir and the Freundlich models displayed the excellent fitting properties. The optimal kinetic model tended to transfer to the pseudo-second-order from the pseudo-first-order after cold plasma modification. The BCMFs activated by plasma showed a synergistic single/multi-layer adsorption mechanism with a complex physicochemical adsorption. The HCHO adsorption performance was positively correlated with its concentrations but negatively correlated with environmental temperature.