Enhancing the adsorption kinetics of model gasoline emissions in a biochar-carbon nanostructures composite that provides accessible adsorption sites.

The environmental and health implications caused by volatile organic compounds (VOCs) from gasoline emissions require the development of adsorbents to overcome the slow and ineffective gas-phase adsorption of microporous activated carbons in automotive containers. This research presents the physicochemical properties of a novel adsorbent prepared from lignocellulosic waste biochar and carbon nanostructures synthetized by applying carbon pulses at low temperature of chemical vapor deposition. Moreover, the kinetic adsorption of aliphatic and aromatic VOCs as model gasoline emissions was explored. Electron microscopy analysis displayed the growth of carbon nanotubes, carbon nanofibers, and onion-like carbon, doubling the biochar surface area from 120 to 240 m² g⁻¹, without developing micropores. Raman analysis suggested that the growth of carbon nanostructures on the biochar promoted a higher graphitization degree of the adsorbent, inducing a more hydrophobic and basic surface (pH PZC = 10.3). Results unveiled a 1.30–1.81-fold increase in adsorption capacity for aliphatic and aromatic VOCs after improving the biochar with carbon nanostructures. This novel composite had up to 2.60 and 0.98 times more benzene and toluene uptake, respectively, than a commercial activated carbon, as well as a similar removal capacity for pentene and hexane molecules. Additional finding of this study provided evidence that the VOCs adsorption is not only related to the textural properties of the novel composite, but also to its surface chemistry. Overall, the present novel composite offers a promising approach for gasoline emissions recovery as a potential alternative to commercial activated carbon. [Display omitted] • Adsorbents were developed from waste biomass to capture automotive emissions. • Pulses CVD increased biochar surface but no microporosity. • Removal rates of up to 0.98 times faster than AC were achieved. • Remarkable adsorption capacity of the smaller VOCs was accomplished. • Improved biochar had a high selectivity for nonpolar aromatic VOCs. [ABSTRACT FROM AUTHOR]