Control of pore structure and surface chemistry of activated carbon derived from waste Zanthoxylum bungeanum branches for toluene removal in air.

Abstract

Activated carbon adsorption has been considered the most efficient technology toward VOC removal. The waste biomass as alternates solved the problems of high price and nonrenewable of traditional raw materials. The waste Zanthoxylum bungeanum branches were firstly selected as raw materials to prepare activated carbons. Interestingly, the pore structure and surface chemistry can be successfully controlled by adjusting the heating rate. The hierarchical porous carbons exhibited great potential for toluene adsorption. The micro-mesopore structure possessed unique spatial effect; micropores played a dominant role in adsorption process, especially narrow micropores (pore size ≤ 1.0 nm) emerged stronger adsorptive force toward toluene molecules due to overlapping attractive forces from neighboring pore walls. And mesopores not only displayed excellent transport diffusion but also provided adsorption sites. Additionally, the high graphitization degree enhanced the interaction between graphene layer equipped electron-rich regions and π-electrons on the aromatic ring by the π-π conjugated effect. The hydroxyl and carbonyl functional groups served as chemisorption sites and led to higher adsorption amounts. Fortunately, the regeneration can be achieved by thermal treatment at the low temperature (≤ 150 °C) or even gas purging at room temperature (20 °C), which avoided an explosion accident in the process of high-temperature regeneration.