Abstract: Biomass-based hierarchical porous carbon materials (ZBCs) were constructed by carbonizing corn straw in presence of a zinc chloride activator. The structure, porosity and surface functional group properties of the ZBCs materials were studied by various characterization techniques. Introducing a small amount of zinc chloride during the thermal activation process can effectively promote the formation of abundant hierarchical pores (including micropores, mesopores and macropores), high specific surface areas (712-1667 m2/g), and enriched surface oxygen-containing functional groups such as carboxyl, hydroxyl and carbonyl groups (5.7-9.0 at.% oxygen contents). The adsorption experimental results show that all ZBCs materials possess strong adsorption capacity for removing phenol from aqueous solution. The maximum adsorption capacity of ZBC2 for phenol can reach 191.2 mg/g at pH=7 and 25℃, and the adsorption performance still remains above 60% of the initial adsorption capacity after five adsorption/desorption cycles. The adsorption behavior of the ZBC2 for phenol follows the Langmuir isothermal adsorption model, the Temkin isothermal model and the quasi-second-order kinetic model, that is a spontaneous endothermic process dominated by monolayer chemical adsorption. Moreover, ZBC2 could work well in aqueous solution within a broad pH range from 3 to 11. The high specific surface area and abundant hierarchical pores of ZBCs materials are conducive to the mass transfer and diffusion of phenol molecules, while the enriched surface oxygen-containing functional groups could promote the adsorption of phenol on the surface and porous channels of ZBCs through generating hydrogen bonds, electrostatic adsorption, and π-π bonds interactions.

Key words: Corn straws, Biomass-based, Hierarchical porous carbon, Adsorption; Phenol