Preparation of Quercus mongolica leaf-derived porous carbon with a large specific surface area for highly effective removal of dye and antibiotic from water

Abstract

Quercus mongolica leaf (QL), an easily available biomass, was used as the precursor for preparing the hierarchical porous carbon with a large specific surface area and high adsorption capacities toward the representative dye and antibiotic. After being carbonized, QL was further chemically activated, and potassium hydroxide was proved to be a better activator than sodium hydroxide. The QL-derived porous carbon (PCQL) exhibited abundant micro- and mesopores, and the specific surface area reached 3275 m 2 g −1 . The performances of PCQL were evaluated through adsorbing rhodamine B (RhB) and tetracycline hydrochloride (TC) from water. Four adsorption isotherm models (the Langmuir, Freundlich, Sips, and Redlich-Peterson models), three adsorption kinetic models (the pseudo-first-order, pseudo-second-order, and intra-particle diffusion models), and the thermodynamic equations were used to investigate the adsorption processes. The pseudo-second-order kinetic model and the Sips isotherm model fitted the experimental data well, which indicates that the adsorption processes were controlled by the amount of adsorption active sites on the surface of PCQL, and these adsorption active sites had different affinities for the adsorbates. The maximum adsorption capacities of PCQL toward RhB and TC were 1946.0 and 1479.6 mg g −1 , respectively, based on the Sips model. The thermodynamic analysis indicates that the adsorption of PCQL toward adsorbents was spontaneous physical processes accompanied by the increasing disorder degree. The adsorption mechanism was attributed to the combination of the pore-filling, hydrogen bond, and π-π interactions. Moreover, in the fixed-bed experiments, the Yoon-Nelson model fitted the breakthrough curves well, and about 8 L wastewater containing RhB (200 mg L −1 ) may be effectively treated by 1.0 g of PCQL. Above results indicate that QL is a promising precursor for preparing functional porous carbon materials.