Preparation and characterization of high-surface-area activated carbon fibers from silkworm cocoon waste for congo red adsorption

Herein, we report the preparation of activated carbon fibers from silkworm cocoon waste via the combination of (NH4)(2)HPO4-pretreatment and KOH activation. The morphology, phase structure and surface chemistry constitute of the obtained ACFs were characterized by X-ray diffraction, IR spectroscopy, Micro Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, thermal analysis and N-2 adsorption-de-sorption isotherm. The effects of various factors such as the concentration of (NH4)(2)HPO4 and the activation time of KOH were also evaluated. These results demonstrated that the synthesized ACFs retained the fibrous morphology of silkworm cocoon waste, and exhibited highly defective graphite layer structure. A large amount of surface oxygen-containing functional groups were found on the ACFs surface. The obtained samples exhibited high BET surface areas ranging from 1153 to 2797 m(2) g(-1), total pore volumes of 0.64-1.74 cm(3) g(-1) with micropore volume fractions between 75.2 and 93.6%. In addition, we also evaluated the congo red (CR) adsorption performance of the obtained ACFs. The CR adsorption fitted well to the pseudo-second-order kinetic model. Adsorption isotherm data indicated that the adsorption of CR onto ACFs was monolayer adsorption which followed well the Langmuir isotherm model. The maximum adsorption capacity of CR was 512 g kg(-1). The mechanism of the adsorption process was also described from the intra-particle diffusion model. (C) 2015 Elsevier Ltd. All rights reserved.