Adsorption of AgNO₃ onto bamboo hemicelluloses in aqueous medium

An insight into the adsorption behavior between hemicellulose biomass and metal ions is important to utilize hemicelluloses as adsorbent. In this study, bamboo hemicelluloses were used as adsorbent for AgNO₃ in aqueous medium. The adsorption amount of AgNO₃ onto hemicelluloses was determined through an inductively coupled plasma-atomic emission spectrometer (ICP-AES). The morphology and the elemental composition of the recovered hemicelluloses were characterized using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) techniques, respectively. The filtrate after removing undissolved hemicelluloses was analyzed by ultraviolet-visible spectroscopy (UV-vis). Results demonstrated that the obtained highest adsorption amount of AgNO₃ onto hemicelluloses was 42.82 mg/g under the conditions discussed. Some Ag⁺ was in situ reduced by hemicelluloses to form silver nanoparticles. Ag⁺ and the formed silver nanoparticles possibly destroyed the hydrogen-bonding network of hemicelluloses, resulting in the stretch of molecules and formed rod-like agglomerates with irregular length. Even an agglomerate with the length of 420 nm was found. The side chains and the newly formed carboxyl groups through oxidation of hemicelluloses by silver ions removed away from the hemicelluloses during adsorption. A part of Ag⁺ and silver nanoparticles were adsorbed on the unresolved hemicelluloses, and the other part was dispersed in the aqueous solution.