Promotion effects of nitrogenous and oxygenic functional groups on cadmium (II) removal by carboxylated corn stalk

Carboxylated corn stalk was prepared successfully by introducing amide and carboxyl groups into the cellulose structure, and were utilized as an efficient adsorbent to remove cadmium ions from an aqueous solution in batch adsorption process. The maximum adsorption capacity could be achieved 47.17 mg/g at the initial pH 5.8 of aqueous solution, significantly higher than most reported adsorbents. Meanwhile, changing of temperature could not greatly affect during the adsorption process. In addition, this adsorbent had a high selectivity of the cadmium ions in co-existing ions solution, but lead ions exerted obviously a compete effect upon the adsorption of cadmium ions. The adsorption isotherm could be correctly simulated by Langmuir and Freundlich isotherms. Whereas, the adsorption kinetics followed the pseudo-second-order kinetic model. Also, Thermodynamic parameters confirmed that adsorption was exothermic and chemisorption in nature. Based on the results of X-ray photoelectron spectra, the adsorption mechanism was ascribed mainly to the coordination complex between cadmium ions and the oxygen of carbonyl groups, relative to the effect of the nitrogen of amine groups. Regeneration of the adsorbent was performed with 0.1 g/L ethylenediaminetetraacetic acid to provide five cyclical regeneration. (C) 2018 Elsevier Ltd. All rights reserved.