Investigating the adsorption behavior and mechanism of Eu(III) and Au(III) on β-cyclodextrin/polyethylenimine functionalized waste paper

A bio-adsorbent (DAWP-PEI-β-CD) was facilely prepared by introducing polyethylenimine (PEI) and β-cyclodextrin (β-CD) into dialdehyde waste paper (DAWP) via a facile two-step method. The structures, morphologies and compositions of the as-prepared adsorbents were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), solid state nuclear magnetic resonance spectrometry (NMR) and X-ray photoelectron spectroscopy (XPS) techniques. Results showed that the pH values, adsorption temperature and contact time played a vital role in uptake of Eu(III) and Au(III). Meanwhile, the adsorption behavior of Eu(III) and Au(III) could be fitted felicitously with the Langmuir and the pseudo-second-order models, and the maximum adsorption capacities of Eu(III) (pH = 6.0) and Au(III) (pH = 2.0) onto DAWP-PEI-β-CD were 424.2 and 241.3 mg/g, respectively. Further advanced spectroscopy analysis revealed that the elimination of Eu(III) was attributed to host-guest inclusion and surface complexation interaction, while adsorption of Au(III) might stem from a combination of electrostatic attraction, chelation, host-guest inclusion and redox interaction. This study demonstrated that DAWP-PEI-β-CD was a promising environmental functional material to separation and enrichment of Eu(III) and Au(III) from contaminated water. Graphical abstract