β-Cyclodextrin-crosslinked polymeric adsorbent for simultaneous removal and stepwise recovery of organic dyes and heavy metal ions: Fabrication, performance and mechanisms

The currently reported adsorbents for wastewater purification generally have only limited adsorption capacity towards a single type of pollutant; few of them can simultaneously remove multiple types of pollutants from cocontaminated water with high efficiency. In this work, a kind of β-Cyclodextrin based polymeric adsorbent (PCD-VI) with an expanded “pocket” structure was created, and it exhibited excellent adsorption capacities for different kinds of pollutants, cationic rhodamine B (RB), anionic Congo red (CR) and cadmium ion (Cd(II)) in a mono-component solution. Since the “pocket effect” (composed of cavity inclusion and π-π interactions), electrostatic attraction and coordination were the dominant mechanisms for RB , CR and Cd(II) adsorption, respectively, competitive adsorption was effectively avoided in the simultaneous adsorption process. RB and Cd(II) exhibited a synergistic effect in the RB-Cd(II) binary solution; the coexisting Cd(II) showed a negligible effect on CR adsorption at lower CR concentrations (≤400 mg L −1 ), while the removal of Cd(II) was prominently promoted by the coexisting CR in the CR-Cd(II) binary system. More importantly, RB and Cd(II) could be recovered separately, and PCD-VI could be recycled without a serious decline in performance even after five sequential adsorption-desorption cycles in the RB-Cd(II) binary system. Our studies suggest promising strategies for fabrication and application of advanced adsorption materials in water pollution remediation.