Polydopamine modified cyclodextrin polymer as efficient adsorbent for removing cationic dyes and Cu2+

An eco-friendly polydopamine composite adsorbent (CD-CA/PDA) based on cyclodextrin polymer was prepared for cationic dyes and metals removing. CD-CA/PDA, combining the advantages of cyclodextrin and polydopamine, which has quite abundant carboxyl and catechol groups, so methylene blue (MB), malachite green (MG), crystal violet (CV) and copper ion (Cu2+) can be easily removed by electrostatic force. Adsorption kinetic results showed all adsorption process fitted well with pseudo-second-order model. In addition, the isotherm fitted results showed that the adsorption processes of CD-CA/PDA on MG and Cu2+ were consistent with sips model, while the adsorption processes of MB and CV agreed well with Freundlich and Langmuir model, respectively. The fitted adsorption capacities of CD-CA/PDA for MB, MG, CV and Cu2+ were 582.95 mg/g (1.82 mmol/g), 1174.67 mg/g (3.22 mmol/g), 473.01 mg/g (1.16 mmol/g) and 73.64 mg/g (1.16 mmol/g), respectively. Moreover, it is worth noting that cationic dyes have no competitive adsorption in series. CD-CA/PDA is of great recyclability, and can be reused by at least 5 times. Due to the facile and eco-friendly preparation process and excellent adsorption performance, CD-CA/PDA has a great potential in the field of wastewater treatment.