Polydopamine-coated magnetic nanochains as efficient dye adsorbent with good recyclability and magnetic separability.

High adsorption ability and good separation functionality are necessary to an excellent adsorbent for organic dye removal from wastewater. In this study, core@shell nanostructured magnetic Fe-Fe2O3@polydopamine (PDA) nanochains (defined as Fe-Fe2O3@PDA NCs) were facilely synthesized through self-polymerization of dopamine on the surface of Fe-Fe2O3 NCs. The dye adsorption performance, recyclability and magnetic separability of the Fe-Fe2O3@PDA NCs were investigated through selecting malachite green (MG) as a model organic dye. The effects of initial MG concentration, initial solution pH, temperature, and contact time on dye adsorption were systematically studied. Results show that the adsorption capacity of the Fe-Fe2O3@PDA NCs for MG was 61.22 mg/g at 25 °C. Both π-π stacking and electrostatic interactions might be responsible for the adsorption of MG on Fe-Fe2O3@PDA NCs. The adsorption kinetic follows both pseudo-second-order kinetic and Weber's intraparticle diffusion models. And the adsorption isothermal models fit Langmuir well. Besides, the Fe-Fe2O3@PDA NCs exhibit good recyclable adsorption property towards MG dye.