Surface Modifications of Halloysite Nanotubes with Superparamagnetic Fe3O4 Nanoparticles and Carbonaceous Layers for Efficient Adsorption of Dyes in Water Treatment

Surface modification of halloysite nanotube(HNT) with in situ grown Fe3O4 nanoparticles and carbonaceous layers introduced by a hydrothermal carbonization process of glucose has been achieved. Structure and morphology investigations demonstrate that iron oxide nanoparticles are uniformly anchored on the halloysite and prevent the aggregations of halloysite and carbon, forming a protective layer that stabilizes and improves the property of HNT/Fe3O4/C nanocomposite. Magnetism characterization proves the superparamagnetic behavior of HNT/Fe3O4/C hybrid at room temperature, which makes it easily separated from dye solution under an external magnetic field. Exploration of adsorption ability demonstrates that the maximum adsorption capacity of the as-prepared HNT/Fe3O4/C nanocomposite for methylene blue(MB) is about twice and 1.5 times those of HNT/Fe3O4 and HNT according to Langmuir equation, respectively. The adsorption behavior investigations indicate that HNT/Fe3O4/C hybrid has a heterogeneous structure and shows a non-ideal monolayer adsorption that fits the Redlich-Peterson isotherm, and the adsorption process follows a pseudo-second-order kinetic model. Therefore, the as-prepared HNT/Fe3O4/C hybrid is a fast, separatable and superparamagnetic adsorbent with a good adsorption ability, demonstrating great potential in the application of water treatment.