Core@double-shell structured magnetic halloysite nanotube nano-hybrid as efficient recyclable adsorbent for methylene blue removal

Design and fabrication of structurally optimized absorbents are important for wastewater treatment such as dyes and heavy metals removal. Herein, we reported the core@double-shell structured magnetic halloysite nanotube nano-hybrid absorbent with target micro-structure and high efficiency removal capacity of dyestuffs. Our core@double-shell structured absorbent consisted of a halloysite nanotube as skeleton, an intermediate magnetic nanoparticles coating with more specific surface area and magnetic separation property, and poly(DA + KH550) derivate layer outside provided active adsorption sites. This well-defined core@double-shell configuration was quite distinct from conventional core-shell or hybrid structures. The integrated advantages of HNTs skeleton, Fe3O4 nanoparticles inner shell and poly(DA + KH550) outside shell contributed to the high adsorption capacity of methylene blue (up to 714.29 mg g(-1)) and excellent cycling stability. Furthermore, the novel core@double-shell structured absorbent exhibited better removal efficiency for methylene blue in solution with high pH, and the adsorption process can be described by using the pseudo-second-order model. More importantly, the recycling process of adsorbents was more energetically and economically sustainable by using a permanent magnet. The characteristic high removal capacity, cycling stability and easy separation made core@double-shell structured absorbent promising for the efficient removal of dyestuffs from the wastewater.