Adsorbent with high efficiency, fast removal rate and good reusability is very important for arsenic remediation. Herein, a novel porous magnetic nanocomposite was prepared for efficient arsenic removal by simple one-pot coprecipitation of Fe3O4 NPs on porous halloysite nanotubes/C (HNTs/C) preformed using abandoned polyurethane foam as a template. HNTs were inserted into the pore of polyurethane foam and formed the skeleton of the nanocomposites after sticking by the carbonized phenolic resin. Fe3O4 NPs were well dispersed on the skeleton and finally formed the porous stable HNTs/C/Fe3O4 nanocomposites. The optimized HNTs/C/Fe3O4 showed ultrafast removal rate (>98% arsenic was removed within 10 min), high removal efficiency and good regeneration capacity. It is worth noting that the adsorption efficiency of As (V) by HNTs/C/Fe3O4 was still above 99% after 5 times reuse, indicating the sustainable application. In addition, the application of HNTs/C/Fe3O4 for arsenic adsorption is almost not limited by pH. The chemical adsorption process was confirmed by adsorption kinetics, XPS and isothermal adsorption. The qm of As(III) and As(V) is 34.54 mg/g and 1491.72 mg/g, respectively, which is the highest capacity of As (V) known at present. This study demonstrates an ultrafast, high-efficient and sustainable adsorbent for arsenic treatment in contaminated water, which might also give light on other heavy metals remediation. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.