Removal of direct yellow 12 from water using CTAB-coated core-shell bimagnetic nanoadsorbents

•Nanoadsorbents combine magnetic and sorptive properties in a single particle.•More than 90% of dye removal was obtained.•Adsorption capacity strongly depends on nanoadsorbent mean size.•Nanoadsorbents can be recovered for reuse keeping good removal efficiency.•Removal process can be extended to other synthetic dyes with similar structures.