A one-pot method was used to prepare magnetic Ni/carbon (Ni/C) nanomaterials by catalytic carbonization of linear low density polyethylene (LLDPE) under the combined catalysis of Ni2O3 and polyvinyl chloride (PVC) resin. The yield of Ni/C nanomaterials was determined by the pyrolysis temperature, the type and the content of PVC resin. The yield of magnetic Ni/C nanomaterials first increased and then decreased with increasing PVC content. The obtained carbon nanomaterials mainly consisted of long carbon nanotubes (CNTs) at lower PVC content but short carbon nanofibers and amorphous carbon at higher PVC content. This is attributed to chlorine radicals from the decomposition of PVC resin promoting the dehydrogenation and aromatization of LLDPE macroradical fragments. The obtained magnetic Ni/C nanomaterials were used as adsorbents for the removal of methylene blue (MB) from water and showed an adsorption capacity as high as 165.5-175.2 mg/g, indicating the resultant magnetic Ni/C nanomaterials had potential application in wastewater treatment. (C) 2012 Elsevier B.V. All rights reserved.