A series of meso- and microporous carbons containing magnetic Ni nanoparticles (Ni/C) with a variety of Ni loadings were synthesized by a simple one-pot procedure through carbonization of resorcinol-formaldehyde polymers containing various amounts of nickel(II) acetate. Such composite materials were characterized by N-2 sorption, Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Transmission electron microscope (TEM). The XRD patterns reveal peaks corresponding to face centered cubic nickel with the average size of crystallites of 17-18 nm. SEM and TEM results reveal that the formation of the nanoparticles took place mainly in the carbon spheres (1-2 mu m in size) and on the outer surface as well. The as-prepared composites are characterized by a core-shell structure with well-crystallized graphitic shells about 8-15 nm in thickness. The Raman spectra show that Ni content influences the structure of the carbon. It was also shown that the morphology (particle shape and sizes) and porosity (pore volume and pore size distribution) of the chars are strongly dependent on water and nickel contents in the blends. One of the applications of Ni/C was demonstrated as a magnetically separable adsorbent. (C) 2015 Elsevier B.V. All rights reserved.