The potential application of the magnetic polymer based on nickel(II)-potassium hexacyanoferrate(II/III) (denoted as KNF) for the sorption and separation of anionic species was presented. For the investigations the Cu(II) and Zn(II) complexes with iminodisuccinic acid (IDS) as well as Cr(VI) and As(V) were chosen. Several factors such as resin dose, pH, temperature, phase contact time, concentration, and the presence of interfering ions were studied and optimalized. It was found that more than 90% of the IDS complexes were sorbed on KNF within 30 min of contact time and the process involved the external mass transfer and the intraparticle diffusion. The adsorption could be described by the Temkin and the Dubinin-Radushkevich adsorption equations.