This manuscript describes the synthesis of magnetic composite adsorbents which consist of carbon matrix and magnetic nanoparticles. The carbon matrix originated from simultaneous decomposition and activation of two different precursors, namely glucose and sucrose. KOH and ZnCl2 were used as the activating agents. The inclusion of carbon-encapsulated iron nanoparticles in the course of the synthesis process resulted in mobile composite adsorbents which can be easily separated. The structural features of carbon-encapsulated iron nanoparticles make the developed composite resistant to aggressive corrosion agents. The adsorption performance of the composites was studied in the removal of phenolic compounds from aqueous solutions.