Synthesis of Magnetic Fe 3 O 4 @C Nanoparticles Modified with –SO 3 H and –COOH Groups for Fast Removal of Pb 2+ , Hg 2+ , and Cd 2+ Ions

Core–shell magnetic Fe 3 O 4 @C nanoparticles functionalized with sulfonic and carboxylic acid groups were synthesized and employed to capture heavy metal ions in aqueous media. The Fe 3 O 4 cores possess unique magnetic properties for adsorbent separation, and the –SO 3 H and –COOH groups attached to the surface of the carbon shells determine the efficiency of heavy metal ion removal. Batch adsorption experiments showed that Pb 2+ , Hg 2+ , and Cd 2+ ions can be completely and quickly removed by the Fe 3 O 4 @C nanoparticles. The equilibrium was established within 5 min, and the maximum adsorption capacities of the Fe 3 O 4 @C nanoparticles toward Pb 2+ , Hg 2+ , and Cd 2+ ions were 90.7, 83.1, and 39.7 mg/g, respectively. The removal efficiencies were 96.3, 98.1, and 93.8 % for Pb 2+ , Hg 2+ , and Cd 2+ ions, respectively. This work provides a facile and general approach to synthesize magnetic functional nanocomposites for wastewater treatment.