Potential of carbon nanomaterials for removal of heavy metals from water

Heavy metals, such as, cadmium, lead, nickel and zinc can be removed from water using sorbents. The rate and extent of removal may be enhanced by choice of appropriate sorbents. In this study heavy metal sorption was studied on indigenously synthesized carbon nanomaterials (CNMs). Two CNMs differing in surface morphology were synthesized using turpentine oil in a chemical vapour deposition (CVD) setup by varying the process parameters. Activation and catalyst removal were achieved by post-treatment with HNO3 and KOH. Characterization of the CNMs produced revealed that both comprised of graphitic amorphous carbon, however, while the nanocarbon (NC) produced using cobalt catalyst in N2 atmosphere comprised of varying grain sizes indicative of soot, the nanoporous carbon (NPC) produced using silica catalyst in H2 atmosphere had a distinctive uniformly porous surface morphology. Comparative sorption studies with cadmium, lead, nickel and zinc also revealed greater sorption on NPC compared to NC. Batch isotherms for the various heavy metals using NPC and a commercial activated carbon (AC) widely used for metal sorption revealed that NPC is characterized by significantly higher metal sorption capacity and more favourable sorption energetics. The superior performance of NPC as a sorbent may be due to its unique nanoporous structure.