Carbon Nanoparticles as Recyclable Adsorbent for the Removal of Copper Ions

In this study, we reported that oxidized carbon nanoparticles (O-CNPs) could be used as a recyclable adsorbent for Cu2+ removal. O-CNPs were prepared from active carbon through oxidation. The adsorption equilibrium was evaluated in batch experiments and well fitted to the Freundlich model with a K-F value of 19.53 mg/g center dot (L/mg)(1/n). The adsorption kinetics was described by the pseudo-first order model, giving a k(2) value of 0.00619/min. The intraparticle model fitting suggested that the adsorption involved both intraparticle diffusion and surface diffusion. In the thermodynamics study, the negative Delta G suggested that the adsorption was spontaneous and physisorption in nature. The positive Delta H indicated that the adsorption was endothermic. Higher pH, lower ionic strength and higher temperature benefited the adsorption. Moreover, the adsorption of Cu2+ on O-CNPs was recyclable. After 4 cycles, about 81.3% of the capacity was retained.