Efficiencies and mechanisms of heavy metals adsorption on waste leather-derived high-nitrogen activated carbon

Waste leather, as a high-nitrogen biomass, produced from leather industry aroused wide attention in the light of volume and the environmental problem. High nitrogen activated carbon (HNAC) derived from waste leather as its reusable byproduct was prepared to adsorb various heavy metals (Pb, Cu, Ni, Co) from aqueous solution. Elemental analysis showed that the nitrogen content of HNAC was as high as 5.8%, and six kinds of nitrogen such as pyridine nitrogen and pyrrole nitrogen was found according to X-ray photoelectron spectroscopy characterization. The maximum adsorption amounts of HNAC for Pb, Cu, Ni, and Co were 231.0, 130.0, 106.0, and 104.66 mg/g, respectively. It has been proved that there were four adsorption mechanisms for HNAC to adsorb multiple heavy metals, and the proportions of various mechanisms have been calculated. Especially, the adsorption selectivity of HNAC to Pb was proved by binary metal reaction system, and the highly efficient adsorption is associated with nitrogen functional groups. Therefore, leather wastes seem to be encouraging to prepare HNAC for heavy metals adsorption without adding amino modification reagents.