Acid-treatment effect on the N-doped porous carbon obtained from fish scales for Cr(VI) removal

The authors explore the impact of acid treatments on the N-doped porous carbon obtained from fish scales and its Cr(VI) removal capability. HCl and HNO3 are employed to treat the materials to remove template. The materials were characterized by elemental analysis, N-2 adsorption/desorption isotherms, X-ray photoelectron spectroscopy and so on. Compared with the materials treated with HNO3, the materials treated with HCl have the larger specific surface area leading to the much higher adsorption capacity and faster adsorption rate of Cr(VI). To investigate the adsorption mechanism, the materials after adsorption of Cr(VI) were measured by X-ray photoelectron spectroscopy. It is found that the adsorbed Cr(VI) is partly reduced to Cr(III). The as-produced Cr(III) is in proportion to the content of quaternary-N in the carbons, which demonstrates the redox reaction between the N-doped porous carbon and Cr(VI). Remarkably, the materials carbonized at 800 degrees C treated with HCl reach equilibrium in 100 min and achieve the maximum capacity up to 416.67 mg g(-1).