Mesoporous composite Ni-C-N/SA for selective adsorption of methylene blue from water

A mesoporous Ni-C-N/Silica aerogel (Ni-C-N/SA) was prepared by impregnation of the cationic [Ni(tepa)](2+) complex onto a negatively charged silica aerogel support followed by suitable thermal treatment. And Ni-C-N/SA was applied as an adsorbent for selective adsorption of methylene blue (MB). When [Ni(tepa)](2+) loading is 20% and thermal treatment temperature is 400 degrees C (denoted "NiT20-400/SA"), the adsorption of MB by NiT20-400/SA is 54 mg/g, which is three times that of raw silica aemgel (RSA). However, little adsorption was observed for the anionic dye methyl orange (MO) and large sized cationic dye rhodamine B (RhB), demonstrating that NiT20-400/SA showed selective adsorption for MB. The nitrogen adsorption/desorption results demonstrate that the total pore volume of NiT20-400/SA is about 1.27 cm(3 )g, which is 25.7% higher than that of the RSA. The pore size distribution also changed from a wide range pore size distribution (13-126 nm) in the RSA to a narrow range mesoporous distribution (mainly 5-15 nm) in NiT20-400/SA. All of these results are due to the "binder" effect of [Ni(tepa)](2+) on the RSA surface. XPS shows that multiple-doping with nickel, carbon and nitrogen (Ni-C-N) were successfully added to the RSA surface via the followed pyrolysis of [Ni(tepa)](2+). As temperature increases in the range 200-600 degrees C, Ni, C and N species undergo [Ni(tepa)](2+) -> Ni-C-N -> NiO changes process. The larger total pore volume, suitable pore size distribution, and the unique subject-object interaction between cationic dye and Ni-C-N components results in the increased adsorption capacity and selective adsorption of MB.