Nitrogen-Doped Nanoporous Carbon Nanospheroids for Selective Dye Adsorption and Pb(II) Ion Removal from Waste Water

In the presence of melamine and block copolymers, namely, F108, F127, and P123, nitrogen-doped nanoporous carbon nanospheroids (N@CNSs) were synthesized by the hydrothermal process. The F127-modified sample (CNF127) exhibits the maximum Brunauer-Emmett-Teller (BET) surface area of 773.4 m²/g with a pore volume of 0.877 cm³/g. The microstructural study reveals that nanospheroids of size 50-200 nm were aggregated together to form a chainlike structure for all triblock copolymer-modified samples. The X-ray photoelectron spectroscopy study shows the binding energies of 398.33 and 400.7 eV attributed to sp² (C-N=C)- and sp³ (C-N)-hybridized nitrogen-bonded carbons, respectively. The synthesized N@CNS samples showed selective adsorption of organic dye methylene blue (MB) in the presence of methyl orange (MO) as well as Pb(II) ion removal from contaminated water. The adsorptions for MB and Pb(II) ions followed pseudo-first-order and pseudo-second-order kinetic models, respectively. The sample CNF127 showed the highest adsorption of 73 and 99.82 mg/g for MB and Pb(II) adsorptions, respectively. The adsorption capacity for MB of the copolymer-modified samples follows the order CNF127 > CNP123 > CNF108, which corroborated with the mesoporosity as well as nitrogen content of the corresponding samples. The maximum % adsorption of Pb(II) follows the order CNF127 (99.82%) > CNF108 (98.74%) > CNP123 (91.82%), and this trend is attributed to the BET surface area of the corresponding samples. This study demonstrates multicomponent removal of water pollutants, both organic dyes and inorganic toxic metal ions.