Melamine/Polypyrrole-Derived Porous Carbons for Effective Adsorptive Removal of Herbicides from Water.

Nitrogen-enriched porous carbons were prepared for the first time via pyrolysis (at different temperatures) of melamine-loaded polypyrrole. The melamine/polypyrrole-derived carbons (MPpDCs) and the carbon prepared from pure polypyrrole were characterized with various means; it was found that melamine increased the contents of nitrogen and total acidic or basic groups in the obtained carbon. The derived carbons were applied to the adsorptive removal of three herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D), clofibric acid, and methylchlorophenoxypropanoic acid from water. The optimized adsorbent, MPpDC(800), showed the highest adsorption capacity (510 mg/g) for 2,4-D removal compared with other reported results. Hydrogen bonding and π-π stacking could be suggested as a plausible adsorption mechanism, based on the adsorption and surface charge under wide pH conditions, X-ray photoelectron spectroscopic analyses of MPpDC(800) with or without adsorption of 2,4-D, and calculations. The facile regeneration of MPpDC(800), via ethanol washing, was also confirmed. Therefore, MPpDC(800) could be suggested as a potential adsorbent for the removal of herbicides from water.