Understanding the interactions between ionizable organic compounds and biochar is of great importance to evaluate the effects of biochar on bioavailability and the leaching/runoff of herbicides and hazardous organic compounds from agricultural fields. We report here the interactions between a group of heteroaromatic amines and biochars prepared at different pyrolysis temperatures (300�700 oC, referred as B300�B700). These heteroaromatic amines (including a triazine herbicide, prometon, pKa = 4.3; quinoline, pKa = 4.9; and pyridine, pKa = 5.2) displayed a strong and slow sorption on biochars, and the sorption of cationic species on biochars was generally much slower than their corresponding neutral counterparts. The pore size distribution of biochars has a considerable effect on the pore diffusion of prometon and quinoline molecules but little effect on the diffusion of a simple compound, pyridine. The sorption rate of prometon and quinoline species peaked at B500 that has the highest ratio of mesoporosity to microporosity, suggesting that mesopores (2�50 nm) are critical for facilitating accessibility of relatively large organic species to the inner parts of biochars. In addition, the sorption intensity of both the neutral and cationic species peaked at B500, and interestingly the N2� and CO2�probed surface areas of biochars do not correlate with the sorption of either neutral or charged species. Such finding challenges the common assumption about the correlation between organic compound sorption and the surface area of porous carbonaceous materials determined by simple, inert gases (i.e., N2 and CO2).

Interactions of biochars of varied meso- and micro-porosities with charged and neutral heteroaromatic compounds including a triazine herbicide

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.