Sorption of simazine to corn straw biochars prepared at different pyrolytic temperatures

Simazine sorption to corn straw biochars prepared at various temperatures (100-600 degrees C) was examined to understand its sorption behavior as influenced by characteristics of biochars. Biochars were characterized via elemental analysis, BET-N-2 surface area (SA), MR and C-13 NMR. Freundlich and dual-mode models described sorption isotherms well. Positive correlation between log K-oc values and aromatic C contents and negative correlation between log K-oc values and (O + N)/C ratios indicate aromatic-rich biochars have high binding affinity to simazine (charge transfer (pi-pi*) interactions) and hydrophobic binding may overwhelm H-bonding, respectively. Dual-mode model results suggest adsorption contribution to total sorption increases with carbonization degree. Positive correlation between amounts of adsorption (Q(ad)) and SA indicates pore-filling mechanism. Comparison between our results and those obtained with other sorbents indicates corn straw biochars produced at higher temperature can effectively retain simazine. These observations will be helpful for designing biochars as engineered sorbents to remove triazine herbicides. (C) 2011 Elsevier Ltd. All rights reserved.