Molecular Structure of Corncob‐Derived Biochars and the Mechanism of Atrazine Sorption

Abstract

This study evaluated the sorption of atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] to biochars and thereby explored their potential use as an efficient and low‐cost soil amendment for mitigating and removing agricultural contaminants. Biochars derived from corncobs (Zea mays L.) produced at incremental pyrolysis temperatures (350–650°C in 100°C intervals) were characterized using elemental analysis, specific surface area, scanning electron microscopy, x‐ray diffractometry, and Fourier‐transform infrared spectra to estimate the relationship between the physical and chemical properties of biochars and the treatment temperature. Generally, carbonization, aromatization, and specific surface area increased with the elevation of temperatures, whereas the occurrence of polar functional groups and crystallinity decreased. The sorption isotherms fit the Freundlich equation well. A negative correlation between the logarithm of the concentration‐dependent distribution coefficient Koc and H/C and (O + N)/C ratios suggested that the presence of aromatic C and hydrophobic structures are advantageous for biochars to sorb atrazine in aqueous solutions. Biochar prepared at 650°C has a relatively developed void space structure and therefore a much larger surface area than when prepared at lower pyrolysis temperatures, indicating that pore filling has occurred. These results may provide a reference for biochar design and application in agricultural pollution control.