Adsorption of Pyraclostrobin in Water by Bamboo-Derived and Pecan Shell-Derived Biochars

Pyraclostrobin is a potent extensive-spectrum fungicide widely used in agricultural production but poses a substantial threat to aquatic life. Therefore, there is an urgent need to remove pyraclostrobin from the ecological environment. This study reports the adsorption of pyraclostrobin in water using pecan-shell biochar, bamboo biochar, and their deashing products. The kinetics and isotherms indicate that the pseudo-second-order kinetics and Freundlich model are the most suitable for both types of biochar. The thermodynamic results demonstrate that the adsorption process of biochar is spontaneous and exothermic. Combined with characterization and factor analysis experiments, it is revealed that the adsorption of pyraclostrobin on biochar is attributed to various mechanisms, including pore filling, hydrophobic interactions, π-π and p-π interactions, and hydrogen bonding. At the initial concentration of 0.5 mg·L−1, the adsorption rates of pyraclostrobin of the four biochar samples (<0.075 mm) reached 67–80% within 5 min. These findings suggest that both pecan-shell and bamboo biochars are efficient pyraclostrobin adsorbents, with the former showing better outcomes. There is still an adsorption rate of >97% after 5 cycles of adsorption by two types of biochars. Deashing significantly enhances the adsorption efficiency of pecan biochar, but it has an insignificant effect on bamboo biochar. This study will aid in the selection of cost-effective and ecofriendly adsorbents to reduce the environmental risk associated with pyraclostrobin.