ZnCl2 and thiourea co-modified biochar for effectively removing quinclorac in water and soil: Mechanism and alleviating its phytotoxicity on tobacco plants

The overuse of herbicide may cause pollution in water and soil environment, affecting the growth of crops. And how to reduce herbicide residues has aroused extensive attention. In this work, a novel modified biochar (Zn/SN-BC) was prepared with reed straw as raw material, ZnCl2 and thiourea as modifiers to remove quinclorac (QC) residues in water and soil. Compared with primitive biochar, Zn/SN-BC, benefiting from higher specific surface area (766.5 m2·g−1), improved pore characteristics and abundant reactive sites (−C = O, −COOR, −C-N, −C-S, ZnS, etc), showed excellent adsorption capacity towards QC (235.9 mg·g−1), which was much higher than others reported before. According to the characterization results, it was revealed that Zn/SN-BC adsorbed QC through pore filling, hydrogen bonding, π-π conjunction, electrostatic attractions and other chemical interactions. The column leaching and pot experiments demonstrated that Zn/SN-BC could reduce QC leaching and bioavailability in soil, and effectively alleviate its phytotoxicity on tobacco plants. This study gives a new insight into the application of biochar-based materials for the treatment of herbicide residues in agricultural environments.