Synthesis of oxygen-rich functional groups biochar for high-efficiency adsorption of herbicide and as a potential carrier for pH-responsive slow release

To improve the utilization rate of herbicides and reduce their environmental residues, it is urgent to develop a simple and low-cost method to prepare slow-release pesticides. In this study, a biochar (280CPFe) with a high surface area and rich oxygen-containing functional groups was synthesized by low temperature (280°C) boiling strategy, which was used as a carrier to prepare pH-responsive slow-release herbicide. The obtained biochar has a high adsorption capacity of 153.59 mg·g⁻¹ for quinclorac (QNC). The release rates of QNC-280CPFe are 21%, 56%, and 90% at the initial pH of 3, 5, and 11, respectively. The controlled release behavior of QNC-280CPFe is related to its adsorption mechanism, in which the pore filling and functional group adsorption are mainly responsible for the adsorption of QNC on 280CPFe. Compared with QNC alone, QNC-280CPFe slow-release herbicide has a good control effect on Barnyard grass but does not affect the normal growth of rice. Therefore, this study provides a simple, low-cost cost, and environmentally friendly biochar carrier for preparing slow-release herbicide, improving its utilization rate and reducing its environmental pollution risk.