Rapid effectual entrapment of pesticide pollutant by phosphorus-doped biochar: Effects and response sequence of functional groups

The purpose of this study is to clarify the mechanism of P-doped biochar adsorbing pesticide pollutants such as 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution. Through environmental interference, adsorption isotherms and kinetic experiments, the mechanism evolution of 2,4-D adsorption by the inherent structure of biochar and the species difference of phosphorus-oxygen groups was investigated. Under controlled nitrogen flow, among the P-doped biochar produced at different pyrolysis temperatures (300, 500 and 700℃), the P-doped biochar produced at 700℃ (PBC-700) showed the best 2,4-D adsorption capacity (146.41 mg g−1). The adsorption of 2,4-D largely depends on the characteristic surface functional groups, specific surface area and porosity of biochar. In the adsorption process, hydrogen bonding and π-π EDA interaction dominate, and electrostatic force and pore filling play an auxiliary role. The chemisorption function of PBC-700 was weaker than that of PBC-300. The density functional theory (DFT) calculation results showed that the incorporation of P species regulated the electronic structure and surface charge distribution of the biochar. The two-dimensional correlation spectroscopy (2D COS) analysis revealed the order of the main functional groups involved in the adsorption process. Furthermore, the good recovery capacity improved the feasibility of P-doped biochar to repair surface water polluted by pesticides such as 2,4-D.