High-efficiency control of pesticide and heavy metal combined pollution in paddy soil using biochar/g-C3N4 photoresponsive soil remediation agent

The control of pesticide and heavy metal combined pollution in the paddy field is of great significance in terms of controlling agriculture nonpoint source pollution. Herein, an alkali-modified biochar (BCNaOH)/graphitic carbon nitride (g-C3N4) photoresponsive soil remediation agent was synthesized to control the pesticide and heavy metal compound pollution in paddy fields. Compared with g-C3N4, the photocurrent density increased 2.72 times for BCNaOH/g-C3N4, exhibiting a strong photocatalytic activity. In the simulated compound pollutant solution, the simultaneous Atrazine (ATZ) degradation and Pb sorption efficiencies of BCNaOH/g-C3N4 reached 94.70 % and 47.75 % under visible light irradiation, respectively. In the paddy field, both ATZ and Pb concentrations were well controlled in the overburden water and paddy soil. ATZ and Pb in overburden water reached 0 mg/L and 0.24 μg/L, respectively, and in paddy soil decreased by 60.21 % and 65.49 %, respectively. Excellent ATZ degradation performance was due to the construction of an intact photogenerated electron transfer pathway via the π-π stacking structure. Meanwhile, excellent Pb removal performance was due to the strong sorption capability of BCNaOH. The results provided a cost-effective photoresponsive soil remediation agent with good pesticide and heavy metal combined pollution control performance for paddy fields.