Biochar for simultaneously enhancing the slow-release performance of fertilizers and minimizing the pollution of pesticides.

Biochar has been extensively studied as a promising carrier material for fertilizers and an ideal adsorbent for the removal of pesticides. Yet, the application of biochar for simultaneously eliminating the pollution from the agricultural use of fertilizers and pesticides remains unexplored. Herein, we develop P-loaded biochar-based fertilizers (PBC) by the co-pyrolysis of cotton straw and H3PO4. The slow-release performance of PBC and their adsorption properties toward pesticides are investigated. The results indicate that the PBC leads to the improvement of adsorption performance, with the maximum adsorption capacities of lambda-cyhalothrin (LAC) for PBC and pristine biochar are 55.90 mg/g and 42.71 mg/g, respectively. Additionally, the adsorption of LAC is beneficial for the improvement of slow-release performance of PBC. The release ratios of P from PBC within 30 days reach 100.0% and 83.5% in water and LAC solution, respectively, demonstrating the existence of synergistic effects between the adsorption of pesticides and the slow release of nutrients. The mechanistic investigation reveals that the pretreatment of H3PO4 facilitates to activate more surface functional groups of PBC, contributing greatly to the improved adsorption of LAC. The adsorption of LAC reduces the BET of PBC with pore filling, enabling slower release rate of nutrients from PBC.