Enhanced passivation of lead and cadmium from contaminated farmland using biochar with tailored pore properties: Performance and mechanisms.

[Display omitted] • The porous PBC PB was successfully synthesized by one-step KHCO 3 -activated pyrolysis. • The PBC PB has excellent passivation performance with a high S BET of 1342.07 m2/g. • PBC PB could significantly reduce the bioavailability and bioaccumulation of Pb/Cd. • Precipitation, complexation and cation-π interaction convert Pb/Cd to stable species. The porous biochar (PBC PB) was prepared by one-step KHCO 3 -activated pyrolysis of corn stalks, which showed excellent passivation properties for Pb/Cd in soil (48.99 % or 46.74 %). Characterization results revealed that the PBC PB possessed a dense and network-like pore structure with a huge specific surface area of 1342.07 m2/g, which was conducive to the passivation of Pb/Cd. Batch experiments showed that PBC PB had excellent adsorption properties with the maximum absorption capacity of 117.61/48.24 mg/g. After 30 d of remediation, the bioavailable-Pb/Cd contents in 5.0 % of PBC PB treatment were reduced by 47.06 % and 58.42 %, respectively. The speciation transformation results uncovered that the contents of unstable Pb/Cd components gradually decreased with the increase of PBC PB dosages, ultimately transforming into stable residual components. In addition, the PBC PB could effectively increase the contents of soil available nutrients and enhance functional enzyme activities, which contributed to promoting the growth of cucumber seedlings. Meanwhile, PBC PB strongly alleviated the oxidative damage of Pb/Cd to cucumber seedlings by significantly reducing the Pb/Cd accumulation and antioxidant oxidase activity of cucumber seedlings. Furthermore, precipitation, complexation, as well as cation-π interaction were the primary passivation mechanisms of PBC PB for Pb/Cd. Overall, the study provided a reasonable design of porous carbon-based materials for the remediation of Pb/Cd-contaminated soil. [ABSTRACT FROM AUTHOR]