This study introduces a novel biochar, Zr-P-modified nanomagnetic herbal-derived biochar (ZMBC), synthesized from Chinese herbal residues, addressing the issue of heavy metal (HM) contamination in soil and water. With 19.4% of Chinese farmland soils contaminated primarily by lead (Pb) and cadmium (Cd), finding practical remediation methods is essential.

ZMBC demonstrates superior Pb2+ and Cd2+ removal compared to traditional biochar and nanomagnetic biochar, achieving reductions of 51.3% and 56.1%, respectively. The adsorption behavior aligns with established models such as pseudo-second-order, intra-particle diffusion, and Langmuir.

Produced through zirconium-phosphate modification of nanomagnetic biochar derived from herbal residues, ZMBC exhibits an adsorption capacity for Pb2+ (357.1 mg g−1) and Cd2+ (136.2 mg g−1) that surpasses conventional biochars.

In soil applications, ZMBC alters the mobile fraction of Cd2+ and Pb2+, reducing DTPA-extractable Pb2+ by 51.3% and Cd2+ by 56.1%. The addition of ZMBC to contaminated soil decreases Cd and Pb levels in wheat roots and shoots, showcasing its efficacy in mitigating metal uptake by plants.

This study pioneers the investigation of ZMBC’s influence on soil bacterial communities. The addition of ZMBC enhances metal-resistant bacteria, potentially amplifying soil bacteria suitable for bioremediation of metal-contaminated soil.

ZMBC proves to be a promising candidate for the remediation of metal-contaminated water and soil, with its superior adsorption capacity, positive impact on soil bacteria, and recyclable nature positioning it as a practical solution to address the challenge of heavy metal pollution in agricultural ecosystems.