Hydrangea-like biomimetic MgO-modified coconut shell biochar for remediation of multi-media heavy metal pollution: Morphological innovation and underlying mechanisms.

Metal oxide-modified biochar have emerged as prominent adsorbents for tackling heavy metal contamination. However, their typical granular structure is prone to accumulate on biochar and clog the pores of biochar. This study developed a hydrangea-like MgO-modified biochar (X-MBC) to overcome this limitation and investigated its effectiveness and mechanisms in remediating heavy metal pollution across the "water-soil-plant" multi-media system. The findings revealed that 2-MBC exhibited maximum adsorption capacities of 978.58 mg/g for Cd2 + and 1605.78 mg/g for Pb²⁺ in aqueous solution. In the soil system, the application of 2-MBC reduced the bioavailability and mobility of heavy metals. This adsorption and immobilization effect was associated with coordination and complexation by chemical functional groups, ion exchange at Mg-O sites, and pore confinement effects. In the plant system, the amendment of 2-MBC promoted the growth of soybeans, which was attributed not only to the immobilization of heavy metals in the soil and the enhancement of soil enzyme activity by 2-MBC itself, but also to its role in altering the microbial community composition to enrich functional microorganisms with heavy metal resistance, collectively alleviating metal-induced stress on soybeans. The results of this study provide an optimized strategy for fabricating metal oxide-modified biochar and demonstrate the applicability of X-MBC for remediating multi-media heavy metal pollution.