Edge nucleation and bridging effect synergistically in-situ sealed multiple heavy metals in soils

The development of broad-spectrum remediation materials for soil heavy metals is an urgent problem in the environmental field. This study utilized oxygen-sulfur synergy sites in sulfonated cellulose/chitosan self-assembled gel (SMCG), which exhibited high affinity for Cu(II) and Ni(II), to induce and construct Cu-Ni bimetallic sulfides in situ. Through coupling with edge nucleation of Pb(II), Zn(II), and Cd(II), five heavy metals (Cu(II), Ni(II), Pb(II), Zn(II), and Cd(II)) were immobilized over the long term. In soil experiments, SMCG achieved an average passivation efficiency exceeding 98 % (exhibiting optimal performance under a wide temperature range at a dosage of 10 wt% and moisture content between 40 % and 60 %) and demonstrated broad-spectrum remediation capability by inducing silicate nucleation of Pb(II), Zn(II), and Cd(II) and facilitating coprecipitation of Cu-Ni bimetallic sulfides. Notably, Ni(II) enhanced the stability of Cu-S bonds through electron-donating effects, maintaining high passivation efficiency even following 90 days of aging. In summary, a paradigm shift from "soil remediation via exogenous materials" to "material-driven soil self-healing" was realized by using degradable materials to fix heavy metals through an intrinsic nucleation mechanism of soil, thereby providing a new direction for the development of heavy metal remediation materials (mitigating the risk of soil salinization associated with excessive exogenous material introduction). Furthermore, the multi-mechanism coupling strategy offers novel insights and a theoretical foundation for developing materials to remediate complex heavy metal-contaminated sites.