Mechanisms of resilient iron-based nanomaterials resisting environmental disturbances in arsenic-contaminated soil remediation

Environmental fluctuations like alternating dry-wet (DW) and freeze-thaw (FT) events significantly affect the long-term stability of arsenic (As) immobilized by iron‑based materials in soils. However, achieving stable As immobilization under these fluctuating conditions remains a major challenge. Herein, we develop a resilient chrysotile-based Fe/Ti (TiFe-Chy) nanomaterial for As immobilization in soils under environmental fluctuations. Results show that FT cycling has a negligible effect on As immobilization by TiFe‑Chy, while DW alternation leads to a slight decline. Following 150 days of incubation, the long-term As immobilization rate of TiFe-Chy was higher than that of commercial layered double hydroxide under the DW and FT scenarios, respectively. Sequential extraction analysis indicates that TiFe‑Chy promotes the transformation of non-specifically and specifically adsorbed As into a more stable Fe oxide bound As fraction through complexation with its surface -OH groups, markedly reducing the risk of As re-release to groundwater. Notably, solid phase characterization confirms that the FT processes do not alter the chemical properties of the TiFe‑Chy. Moreover, the high crystallinity and structural stability of TiFe‑Chy effectively suppressed microbially mediated iron reductive dissolution under DW scenario, with a 98 % reduction compared to ferrihydrite, thereby enhancing its long-term As immobilization. These findings offer valuable insights into the design of resilient iron-based materials for sustainable heavy metal remediation in soils under environmental fluctuations.