The Stabilization Efficiency and Microbial Ecological Impact of Ferrihydrite-Modified Montmorillonite on Tungsten-Contaminated Soil

Tungsten (W), a transition element, is widely used across industries such as metallurgy, electronics, and military, but its mining and smelting have led to significant environmental concerns due to its accumulation in soil. This study aimed to develop an effective and environmentally friendly method to remediate W-contaminated soil using ferrihydrite-modified montmorillonite, a composite material with enhanced adsorption capacity. The main objectives were to assess the impact of iron loading on the material properties and adsorption efficiency, evaluate its stabilizing effects on W in soil, and examine its influence on the soil microbial community. The results demonstrated that the introduction of ferrihydrite significantly increased the surface area and porosity of montmorillonite, improving its capacity to adsorb W. W extracted by EDTA from the treated soil decreased by 53.13-89.88%, indicating that modified montmorillonite facilitated the transformation of exchangeable W into more stable forms, such as Fe/Mn fractions. The soil pH and organic content increased post-treatment, and the microbial community diversity was restored, with a more stable structure observed. Adsorption experiments confirmed that W adsorption followed the Langmuir and pseudo-second-order models, with Fe-OH groups playing a key role in the process. The modification did not induce redox changes in W, suggesting minimal ecological disruption. This study concluded that ferrihydrite-modified montmorillonite is a promising approach for W-contaminated soil remediation, offering high stabilization efficiency and low ecological risk, making it a sustainable solution for addressing heavy metal pollution.