Abstract:

The modified fibers exhibit excellent heavy metal adsorption capacity and mechanical strength, offering broad application potential in the remediation of contaminated soil. Jute was used as a fiber material, which was modified by pyromellitic dianhydride, polyaniline and hydrogen peroxide respectively. The study examined the solidification efficiency of modified jute fiber in conjunction with cement, utilizing indicators such as unconfined compressive strength, cation exchange capacity (CEC), electrical conductivity (EC), and pH value. Additionally, the toxicological evolution of this material was analyzed using the acetic acid buffer solution method. The results indicate that the optimal combination of modified jute fiber and cement co-solidification effectively enhances strength and mitigates toxicity release. The unconfined compressive strength of the co-solidified contaminated soil exceeds that of cement-only solidification by 76.78%. Furthermore, the leaching toxicity and its fluctuation under 10 freeze-thaw cycles are reduced by 64.73% and to one-third of the original level. The hydrolysis of jute produces alkaline cellulose, which effectively elevates the pH of cement-solidified contaminated soil. The modification of carboxyl acid functional groups promotes hydration reactions via neutralization, thereby enhancing the formation of calcium silicate hydrate (CSH). The introduction of jute, especially modified fibers, significantly improves the EC and CEC. Under the co-solidified function of fiber and cement, the increase of EC can reach 2.25 times that of cement-only solidification, which is the key to enhance the stability of adsorption. However, due to the influence of fiber agglomeration, particle polymerization, and electrostatic repulsion between metal ions, the strength and leaching toxicity of solidified contaminated soil are not positively correlated with fiber dosage and length. Among the three modification methods, the jute fiber modified with pyromellitic anhydride exhibits a robust adsorption and solidification effect, which is minimally influenced by fiber length and dosage. Furthermore, it demonstrates superior performance in terms of strength and toxicity control indicators. Considering both engineering applications and ecological development requirements, pyromellitic dianhydride-modified jute fiber (with a dosage of 0.9% and a fiber length of 18 mm) is more suitable for enhancing the effectiveness of cement in treating heavy metal-contaminated soil.

Key words: heavy metal contaminated soil, solidification/stabilizing, strength, toxicity, modified fibers, cement