改性黄麻纤维协同水泥固化重金属铅污染土的强度及毒理性分析

Strength and toxicological analysis of heavy metal lead contaminated soil solidified by modified jute fiber and cement

改性纤维兼具良好的吸附能力和机械强度,在污染土治理方面具有广泛的应用前景。优选黄麻作为纤维材料,分别采用均苯四甲酸二酐、聚苯胺和双氧水进行改性,结合无侧限抗压强度、土体阳离子交换量(cation exchange capacity,CEC)、电导率(electrical conductivity,EC)、pH值等指标探究改性黄麻纤维协同水泥的固化效能,并借助醋酸缓冲溶液法分析其毒理性演变规律。结果表明,适宜的改性黄麻纤维协同水泥固化铅污染土可同步实现强度提升和毒性释放的控制,协同固化污染土较单一水泥固化污染土,无侧限抗压强度提高了76.78%,浸出毒性量降低了64.73%,且10次冻融循环作用下浸出毒性的波动缩小至1/3。黄麻纤维水解所生成碱性纤维素会引起水泥固化污染土pH的增大,羧基类酸性官能团的改性有助于借助中和作用进一步促进水化反应,增强水化硅酸钙(calcium silicate hydrate,CSH)凝胶的生成。黄麻特别是改性纤维的引入对于EC和CEC的增益显著,纤维水泥协同固化作用下EC提高量可达单一水泥固化提高量的2.25倍,是增强吸附固化稳定性的关键。但由于纤维团聚、微粒间聚合及金属离子间静电斥力的影响,固化污染土强度和浸出毒性与纤维掺量及纤维长度并非呈正相关关系,3种改性方式中酸酐改性黄麻纤维吸附固化效果受纤维长度和掺量影响较小,且在强度和毒性控制指标方面均表现良好,统筹考虑工程应用和生态发展需求,纤维掺量0.9%+纤维长度18 mm的酸酐改性黄麻纤维适合用于协同水泥进行重金属污染土的固化处置。

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.