矿物胶体对纳米零价铁固定土壤中铀和铅的影响机理研究

STUDY ON THE INFLUENCE MECHANISM OF MINERAL COLLOIDS ON THE IMMOBILIZATION OF URANIUM AND LEAD IN CONTAMINATED SOIL TREATED BY NZVI

付雪

11930316

硕士

材料工程

易树平

2021-05-14

2021-06-04

南方科技大学

深圳

纳米零价铁（nano zero-valent iron, nZVI）是一种有效的土壤和地下水重金属污染物修复剂，已成为环境修复领域当前的研究热点之一。但在进行原位化学修复时，矿物胶体作为土壤环境介质中广泛存在的活跃组分之一，可能会成为地下环境中污染物的吸附剂或迁移载体，也可能会对纳米颗粒的稳定性产生影响，进而影响到对污染物的修复效果。基于以上背景，本研究针对高岭石胶体和氢氧化铝胶体对nZVI固定土壤中铀和铅的影响机制问题，采用TCLP(toxicity characteristic leaching procedure)毒性浸出实验和逐级提取实验，利用扫描电镜（SEM）和X射线衍射（XRD）对nZVI固定前后土壤样品进行表征，研究了反应时间、矿物胶体种类、矿物胶体投加量、土壤污染类型以及污染浓度等条件对nZVI固定铀和铅的影响及机理。主要取得如下结论：（1）时间对nZVI固定土壤中铀和铅存在一定的影响，随着时间延长，nZVI对铀和铅的固定效果逐步提高，证明铀和铅等重金属污染物在土壤中的沉积、结合、迁移、转化等环境行为是动态的过程;（2）nZVI固定铀的主要机理为还原沉淀作用，nZVI固定铅的主要机理为吸附和还原双重作用；（3）经过nZVI固定后，铀和铅均以较稳定的结合态存在于土壤中。铀的形态分布以铁锰氧化物结合态为主，铅的形态分布主要为铁锰氧化物结合态和残余态；（4）在低污染浓度下，随着矿物胶体的增加，对土壤中铀和铅的固定率整体呈现了先增加后趋于稳定的趋势，高岭石胶体和氢氧化铝胶体主要通过表面吸附作用来提高对铀和铅的固定效果；（5）土壤样品在固定前后的XRD图谱显示nZVI与铀和铅反应后的腐蚀产物主要为α-FeOOH。研究结果一方面可以为铀和铅污染土壤的修复提供科学依据，另一方面也为研究矿物胶体对纳米颗粒原位修复土壤的潜在影响提供了思路。

Nano zero valent iron (nZVI) is an effective remediation agent for heavy metal pollutants in soil and groundwater. It has become one of the current research hot issues in the environmental remediation field. However, mineral colloid, as one of the widely existing active components in soil environmental medium, may become adsorbent or transport carrier of pollutants in underground environment, and may also affect the stability of nanoparticles. Therefore, it may affect the in-situ remediation effect of pollutants. Based on the above background, this study aimed at the influence mechanism of kaolinite colloid and aluminum hydroxide colloid on the immobilization of U and Pb in contaminated soil treated by nZVI. The effects of reaction time, mineral colloid type, mineral colloid dosage, soil pollution type and pollution concentration on the immobilization of U and Pb treated by nZVI were studied by toxicity characteristic leaching procedure and sequential extraction procedure. And besides, the soil samples before and after immobilization were characterized by scanning electron microscope and X-ray diffraction. The main conclusions are as follows：(1)Time has an effect on the immobilization of U and Pb in contaminated soil treated by nZVI. With the extension of time, the immobilization effect of nZVI on U and Pb is gradually improved, which proves that the environmental behavior of the deposition, combination, migration and transformation of heavy metal pollutants in soil is a dynamic process.(2)The main mechanism of nZVI immobilization of U is reduction precipitation, and the main mechanism of nZVI immobilization of Pb is adsorption and reduction.(3)Both U and Pb exist in the soil in a relatively stable bound state after being immobilized. The speciation distribution of U is mainly iron-manganese oxide bound, while that of Pb is mainly iron-manganese oxide bound and residual. (4)With the increase of mineral colloid, the immobilization effect of nZVI on U and Pb first increases and then tends to be stable. Kaolinite colloid and aluminum hydroxide colloid mainly improve the immobilization effect on target pollutants through surface adsorption and maintaining alkaline environment. (5)The XRD patterns of soil samples before and after immobilization show that the main corrosion product of nZVI after reaction with U and Pb is α-FeOOH. On the one hand, the research results can provide a scientific basis for the remediation of U and Pb contaminated soil, on the other hand, it can also provide ideas for the study of the potential effect of mineral colloids on the in situ remediation of soil by nanoparticles.

纳米零价铁 矿物胶体 影响机理 铀 铅

nZVI mineral colloids influence mechanism uranium lead

中文

独立培养

南方科技大学

付雪. 矿物胶体对纳米零价铁固定土壤中铀和铅的影响机理研究[D]. 深圳. 南方科技大学,2021.