Size fractionation of montmorillonite colloids through saturated porous media and their heterogeneous contribution to the transport of Pb2+

IF 5.3 2区 地球科学 Q2 CHEMISTRY, PHYSICAL
Lulu Lu , Xiaochen Peng , Zhiwei Chen , Kunyu Wen , Usman Farooq , Taotao Lu , Zhichong Qi , Weifeng Chen
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引用次数: 0

Abstract

The size fractionation of colloids is an important process while they migrate through porous media. To date, the information about the contribution of the size fractionation of clay colloids on heavy metal mobility during their co-transport process is limited. Herein, taking montmorillonite as a typical clay mineral, the size fractionation characteristics (> 2.0 μm, 1.2–2.0 μm, 0.45–1.2 μm, 0.1–0.45 μm, and < 0.1 μm) of colloidal montmorillonite particles after passing through saturated sand and their different contribution to Pb2+ transport were investigated. The results indicated that the extent of Pb2+-mobilizing ability of colloids at pH 7.0 was higher than that at pH 5.0, ascribed to more Pb2+ adsorbed to the colloids and greater mobility of colloids at higher pH values. Generally, the contribution of colloid size fractions on Pb2+ mobility followed the order of (> 2.0 μm) > (< 0.1 μm) > 0.45–1.2 μm > 0.1–0.45 μm ≈ 1.2–2.0 μm, which depended on the colloid size distribution in the effluents (i.e., the larger proportion of fractions exhibited greater contribution to the enhancement of Pb2+ mobility in this work). However, the relative contaminant-mobilizing abilities of different colloid size fractions (obtained by normalizing the fraction-facilitated Pb2+ breakthrough with the respective fraction breakthrough) increased with the decrease in colloid size, which stemmed from the relatively higher mobility and greater metal-binding capacities of smaller size fractions. Additionally, the differences in the relative contaminant-mobilizing abilities of different fractions decreased with decreasing sand grain sizes (20–40 mesh (0.425–0.85 mm), 40–60 mesh (0.25–0.425 mm), and 60–80 mesh (0.178–0.25 mm)), which was related to the different mobility of the colloid size fractions. In summary, these findings indicate that size fractionation of natural colloids plays a critical role in heavy metal mobility and retention in groundwater systems.
饱和多孔介质中蒙脱土胶体的粒径分异及其对Pb2+输运的非均质贡献
胶体在多孔介质中运移时,粒径分馏是一个重要的过程。迄今为止,关于粘土胶体在其共输运过程中对重金属迁移率的贡献的信息有限。本文以蒙脱土为典型粘土矿物,对其粒度分选特征(>;2.0μm, 1.2 - -2.0μm, 0.45 - -1.2μm, 0.1 - -0.45μm, & lt;研究了0.1 μm)的蒙脱土胶体颗粒通过饱和砂后对Pb2+迁移的不同贡献。结果表明,在pH 7.0时,胶体对Pb2+的动员能力明显高于pH 5.0时,这是由于pH值越高,胶体吸附的Pb2+越多,流动性越强。一般来说,胶体粒径分数对Pb2+迁移率的贡献顺序为(>;2.0 μm) >;(& lt;0.1 μm) >;0.45-1.2 μm >;0.1 ~ 0.45 μm≈1.2 ~ 2.0 μm,这取决于出水中胶体粒径的分布(即在本研究中,颗粒比例越大,对Pb2+迁移率的增强贡献越大)。然而,随着胶体粒径的减小,不同粒径组分的相对污染物动员能力(通过将组分促进的Pb2+突破与相应组分的突破正化而获得)增加,这是由于较小粒径组分具有相对较高的迁移率和更大的金属结合能力。此外,随着粒径的减小(20 ~ 40目(0.425 ~ 0.85 mm)、40 ~ 60目(0.25 ~ 0.425 mm)和60 ~ 80目(0.178 ~ 0.25 mm)),不同组分的相对污染物动员能力差异逐渐减小,这与胶体粒径组分的迁移率不同有关。综上所述,这些研究结果表明,天然胶体的粒径分异对地下水系统中重金属的迁移和滞留起着至关重要的作用。
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来源期刊
Applied Clay Science
Applied Clay Science 地学-矿物学
CiteScore
10.30
自引率
10.70%
发文量
289
审稿时长
39 days
期刊介绍: Applied Clay Science aims to be an international journal attracting high quality scientific papers on clays and clay minerals, including research papers, reviews, and technical notes. The journal covers typical subjects of Fundamental and Applied Clay Science such as: • Synthesis and purification • Structural, crystallographic and mineralogical properties of clays and clay minerals • Thermal properties of clays and clay minerals • Physico-chemical properties including i) surface and interface properties; ii) thermodynamic properties; iii) mechanical properties • Interaction with water, with polar and apolar molecules • Colloidal properties and rheology • Adsorption, Intercalation, Ionic exchange • Genesis and deposits of clay minerals • Geology and geochemistry of clays • Modification of clays and clay minerals properties by thermal and physical treatments • Modification by chemical treatments with organic and inorganic molecules(organoclays, pillared clays) • Modification by biological microorganisms. etc...
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