Heavy metals containment by vertical cutoff walls backfilled with novel reactive magnesium-activated slag-bentonite-sand: Membrane and diffusion behavior

Fu, Xiaonan; Wu, Hejun; Zhang, Run; Jiang, Zhe-Yuan; Reddy, Krishna R.; Du, Yao

doi:10.1016/j.jclepro.2021.129623

Cited by 22 publications

(8 citation statements)

References 31 publications

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“…For example, the tortuosity factor of montmorillonite is the smallest (0.15–0.20), followed by those of kaolin and clay that are similar (0.24–0.50 and 0.28–0.46, respectively), silty clay (0.08~0.30), sandy soil (0.28), and sand, which is the largest (0.47–0.51). The tortuosity factor of sand–bentonite has the largest variation range (0.01–0.84) [ 56 , 57 , 58 , 59 , 60 ].…”

Section: Diffusion Of Pollutants Through Gm/gcl/almentioning

confidence: 99%

Review of the Anti-Pollution Performance of Triple-Layer GM/GCL/AL Composite Liners

Huang

Zhang

et al. 2022

Membranes

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Landfill leachates contain several types of pollutants and complex components, which pollute soils and groundwater. To compensate for the limitations of single-layer and double-layer liners, a triple-layer liner system composed of a geomembrane (GM), geosynthetic clay liner (GCL), and attenuation layer (AL) was invented and widely used in landfill anti-pollution systems. In this paper, the available literature on triple-layer GM/GCL/AL composite liners is summarized. First, the four main transport processes of pollutants through the composite liner, including convection, diffusion, adsorption, and degradation, were analyzed, and the anti-pollution performances were evaluated. According to this, the pollutant transport model considering the transport activity and transport state was classified, and the solution methods were summarized. Finally, the breakthrough time expressions of the composite liners were determined, which provided a base for evaluating their long-term performance and predicting the service life. The purpose of this literature review is to scientifically evaluate the anti-pollution performance of GM/GCL/AL and provide a scientific base and theoretical guidance for extending its application.

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Section: Diffusion Of Pollutants Through Gm/gcl/almentioning

confidence: 99%

Review of the Anti-Pollution Performance of Triple-Layer GM/GCL/AL Composite Liners

Huang

Zhang

et al. 2022

Membranes

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“…Recently, Wu et al [8,15,16], Fu et al [17], and Ni [18] developed an MSBS backfill with the merits of lower hydraulic conductivity, superior chemical compatibility, and greater environmental friendliness compared to the conventional backfills consisting of sand and cement, sand and cement-activated slag regardless of bentonite inclusion. The MSBS backfill consisted of reactive MgO, GGBS, conventional bentonite, and sand.…”

Section: Introductionmentioning

confidence: 99%

Engineering Properties of Novel Vertical Cutoff Wall Backfills Composed of Alkali-Activated Slag, Polymer-Amended Bentonite and Sand

Jiang

Shi

et al. 2023

Polymers

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The workability, hydraulic conductivity, and mechanical properties are essential to contaminant containment performance of cementitious backfills in vertical cutoff walls at contaminated sites. This study aims to investigate the engineering properties of a novel vertical cutoff wall backfill composed of reactive magnesia (MgO)-activated ground granulated blast furnace slag (GGBS), sodium-activated calcium bentonite amended with polyacrylamide cellulose (PAC), and clean sand (referred to as MSBS-PAC). Backfills composed of MgO-activated GGBS, sodium-activated calcium bentonite, and clean sand (referred to as MSBS) were also tested for comparison purposes. A series of tests were conducted which included slump test, flexible-wall hydraulic conductivity test, and unconfined compression test. The pore size distributions of two types of backfills were investigated via the nuclear magnetic resonance (NMR) technique. The results showed the moisture content corresponding to the target slump height was higher for MSBS-PAC backfill than that for MSBS backfill. The MSBS-PAC backfill possessed lower pH, dry density, and higher void ratio at different standard curing times as compared to MSBS backfill. The unconfined compressive strength and strain at failure of the MSBS-PAC backfill were noticeable lower than those of the MSBS backfill. In contrast, the hydraulic conductivity of MSBS-PAC backfill was approximately one order of magnitude lower than that of the MSBS backfill, which was less than 10−9 m/s after 28-day and 90-day curing. Lower hydraulic conductivity of MSBS-PAC backfill was attributed to the improvement of pore structure and pore fluid environment by PAC amendment.

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“…Yu [ 24 ] confirmed that the permeability of the material is reduced because the tiny cavity structure of PMB causes many obstacles when the liquid flows through the matrix. There are also many researchers who believe that clay materials exhibit semi-permeable membrane behavior, referring to the ability of clay to restrict the migration of dissolved chemicals or solutes [ 25 , 26 , 27 ]. The impermeability mechanism of PMB is very complex, and almost no researchers have explored the process of permeability from the perspective of material osmotic pressure.…”

Section: Introductionmentioning

confidence: 99%

Study on Preparation of Polymer-Modified Bentonite and Sand Mixtures Based on Osmotic Pressure Principle

Zhang

et al. 2022

Materials

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Polymer-modified bentonite and sand mixtures (PMBS) are widely used in the engineering field due to their low cost and low permeability. In this study, different ionic types of polyacrylamides were used to modify bentonite to improve its swelling properties and impermeability. The physicochemical properties of polymer-modified bentonite were characterized by X-ray diffraction, particle size distribution, IR spectroscopy, SEM, and free swell index (FSI) to further demonstrate the successful organic modification of bentonite. To investigate the impermeability mechanism of PMBS from the perspective of osmotic pressure, the colloidal osmotic pressure of bentonite and hydraulic conductivity were compared. The results showed that anionic polyacrylamide (APAM) had the most obvious improvement on the swelling properties of bentonite, and 3% APAM increased the FSI of bentonite from 15 mL/2 g to 41 mL/2 g. With the increase in polymer dosage, the colloidal osmotic pressure of bentonite increased and the hydraulic conductivity of PMBS decreased significantly. The interior of PMBS is equivalent to a highly concentrated bentonite–sand–water system. When the colloidal osmotic pressure in the restricted space is higher than the external hydraulic pressure, it will prevent infiltration from occurring. When the external hydraulic pressure exceeds the high concentration of bentonite colloid osmotic pressure, the hydraulic conductivity may increase rapidly. Therefore, the impermeability of PMBS depends on the colloidal osmotic pressure of bentonite. Finally, it was confirmed that PMBS had a self-healing capacity by simulating damage to PMBS.

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Heavy metals containment by vertical cutoff walls backfilled with novel reactive magnesium-activated slag-bentonite-sand: Membrane and diffusion behavior

Cited by 22 publications

References 31 publications

Review of the Anti-Pollution Performance of Triple-Layer GM/GCL/AL Composite Liners

Review of the Anti-Pollution Performance of Triple-Layer GM/GCL/AL Composite Liners

Engineering Properties of Novel Vertical Cutoff Wall Backfills Composed of Alkali-Activated Slag, Polymer-Amended Bentonite and Sand

Study on Preparation of Polymer-Modified Bentonite and Sand Mixtures Based on Osmotic Pressure Principle

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