Impacts of presence of lead contamination in clayey soil–calcium bentonite cutoff wall backfills

Du, Yan-Jun; Fan, Ri-Dong; Reddy, Krishna R.; Liu, S.-Y.; Yang, Yu

doi:10.1016/j.clay.2015.02.006

Cited by 98 publications

(44 citation statements)

References 45 publications

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“…Recently, an empirical equation based on the framework of KC equation was used to predict the k of clean (uncontaminated) as well as leadcontaminated clayey SB backfills (Fan et al, 2014b;Du et al, 2015) and sandy SB backfills (Fan et al, 2014b). The KC equation is commonly used to estimate hydraulic conductivity and it is expressed by:…”

Section: Prediction Of Hydraulic Conductivitymentioning

confidence: 99%

“…Previous studies suggest that soil-bentonite mixtures and Na-bentonite, depending on the nature and concentration of the contaminants, may undergo a considerable increase in permeability when they are exposed to salts, heavy metals and organic solutions (Lo and Yang, 2001;Mishra et al, 2009;Yong et al, 2009;Fan et al, 2013;Du et al, 2015). Such a substantial change in hydraulic conductivity is attributed to the squeezing of diffuse double layer of hydrated bentonite (Mishra et al, 2009;Yong et al, 2009;Fan et al, 2013;Du et al, 2015). Recently, the use of polymerized Na-bentonite is also proposed to improve the chemical compatibility of soil-bentonite backfills (Bohnhoff and Shackelford, 2014).…”

Section: Introductionmentioning

confidence: 96%

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Workability, compressibility and hydraulic conductivity of zeolite-amended clayey soil/calcium-bentonite backfills for slurry-trench cutoff walls

Fan

Liu

et al. 2015

Engineering Geology

104

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Section: Prediction Of Hydraulic Conductivitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Workability, compressibility and hydraulic conductivity of zeolite-amended clayey soil/calcium-bentonite backfills for slurry-trench cutoff walls

Fan

Liu

et al. 2015

Engineering Geology

104

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“…In order to investigate the impact of Pb concentrations on hydraulic conductivity of conventional back lls SB, the MFP tests on SB specimens permeated with Pb(NO 3 ) 2 solution with 0 to 50 mM (0, 5,10,15,20,30,40, and 50 mM) were conducted, and the applied pressure was 100 kPa.…”

Section: Relationship Between Hydraulic Conductivities and Pbmentioning

confidence: 99%

Hydraulic Conductivity of Polymer‐Amended Sand‐Bentonite Backfills Permeated with Lead Nitrate Solutions

Shen

Wei

2018

Advances in Civil Engineering

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Hydraulic conductivity of sand-bentonite (SB) backfills amended with polyanionic cellulose (PAC) to lead nitrate (Pb(NO3)2) solutions was evaluated experimentally in this study. PAC-amended sand-bentonite (PSB) backfills were synthesized by mixing sand-bentonite mixture with 0.3 to 1.2% dry PAC (by total dry mixture mass) and mixed with a certain weight of conventional bentonite (CB) slurry. The rheology properties including the filtrate loss, viscosity, density, and pH testes of slurry with various bentonite dosages were measured to determine the reasonable CB dosage of slurry. The slump tests on PSB backfills with various mass slurries were conducted to determine the corresponding water content of backfills with slump 125 ± 5 mm. Under the applied pressure 100 kPa, the hydraulic conductivity to Pb(NO3)2 solutions (kc) of PSB backfills with various PAC contents was evaluated based on the modified filter press (MFP) tests, to ascertain the optimum PAC content of PSB backfills when permeated with Pb(NO3)2 solutions. Index properties, including the specific gravity (Gs) and liquid limit (wL) of PSB backfills, were measured after MFP tests. The MFP tests for PSB backfills were then conducted under various applied pressures to obtain the relationship between void ratio (e) and hydraulic conductivity of backfills. Finally, the flexible-wall permeability test (FWP test) under osmotic pressure 100 kPa was conducted to verify the effectiveness of the MFP test. The results indicate that slurry with 8% bentonite dosage is the reasonable choice in slurry wall construction. PSB has lower GS and higher wL compared to SB; increasing Pb concentration leads to GS of PSB increased and wL of PSB decreased. PSB with 0.6% PAC content is supposed as the optimum proportion of backfills when permeated with concentrated Pb(NO3)2 solution. PAC adsorbs large amount of bound water, which leads to higher water content (w) and e of PSB backfills, while lead ions (Pb) cause the diffuse double layer (DDL) of bentonite compressed and e of PSB backfills reduced. The kc of PSB-0.6 remains lower than 10−9 m/s and increases less than 10 times though the Pb concentration was up to 500 mM, demonstrating that the hydraulic performance of backfills can be improved effectively in Pb(NO3)2 solution by the additive PAC. The comparison results between k from MFP tests and FWP tests show that the MFP test is an effective and easy evaluation of hydraulic conductivity of backfills.

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“…For instance, chemical contaminants, such as lead ions, generally give negative effects on the soil's geotechnical properties. The liquid limit, specific surface area, pH and compression index of soil decreased as the increasing Pb concentration in the clayey soil used as cutoff wall backfills [14]. Besides, the hydraulic conductivity even exceeded the typical regulatory limit of 10 -9 m/s when the Pb concentration exceeded a threshold value of 120 mmol/L.…”

mentioning

confidence: 94%

Untitled

2018

Int J Earth Sci Geophys

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Nanoscale Zero Valent Iron (NZVI) is the most widely used engineering nanomaterials in the remediation of contaminated site. This study investigated the effect of NZVI treatment on the physicochemical properties of Lead (Pb)-contaminated soil to improve the understanding of the soil improvement. The changes of soil physicochemical properties were investigated using the concentration range of 0.2%, 1%, 5%, and 10% NZVI g/g dry soil. Results showed that the introduction of NZVI to the Pb-contaminated soil resulted in substantial changes in the surface physicochemical properties. The ferric and ferrous ions, and the lead ions were released at the same time from the corrosion of NZVI precipitation, and from the surface of soil particles, respectively, amongst which, part of exchangeable lead ions were reduced to Pb(I) and/or Pb 0. A general change in the soil's electrical conductivity, BET surface area, soil buffering capacity, and soil's particle size was confirmed. A conclusion was drawn that the mass transfer of NZVI and its induced precipitation of Fe/Pb ions made a great contribution to the changes of soil physicochemical properties. This study could make for the application of nanomaterials in remediation of contaminated sites, especially for the brownfield remediation and backfill usage after the contaminated soil was remediated.

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Impacts of presence of lead contamination in clayey soil–calcium bentonite cutoff wall backfills

Cited by 98 publications

References 45 publications

Workability, compressibility and hydraulic conductivity of zeolite-amended clayey soil/calcium-bentonite backfills for slurry-trench cutoff walls

Workability, compressibility and hydraulic conductivity of zeolite-amended clayey soil/calcium-bentonite backfills for slurry-trench cutoff walls

Hydraulic Conductivity of Polymer‐Amended Sand‐Bentonite Backfills Permeated with Lead Nitrate Solutions

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