Predicting the properties of bentonite-sand mixtures

Mollins, L. H.; Stewart, Douglas I.; Cousens, T. W.

doi:10.1180/claymin.1996.031.2.10

Cited by 138 publications

(69 citation statements)

References 14 publications

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“…Sand-bentonite mixtures have been used in the construction of landfill liners (Mollins et al, 1996). Bentonite is composed mainly of montmorillonite clay mineral.…”

Section: Introductionmentioning

confidence: 99%

Sand–Attapulgite Clay Mixtures as a Landfill Liner

et al. 2006

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Absrtract. This paper investigates the potential use of sand-attapulgite (palygorskite) mixtures as a landfill liner. The sand and attapulgite clay used in this study were brought from Wahiba (eastern Oman) and Al-Shuwamiyah (southern Oman), respectively. Initially the basic properties of the sand and clay were determined. Then the attapulgite clay was added to the sand at 5, 10, 20 and 30% by dry weight of the sand. The sand-attapulgite clay mixtures were subjected to mineralogical, chemical, microfabric and geotechnical analyses. The X-ray diffraction (XRD) qualitative analysis showed that attapulgite is the major clay mineral. The chemical compounds, exchangeable cations and cation exchange capacity (CEC) for the samples were determined. The CEC for the sand-clay mixtures is low but increases with the increase in clay content. The scanning electron microscope (SEM) examination showed that the addition of clay developed coating between and around the sand grains which results in filling the voids and reducing the hydraulic conductivity of the sand-clay mixtures. The hydraulic conductivity values for the pure clay and sand + 30% clay mixture prepared at 2% above optimum water content are slightly higher than hydraulic conductivity requirements for landfill liners but can be acceptable. The geotechnical study which included grain size distribution, Atterberg limits, specific gravity, compaction, hydraulic conductivity and shear strength tests showed that the sand+30% clay mixture prepared at 2% above optimum water content can be considered to satisfy the requirements for landfill liners. For all sand-clay mixtures no swelling was recorded and the addition of clay to the sand improved the shear strength.

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“…Sand-bentonite mixtures have been used in the construction of landfill liners (Mollins et al, 1996). Bentonite is composed mainly of montmorillonite clay mineral.…”

Section: Introductionmentioning

confidence: 99%

Sand–Attapulgite Clay Mixtures as a Landfill Liner

et al. 2006

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“…Fan et al [9] concluded that sand-bentonite mixes with low bentonite contents may possess a relatively looser structure and in turn a greater k value as compared to the mixes when the bentonite content is higher. According to Mollins et al [26], very low bentonite content in the sand-bentonite mixes can result in uneven bentonite distribution within the mixture, which can lead to higher hydraulic conductivity than would be estimated for a uniform mix which may also lead to high swelling and shrinkage. Thus, the 5% soilbentonite mix may be disregarded in case of sand and coal ash.…”

Section: Hydraulic Conductivitymentioning

confidence: 99%

Hydraulic conductivity and compressibility characteristics of bentonite enriched soils as a barrier material for landfills

Sobti

Singh

2017

Innov. Infrastruct. Solut.

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An experimental program was undertaken for the index and engineering properties (compaction, hydraulic conductivity and consolidation) of various mix proportions of sand, silt and coal ash with bentonite as an admixture to act as a barrier material for landfills. Thirtyfour mixes were tested in all with different categories of mixes comprising of bentonite-sand, bentonite-sand-coal ash, bentonite-coal ash, bentonite-silt and bentonite-siltcoal ash mixes with bentonite content varying from 0 to 40% and coal ash from 0 to 90%. A series of hydraulic and mechanical tests were conducted to assess the Atterberg's limits, hydraulic conductivity, compressibility characteristics, etc. of the mixes. The influence of bentonite and coal ash content, effective consolidation pressure and void ratio on the hydraulic conductivity and consolidation indices (compression index, swell index, coefficient of consolidation) was studied. The hydraulic conductivities of the sandbentonite mixtures decreased from 1.75 9 10 -5 to 3.34 9 10 -11 m/s, when the bentonite content increased from 0 to 40%. An optimum amount of admixture viz. bentonite to be added to the base materials i.e. sand, silt and coal ash to obtain different category of mixes was ascertained. Disregarding the 5% soil-bentonite mix in case of sand and coal ash, an optimum mix of 10% sand-bentonite, 10% coal ash bentonite and a range of 5-10% for silt-bentonite is recommended for use as a barrier material considering the present study. The addition of coal ash to bentonite had a favourable effect on the properties of the mix in terms of hydraulic conductivity, to act as a barrier material.

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“…Bentonite is suitable to isolate nuclear wastes and groundwater because of its low hydraulic conductivity, high swelling property, good self-sealing capacities, and so forth [1], Bentonite is also used as buffer material or back�ll material according to its function and location in the nuclear waste disposal �eld [2].…”

Section: Introductionmentioning

confidence: 99%

Sorption of Uranium(VI) and Thorium(IV) by Jordanian Bentonite

Khalili

Salameh

Shaybe

2012

Journal of Chemistry

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Puri�cation of raw bentonite was done to remove quartz. is includes mixing the raw bentonite with water and then centrifuge it at �50 rpm; this process is repeated until white puri�ed bentonite is obtained. �RD, �RF, FTIR, and SEM techniques will be used for the characterization of puri�ed bentonite. e sorption behavior of puri�ed Jordanian bentonite towards UO 2 2+and  4+ metal ions in aqueous solutions was studied by batch experiment as a function of pH, contact time, temperature, and column techniques at 25.0 ∘ C and pH = 3. e highest rate of metal ions uptake was observed aer 18 h of shaking, and the uptake has increased with increasing pH and reached a maximum at pH = 3. Bentonite has shown high metal ion uptake capacity toward uranium(VI) than thorium(IV). Sorption data were evaluated according to the pseudo-second-order reaction kinetic. Sorption isotherms were studied at temperatures 25.0 ∘ C, 35.0 ∘ C, and 45.0 ∘ C. e Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) sorption models equations were applied and the proper constants were derived. It was found that the sorption process is enthalpy driven for uranium(VI) and thorium(IV). Recovery of uranium(VI) and thorium(IV) ions aer sorption was carried out by treatment of the loaded bentonite with different concentrations of HNO 3 1.0 M, 0.5 M, 0.1 M, and 0.01 M. e best percent recovery for uranium(VI) and thorium(IV) was obtained when 1.0 M HNO 3 was used.

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Predicting the properties of bentonite-sand mixtures

Cited by 138 publications

References 14 publications

Sand–Attapulgite Clay Mixtures as a Landfill Liner

Sand–Attapulgite Clay Mixtures as a Landfill Liner

Hydraulic conductivity and compressibility characteristics of bentonite enriched soils as a barrier material for landfills

Sorption of Uranium(VI) and Thorium(IV) by Jordanian Bentonite

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