Calcium bentonite and sodium bentonite as stabilizers for roads unbound

ABSTRACTA backfill placed between a nuclear waste canister and the host geology of a nuclear waste repository can impede the migration of water through the waste package and retard the movement of radionuclides into the geologic formation. Hydraulic conductivities and swelling pressures are being determined as functions of the density of the compacted backfill, temperature, radiation dose, hydraulic head and the chemical composition of the permeating fluid. Bentonite clays and bentonite/sand mixtures have received initial emphasis. Sodium bentonite and calcium bentonite samples compacted to a dry density of 2.1 g/cm3 had hydraulic conductivities in the range of 10−12 to 10−13 cm/s. In addition, batch distribution ratios (Rd) for Sr, Cs, Am, Np, I, U and Tc have been measured for a number of candidatebackfill materials. Both initial permeability and sorption studies have used a synthetic basaltic ground water.

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Calcium bentonite vs sodium bentonite: The potential of calcium bentonite for soil foundation

Materials Today Proceedings ◽

10.1016/j.matpr.2021.02.386 ◽

2021 ◽

Cited By ~ 1

Author(s):

Nurmunira Muhammad ◽

Sumi Siddiqua

Keyword(s):

Sodium Bentonite ◽

Soil Foundation ◽

Calcium Bentonite

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Influence of Rehydration and Activation on Cation Exchange Capacity and Swelling Index of Foundry Sodium Bentonite from Different Deposits.

MRS Advances ◽

10.1557/adv.2020.224 ◽

2020 ◽

Vol 5 (26) ◽

pp. 1397-1404

Author(s):

Farai Chrispen Banganayi ◽

Didier Kasongo Nyembwe

Keyword(s):

Cation Exchange ◽

Sodium Carbonate ◽

Cation Exchange Capacity ◽

Exchange Capacity ◽

Sodium Bentonite ◽

Commercial Grade ◽

Iron Castings ◽

Calcium Bentonite ◽

Made In

ABSTRACTBentonite is the most widely used foundry binder. Most of the iron castings are made in greensand systems which make use of bentonite as a binder. The bentonite used in greensand moulding is usually activated with sodium carbonate to achieve desirable properties. Activation of bentonite is known to improve mould related properties like giving a high wet tensile strength and improving the durability. The practice of activation is more common with calcium bentonite. A number of bentonite deposits tend to remain unbeneficiated due to their low cation exchange capacity (CEC) which are regarded as low quality commercial grade. The primary characteristic that shows the increased activation is the swelling index of the bentonite. This study investigated the influence of rehydration and activation in improving the quality of low commercial grade sodium bentonite. The bentonite samples were activated with sodium carbonate. Rehydration and activation was seen to improve the CEC and swelling index. The increase in CEC and swelling index was however not consistent with the gains in sodium.

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Adsorbents for the Sequestration of the Pimelea Toxin, Simplexin

Proceedings ◽

10.3390/proceedings2019036090 ◽

2020 ◽

Vol 36 (1) ◽

pp. 90

Author(s):

Gordon ◽

Hungerford ◽

Laycock ◽

Ouwerkerk ◽

Fletcher

Keyword(s):

Rumen Fluid ◽

Screening Method ◽

Binding Activity ◽

Rapid Screening ◽

Sodium Bentonite ◽

Arid Rangelands ◽

Future Work ◽

Calcium Bentonite ◽

Binding Mechanisms

Pimelea poisoning affects cattle grazing arid rangelands of Australia, has no known remedy and significant outbreaks can cost the industry $50 million per annum. Poisoning is attributable to consumption of native Pimelea plants containing the toxin simplexin. Charcoal, bentonite and other adsorbents are currently used by the livestock industry to mitigate the effects of mycotoxins. The efficacy of such adsorbents to mitigate Pimelea poisoning warrants investigation. Through a series of in vitro experiments, different adsorbents were evaluated for their effectiveness to bind simplexin using a simple single concentration, dispersive adsorbent rapid screening method. Initial experiments were conducted in a rumen fluid based medium, with increasing quantities of each adsorbent: sodium bentonite (Trufeed®, Sibelco Australia), biochar (Nutralick®Australia) and Elitox® (Impextraco, Belgium). Data showed the unbound concentration of simplexin decreased with increasing quantities of each adsorbent tested. Sodium bentonite performed best, removing ~95% simplexin at 12 mg/mL. A second experiment using a single amount of adsorbent included two additional adsorbents: calcium bentonite (Bentonite Resources, Australia) and a synthetic adsorbent (Waters, USA). The concentration of simplexin remaining in the solution after 1 h, the amount able to be desorbed off the adsorbent-toxin matrix with replacement fresh fluid, and the amount remaining bound to the adsorbent were measured. All samples containing an adsorbent were statistically different compared to the blank (p < 0.05), indicating some binding activity. Future work will explore the binding mechanisms and behaviour of the toxin-adsorbent complex in the lower gastrointestinal tract.

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Preparation and characterization of purified Na-activated bentonite from Karak (Pakistan) for pharmaceutical use

Clay Minerals ◽

10.1180/claymin.2013.048.4.03 ◽

2013 ◽

Vol 48 (4) ◽

pp. 595-603 ◽

Cited By ~ 12

Author(s):

L. A. Shah ◽

N. S. Khattak ◽

M. G. S. Valenzuela ◽

A. Manan ◽

F. R. Valenzuela Díaz

Keyword(s):

Elemental Content ◽

X Ray Diffraction ◽

Sodium Bentonite ◽

E Coli ◽

Trace Elemental ◽

Activated Bentonite ◽

Sedimentation Volume ◽

Swelling Volume ◽

Calcium Bentonite

AbstractThe purpose of this paper was to prepare purified Na- bentonite with improved properties for use in the pharmaceutical industry. Calcium bentonite from the Shagia region of Karak district, Pakistan, was activated with various proportions of sodium carbonate (2, 3, 5 and 8 wt.%) and purified by sedimentation to remove impurities, especially quartz. X-ray diffraction (XRD), and swelling volume confirmed the conversion of raw bentonite to sodium bentonite by using 5% Na2CO3. The sodium bentonite (K5) obtained by activation met the chemical and microbiological requirements set by the pharmacopeias regarding the toxic trace elemental content (Pb and As), absence of E. coli, total aerobic microbial contents and physicochemical properties such as swelling volume, pH and sedimentation volume. Therefore K5 bentonite could be designated as potentially suitable for pharmaceutical applications. The CEC, surface area, porosity, pH, gel formation and swelling volume indicated that K5 bentonite could be used in the formulation of oral suspension and in topical application.

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Numerical Simulation of Alteration of Sodium Bentonite by Diffusion of Ionic Groundwater Components

MRS Proceedings ◽

10.1557/proc-112-415 ◽

1987 ◽

Vol 112 ◽

Cited By ~ 1

Author(s):

J. S. Jacobsen ◽

C. L. Carnahan

Keyword(s):

Numerical Simulation ◽

Ion Exchange ◽

Nuclear Waste ◽

Chemical Properties ◽

Sodium Bentonite ◽

Compacted Bentonite ◽

Transport Code ◽

Complexation Reactions ◽

Aqueous Complexation ◽

Calcium Bentonite

AbstractBecause of its ability to retard the movement of radionuclides, sodium bentonite is being considered as a packing and backfilling material in a number of nuclear waste isolation programs. Few studies, however, have considered how the chemical properties of the bentonite backfill will vary with distance from the canister and change in time as groundwater constituents diffuse through the bentonite. Of particular importance is the conversion of sodium bentonite to calcium bentonite by ion exchange, which will in turn affect the migration of cationic radionuclides, such as Cs+ and Sr2+, leaking from a waste canister.Experiments measuring the movement of trace amounts of radionuclides through compacted bentonite have typically used unaltered bentonite. Models based on experiments such as these may not lead to accurate predictions of the migration through altered or partially altered bentonite of radionuclides that undergo ion exchange. To address this problem, we have modified an existing transport code to include ion exchange and aqueous complexation reactions. The code is thus able to simulate the diffusion of major ionic groundwater components through bentonite and reactions between the bentonite and groundwater. Numerical simulations have been made to investigate the conversion of sodium bentonite to calcium bentonite for a reference groundwater characteristic of deep granitic formations.

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Competitive adsorption of organic solvents using modified and unmodified calcium bentonite clay mineral

10.31221/osf.io/w9dj6 ◽

2019 ◽

Author(s):

Chem Int

Keyword(s):

Adsorption Isotherm ◽

Adsorption Capacity ◽

Organic Solvents ◽

Competitive Adsorption ◽

Correlation Factor ◽

Isotherm Model ◽

Isotherm Models ◽

High Concentration ◽

Dual Purpose ◽

Calcium Bentonite

Dodecyltrimethylammonium bromide (DTAB)–modified and unmodified calcium bentonite were both used for the competitive adsorption of aromatics (xylene, ethylbenzene and toluene) and petroleum products (gasoline, dual purpose kerosene and diesel) from their aqueous solution. Infrared spectroscopy (IR) and expansion tests (adsorption capacity and Foster swelling) measurement were performed in order to evaluate the performance of the adsorbents. The Foster swelling index and adsorption capacity of the DTAB modified calcium bentonite in the organic solvents follow the trend: xylene > ethylbenzene > toluene > gasoline > dual purpose kerosene (DPK) > diesel > water. However, the adsorption capacity of the adsorbent in diesel outweighed the adsorption capacity in DPK at high concentration of DTAB indicating that diesel has higher affinity for high DTAB concentration than DPK. The percentage removal of the solvent is directly proportional to the concentration of DTAB used in modifying the bentonite as well as the contact time between the adsorbent and the solvent, hence modified calcium bentonite adsorbed a higher percentage of organic solvents than the unmodified calcium bentonite. The adsorption characteristics of both adsorbents improved remarkably after proper agitation of the organic solvents, the unmodified calcium bentonite however adsorbed more water than the modified bentonite. Data obtained from adsorption isotherm models confirms that Freundlich adsorption isotherm model was favored more than Langmuir adsorption isotherm model with the correlation factor (R2) of the former tending more towards unity. The adsorption of ethylbenzene using DTAB modified and unmodified calcium bentonites follow a pseudo second order kinetics mechanism, suggesting that the rate determining step of adsorption involves both the adsorbent and the organic solvent.

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