Magnesium Bentonite Research Articles

Rheological properties of magnesium bentonite and sepiolite suspensions after dynamic ageing at high temperatures

Abstract The rheological properties of three Na-activated, trioctahedral Mg-bentonites (hectorite clay from the CMS Source Clay Project repository, saponite clay from Spain and stevensite clay from Rhassoul, Morocco) and a sepiolite clay from Greece were examined after dynamic ageing at temperatures up to 230°C. The 5% w/v suspensions were prepared by dispersing the clay mineral samples in distilled water. The suspensions underwent dynamic, thermal ageing for 16 h before determination of the viscosity, filtration loss, filter cake thickness and pH and the concentration of dissolved Na+ and Mg2+. Thermal ageing contributed to the dispersion of clay particles, with a direct effect on plastic and apparent viscosity, introducing pseudoplastic behaviour. With the exception of the stevensite clay at 230°C that displayed limited dissolution at 230°C and partial conversion to kerolite, the clays were stable at high temperatures. The Na-activation of all clays except for stevensite was not adversely affected by thermal ageing. Thermal ageing of stevensite at 230°C facilitated Na exchange and yielded suspension with high viscosity and low filtrate loss. Only the suspensions of hectorite and those of stevensite aged at 230°C met with American Petroleum Institute specifications. The thermal behaviour and rheological properties of the clays might be interpreted according to the intrinsic properties of the clay minerals, such as layer charge and charge distribution.

Extraction of transportation grade fuels from waste LDPE packaging polymers using catalytic pyrolysis

The recovery of liquid fuel from waste polymers through pyrolysis is an intelligent approach to minimize environmental impact and reduce fossil fuel demand in the future. Pyrolysis is an effective method to extract pyrolysis oil (PO) from waste polymers. The addition of catalysts during the pyrolysis process further improves the molecule cracking rate, oil yield and reduce the processing duration. This study investigates, the effect of magnesium bentonite catalysts on pyrolysis of low-density polyethylene (LDPE) with different percentages such as 1, 2, 3, and 4 by weight and analyse the quality and yield percentage of extracted liquid. During the experimentation, the pyrolysis is performed under different catalyst levels at a constant temperature of 340˚C. From the result, it is noted that the pyrolysis process with 1% and 2% of catalysts increased PO extraction rate with better fuel properties. The pyrolysis process with 1% of catalysts resulted with 77.97% of PO, 14.23% of residue and 7.79% of gas with average fuel properties which has higher PO extraction rate compared to other catalyst concentrations. The pyrolysis process with 2% of catalysis has resulted 69.6 % of PO, 24.01% of residue and 6.12% of gas with better fuel properties than other catalysts percentages and possess similar properties of petroleum diesel. It has high cetane number, heating value and low viscosity of 51.6, 43.421 MJ kg−1 and 2.73 m2 s−1 respectively compared to other catalysts percentage.

Fabrication of magnesium bentonite hollow fibre ceramic membrane for oil-water separation

In this study, low-cost magnesium bentonite (MB) was used for the fabrication of bentonite hollow fibre (BHF) membrane with high pure water flux. MB powder was initially characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), particle size distribution (PSD) analyser, Brunnauer -Emmett- Teller (BET) method, and field emission scanning electron microscope (FESEM). The BHF membrane obtained was then fabricated through dope suspension mixing, phase inversion and sintering process. The dope suspension was prepared by mixing MB, dispersant, polymer binder, and solvent using a planetary ball mill. While the spinning process was carried out at the extrusion rate of 8 mL/min, a fluid bore rate of 10 mL/min and air gap of 5 cm, and this was followed by sintering operation at 950 °C, 1000 °C, 1050 °C, and 1100 °C. The resulting BHF membrane was characterized by scanning electron microscopy (SEM) and XRD; the porosity test, water flux and oil rejection were also examined. The SEM surface morphology of BHF at sintering temperature of 950 °C showed spongy-like and nested macrovoids structure; the porosity was 49.09% with a mean pore size of 3.9 µm. The performance test on the bentonite-based hollow fibre membrane showed that the membrane prepared at 20 wt% and sintering temperature of 1000 °C, which induced high and stable permeate water flux and oil rejection of BHFC membrane were 544 L/m2 h and 97%, respectively. The results have shown that the presence of magnesium in bentonite can enhance and promote the needed support material for the fabrication of hollow fibre ceramic membrane.

Influence of various bentonites on the mechanical properties and impermeability of cement mortars

The durability of cement mortar depends mainly on its impermeability properties. In this study, three different types of bentonite—sodium bentonite (Na-bent), calcium bentonite (Ca-bent), and magnesium bentonite (Mg-bent)—were added to a cement mortar at different proportions to investigate their effect on the mortar strength and impermeability. The results show that the three types of bentonite provide a significant improvement in the performance of cement mortar, and with increasing bentonite content, this effect is increasingly obvious. For samples with a bentonite content of 10 wt%, the improvement in compressive strength, flexural strength, and permeability with Na-bent can reach 77.5%, 54.5%, and 115.7%, respectively; the corresponding improvements with Ca-bent can reach 62.2%, 47.9%, and 101.9%, while those with Mg-bent can reach 71.6%, 52.2%, and 137.3%, respectively. The waterproofing performance of cement mortar containing Mg-bent is the best, with a maximum impermeability pressure 2.37 times that of the reference group, followed by Na-bent, and finally Ca-bent; however, the lowest impermeability pressure is also 2.02 times that of the reference group. In general, the addition of bentonite improved the strength and impermeability of the cement mortar and has potential application value for improving the durability of cement mortars.

The boron isotope geochemistry of smectites from sodium, magnesium and calcium bentonite deposits

The mineralogical, chemical and isotopic analyses of smectites, with variable interlayer cation occupancies, from bentonite deposits in various depositional environments, reveal new insights into the boron sources and the fluids involved in bentonitization in marine and non-marine environments.Smectites from bentonites have non-exchangeable, structural boron concentrations of 0.2 to 196 μg/g B. Smectites from sodium bentonites have higher boron concentrations (>30 μg/g) than those from magnesium or calcium bentonites. Most smectites have a small, interstratified illitic component that has a major influence on boron concentrations, requiring the use of modified fluid-mineral boron partitioning coefficients, which indicate that bentonites formed from fluids of highly variable boron concentrations of <0.1 mg/L B to >100 mg/L B, and a chlorine content of 76.4 mg/L to 59,076 mg/L. The sodium bentonites formed from boron-rich saline fluids or brines whereas the fluids involved in calcium and magnesium bentonite formation have a more variable boron composition and salinity.The δ11B values of the structural boron in tetrahedral sites of smectites range from −30.1‰ to +12.2‰. The smectites from terrestrial depositional settings have δ11B values of −30.1‰ to about 0‰, whereas smectites from marine depositional settings have negative as well as positive δ11B values. The boron isotope values indicate that all examined bentonites from terrestrial depositional settings as well as many bentonites from marine depositional settings formed from basinal fluids or brines.The boron isotope geochemistry of smectites is demonstrated to be a tool for elucidating the fluids involved in the formation of clay mineral deposits. It also has great potential for tracing fluids in other settings involving authigenic clay minerals such as sedimentary basins and surficial crystalline rocks, as well as man-made applications such as in disposal sites for highly active nuclear waste.

Competitive Adsorption of Xylene and Toluene on Modified and Unmodified Magnesium Exchanged Bentonite Clay Mineral

Cetyltrimethylammonium bromide (CTAB) – modified and unmodified magnesium exchanged bentonite were used for the competitive adsorption of m-xylene and toluene from their aqueous solution. Infrared spectroscopy (IR, adsorption capacity and Foster swelling measurements were performed using Fourier Transform Infrared Spectrophotometer to evaluate the performance of the adsorbents. The FT-IR results indicated that the quaternary ammonium salts (Cetyltrimethylammonium bromide) were intercalated between the layers of the bentonite clay. The Foster swelling test results indicated that the affinity of CTAB occurred in the treated clay as tested in all organic solvents (diesel, kerosene, gasoline, toluene and m-xylene), with and without agitation. The result showed that modified magnesium bentonite swelled more than the unmodified and the order of the swelling factor is; m- xylene > toluene > gasoline > diesel > DPK > water. However, when the assay was performed under agitation, it yielded higher swelling capacity and all the organic solvents used in this investigation showed good compatibility after organophilization. The modified clay exhibited very high capacity of adsorption compared to unmodified samples. The m-xylene and toluene uptake follows a pseudo second order kinetics mechanism, suggesting that the rate determining step of adsorption involves the two adsorbates competitively adsorbed on the adsorbent sites. Modified magnesium bentonite has a higher percentage removal and higher adsorption capacity than raw or unmodified magnesium bentonite. These adsorbents (modified magnesium bentonite) are therefore recommended for use by water treatment and petrochemical industries for removal of hydrocarbons (m- xylene and toluene) from their waste water and effluents.

Thermal behaviour of clays and clay-water mixtures for pelotherapy

To prepare peloids for thermotherapy, the thermal behaviour of their component clay pastes needs to be known. This study was designed to experimentally determine the specific heat capacity and cooling kinetics of pastes prepared by adding different proportions of water to eight commercially available clays of different composition. According to exponential equations fitted to the cooling curves for the pastes, a new parameter designated the relaxation time is proposed. Using this parameter, the clayey pastes could be classified on the basis of rate of heat release. According to its specific heat capacity and relaxation time, Na-activated magnesium bentonite emerged as the most suitable clay material to prepare peloids with applications in thermotherapy.

A study of tubes produced in plants infected with a strain of turnip yellow mosaic virus.

Abstract Electron microscopic examination of crude specimens made from plants infected with a necrotic strain of turnip yellow mosaic virus showed that infection led to the production of tubes as well as virus particles. These tubes, which usually appeared to occur in coaxial groups, were between 110 and 250 mμ wide and up to several microns long. With the aid of magnesium bentonite and differential centrifugation, almost pure preparations of the tubes could be made from the sap of infected plants. Such preparations contained mainly protein and were serologically related to the virus. Optical diffractometry and photographic integration techniques applied to electron micrographs of the tubes, revealed that they were made up of hexagonally packed, hexagonal rosettes, comparable in size to the hexamer morphological subunits of the virus. Strong evidence of a clockwise skew on the rosettes was obtained. The orientation of the hexagonal lattice was not the same on all tubes, but the variation was limited, the short axes of the hexagons comprising the lattice always lying within 15 degrees of the tube axis. Moreover, optical diffractometry of shadowed carbon replicas of the tubes revealed that in all but a small minority, the long-running rows of hexagons of the lattice formed right-handed helices. Cones, structurally related to the tubes, were occasionally found. There was no evidence that tubes were produced in plants infected with three other strains of turnip yellow mosaic virus, but a small number of tubes about 55 mμ in width were seen in specimens made from pumpkins infected with wild cucumber mosaic virus.

Differential adsorption of the two components of wild cucumber mosaic virus by bentonite

The adsorption of wild cucumber mosaic virus by magnesium bentonite showed a marked dependence on pH and magnesium ion concentration. At a concentration of Mg ++ of 5 × 10 −4 M, the adsorption of each component of the virus (0.5 mg/ml) by bentonite (5 mg/ml) changed from almost zero at pH 7.55 to 100% at pH 6.86. Under certain conditions of pH and Mg ++ concentration a differential existed in the adsorption of the two components of the virus. In our tests this differential was maximum at pH 7.15 and a Mg ++ concentration of 5 × 10 −4 M when 100% of the top component and only 15% of the bottom component was adsorbed. Under salt conditions which led to differential adsorption of the components, their electrophoretic mobilities were different. As the particles adsorbed onto bentonite could be approximately quantitatively eluted from the bentonite by means of Na 3EDTA, the differential adsorption suggests a convenient method of separating the two components. Tests carried out on turnip yellow mosaic virus gave no indication of a differential in adsorption between the two components of this virus.

The use of bentonite in the purification of plant viruses

Tests were made on the affinity of the major normal particulate components of sap and of a number of plant viruses for magnesium bentonite in solutions containing various concentrations of MgSO 4 and NaK phosphate buffer, pH 7.4. Ribosomes, 18 S protein, and the green material in sap were all readily absorbed by bentonite in solutions containing magnesium at a concentration of 10 −3 M or more. Several viruses, however, were not adsorbed under these conditions, so methods for purifying a number of them were developed using bentonite in combination with differential centrifugation. Viruses such as those of turnip yellow mosaic and carnation mottle were readily purified using bentonite in 5 × 10 −3 M magnesium, but others such as tobacco mosaic virus and wild cucumber mosaic virus were adsorbed under these conditions, and a magnesium concentration of 10 −3 M had to be used. In the purification of the bean form of tobacco mosaic virus it was necessary to use an even lower concentration of magnesium, but under these conditions the usefulness of the bentonite was reduced. All strains of one virus did not necessarily have the same affinity for bentonite and there was also an adsorption differential between the top and bottom components of wild cucumber mosaic virus. The main advantages of using bentonite in the purification of viruses are that time is saved in the operation and contamination of the product with ribonuclease is reduced or eliminated.