Toxic dyes must be removed from waste water coming from the textile and paint industries. Adsorption is one possible method of removing dyes under ‘soft’ conditions, without the generation of secondary hazardous materials. The present study used the carbonate-containing layered double hydroxides (LDH), Mg-Al and Mg-Zn-Al (with a M2+/M3+ ratio of 3), as adsorbents to remove two industrial colorants, Astrazon Remazol Brilliant Blue and Direct Red, present in low concentrations in aqueous solutions. The physicochemical properties of adsorbents at the surfaces of LDH, as well as the properties of the solutions containing the dyes control how the colorants are removed. Both fresh and calcined LDH were effective in the removal experiments, with effectiveness ranging from 50 to 100%. Analysis of kinetic data demonstrated that the adsorption process fitted the pseudo-second-order model better than the pseudo-first order model, information which is useful for system design in the treatment of wastes from the textile industry. Parameters such as pH of solutions and concentration of dye in solution influenced mainly the initial adsorption rate.

Intercalation of montmorillonites with a mixture of intercalates has not been studied extensively. The objective of the present investigation was to study the effects of phosphonium-based intercalate mixtures on the properties (organic loading and basal spacing) of montmorillonite. These phosphonium-intercalated montmorillonites are promising candidates as high-temperature stable nanofillers for application in clay polymer nanocomposites.

Two salts with different cationic heads and chain lengths were mixed in varying molar ratios and the mixtures were intercalated into the interlayer space of montmorillonite. Two sets were chosen based on the chain length and the cationic head-group structure of the two intercalated salts (referred to hereafter as set 1 and set 2). The resultant intercalated montmorillonite was characterized by thermogravimetric analysis, X-ray diffraction, and transmission electron microscopy. The organic loading of the intercalated montmorillonite increased with the proportion of longer carbon-chain intercalate in the mixture. The intensity of the characteristic XRD peak of each intercalate varied with the mole fraction percent of that intercalate in the solution mixture. No marked synergistic effect of the intercalate mixture on the basal spacing and organic loading properties of the intercalated montmorillonite was observed — the proportional influence of individual components was found to be more prominent.

Seven sedimentary bentonite deposits were investigated in the Miocene series of the Pannonian Basin. The following stratigraphic and genetic characteristics were significant: (1) all deposits were formed within a transgressive series of a given Miocene sequence; and (2) it is possible that the source material of the bentonites is rhyolitic, confirmed by radiometric data proving simultaneous rhyolite tuff volcanism.

A detailed investigation on three lithologically different bentonite horizons within the same transgressive series was made at Sajoábaábony to determine the source material and to determine the causes of the differences. X-ray diffraction, differential thermal analysis and geochemical data of the different lithological types show that they all have rhyolitic source material, although in the case of the lowermost horizon the existence of reworked material from an underlying andesite tuff series is also presumed. The main difference is the degree of weathering. Considering the ratio between the amorphous phase and the montmorillonite, the amorphous volcanic glass can be regarded as the main source of the montmorillonite formation. The differences in the degree of alteration can be related to the changing characteristics of the tuff accumulation and the sedimentation. Transgression decreases the sedimentation rate allowing the optimal alteration of the amorphous phase. The increasing intensity of the tuff accumulation can also limit the bentonite formation because rapid deposition and burial present too little time for the optimal alteration of the amorphous phase.

Summarizing the results from the stratigraphic interpretation of the bentonite deposits and from the comparative analyses of the different bentonite horizons within the same transgressive systems tract, we can state that the relationship of the tectonic-related tuff accumulation and the eustasy-related sedimentation rate can affect both the possibility of bentonite formation in macro-scale and the degree of bentonitization in micro-scale.

Ecologic building materials such as adobe bricks have become of greater economic importance in recent years. In the present work, the addition of selected materials to improve the compressive and bending strengths of adobe bricks was tested. The raw material (loam UD) was analyzed for its mineralogical and chemical composition. The loam studied consisted of quartz, feldspar, and the clay minerals chlorite, vermiculite, illite, and kaolinite. Prerequisites for using this loam for brick making were its grain-size distribution and the absence of expandable clay minerals.

To optimize the compressive and bending strengths of the adobe bricks, seven natural and ‘eco-friendly’ synthetic additives were admixed with the raw material and homogenized.

From this material, small adobe bricks and bars were made. One series of bricks and bars was made without additives but instead was coated with a hydrophobic impregnation cream. The bricks were stored for up to 20 days at 100 and 75% relative humidity (RH). After 1, 5, and 20 days, the compressive and bending strengths were measured to identify the critical humidity level for brick strength. The compressive and bending strengths of loam UD at dry conditions without additives showed values of 9 N/mm2 and 4.8 N/mm2, respectively. With some of the additives, the strength improved by up to 30%. The greatest increases in strength were achieved by mixing the loam with Acronal S650. Finely ground trass and diatomite also increased the dry strength. After storage at high levels of RH, these mixtures lost >50% strength. In contrast, the loam mixed with blast-furnace slag has a small initial strength but showed the smallest decreases in strength after exposure to high levels of RH.

The Hercynian metamorphic event is poorly characterized in internal zone complexes of the Betic Cordillera (Spain), as it has been, to a great extent, overprinted by the mineral assemblages formed during the Alpine event. Identification of the signals of the Hercynian episode is easier in series largely unaffected by the Alpine event, such as Intermediate units between the Maláguide and the Alpujárride Complexes, which consist of a set of thrust slices. With the aim of characterizing the Hercynian paragenesis, a detailed comparison of the mineral assemblages of Paleozoic and overlying Triassic sequences, unaffected by the pre-Alpine event, was carried out. Mineral assemblages were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, electron microprobe, and transmission-analytical electron microscopy. A rapid increase in the illite crystallinity values was observed at the Triassic—Paleozoic transition in the upper tectonic slices. In addition, the diagenetic to anchizonal dickite-, sudoite-, and pyrophyllite-bearing assemblages, characterizing the Triassic rocks, contrast with Paleozoic assemblages consisting of white K-mica ± paragonite + chlorite + mica-chlorite and chlorite-vermiculite mixed layers + garnet, suggesting that this assemblage corresponds to the Hercynian metamorphic event. This assemblage records temperatures on the order of 400ºC and an intermediate pressure regime. Paleozoic rocks contain, in addition, tobelite, which comprises some of the detrital grains and strongly masks the illite crystallinity values. Tobelite has been identified only in the upper thrust slices, suggesting that changes in the detrital input is primarily responsible for the disappearance of tobelite at the transition from the Maláguide to the Alpujárride domain. Tobelite appears finely intergrown with white K-mica and its origin is uncertain. It could have been inherited as tobelite, but a more likely hypothesis is that the intergrowths of white K-mica and tobelite were formed at low temperature from an NH4-bearing mica precursor.

A series of experiments was set up, the purpose of which was to determine factors affecting long-term settling characteristics of some suspensions of clay-sized materials. Suspensions of approximately 8 g per 1. were prepared using Georgia kaolin, Mississippi bentonite, Wyoming bentonite, Iowa illite and finely ground quartz. In addition, 2 g and 16 g per 1. suspensions of kaolinite were prepared. All suspensions were observed for 2-week periods at constant temperatures of 19°C; kaolinite suspensions were also observed at 2°, 10°, 25° and 31°C.

After settling 3–4 days at 19°C, layering formed in all clay suspensions, and all the tops of the layers contained higher concentrations of suspensoid than bottoms. Tops and bottoms of the layers were parallel to liquid top surfaces.

At 2°C, no stratification developed in kaolinite suspensions. At 10°C, layering formed only in 2 g per 1. suspensions after 3 months of settling. At higher temperatures, layering formed after 3–4 days of undisturbed settling. Two grams per liter kaolinite suspensions formed five distinct layers; 8 g per 1., nine layers; and 16 g per 1. suspensions formed a many-layered, banded structure after approximately 2 weeks.

If layered suspensions were cooled, the layers were not disturbed. However, layering was very responsive to heating: they expanded and tilted downward away from the heat source. With prolonged heating, layering disappeared.

These experiments show that temperature and concentration markedly affect long-term settling characteristics of fine-grained suspensions. Layering forms most readily in water with relatively low viscosity and density. If such layered suspensions were formed in nature, such features as graded bedding, lamination, or varving probably would result after complete settling.

Clay mineral associations in saprolite of two andesites from the Cascade Range of northeastern California were determined. Sesquioxidic allophane with a high CEC delta value dominates the clay fraction of the least weathered saprolite in each series (47% and 37% in hypersthene andesite and olivine andesite saprolites, respectively). With further weathering, the content of amorphous clay remains high (over 30% in all cases) but the CEC delta value of the clay drops markedly. The amorphous material in the more weathered saprolite has the properties of halloysitic allophane. Halloysite, present in all saprolites, is highest in concentration (over 30%) in the more strongly weathered members of each of the saprolite series. Formation of sesquioxidic allophane during early stages of weathering and its transformation to halloysitic allophane and halloysite during later stages of weathering are supported by X-ray diffraction, electron microscopic, DTA, elemental analysis, and CEC delta value data.

The efficient separation of hexane isomers from the light naphtha fraction is a significant challenge in the petrochemical industry. 5A zeolite adsorbent is used commercially to sieve alkane isomers. In this study, 5A zeolites were synthesized using a low-cost natural clay mineral precursor, i.e. palygorskite (PAL), with the addition of crystallization directing agent (CDA). By varying the mass ratio of CDA/deionized water, 5A zeolites were obtained as CDA-5%, CDA-7.5%, and CDA-10%. All products were submicron particles with an average particle size of 400–800 nm. A sieving test of CDA-induced 5A zeolites was carried out on hexane adsorbates including n-hexane (nHEX), 2-methylpentane (2MP), and 3-methylpentane (3MP). According to vapor-phase batch adsorption experiments, a significant equilibrium amount (0.149 g/g) of nHEX and only 0.0321 g/g 2MP and 0.0416 g/g 3MP were adsorbed on the 5A zeolite product with CDA-5%. The dynamic adsorption performance of 5A zeolite (CDA-5%) was evaluated by breakthrough curves of binary mixtures of nHEX/2MP and nHEX/3MP. Palygorskite 5A (PAL 5A) zeolite achieved maximum dynamic adsorption capacities of nHEX (0.16 g/g in both cases) at 200°C and 1.2 MPa total pressure. This work provided an economic alternative for the synthesis of 5A zeolites using natural clay minerals instead of chemical raw materials.

The removal of pesticide contaminants from water is a key priority in environmental remediation, and requires intensive effort; this necessitates modification of the properties of pillared clays (PILCs) such as porosity, pore-volume, surface area, and synthesis methods. The purpose of the present study was to test the ability of Al-pillared bentonite (Al-PILB), using [Al13O4(OH)24(H2O)12]7+ and [Al30O8(OH)56(H2O)24]18+ (keggin cations, Al13 and Al30) as pillars, to adsorb chlorinated pesticides from contaminated water. In order to maximize intercalation and uniformity of layer stacking, various ratios of the nitrate forms of the synthesized keggin cations were intercalated into the natural bentonite (BT). The synthesized materials (Al-PILBs) were characterized by various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Fourier-transform infrared (FTIR) spectroscopy, UV-Vis spectroscopy, and N2 adsorption-desorption measurements. Increases in basal spacing, surface area, and pore volume were observed. The adsorption capacity of the Al-PILBs for 17 types of chlorinated pesticides from contaminated water was better than using the BT alone, e.g. for heptachlor epoxide, dieldrin, and endrin at natural pH, the maximum adsorptions obtained at equilibrium solution concentrations of 16, 20, and 20 μg/L, respectively, were 59.2, 59.15, and 60 μg/g, whereas corresponding values using pristine BT were 34.68, 39.45, and 38.9, respectively. The data were best described by the Freundlich adsorption model.

Several procedures for hydrothermal synthesis of saponite can be found in the literature. They differ in terms of the preparation conditions of the precursor and of the synthesis temperature. The objective of the present study was to investigate how these two parameters influence the structure of the final synthesis product. The precursor was prepared from Mg(NO3)2, Al(NO3)3, and Na4SiO4 in three different ways: as a gel, a dried gel, and a calcined gel. The influence of the synthesis temperature on the structure of saponite was investigated in the range 90–200°C. The results showed that the use of a calcined precursor yielded a single mineral phase, saponite, with up to 90% aluminum in tetrahedral configuration. In comparison, the use of a gel precursor resulted in a product with only 60% aluminum in the tetrahedral configuration. The synthesis temperature had no significant effect on the saponite structure. The reported synthesis method showed the possibility of obtaining saponite with superior characteristics, in terms of crystallinity, surface acidity, and thermal stability compared to the natural mineral, even at 90°C, and thus with greater potential for industrial application.

Ludox HS SiO2 sols at high concentrations show a peak in small angle x-ray scattering (SAXS) reminiscent to a “structure.” The appearance of such a peak was found to depend crucially on the thickness of the sample cell used for SAXS measurements. The thinner the cell used, the more prominent the peak. When the thickness was larger than 2 mm, it was no longer observable. When sols were treated with activated charcoal powders (in order to remove a surfactant) the peak became less prominent.

For the cases where clear features for structure were absent (thick sample regime), the Smoluchowski scheme was utilized to study the nature of sols. Namely, the distribution of the Smoluchowski species were estimated by numerically calculating the size distribution of particles directly from SAXS data. The distribution was found basically bimodal, and the main distribution peak, particularly for dilute sols (less than 5 wt%), was consistent with primary particles of SiO2. The second distribution peak was strongly dependent on the concentration of SiO2 particles. The observed trend was that the higher the concentration of SiO2 particles, the more prominent the second distribution peak and the locus of the maximum tended to move toward a smaller value in diameter. This behavior of the second distribution peak of the Smoluchowski species is no doubt a manifestation of the interparticle correlation. The observation of such behavior may provide a convenient means to characterize sols with interparticle correlation. This method was also applied for characterizing gels formed when the pH values were altered.

Thin clay films prepared from aqueous suspensions of the potassium or sodium salt of picloram (4-amino-3,5,6-trichloropicolinic acid) with Al-, Fe-, or Cu-saturated montmorillonite or with montmorillonite coated with hydrous oxides of Al, Fe, or Cu were examined in an air-dry condition by infrared (IR) techniques to elucidate possible modes of interaction between picloram and the mineral surfaces. Deuteration was used to confirm band assignments of picloram and its salts prior to interaction with montmorillonite. Picloram interactions with Al- and Fe-saturated montmorillonite and with montmorillonite coated with hydrous oxides of Al and Fe were concentration dependent. At high picloram concentrations similarities with the IR spectrum of potassium picloram indicated that much of the picloram was present in the salt form. As the concentration of picloram was reduced below that equivalent to 1 meq/g clay, the IR spectrum indicated the presence of the monomeric acid on the mineral surface. The spectrum of picloram on montmorillonite with a coating of copper hydrous oxide was similar to that of a Cu-picloram complex indicating coordination type bonding. The spectrum of picloram with Cu-saturated montmorillonite did not correspond to any of the other spectra of picloram examined. The interaction of picloram with montmorillonite coated with a hydrous oxide coating of Cu and with Cu-saturated montmorillonite were independent of picloram concentration in the range 2.20-0.44 meq/g clay.

The Porters Creek Formation is mined as an absorbent clay in Illinois, Mississippi, Missouri, and Tennessee. The absorptive properties of the Porters Creek Formation are due to the high content of smectite which constitutes >50% of the minerals present. Analyses of 220 samples of the Porters Creek collected in Illinois, Missouri, and Tennessee indicate that the smectite content is highest on the western side of the Mississippi embayment and that the kaolinite content is highest on the northeastern side. The major influx of detritral clays appears to have entered the embayment from a large river on the northeast side. A major control of the distribution of clay minerals during the time of Porters Creek deposition was differential flocculation of kaolinite, illite, and smectite, as evidenced by the numerous syneresis cracks on bedding planes in the area of greatest kaolinite content. Estimates of the smectite, illite, and kaolinite contents suggest both horizontal and vertical variations among these clay minerals. In certain localities the oxidation of pyrite has created acid conditions, which apparently were conducive to the formation of authigenic halloysite.

Dry, homoionic systems of two montmorillonites and a kaolinite were treated with NH3 and then evacuated exhaustively to eliminate any physically adsorbed ammonia. It was concluded that the NH3 retained by the minerals was associated with the exchangeable cations. The mechanism of this adsorption process is the same as that which leads to the formation of inorganic ammines, namely, the mutual attraction between unshared electrons in the NH3 molecules and ionic centers of positive charge. This sorption process is reversible at elevated temperatures and is described by the equation, nNH3 + CX ⇄ (nNH3 · C)X, where n is the number of NH3 molecules associated with each exchangeable cation, C, on exchange complex X. Accordingly, n is a coordination number and has the following values for the cations indicated: NH4, 0; K, 0; H, 1; Ca, 2; Mg, 2; Alin, 3; Alex, 6. Here in and ex refer to interior and exterior exchange sites respectively. The retention of NH3 by cations which saturate the exchange complex of clays was shown to be analogous to the formation of ammoniates by reaction of NH3 with inorganic salts.

A reduced retention of NH3 by the Mg and Al 1:1 systems was ascribed to the possibility that exchangeable Mg and Al on kaolinite occur as hydroxy complexes.

A significant amount of NH3 was adsorbed to the weak acid hydroxyl groups on the broken clay edges, Relative to exchange capacities this phenomenon was greater in magnitude on the 1:1 than on the 2:1 clays.

Energies of NH3 adsorption on CaCl2, Ca-bentonite and NH4-bentonite were determined. Values of △H as a function of temperature were shown to be different for the Ca and NH4-clay systems. The data indicated stronger energies of retention of NH3 by the Ca-clay than for the NH4 clay. The thermodynamic data thus support the mechanisms proposed here.

K-saturated kaolinite was titrated in 13 different solvents with tetrabutylammonium hydroxide using a combination electrode for potentiometric determination. The titer of base required to reach the final potentiometric endpoint was dependent on the solvent and increased according to the following solvent order in both the presence and absence of excess neutral salt: methanol ⩽ water < ethanol ⩽ 1-propanol < 1-butanol < 2-propanol < DMF < t-butanol < DMSO < pyridine ⩽ acetonitrile ⩽ methylethyl ketone < acetone. With the protic solvents, titratable acidity increased according to decreasing dielectric constant of the solvent and increasing size and/or branching of the aliphatic constituent. The largest titratable acidities were obtained in the dipolar aprotic solvents with negligible basic character (e.g., acetonitrile, acetone, methylethyl ketone). These results are discussed in terms of solvent properties, solvation characteristics of ions in the solvents, and acid-base behavior of crystalline edge sites.

Low albite and maximum microcline were the two feldspars identified in Coal Measures mudrocks. Standard feldspars were then used to spike a mudrock base to construct standard working curves based on X-ray powder diffraction peak areas. Boehmite was added as an internal standard and also to correct for orientation effects. The samples were ignited at 950°C before the addition of the internal standard. This is advantageous for several reasons, but a disadvantage is that albite was found to undergo partial conversion to K-feldspar. The conversion was not total and the original albite content could be determined. This method is an extension of an existing method for quartz and therefore feldspars and quartz can be determined simultaneously.

Sulfonated carbon is a green, solid acid catalyst but its surface area, separation, and recovery after utilization need to be improved. The objective of the present study was to provide an environmentally friendly and economical method to prepare magnetic sulfonated carbon composite catalyst with a large surface area using palygorskite (Plg) as the support. A magnetic sulfonated carbon/Fe3O4/Plg composite catalyst was prepared via simultaneous calcination and sulfonation of the mixture of source, p-toluenesulfonic acid (TsOH), and Fe3O4/Plg. Fe3O4 nanoparticles and Plg nanorods were encased by a carbon layer derived from sucrose and TsOH. The composite catalyst exhibited good magnetic properties and high catalytic performance for the esterification of oleic acid with methanol. Oleic acid conversion reached 88.69% after the first catalytic cycle. Plg nanorods replaced sucrose and increased the catalyst’s surface area. The introduction of Fe3O4 nanoparticles improved further the acid content and oleic-acid conversion and achieved 70.31% after five cycles. The catalyst was recycled easily using an external magnetic field and its magnetic property remained unchanged due to the protection of the carbon layer.