Reflectance spectroscopy is a rapid and non-destructive method that can be used to detect organic compounds in geologic samples over a wide range of spatial scales that includes outcrops, hand samples, drill cores, and planetary surfaces. In order to assess the viability of this technique for quantification of organics and aliphatic compounds in particular, the present study examines how clay mineralogy, water content, and albedo influence the strength of organic absorptions in near-infrared (NIR) reflectance spectra. The effects of clay structure and water content are evaluated using kaolinite, smectite (montmorillonite), and a mixed-layer illite-smectite as starting materials. Absorption strengths for C—H absorptions are compared to known total organic carbon (TOC) values using both reflectance spectra and single scattering albedo (SSA) spectra derived from a Hapke radiative transfer model. A linear relationship was observed between band depth and TOC for each sample suite, but strong albedo variation led to non-unique trends when band depths were calculated from reflectance spectra. These effects were minimized by conversion to SSA, for which band depth-TOC trends were similar for all mixture suites regardless of albedo or hydration level, indicating that this approach may be more broadly applicable for clay and organic-bearing samples. Extrapolation of band depth-TOC trends for the synthetic mixtures suggested a very conservative lower limit of detection of <1 wt.% TOC, but preliminary results for natural organic-bearing shales indicated that detection limits may be an order of magnitude lower.

Among the volumes of Adam drawings at Sir John Soane’s Museum in London, number 53 is unique. Whereas its companion volumes were pieced together after Robert Adam (1728–92) and James Adam (1732–94) had died, number 53 was compiled while the Adam office was in business. Comprising record drawings of frieze designs from numerous commissions undertaken by the Adam brothers throughout their career, the volume is the work of a single hand and was produced as a cohesive project. However, despite the extent of Adam scholarship and the unusual nature of the volume, number 53 has received almost no attention. Its date, authorship and purpose are here the subject of detailed observation for the first time.

The adsorptive behavior of clinoptilolite (Cpt) zeolite in its raw and nickel-exchanged form towards m-xylene/p-xylene/ethylbenzene unary, binary, and ternary mixtures was investigated. The motivation behind the research was to elucidate whether Cpt in its raw or ion-exchanged form could exhibit distinctive selective adsorption behavior. The natural Cpt (Si/Al atomic ratio = 4.59) was ion-exchanged twice with 0.5 M Ni(NO3)2 solution at 80°C for 6 h. Adsorption experiments were done at 40°C, using a 4 vol.% solution of the aromatic materials in iso-octane. The maximum amount of the total specific adsorption capacity for binary solute systems was ~0.8 and ~2.0 mmol g–1 for the raw and ion-exchanged Cpt, respectively. For the ternary solute systems, unexpectedly, this capacity increased to ~2.0 and ~3.0 mmol g–1, respectively. For binary mixtures, both forms of Cpt were selective for p-xylene. For ternary mixtures, both forms exhibited a clear selectivity for m-xylene but the Ni-exchanged Cpt was significantly higher over the concentration range studied. The unexpected increase in the adsorption capacity in ternary systems was attributed to the expulsion of tightly bound trace water molecules hindering the access of xylene molecules to the 10-member ring channels of the zeolite framework. Substitution of Mg2+ by Ni2+ in the 10-member ring channels enhanced the adsorption capacity by providing more space and stronger electrostatic interactions between the new cation and the polar m-xylene molecule.

Oxidation-reduction processes within natural systems greatly influence the properties of sediments, soils and clays. The objective of this experimental study was to gather new evidence for the effects of changes in redox conditions (reduction and reoxidation) on structural properties of ferruginous smectite and to understand better the mechanisms involved. The <2 µm fraction of a ferruginous smectite (sample SWa-1), which contains 17.3 wt.% of total structural Fe, was studied by infrared (IR) spectroscopy. The pure Na-saturated clay was reduced by Na dithionite for 10 to 240 min to obtain various Fe(II):(total Fe) ratios ranging from 0 to 1.0. Selected reduced samples were then reoxidized completely by bubbling O2 gas through the suspensions for up to 12 h. Infrared spectra of the initially unaltered, reduced and reduced-reoxidized samples were collected. Reduction generated changes in the three studied spectral regions (O-H stretching, M-O-H deformation, and Si-O stretching), indicating that major modifications occurred within the clay crystal beyond merely a change in Fe oxidation state. partial dehydroxylation and redistribution of Fe, and perhaps Al, cations occurred upon reduction of SWa-1, changing the structural properties of its tetrahedral and octahedral sheets. Water molecules, probably generated by dehydroxylation within the octahedral sheet upon reduction, were tightly bound to the clay surface and were possibly trapped within the clay structure. Except for dehydroxylation and the Fe oxidation state, all these modifications were largely irreversible. The tightly bound water was not completely removed upon reoxidation and the cationic rearrangements generated during reduction were not reversed: either they were preserved as in the reduced state or cations were redistributed into a different configuration from the unreduced clay.

Illite age analysis (IAA) is a classical method for extracting diagenetic and detrital ages from mixed ages measured by K-Ar. This approach is based on measuring the masses of diagenetic and detrital illitic components in a few different grain-size fractions of one rock sample and measuring the mixed ages of these fractions. The 1Md illitic polytype is usually considered to be diagenetic, while 2M1 is considered detrital. A plot of the function: exp(λt)−1 (where t is time and λ is the decay constant) vs. weight percent of the detrital fraction is constructed. On the basis of linear extrapolation to end-member fractions, the diagenetic and the detrital age is obtained. This approach does not take into account various K contents in different polytypes (%Kdetrital and %Kdiagenetic). In order to do that, the detrital mass fraction (wt.%detrital) should be recalculated into the percentage of detrital K (%Id(K)):

Analytical constraint of the K content of different polytypes is very difficult, so a new approach to this problem has been developed. In the present study, the plot of 40Ar*/40K vs. %Id(K) for a precisely determined ratio of 40Kdetrital/40Kdiagenetic was observed to be linear. On the basis of this observation, a computer program, MODELAGE, was written in the Java programming language using as input a few measured detrital illite mass fractions along with the mixed K-Ar ages of the relevant grain fractions. It then calculates the end-member ages and the 40Kdetrital/40Kdiagenetic ratio using genetic algorithms.

The errors in diagenetic and detrital illite mass-fraction determination mean that the 40Kdetrital/40Kdiagenetic ratio and the end-member ages can be evaluated only with some uncertainty. The best results are obtained if the measured mass fractions represent a relatively broad range. Constraining one of the unknowns (particularly the 40Kdetrital/40Kdiagenetic ratio) improves the results significantly.

Evaluation of data obtained from the literature using the proposed approach leads to the conclusion that the 40Kdetrital/40Kdiagenetic ratio is often >1.00, and some of 1Md illite polytype materials may be of detrital origin. If this is not the case, if a broad range of mass fractions is covered, and if the differences between end-member ages are relatively small, IAA analysis still gives appropriate results, even if the true 40Kdetrital/40Kdiagenetic ratio is different from 1.00.

Several micas containing different octahedral and interlayer cations were synthesized at different temperatures under conventional- and microwave-hydrothermal conditions and these phases were characterized by powder X-ray diffraction, solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy, scanning electron microscopy and Fourier transform infrared spectroscopy. A Zn K-mica with Zn in the octahedral sheets and K in the interlayers was synthesized in the temperature range 150–200°C and a novel Zn Rb-mica with Zn in the octahedral sheets and Rb in the interlayers was synthesized at 200°C. The synthesis of either Mg, Co or Ni K-micas, however, was found to be difficult or impossible at these low temperatures. Solid-state 29Si MAS-NMR revealed that the Al in the tetrahedral sites is disordered with several nearest-neighbor Si environments. In general, microwave-assisted hydrothermal conditions led to better crystallization of the Zn K-micas compared with the conventional method.

Garnierites represent significant Ni ore minerals in the many Ni-laterite deposits worldwide. The occurrence of a variety of garnierite minerals with variable Ni content poses questions about the conditions of their formation. From an aqueous-solution equilibrium thermodynamic point of view, the present study examines the conditions that favor the precipitation of a particular garnierite phase and the mechanism of Ni-enrichment, and gives an explanation to the temporal and spatial succession of different garnierite minerals in Ni-laterite deposits. The chemical and structural characterization of garnierite minerals from many nickel laterite deposits around the world show that this group of minerals is formed essentially by an intimate intermixing of three Mg-Ni phyllosilicate solid solutions: serpentine-népouite, kerolite-pimelite, and sepiolite-falcondoite, without or with very small amounts of Al in their composition. The present study deals with garnierites which are essentially Al-free. The published experimental dissolution constants for Mg end-members of the above solid solutions and the calculated constants for pure Ni end-members were used to calculate Lippmann diagrams for the three solid solutions, on the assumption that they are ideal. With the help of these diagrams, congruent dissolution of Ni-poor primary minerals, followed by equilibrium precipitation of Ni-rich secondary phyllosilicates, is proposed as an efficient mechanism for Ni supergene enrichment in the laterite profile. The stability fields of the solid solutions were constructed using [log aSiO2(aq), log ((aMg2+ aNi2+)/(aH+)2)] (predominance) diagrams. These, combined with Lippmann diagrams, give an almost complete chemical characterization of the solution and the precipitating phase(s) in equilibrium. The temporal and spatial succession of hydrous Mg- Ni phyllosilicates encountered in Ni-laterite deposits is explained by the small mobility of silica and the increase in its activity.

Electrical measurements are used in various fields of geoscience and technology, e.g. gas/oil exploration or landslide-barrier monitoring. Although clays are amongst the most conducting geomaterials their electrical properties are not yet fully understood. For example, in a recent high-level-radioactive-waste repository large-scale test, a bentonite barrier was monitored geoelectrically. To facilitate interpretation of the results, the reasons for the observed differences in the electrical conductivity must be understood (e.g. changes in water content, temperature, salinity of pore water, etc.). To improve understanding of the electrical properties of clay minerals, in situ measurements must be combined with laboratory measurements. In situ measurements allow the characterization of the material in its natural state and laboratory measurements, for small sample amounts, allow the user to vary relevant parameters systematically such as water content, temperature, the salinity of the pore water, or even the cation population if swelling clay minerals are present. In situ measurements using different electrode distances, from m to cm range, proved that small-scale investigations are essential because of small-scale material heterogeneities. In the laboratory, all the relevant parameters mentioned above can be controlled more easily for small sample amounts. In the present study three different small-scale devices (SSM1–SSM3) were compared. The geometry factor, K, was determined both by calculation and by a calibration against solutions of different conductivity. Calculated and measured geometry factors were in good agreement. SSM1 and SSM2 — both with four pin-shaped electrodes — were found to be particularly applicable for in situ measurements. SSM2, with point contacts at the tips of the pins, was considered to be an improvement over SSM1 because the effects of both water content and temperature gradients (which are particularly relevant near the surface) were less pronounced using SSM2. SSM3, in which the contacts are placed at the bottom of a 4.5 mL trough, proved to be useful when systematically varying all of the parameters influencing the electrical properties in the laboratory.

Aflatoxins in contaminated corn do not degrade in corn fermentation solution (CFS) during biofuel production; rather, they are enriched in the co-product, dried distillers grain. Aflatoxin B1 (AfB1) is the most toxic form of all aflatoxins. Removing AfB1 from CFS is desirable to minimize its toxicity to animals. Smectites can adsorb AfB1 from aqueous solutions and, therefore, inactivate the toxin, but proteins in CFS inhibit the adsorption of AfB1 by smectites. The current study aimed to minimize the interference by CFS in adsorption of AfB1 on smectite by modifying a calcium-smectite (Ca-3MS) with a small nutritive organic compound, e.g. carnitine, choline, arginine, histidine, or tryptophan. The organo-smectites were characterized by X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy, and adsorption of AfB1 in CFS by these composites was examined. Various degrees of intercalation of the organic nutrients into the smectites were observed with XRD and FTIR. After immersing the smectite and organo-smectites in the CFS, the d001 values of Ca-3MS expanded to ~1.82 nm due to protein interaction, but the organo-smectites were confined to ~1.39 nm, which indicated that the protein had limited access to the organo-smectite interlayers. The IR bands at ~1652, 1544, 1538, and 1454 cm–1 from the organo-smectites revealed, however, that complete protein inhibition was not achieved. The organo-smectites were capable of adsorbing AfB1 in simple aqueous solution with maximal adsorption capacity up to 0.55 mol kg–1. Significantly greater (p ≤ 0.05) AfB1 adsorption was achieved by choline- and carnitine-modified smectites compared with the original Ca-3MS in the presence of competing protein (pepsin) in simple aqueous solution. In real CFS, both AfB1 adsorption capacities (Qmax) and affinities (K) by all organo-smectites were greater (Qmax = up to 0.45 mol kg–1 and K = up to 0.165 μM–1) than those by Ca-3MS (Qmax = 0.22 mol kg–1 and K = 0.031 μM–1). The study suggested that using smectites modified with an organic nutritive compound could be an effective, economical, and safe strategy for removing mycotoxins, including aflatoxins, during biofuel production.

Two reference halloysites from New Zealand (Te Puke and Opotiki) were studied by X-ray diffraction under (1) various levels of relative humidity (RH) from 95 to 0% (dehydration), and (2) various temperatures increasing from 25 to 120°C (dehydration). They were also studied by differential thermal and thermogravimetric analyses at 40 and 0.2% RH. The impact of freeze drying along with the influence of cation saturation (Ca and K) on halloysite hydration were studied. The dehydration of the two halloysite samples upon decrease in RH started below 70% RH. However, the dehydration of Opotiki was still incomplete at ∼0% RH regardless of the saturation cation whereas Te Puke was completely dehydrated at ∼10% RH. For each sample, the decrease in RH and the increase in temperature induce similar dehydration behavior, but the dehydration processes of the Opotiki and Te Puke samples are different. The dehydration of Te Puke proceeds with one intermediate hydration state reacting as a separate phase due to the presence of ‘hole’ water molecules. The dehydration of the fully hydrated Opotiki halloysite gives a dehydrated phase and no 8.6 Å phase. The results suggest the presence of different types of water molecule, the ‘associated’ and the ‘hole’ water, controlling the dehydration behavior of halloysites. Freeze-dried halloysite samples are essentially dehydrated and the size of their coherent scattering domains is strongly reduced. Rehydration experiments performed after dehydration either at 95% RH or by immersing the sample in water for 3 months result in their partial rehydration. Calcium saturation promotes the rehydration process. The results suggest the presence of interlayer cations in the Opotiki sample, Ca ions being associated with the strongly held ‘hole’ water. As a result of this study, we assert that the (de)hydration behavior of halloysite is highly heterogeneous and cannot be generalized a priori.

A new model is proposed for analysis of the source clays used to create ceramics, based on geographic, petrographic, mineralogical, mineral-chemistry, and geochemical criteria. The development of this model became feasible after the discovery of a Pliocene volcanic clay horizon on NWAegina Island, Greece. The volcanic clay contains smectite, mixed-layer chlorite-smectite, biotite, and palygorskite and has greater feldspar content than the underlying Pliocene marls, which contain R0 mixed-layer illitesmectite, mica, dolomite, serpentine, talc and gypsum, and, in some places, palygorskite. The two units have distinct geochemical characteristics. In general the Pliocene volcanic clay is richer in SiO2, Al3O3, and Fe2O3 and poorer in Na2O, MgO, and P2O2 than the Pliocene marls. The Nb, Zr, Hf, Th, and rare earth element (REE) contents are also significantly greater in the Pliocene volcanic clay and comparable to those of the dacitic rocks of the island, reflecting the volcanic origin of the clay.

The proposed model was used to identify the source-clay materials that were used for the production of ceramics on the island of Aegina (Aeginetan Ware). All five criteria should be considered in any provenance study. The use of individual criteria on their own can lead to ambiguous conclusions. In the present study the geochemical criterion was particularly helpful. It provided robust evidence for the nature of the source clay. The Pliocene volcanic clay horizon and the underlying Pliocene marls are the candidate raw materials for Aeginetan Ware. Although the Pliocene marls have been invoked as raw materials for Greek Bronze Age (~3000–1100 BC) Aeginetan ceramics and are used as raw materials by modern Aeginetan ceramists, the geochemical characteristics of a large set of Bronze Age Greek Aeginetan sherds with fine and coarse fabrics coincide with those of the Pliocene volcanic clay. This comparative and cumulative evidence suggests that the Pliocene volcanic clay was the main source clay for ancient Aeginetan ceramics, regardless of the fabric (coarse or fine) and that admixture of different sources might not be necessary for fine-grained ceramics.

The surface modification of Zeolite 4A using cetyl trimethyl ammonium bromide (CTAB) as a modifier via an ultrasonic method was carried out and the surface physicochemical properties measured. Response surface methodology (RSM) was developed with CTAB concentration, handling time, and handling temperature as variables, to help predict the performance of the modified zeolite under particular conditions. The influence of organic-modified surface treatment and of the amount of modified zeolite on the water-absorption capability of starch-g-poly (acrylic acid) hydrogel composites was also assessed. The results showed that the channels and skeleton structure of zeolite 4A were unchanged after organic modification by CTAB and the surface modification was effective. The results suggest that organic-modified zeolite 4A has improved the water-absorption capability.

Evidence for the formation of maghemite from goethite due to a bushfire on acid sulfate soil at East Trinity, Australia, is presented. Oxidation of pyrite-bearing acid sulfate soils led to precipitation of goethite-impregnated leaf litter. During a major bushfire, goethite with a crystal size calculated from broadening of the 110 reflection of ∼9 nm was converted to microcrystalline maghemite (size 12 nm, 220 reflection) and hematite (17 nm, 104 reflection) in a matrix of partly combusted plant litter. Replication of this natural formation of maghemite from goethite was achieved in the laboratory by burning goethite-impregnated leaf litter.

The influence of dissolved species and particle morphology on the electrokinetic behavior and the initial yield stress values of Cuban lateritic aqueous suspensions was studied. The lateritic samples were mixtures of serpentine and goethite in different relative proportions. The addition of silicate and Mg ionic species, which are normally found in natural waters used in industrial processes, affected the electrokinetic and flow behavior of the lateritic suspensions. Specific adsorption of these species on particle surfaces was shown by a shift of the isoelectric point and the maximum of the initial yield stress to more acidic pH (Si ionic species adsorption) and more basic pH (Mg ionic species adsorption), when compared to suspensions containing only non-adsorbing electrolytes. The initial yield-stress values determined in samples consisting entirely of goethite varied from sample to sample. A detailed crystallochemical characterization revealed that these changes were associated with the axial ratio (i.e. ratio of particle length to width) of the mineral particles. Goethite samples with larger particle size (smaller number of particles for a given solid concentration) and greater axial ratios presented initial yield-stress values greater than those goethites with smaller particle size and lower axial ratio.

Heavy metals in the environment are a problem due to their toxicity and bioaccumulation. Adsorptive removal of heavy metals by clay minerals has garnered increasing attention due to the abundance, low cost, and exceptional physicochemical properties of the clays. The purpose of the present study was to investigate the utilization of two Turkish sepiolite samples, nodular sepiolite (NS) and industrial sepiolite (IS), as adsorbents in removing Ni2+ ions from aqueous solutions. The specific surface areas of NS and IS are 182.19 m2 g–1 and 63.78 m2 g–1, respectively. The effects of adsorbent dosage, initial pH, contact time, initial concentration, and temperature on the adsorption of Ni2+ ions onto the sepiolite samples were investigated using a batch method. The optimum adsorbent dosage was determined as 0.6 g/50 mL of adsorbent and the optimum pH value was 6.0, for both sepiolite samples. The adsorption process obeyed the Freundlich isotherm model (KF: 4.89–9.73 mg1–1/n L1/n g–1 for NS and 4.27–6.42 mg1–1/n L1/n g–1 for IS) and the pseudo-second order kinetics model (k2: 0.0049–0.0397 g mg–1 min–1 for NS and 0.0688–0.1195 g mg–1 min–1 for IS). The adsorption process was spontaneous and endothermic, and the randomness increased. The samples exhibited large adsorption capacities through three cycles of adsorption-desorption tests. The results revealed that the sepiolite samples are promising as cost-effective adsorbents for the removal of Ni2+ ions from aqueous solutions.

Titanium was introduced into the clay structure by cation exchange with polymeric Ti cations which were formed by partial hydrolysis of Ti alkoxide in HCl. X-ray diffraction, N2 adsorption-desorption, chemical analysis, thermogravimetric analysis, differential thermal analysis, temperature-programmed desorption of ammonia and temperature-programmed reduction were used to characterize the resulting Ti-pillared clays (Ti-PILCs). Titanium methoxide allows the synthesis of a solid with a large basal spacing (26 Å), a large surface area (360 m2/g), a significant amount of micropore surface area (90%), and notable acidity. Moreover, Ti-PILCs obtained from methoxide were found to be thermally stable up to 500°C. A correlation between the increase in acidity and the increases in both microporosity and Ti content was observed. The surface area, the micropore volume, the acidity and the d001 peak intensity all increased upon increasing the amount of Ti added to the preparation (up to ∼15 mmoles of Ti/g clay). The use of an aqueous suspension of 0.13 wt.% of clay yielded the best structural and textural properties in terms of subsequent use of the clay as a catalyst.

A novel method for the analysis of clay minerals using Fourier transform infrared spectroscopy is presented. Clay mineral suspensions are dried on a Si wafer substrate for transmission infrared (IR) analysis. Four natural Source Clays from the Source Clays Repository of The Clay Minerals Society, SWy-2, SAz-1, SHCa-1 and KGa-1b, as well as the synthetic hectorite, Laponite RD, were analyzed using the described method with signal to noise (s/n) ratios in excess of 100,000 for the strongly absorbing Si-O stretching frequency. Scanning electron microscopy (SEM) images show that the mineral films possess suitable uniformity and low surface roughness for transmission IR measurements that is confirmed by minimal deviations in the baseline of collected IR spectra. The IR spectra are generated and peak locations are compared to previously reported values, generated from KBr pellet and attenuated total reflectance methods.

River-dominated delta areas are primary sites of active biogeochemical cycling, with productivity enhanced by terrestrial inputs of nutrients. Particle aggregation in these areas primarily controls the deposition of suspended particles, yet factors that control particle aggregation and resulting sedimentation in these environments are poorly understood. This study was designed to investigate the role of microbial Fe(III) reduction and solution chemistry in aggregation of suspended particles in the Mississippi Delta. Three representative sites along the salinity gradient were selected and sediments were collected from the sediment-water interface. Based on quantitative mineralogical analyses 88–89 wt.% of all minerals in the sediments are clays, mainly smectite and illite. Consumption of ${\text{SO}}_4^{2-}$\$\end{document} and the formation of H2S and pyrite during microbial Fe(III) reduction of the non-sterile sediments by Shewanella putrefaciens CN32 in artificial pore water (APW) media suggest simultaneous sulfate and Fe(III) reduction activity. The pHPZNPC of the sediments was ⩽3.5 and their zeta potentials at the sediment-water interface pH (6.9–7.3) varied from −35 to −45 mV, suggesting that both edges and faces of clay particles have negative surface charge. Therefore, high concentrations of cations in pore water are expected to be a predominant factor in particle aggregation consistent with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Experiments on aggregation of different types of sediments in the same APW composition revealed that the sediment with low zeta potential had a high rate of aggregation. Similarly, addition of external Fe(II) (i.e. not derived from sediments) was normally found to enhance particle aggregation and deposition in all sediments, probably resulting from a decrease in surface potential of particles due to specific Fe(II) sorption. Scanning and transmission electron microscopy (SEM, TEM) images showed predominant face-to-face clay aggregation in native sediments and composite mixtures of biopolymer, bacteria, and clay minerals in the bioreduced sediments. However, a clear need remains for additional information on the conditions, if any, that favor the development of anoxia in deep- and bottom-water bodies supporting Fe(III) reduction and resulting in particle aggregation and sedimentation.