Search

A kind of layered Li2MSiO4 material, Fe saponite with Na+ pillaring (Na+-FSAP) was developed as a low-cost and environment-friendly lithium-ion storage material. The Na+-FSAP follows the insertion/deinsertion working mechanism accompanied by valence change of Fe from Fe1.86+ to Fe2.71+ (average value) after stabilization, and displays a specific capacity of 125 mAh g–1 at 50 mA g–1 with retention ratio of 80.8% after 75 cycles. The Na+-pillaring effect and abundant structural water in the gallery urge Li+ migrate rapidly, resulting in a large Li+ diffusion coefficient within a range of 10−6.5–10−7.5 cm2 s−1. Thus, the Na+-FSAP provides a model material to design electrode materials with rapid lithium-ion migration and has great potential to take place of polyanionic-type Li2MSiO4 (M = Mn, Fe, Co) cathode materials.

The presence of hydrous minerals in carbonaceous chondrites has been considered as an important evidence for the former presence of liquid water in parent asteroids. However, the evolution of water–rock reactions in hydrous asteroids remains not well constrained. Here, we conduct water–rock type experiments and chemical equilibria calculations under low-temperature hydrothermal and reducing conditions to investigate the alteration process and secondary mineral assemblages of chondritic rock in the earliest alteration stage. Using synthetic chondrite (mixtures of olivine (forsterite95), orthopyroxene (enstatite95), silicate glass, troilite and Femetal) as a starting material, our experiments were conducted at temperatures of 25°C–80°C for time periods between 1 to 460 days at a water-to-rock mass ratio of 10. A combination of X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses revealed that the primary secondary phases consisted of pyrrhotite, an amorphous SiO2-rich phase and saponite at 80°C, while the secondary phase consisted of an amorphous SiO2-rich phase and saponite at 25°C. At both temperatures, the SiO2-rich phases and saponite densely covered the surface of the primary phases. The Fe/Mg ratios of saponite and amorphous SiO2-rich phases showed clear difference between 80°C and 25°C. Saponite that was formed at 80°C was richer in Fe than the initial silicate phases, and the highest Fe/Mg ratios were obtained in the saponite encrusting the troilite and Femetal. These results suggest that the Fe distributed from the troilite and Femetal induced the formation of Fe-rich saponite. Some of the secondary minerals observed from our alteration experiments were consistent with those expected by chemical equilibria calculations. However, the formation of serpentine, the dominant secondary mineral expected from chemical equilibria calculations, was not observed in our experiments up to 460 days, probably because the preferential dissolution of SiO2-rich silicate glass in the earliest stage of alteration induced the formation of saponite rather than serpentine. The secondary mineral assemblage and its morphological characteristics, as observed by our alteration experiments, showed similarities with carbonaceous chondrites such as CM2 and CO3 chondrites. This alteration might be explained by water–rock reactions at low temperatures and by the short time alteration. These findings better constrain the temperatures and timescales of aqueous alterations in hydrous asteroids, as well as the role of water in the early solar system bodies.

Surface-fixation induced emission is a fluorescence enhancement phenomenon, which is expressed when dye molecules satisfy a specific adsorption condition on the anionic clay surface. The photophysical behaviors of two types of cationic acridinium derivatives [10-methylacridinium perchlorate (Acr+) and 10-methyl-9-phenylacridinium perchlorate (PhAcr+)] on the synthetic saponites with different anionic charge densities were investigated. Under the suitable conditions, the fluorescence quantum yield (Φf) of PhAcr+ was enhanced 22.3 times by the complex formation with saponite compared to that in water without saponite. As the inter-negative charge distance of saponite increased from 1.04 to 1.54 nm, the Φf of PhAcr+ increased 1.25 times. In addition, the increase in the negative charge distance caused the increase in the integral value of the extinction coefficient and the radiative deactivation rate constant (kf) and the decrease in the nonradiative deactivation rate constant. It should be noted that the 2.3 times increase in kf is the highest among the reported values for the effect of clay. From these results, it was concluded that the photophysical properties of dyes can be modulated by changing the charge density of clay minerals.

The fine fraction of clay from Tagaran (TC) was characterized with X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), and Fourier-Transform Infrared Spectroscopy (FT-IR) and compared with the fine fraction of Topkhana clay (TPC). Both, TC and TPC were dominated by a trioctahedral swelling clay mineral (saponite). The use of TC was investigated for the adsorptive removal of methylene blue (MB) from blood film preparation washing waste of medical laboratory and undergraduate microbiology laboratory wastewater of the University of Sulaimani. The effect of initial pH of the dye solution was negligible at the studied range of dye concentration. The optimum adsorbent (TC) dose was 5 g/L for 50 mg/L of MB with an optimum equilibration time of 120 minutes. Adsorption isotherms were fitted to Langmuir and Redlich-Peterson isotherms by non-linear regression method. Pseudo-second-order kinetics best describe the analytical results. The thermodynamic parameters confirmed spontaneous endothermic adsorption. The study showed that local clays can be used to clean MB contaminated wastewaters.

The effect of copper on various acid saponite supported Ni–Cu bimetallic catalysts, prepared with different Ni : Cu ratios, was studied for the liquid phase hydrogenolysis of glycidol on a batch reactor at 393 and 453 K. Characterization of the catalysts showed that Ni and Cu are in close contact as the XRD measurements evidenced the formation of an alloy. H2 chemisorption results revealed that the measured metallic area progressively decreased with an increase in the wt% of copper. In the presence of high metal activity (higher Ni wt%), the formation of 1,2-propanediol (1,2-PD) outweighed, while acid activity led to the formation of dimerization and oligomerization products. The addition of Cu and the increase of the reaction temperature decreased the diol formation but boosted the 1,3-PD/1,2-PD ratio. This could be explained by an improvement of the collaborative effect between the metal Ni and the H+ of the saponite. Therefore, the presence of an appropriate amount of Cu allowed the control of the hydrogenation capacity of Ni and enhanced the collaborative effect of Ni and H+ favouring the formation of 1,3-propanediol with respect to 1,2-propanediol.

The issue of grinding saponite–titanium composites has not been considered in the machine building industry yet. The reason is that the chips are stuck on the working surfaces of abrasive tools made of silicon carbide and electrocorundum. This is due to the high adhesive activity at operating cutting temperatures between the composite and traditional abrasives. The article aims at studying the grinding of saponite–titanium composites using abrasive tools in various cutting modes based on parametric and non-parametric statistical methods. To solve this problem, high porous wheels (HPW) made of cubic boron nitride CBN30 with 100 % concentration on a bond V (K27), a pore-forming KF40, varied grains: B76, B126, B151 (ISO 6106:2013) – and hardness: M and O (ISO 525:2013) were used to grind saponite–titanium composites. Additionally, the Norton wheels from green silicon carbide with a normal porosity 39C (46; 60) K8 VK and with different grain size were tested. Norton wheels provide reduction of roughness height by 1.4–1.5 times in comparison with boron nitride HPW. These are recommended for the finishing grinding stage and HPW CBN30 – the preliminary to reduce the thermal effects on composites. By processing stability, the Norton wheels with grain 46 rank first, and among boron nitride HPW – CBN30 B76 100 OV K27–KF40.

Because they are so widespread, the use of saponites is significant in many industries. The modification of saponite-rich clay minerals is known to improve their existing characteristics and may provide new functional properties. The objective of the present paper was to characterize the effects of adding nanosized graphene-like molybdenum (Mo) and tungsten (W) sulfides on the textural and surface characteristics of composites based on native saponite and saponite pre-modified with nanoscale magnetite. The textural characteristics were investigated by the nitrogen adsorption-desorption method and scanning electron microscopy. The total acidity, Hammett Bronsted centers, and Quasi-Equilibrium Thermo Desorption (QE-TD) Lewis centers were characteristics used to probe the acid-base properties of the modified composites. In all cases, modification proved to have a significant effect on both the surface and textural properties of the clay matrix. Modification of the native saponite by graphene-like Mo and W sulfides resulted in a decrease in the specific surface area, except a slight increase in the surface area of the magnetite-containing saponite was observed. Analysis of the acid-base characteristics of native and magnetite-modified saponite (MMS) indicated the ability of modified MoS2 and WS2 additives to alter the acid-base state of the surface. The addition of graphene-like Mo and W sulfides increased the total acidity of native and MMS, with MoS2 modification being more promising because, in almost all the samples, saponite composite materials increased the number of both Bronsted and Lewis active centers compared with WS2, which was determined by the corresponding methods. The acid-base characteristics of the saponite-containing samples, which were studied in an aqueous medium by various methods, are in good correlation with each other, and are consistent with the sorption activity of cationic and anionic dyes.

This study investigated the adsorption of a non-ionic water-insoluble organic molecule (meso-tetraphenylporphyrin, TPP) on a trioctahedral layered aluminosilicate (saponite, SP) in organic solvents...

Green conversion in organic synthesis is one of the interesting and important topics in green chemistry. The use of heterogeneous catalysis instead of homogeneous catalysis offers some advantages, such as easy separation and reusability. In this research, a heterogeneous acid catalyst was prepared from saponite by immobilizing ZnO in the form of a pillared clay (Zn/PILS) and Zn supported on porous clay heterostructure (Zn/PCH). Physicochemical studies involving X-ray diffraction measurement, surface analysis using a gas sorption analyzer, and surface acidity measurement were performed. Results indicated that the increasing surface acidity and the high specific surface area of the material were the relevant physicochemical properties that facilitate environment-friendly citronellal cyclization. The higher values for both parameters in Zn/PCH than in Zn/PILS linearly affected citronellal conversion and the selectivity for isopulegol production. Zn/PCH demonstrated a conversion rate of 98.9% for a 3-hour reaction and a selectivity of 100% for isopulegol production, and it exhibited reusability properties. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

An ultrathin film was prepared by hybridizing a cationic Ir(III) complex with exfoliated nanosheets of clay minerals such as natural montmorillonite (denoted by MON) or synthetic saponite (denoted ...

International audience; Lacustrine carbonates formed in rift settings are increasingly studied not only as archives of Earth chemical and climatic history but also as potential hydrocarbon source rocks and/or reservoirs. The role of magmatic gases in their formation and diagenetic evolution, hence in their reservoir properties, remains unclear. We studied the first meter of carbonate sediment of the Dziani Dzaha volcanic crater lake (Mayotte Island) and developed a reactive-transport model with CrunchFlow software that allows the quantification of diagenetic reactions by considering depth-dependent burial rates and sediment compaction. The model is constrained by the previously documented solid-phase compositions of the lake sediment and new data consisting of 14C dating of plant macroremains to characterize the sediment age model, chemical composition of sediment pore waters, and chemical and isotopic composition of gases dissolved and bubbling through the lake. These new data reveal a massive magmatic CO2 contribution to the dissolved inorganic carbon of the lake, which fuels the primary productivity and carbonate formation. A pH value of 9 in the surface sediment pore waters induces supersaturation relative to aragonite, hydromagnesite, and saponite. At 1 m depth in the sediment, our model predicts that magmatic CO2 inflows and organic matter degradation account for 22 and 2 mol % dissolved inorganic carbon, respectively. The magmatic CO2 inflows result in a pH decrease at depth, leading to the destabilization of hydromagnesite, while saponite and aragonite remain stable. These results demonstrate the role of magmatic CO2 in fueling carbonate production and controlling the diagenetic evolution of sediment mineralogy.

Based on experimental studies, the possibility and efficiency of usage of montmorillonite, saponite, and clinoptilolite as separation membranes during electroosmotic fractionation of hydrogen isotopes in an aqueous electrolyte solution was evaluated. For the experiments, the following samples were used: bentonite (Cherkasy deposit) with a content of montmorillonite of 75% (hereinafter referred to as montmorillonite), saponite (Varvariv deposit) and clinoptilolite (Sokyrnytsya deposit). It was found that under the influence of an electric field, electroosmotic filtration of the tritiated electrolyte occurs through weakly permeable membranes. Depending on the structural features of the mineral substance, various proton conductivity of the membranes was recorded, which determines the different intensity of the redistribution of ions of dissociated HTO molecules between the anode and cathode chambers. The largest difference between the specific activity of tritium in the anolyte and catholyte was obtained in the system where the mineral membrane was made of saponite (11% and 26% of the specific activity of tritium in the initial HTO, respectively). The least was the stability of the montmorillonite membrane. Its destruction upon interaction with a Na2CO3 solution led to electrolyte leakage and a decrease in the extraction of tritium from the filtrate (catholyte). The use of clinoptilolite when creating a composite with montmorillonite made it possible to increase the stability of the membrane and additional possibilities for fractionating hydrogen isotopes in an electrolyte. Electroosmotic filtration of the electrolyte was accompanied by fractionation of hydrogen isotopes in the mineral membranes of the experimental systems. The largest isotope effect was obtained in montmorillonite and composite montmorillonite-zeolite membranes, where the fractionation coefficient α in the fraction extracted from the interlayer space was 1.16 and 1.12, respectively. In a composite membrane, where the amount of clinoptilolite was 67.5%, isotopic hydrogen fractionation was also observed in the surface-adsorbed fraction (α = 1.5) and in a structurally bound form (α = 1.1). The use of saponite as an electroosmotic membrane leads to a smaller isotope effect than in a montmorillonite membrane, and is manifested in surface-adsorbed water (α = 1.08) and in the interlayer space (α = 1.02). The addition of quartz sand to montmorillonite reduces the efficiency of fractionation of hydrogen isotopes detected only in the surface-adsorbed fraction (α = 1.02).

The fine fraction of the Tagaran natural clay (TC) from the Kurdistan region of Iraq-Sulaimani was characterized and used to remove Cd ions from industrial swage. Using XRF, XRD, SEM, and FTIR, the dominant clay mineral of the Tagaran clay mineral was identified as saponite, with minor amounts of chlorite. The clay was examined for its efficiency to adsorb and remove (Cd2+) in the presence of other heavy metal contaminants from Sulaimani industrial zone sewage by a batch method. The effect of initial pH, equilibrium time, temperature, clay dosage, and Cd2+ concentration was studied. Results were evaluated using Langmuir, Freundlich, Temkin, and Redlich-Peterson isotherms. The kinetics could be best fitted to pseudo-second-order reaction kinetic model. In addition, the activation energy and the amount of calculated and experimentally determined heavy metal loads were consistent. The thermodynamic studies showed spontaneous endothermic adsorption. The trioctahedral smectite (saponite) showed a good efficiency for the adsorption of Cd2+ from the real sample (up to 100%) which at least partly can be explained by cation exchange. Tagaran clay is a candidate material for the production of an adsorber material for removing Cd2+ from aqueous solutions.

In this article, a novel method, amidation, was used to modify saponite. Amidated ammonium citrate intercalated saponite (Aa-saponite) was synthesized by amidation reaction. The structure of Aa-sap...

Conversion of hydrotalcite (Ht) to saponite was observed by hydrothermal alkaline alteration of metal oxides. The conversion was through a pathway of hydration-dissolution-precipitation. It involved several critical steps, including the construction of Ht from metal oxides, dissolution of Al3+ from Ht, condensation of metasilicate anions with Ht, and finally crystallization of saponite. The condensation was favored by relatively low Mg/Al ratios of Ht, along with high concentrations of Al3+ and silicate oligomers in the environment, resulting in highly crystalline saponite. The latter conversion was greatly accelerated by the isomorphous substitution of Al3+ for Si4+ in silicate oligomers. The substitution generated the extra negative charge and led to the aforementioned condensation with Ht surface, thereby promoting the formation of saponite TOT layers. During the process, CO2 is an indispensable component. Initially intercalated as CO32− to form Ht, CO2 was subsequently eliminated from the solid phase, and saponite formed when the layer charge was reversed. Thus, this study presents a novel formation mechanism of saponite from metal oxides via hydrotalcite and contributes to a better understanding of the crystallization, chemical stability, and transformation of Ht to saponite. The results are also relevant to evaluating metal availability and carbon cycling on the surface of the Earth.

Carbon capture using amine-modified porous sorbents is one of the main proposed technologies to reduce the CO2 atmospheric concentration. In this work, a wide series of inexpensive clays have been selected to assess their role as supports of amine-containing sorbents for CO2 capture. Montmorillonite, bentonite, saponite, sepiolite and palygorskite have been hydrated and functionalized by three routes: (a) grafting with aminopropyl (AP) and diethylenetriamine (DT) organosilanes; (b) impregnation with polyethyleneimine (PEI); and (c) double functionalization by impregnating previously grafted samples. XRD, FTIR and N2 adsorption-desorption analyses along with nitrogen content and CO2 adsorption properties (thermogravimetry and fixed bed) have been evaluated for bare and functionalized clays. Under dry conditions (45 °C, 1 bar), grafted and impregnated samples yielded CO2 uptakes as high as 61.3 and 67.1 mg CO2/g ads (for Sepi-DT and Paly-PEI, respectively), with the latter being the best-performing sample in terms of CO2 uptake. On the contrary, double-functionalized samples displayed poor CO2 adsorption properties, probably due to pore-blocking problems related to their high organic loading. The presence of 5% H2O in the feed gas resulted in CO2 uptake increments from 17 to 27%. The adsorption performance of AP, DT and PEI-containing samples was maintained after three adsorption-desorption cycles.

Citral and citronellal are important chemicals in the pharmaceutical and chemical industries, since they can be converted into other more valuable chemicals that are needed in many pathways. From the perspective of green catalysis, the present investigation examines the preparation of a recyclable heterogeneous catalyst of ruthenium-supported saponite clay for microwave assisted catalytic hydrogen transfer. Catalysts were prepared by supporting ruthenium bipyridine cations within saponite interlayers at various ruthenium contents, and the catalysts were then characterized by x-ray diffraction (XRD), gas sorption measurements, and scanning electron microscopy-energy dispersive x-ray spectrometry (SEMEDX) analyses. The catalytic activity was determined using microwave-assisted conversion of citral and citronellal. The prepared catalysts exhibited significant activity in the microwave-assisted catalytic hydrogen transfer of citral and citronellal. The catalytic activity was related to the content of the supported ruthenium in the catalysts, which also contributed to the increased specific surface area and external surface area of the materials.

In a detailed investigation of three active geothermal systems from Greece (Milos), from El Salvador (Chipilapa) and from Japan (Nigorikawa), it was found that smectites are common minerals in vapor dominated reservoirs. These smectites are formed in response to local discharge of boiling fluids in permeable horizons; they can crystallize also in pipelines of powerplants. According to the varying composition of the fluids involved in these geothermal systems (i. e. meteoric waters or sea water), beidellite, saponite and stevensite have been identified at temperature between 180 and 300°C. Montmorillonite has not been observed for these thermal conditions. The association of variable amounts of smectite rich mixed layers including illite/smectite, chlorite/smectite or stevensite/talc with pure smectites suggests that smectites are metastable phases which rapidly evolve toward illite, chlorite or talc via conversion series of mixed layers. These smectites are a potential guide for the recent evolution of vapor dominated geothermal reservoirs.

The solution of the sludge utilization problem and yield increase at processing plants have great importance today all over the world. Disasters associated with the tailings dams failures have madeus develop technologies of tailings sludge utilization as a commercial product, reducing the environmental damage on the regions of mineral extraction. This research aimed to provide new data, methods and an analytical approach to solve the saponite sludge accumulation problem on mining enterprises with silicate coagulant to increase the rate of cycle water clarification for the enrichment process and the recycling of sludge to reduce its hazardous effect. Samples were taken in the deposit located in the north of the European part of Russia, where diamond bearing ore contain montmorillonite minerals, mostly saponite, which is considered to be a perspective secondary product. The content of this mineral in the sludge is above 20 wt.%. Saponite is a clay mineral with the general chemical formula (Ca,Na)0.3(Mg, Fe2+)3(Si, Al)4O10(OH)2·4H2O. The mineral has high adsorption, ion exchange, and catalytic and filtration properties, due to the developed diffuse layer, saponite particles are highly stable in an aqueous medium—the resulting suspension is highly stable and has slow sedimentation. During the research, a positive effect on the sedimentation process of clay saponite particles was established, due to the introduction of a coagulant containing 70% tricalcium silicate, at a dosage of 2 g/dm3 coagulant, the degree of purification of water containing the saponite clay suspension is 99%. The condensed sediment after the thermal drying and with the limestone addition can be used again as a coagulant or secondary product with enhanced properties, therefore, the sludge will be processed, and not stored.

The fit of the smectite structural formula is reviewed. In addition, a group of samples, both dioctahedral and trioctahedral, are studied, demonstrating the influence of interlaminar Mg that can lead to the erroneous classification of smectite if it is not considered., The understanding of the structural formula of smectite minerals is basic to predicting their physicochemical properties, which depend on the location of the cation substitutions within their 2:1 layer. This implies knowing the correct distribution and structural positions of the cations, which allows assigning the source of the layer charge of the tetrahedral or octahedral sheet, determining the total number of octahedral cations and, consequently, knowing the type of smectite. However, sometimes the structural formula obtained is not accurate. A key reason for the complexity of obtaining the correct structural formula is the presence of different exchangeable cations, especially Mg. Most smectites, to some extent, contain Mg2+ that can be on both octahedral and interlayer positions. This indeterminacy can lead to errors when constructing the structural formula. To estimate the correct position of the Mg2+ ions, that is their distribution over the octahedral and interlayer positions, it is necessary to substitute the interlayer Mg2+ and work with samples saturated with a known cation (homoionic samples). Seven smectites of the dioctahedral and trioctahedral types were homoionized with Ca2+, substituting the natural exchangeable cations. Several differences were found between the formulae obtained for the natural and Ca2+ homoionic samples. Both layer and interlayer charges increased, and the calculated numbers of octahedral cations in the homoionic samples were closer to four and six in the dioctahedral and trioctahedral smectites, respectively, with respect to the values calculated in the non-homoionic samples. This change was not limited to the octahedral sheet and interlayer, because the tetrahedral content also changed. For both dioctahedral and trioctahedral samples, the structural formulae improved considerably after homoionization of the samples, although higher accuracy was obtained the more magnesic and trioctahedral the smectites were. Additionally, the changes in the structural formulae sometimes resulted in changing the classification of the smectite.

For the first time, the co-presence in the saponite structure of luminescent Eu(III) and catalytic Nb(V) metal sites was exploited for the simultaneous detection and catalytic abatement of sulfur-containing blister chemical warfare agents. Metal centres were introduced in structural positions of the saponite (in the interlayer space or inside the inorganic framework) following two different synthetic methodologies. The functionalized saponites were able to reveal the presence of a sulfur mustard simulant (2-chloroethyl)ethyl sulfide (CEES) after few seconds of contact time and more than 80% of the substrate was catalytically decomposed after 24 h in the presence of aqueous hydrogen peroxide.

A novel bifunctional saponite clay incorporating gadolinium (Gd3+) and europium (Eu3+) in the inorganic framework was prepared by one-pot hydrothermal synthesis. The material exhibited interesting luminescent and paramagnetic features derived from the co-presence of the lanthanide ions in equivalent structural positions. Relaxometry and photoluminescence spectroscopy shed light on the chemical environment surrounding the metal sites, the emission properties of Eu3+, and the dynamics of interactions between Gd3+ and the inner-sphere water placed in the saponite gallery. The optical and paramagnetic properties of this solid make it an attractive nanoplatform for bimodal diagnostic applications., The combination of gadolinium and europium with synthetic saponite clays leads to the preparation of novel lanthanide-based multifunctional layered platforms, with interesting paramagnetic and optical features exploitable for the development of new systems for luminescent devices and in magnetic/optical diagnostics.

The present work reports the study of the mechanism of grafting of an alkoxysilane on the surface of a synthetic saponite. XRD and SEM/EDX characterizations confirmed the effective synthesis of the clay mineral with structural formula INTNa0.50TET[Si3.50Al0.50]OCT[Mg3]O10(OH)2. The functionalization of this material in its pristine or acid pre-treated form with a cationic silane (tetradecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride) yielded a nanohybrid organoclay with interesting structural and chemical properties highlighted by 29Si solid state NMR, XRD, FTIR, TGA and electrochemical characterizations. The monodentate and bidentate grafting of the alkoxysilane was observed regardless the starting material was pristine or acid pre-treated saponite. The more significant layer-to-layer distance increase observed after the functionalization of acid pre-treated saponite indicated some interlayer intercalation/grafting of the alkoxysilane. Electrochemical characterization (cyclic voltammetry and electrochemical impedance spectroscopy) showed that the modified clay mineral exhibited anionic exchange property due to the presence of grafted cationic alkoxysilane. This anionic exchange capacity was confirmed when successfully applied for the adsorption of the anionic dye Congo Red. In all cases, the acid pre-treatment tended to improve the anion exchange property of the organoclay.

Clay minerals surfaces potentially played a role in prebiotic synthesis through adsorption of organic monomers that give rise to highly concentrated systems; facilitate condensation and polymerization reactions; protection of early biomolecules from hydrolysis and photolysis; and surface-templating for specific adsorption and synthesis of organic molecules. This review presents processes of clay formation using saponite as a model clay mineral since it is shown to catalyze organic reactions, easy to synthesize in large and pure form, and has tunable properties. In particular, a method involving urea is presented as a reasonable analog of natural processes. The method involves a two-step process – 1) formation of the precursor aluminosilicate gel and 2) hydrolysis of a divalent metal (Mg, Ni, Co, Zn) by the slow release of ammonia from urea decomposition. The aluminosilicate gels in the first step forms a 4-fold-coordinated Al3+ similar to what is found in nature such as in volcanic glass. The use of urea, a compound figuring in many prebiotic model reactions, circumvents the formation of undesirable brucite, Mg(OH)2, in the final product by slowly releasing ammonia thereby controlling the hydrolysis of magnesium. In addition, the substitution of B and Ga for Si and Al in saponite is also described The saponite products from this urea-assisted synthesis were tested as catalysts for several organic reactions including Friedel-Crafts alkylation, cracking and isomerization reactions.

Location on territory of Ukraine of great deposits of aluminosilicates together with good facilities for their processing and standardization promotes the study of this raw material, results of which could be useful for the developers of enterosorbents. For search the specific sorptive activity a comparative examination of several materials of silica-alumina and clay nature has been carried out in this work. The X-ray phase analysis, a measuring of specific surface area by the low temperature adsorption–desorption of nitrogen and the method of isotherm of adsorption have been used. It is shown that silica-alumina and clay materials have much less specific surface as compared to silica gel Syloid® 244 FP and carbon sorbent SCN. The sorbents of montmorillonite type (smectite, saponite) are characterized by the highest adsorptive capacity in relation to methylene blue and congo red dyes. Synthetic zeolites NaA and NaX effectively absorb the ions of zinc from solution, significantly overcoming Syloid® 244 FP and SCN which were taken as preparations of comparison. Therefore, on the basis of NaA and NaX the selective enterosorbents for elimination from the organism of toxic metals could be created.

In situ modification with copolymer of 4-vinylpyridine and styrene (molar ratio 3:1) of natural mineral saponite from deposit Tashkivske(Ukraine) by radical polymerization was carried out. Anchorage of organic polymer 4-vinylpyridine-co- styrene on the mineral surface was proved by IR spectroscopy, mass spectrometry and scanning electron microscopy. The amount of immobilized copolymer in the synthesized composite material according to the thermogravimetric analysis is 8.5 wt.%. The recorded adsorption capacity of the composite with respect to Cu(II), Pb(II) and Fe(III) ions was increased in comparison with native mineral saponite.

The aqueously altered CM carbonaceous chondrite meteorites can be used to investigate the nature and transport of volatiles in the early solar system. We present the preliminary results of an effort to collect 2D infrared (IR) spectral maps from the matrix and fine-grained rims (FGRs) of material that surround chondrules and inclusions in the Murchison CM2 meteorite using synchrotron IR micro-spectroscopy. The main features in mid-IR spectra of the matrix and FGRs occur at ∼3500 cm−1 and ∼1000 cm−1 and are attributed to OH/H2O and Si O bonds in phyllosilicates and anhydrous silicates. Minor features in the spectra are attributed to organic species (3000–2800 cm−1), CO2 (2400–2000 cm−1), and carbonates (1500–1380 cm−1). In both the matrix and FGRs we observe correlations between the OH/H2O and phyllosilicate/silicate features confirming that phyllosilicates dominate the mineralogy. This is consistent with previous studies showing that Murchison contains ∼70 vol% phyllosilicates following aqueous alteration on an asteroid parent body. The presence of anhydrous silicates in the matrix indicates that the alteration was heterogeneous at the micron-scale and that the reactions did not reach completion. We highlight a possible correlation between the phyllosilicates and organic species in the matrix, supporting the hypothesis that phyllosilicates may have played an important role in the formation and preservation of simple organic molecules and compounds. In the FGRs variations in the distribution of the phyllosilicate minerals cronstedtite and Mg-serpentine/saponite likely reflect differences in the local geochemical conditions during aqueous alteration on the asteroid.

Chemical and mineralogical investigations of the FEBEX repository demonstration experiment after 18 years confirmed those reactions which were identified in previous large scale tests: Fe-corrosion, Mg-accumulation, cation exchange, and mineral dissolution/precipitation. These reactions were mostly restricted to the bentonite-heater contact. However, other processes were detected. Fe oxidation of carbon-containing steel was dominated by oxic corrosion and hydrolysis possibly through a similar Fischer-Tropsch synthesis reaction, leading to the monitored generation of H2, CO2 and both reduced (alkanes, alkenes) and oxidized non-volatile (carboxylic acids) hydrocarbons, which are in partial equilibrium with CO2/carbonate under oxidation states highly reduced. Therefore, temperature, water, oxygen (due to no gas-tight conditions), and other oxidizing agents regulated the redox state and activities of all species involved in the bentonite barrier, being sulfates reduced to H2S and pyrite, Fe-oxides (hematite/goethite) to magnetite and siderite, and Fe(III)-bearing smectite to saponite and chlorite. These mineral phases were detected as main corrosion products. The dissolved Fe2+ ions generated by reduction of Fe-oxides diffused away forming surrounding greenish halos in the bentonite. Because air was not excluded, most of the corrosion was oxic but locally reducing conditions were established. Significant Mg accumulation was observed at the heater contact, which is related with the highest salinity values of the porewater (Na Mg Ca Cl water-type, 0.41 M ionic strength), the presence of saponite (trioctahedral Mg-smectite), brucite and Fe-rich chlorite; and a modification in the dehydroxylation temperature of the dioctahedral smectite clay mineral particles, together with the precipitation of carbonates and an increase in Ca/Mg at interlayer sites, Na being depleted. The mechanism for the structural clay mineral alteration seems to be Fe(III) structural reduction, rather than the C-steel heater/liner corrosion. Because Fe2+ cations are more stable in trans octahedral sites, rearrangements in crystal lattice seem to have formed cis-trans interstratifications favouring the migration of Mg to octahedral sites and the segregation of Mg2+ trioctahedral domains. Thus, both a solid-state transformation, producing high-charge/low charge layers similar to vermiculite ones; as well as dissolution-precipitation transformation, with the crystallization of a trioctahedral Mg-smectite (saponite), brucite and chlorite in localized zones of the bentonite barrier, seem to be inferred, depending probably on f(O2), temperature, the amount of structural Fe(II) and Mg concentration in the pore water. The observed clay mineral transformations induced changes in some of the physico-chemical properties of the bentonite, decreasing the total cation exchange capacity and BET surface area. However, these modifications were restricted to the bentonite at close contact with the heater. The rest of bentonite from the FEBEX in situ test maintained its performance as an engineered barrier.

Exploration for mineral deposits is becoming increasingly difficult, requiring the use of novel approaches that are reliable and cost-effective. One such approach is the use of vein-hosted mineral chemistry. A number of studies have described the use of vein-hosted mineral chemistry as an exploration tool, but few have assessed a variety of factors that may have controlled the composition of these minerals. An understanding of why and how the composition of minerals varies, however, is critical to the development of robust exploration tools. This contribution combines detailed mineralogy using energy- and wavelength-dispersive spectroscopy, Raman spectroscopy, and μXRD with high-resolution laser ablation ICP-MS trace element analysis to characterize the controls on the chemistry of vein-hosted minerals, and the implications of these controls for the applicability of these minerals for mineral exploration. In and around the Marathon Cu-Pd deposit, veins consist of a complex mixture of phyllo and chain silicates, including chlorite, serpentine, saponite, and Ca-rich amphibole, whereas disseminated alteration consists predominantly of Ca-rich amphibole with lesser chlorite. The abundance of these veins is inversely correlated with the presence of mineralization. Minerals hosted in veins and patchy alteration crystallized from different fluids during temporally distinct events; the veins formed later than the disseminated alteration and from multiple stages of lower-temperature fluids. There is no correlation between the rock types that the veins are hosted by and the composition of the vein minerals, but on a very local scale, the mineral that a vein is hosted by does exhibit a compositional control. Vein minerals that are hosted by magnetite, and to a lesser extent, pyroxene, are enriched in Ti, V, and Cr compared to those hosted by plagioclase. In vein minerals that are hosted by plagioclase, the concentration of Co, Ni, and Zn increase systematically with distance from mineralization. The concentrations of Co, Ni, and Zn in vein minerals hosted by plagioclase also, however, increase systematically with distance from the contact between the mineralized pluton and the underlying Archean country rocks (i.e., the footwall contact). This suggests that the Co, Ni, and Zn in the fluids were likely derived by progressive leaching from pyroxene, olivine, and magnetite as the fluid migrated upwards through the pluton, rather than from the mineralization. Consequently, the correlation between vein-hosted mineral chemistry and sulfide mineralization are misleading. The only vein characteristic that can be used as an exploration tool at Marathon is the inverse correlation between vein density and zones of sulfide mineralization. This study demonstrates that the application of vein and mineral chemistry to mineral exploration needs to be carried out in the context of a careful assessment of the variations and controls on mineral chemistry from the scale of the deposit and its surrounding rocks down to the grain-scale.

Mixed metal oxides (MMO) were transformed to phyllosilicate in the presence of silicate anions under hydrothermal conditions. The product was shown to be saponite with a trioctahedral layer structure by characterization with XRD, FTIR, 27Al and 29Si MAS NMR, HRTEM and TG-DTG. The formation of saponite was through a rehydration-dissolution-precipitation pathway, involving the critical steps such as the reconstruction of MMO to hydrotalcite (Ht), exsolution of Al3+ from Ht, condensation of metasilicate anions with Ht, and finally crystallization of saponite. Isomorphous substitution of Al3+ for Si4+ in silicate oligomers is the key for the above conversion, which generated the negative charge necessary for the condensation between the silicate oligomers and Ht surface and the formation of 2:1 saponite TOT layers. High pH value (over 14.0) favored the condensation of silicate oligomers and led to crystallization of saponite. Thus, we report a novel method for the crystallization of saponite.

Purpose The purpose of this study is to prepare composite of chitosan-modified smectite clays consisting of montmorillonite and saponite clay minerals and their urea adsorption–desorption study. Prepared materials were designed for slow-release fertilizer application. Design/methodology/approach Preparation of the composites was conducted by a simple intercalation of chitosan solution and clay suspension followed by hydrogel beads formation. Physicochemical characterization of materials was performed by X-ray diffraction, gas sorption analysis by using Brunauer–Emmett–Teller surface areas and pore volume, water absorbency and Fourier transform-infrared. Urea adsorption and desorption studies of prepared materials were conducted by using batch method, and the adsorbed and desorbed urea content was analyzed by using high-performance liquid chromatography method. Findings The results revealed that the composites have higher absorptivity and lower absorptivity toward urea from and into water solution compared to raw clay minerals. Adsorption capacity and slow desorption rate of urea from the composites suggested the potential application of the composites as slow urea-releasing agent. Originality/value There are many papers that study the formation of chitosan-clay composites, but the study on the urea adsorption–desorption properties based on chitosan-smectite minerals have not been reported. Intensive study related to physicochemical properties and its related kinetics study is an important basic finding for further applications.

Although abundant evidence exists for past liquid water on Mars, the composition and amount of that liquid water remain unconstrained. The characteristics of liquid water are preserved within weathering profiles, which can be used to interpret past aqueous conditions. Putative weathering profiles consisting of Al-rich units above Fe/Mg-rich units have been documented in numerous locations on Mars. Of these locations, Mawrth Vallis is the largest in area; therefore, understanding the aqueous conditions that could cause such a profile may also help interpret similar transitions in clay mineralogy elsewhere on Mars. The stratigraphy of the Mawrth Vallis region is characterized by an Al-rich unit dominated by kaolinite and/or montmorillonite with Fe-(oxy)hydroxides and/or oxides, overlying an Fe/Mg-rich unit composed of nontronite and/or saponite. To interpret the implications of the possible formation of Mawrth Vallis by weathering, we used the reactive transport code CrunchFlow to model alteration of parent material consisting of: (1) nontronite; (2) nontronite and montmorillonite; (3) nontronite and saponite, and (4) saponite. Results indicate either the enrichment of Al-rich clay minerals in an upper weathered unit from the weathering of Fe/Mg-rich clay minerals, or weathering of saponite producing a nontronite-rich alteration product which would be anticipated to subsequently alter to an Al-clay mineral rich capping unit. Results indicate that the - profiles formed by weathering that have experienced the most aqueous/acidic alteration would be characterized by a thick Al-rich capping unit composed of kaolinite with Fe-(oxy)hydroxides, overlying nontronite. Weathering profiles containing nontronite overlying saponite would be consistent with less weathering than an Al-capping unit, as an Al-rich capping would likely develop with the continued weathering of nontronite. Al-rich units are observed in the areas around Jezero crater, Mars the landing area of the Mars2020 rover Perseverance. Characteristics of weathering profiles such as those examined here can be used in the examination of locations on Mars to help choose environments that contained liquid water with characteristics most conducive to habitability and biosignature preservation.

The control of size and size distribution of semiconducting materials has easily carried out by intercalating in clay minerals with tailoring optical properties and activities. The solid-liquid reaction was applied to fabricate zinc selenide nanoparticles in montmorillonite and saponite containing the interlayer expanders of cetyltrimethylammonium cation and 18-crown-6. Various experimental results including XRD pattern, TG-DTA curve, TEM image and the spectroscopic observations of the products could confirm the formation of zinc selenide nanoparticles in smectites in the presence of cetyltrimethylammonium and the absence of 18-crown-6. The pre-expansion of the interlayer nanospace of smectites with cetyltrimethylammonium and 18-crown-6 promoted the facile intercalation of zinc selenide with controlling their particle size. The size of zinc selenide nanoparticles in cetyltrimethylammonium modified smectites was slightly larger than that in pristine smectites. The evident reason on the higher photoluminescence intensity of zinc selenide in cetyltrimethylammonium modified smectites rather than those of zinc selenide in smectite and bare zinc selenide was due to the host-guest and guest-guest interactions. This preparation procedure may be a facile pathway for controlling the particle size and tailoring the optical performance of the unstable semiconductors.

The Morrón de Mateo bentonite deposit has been studied as a natural analogue of the thermal effect on the bentonite barrier of a geological radioactive waste repository. This deposit was intruded by a volcanic dome that induced hydrothermal activity affecting the smectite clay minerals close to the dome. Previous studies of proximal bentonites indicated that Al-montmorillonites were transformed into Fe-rich smectites with intermediate composition between beidellite and saponite through gradual steps formed by smectites increasingly rich in Mg and Fe. In order to confirm the suggested transformation and the Fe distribution into the smectites, infrared and Mössbauer spectroscopy studies were performed. Infrared spectra of samples away from the dome show typical bands for montmorillonite type with prevailing Al in octahedral positions, while proximal samples also show bands of Fe-rich smectites. Mössbauer data confirm that Fe present in the fine fraction of bentonites is fundamentally located in the smectites structure, mainly as octahedrally coordinated Fe(III). Proximal smectites have a considerably more distorted octahedral environment for Fe(III) which probably stemmed from a significant degree of substitution of Al by Fe(III). These results confirm that an alteration process occurred related to the volcanic intrusion which produced an increase in temperature and Fe-rich solutions responsible for the transformation of Al-montmorillonites.

Alteration of basalt is a ubiquitous process on the vast oceanic crust surface and results in the formation of secondary-phase minerals that include clay minerals and Fe-(oxyhydr)oxides. Thus, this process is a significant consequence of water/rock interactions that could reveal the (bio)geochemical conditions of formation. Core samples at the basalt/sediment interface from a depth of 74.79 m below sea floor (mbsf) were recovered during the International Ocean Discovery Program (IODP) expedition 329 (2010.10.10–2010.12.13) in the South Pacific Gyre (SPG). Two distinct regions of yellow- and red-colored sediment were observed. The mineralogy, elemental composition, Fe oxidation state, and mineral structure of the altered basalt samples were analyzed using transmission electron microscopy (TEM) with selected area electron diffraction (SAED) patterns, energy dispersive spectroscopy (EDS), electron energy loss spectroscopy (EELS), and micro X-ray fluorescence (μ-XRF). In the yellow sediment, K-nontronite and feroxyhyte (δ’-FeO(OH)) were the dominant mineral phases, while Mg-rich smectite (saponite), chlorite, and hematite were found predominantly in the reddish sediment. The appearance of K-nontronite and feroxyhyte mineral assemblages in altered sediment indicated that oxidative conditions prevailed during basalt alteration. Variation in the Fe-oxidation states in the K-nontronite structure, however, may indicate that local reducing conditions persisted throughout the biogeochemical reactions.

An attempt to develop a chiral luminescent probe with enantioselectivity is described. A tris(chelated) iridium(III) complex with bulky ligands, [Ir(bzq)2(phen)]+ (bzqH = benzo[h]quinoline; phen = 1,10-phenanthroline), was synthesized and optically resolved into Δ- and Λ-enantiomers. The complex (denoted as Ir(III)) was emissive in non-polar organic solvents, while in aprotic and protic polar solvents it was less emissive. When Ir(III) was adsorbed by the colloidal particles of synthetic saponite (denoted as SAP), it recovered its emitting capability even in a solvent containing water. Emission from Ir(III) adsorbed by SAP was quenched by adding [Ru(acac)3] (acac = acetylacetonato, denoted as Ru(III)). The Stern–Volmer constant (KSV) exhibited remarkable stereoselectivity; KSV = 15 900 ± 900 M−1 for Δ-Ir(III)/Δ-[Ru(acac)3] (or Λ-Ir(IIII)/Λ-[Ru(acac)3]) and 7000 ± 500 M−1 for Δ-Ir(III)/Λ-[Ru(acac)3] (or Λ-Ir(III)/Δ-[Ru(acac)3]). The dependence of the emission lifetime on the concentration of Ru(III) indicated that quenching proceeded dynamically. On the basis of the molecular model, it was postulated that a microscopic pocket surrounded by the bulky ligands at the top of adsorbed Ir(III) acted as a site discriminating the chirality of an approaching molecule.

The excess of orbital detection of smectite deposits compared to carbonate deposits on the martian surface presents an enigma because smectite and carbonate formations are both favored alteration products of basalt under neutral to alkaline conditions. We propose that Mars experienced acidic events caused by sulfuric acid (H(2)SO(4)) that permitted phyllosilicate, but inhibited carbonate, formation. To experimentally verify this hypothesis, we report the first synthesis of smectite from Mars-analogue glass-rich basalt simulant (66 wt% glass, 32 wt% olivine, 2 wt% chromite) in the presence of H(2)SO(4) under hydrothermal conditions (~200 °C). Smectites were analyzed by X-ray diffraction, Mossbauer spectroscopy, visible and near-infrared reflectance spectroscopy and electron microprobe to characterize mineralogy and chemical composition. Solution chemistry was determined by Inductively Coupled Plasma Mass Spectrometry. Basalt simulant suspensions in 11–42 mM H(2)SO(4) were acidic with pH ≤ 2 at the beginning of incubation and varied from acidic (pH 1.8) to mildly alkaline (pH 8.4) at the end of incubation. Alteration of glass phase during reaction of the basalt simulant with H(2)SO(4) led to formation of the dioctahedral smectite at final pH ~3 and trioctahedral smectite saponite at final pH ~4 and higher. Anhydrite and hematite formed in the final pH range from 1.8 to 8.4 while natroalunite was detected at pH 1.8. Hematite was precipitated as a result of oxidative dissolution of olivine present in Adirondack basalt simulant. Formation of secondary phases, including smectite, resulted in release of variable amounts of Si, Mg, Na and Ca while solubilization of Al and Fe was low. Comparison of mineralogical and solution chemistry data indicated that the type of smectite (i.e., dioctahedral vs trioctahedral) was likely controlled by Mg leaching from altering basalt and substantial Mg loss created favorable conditions for formation of dioctahedral smectite. We present a model for global-scale smectite formation on Mars via acid-sulfate conditions created by the volcanic outgassing of SO(2) in the Noachian and early Hesperian.

In this study, 1,10-phenanthroline molecules were introduced in the interlayer space of a paramagnetic synthetic saponite clay containing both Eu3+ and Gd3+ ions in structural positions. Two samples with different loading of phenanthroline dye were prepared. The resulting hybrid materials possessed improved optical emission properties due to an efficient antenna effect from the phenanthroline to the Eu3+ centers, this effect was demonstrated to be higher than the metal-to-metal Gd3+-Eu3+ energy transfer previously studied. Insights on the relaxometric properties in aqueous solution of the solids after incorporation of the antenna groups were also obtained through NMR relaxometric analyses.

Mineralogy of fine-grained matrix (FGM), fine-grained rim (FGR), chondrule rim, and altered mesostasis of a chondrule from the Asuka (A) 12169 CM3.0 chondrite was investigated by field emission scanning electron microscopy (FE-SEM), synchrotron radiation-based X-ray nano-tomography (SR-XCT), and transmission electron microscopy (TEM). SR-XCT and TEM observations revealed that both FGM and FGR contain abundant amorphous silicate embedding nano-inclusions (most are Fe–Ni sulfide). Although the amorphous silicate is more or less hydrated based on the analysis of the X-ray linear attenuation coefficients in SR-XCT, there are no areas filled by abundant phyllosilicate even in three dimensions. However, FGM and FGR contain ~2-10 μm-sized aggregates composed of tochilinite, nano-inclusions of possible magnetite, and poorly crystalline serpentine without sharp boundaries with the surroundings. It is unlikely that the heterogeneity resulted from brecciation and mixing of materials that experienced different degrees of aqueous alteration, but more likely from a very early stage of aqueous alteration that proceeded heterogeneously depending on locally different chemistry. Chondrule mesostasis near the surface of a chondrule was altered to saponite with tochilinite-rich aggregates. These observations indicate that the degree aqueous alteration of A 12169 is very low and that it is comparable with that of Acfer 094, ALH 77307, and the least altered areas of Paris.

Two flow-through experiments were conducted to assess serpentinization of intact dunite cores. Permeability and fluid chemistry indicate significantly more reaction during the second experiment at 200 °C than the first experiment at 150 °C. Permeability decreased by a factor of 2.4 and 25 during the experiments at 150 and 200 °C, respectively. Furthermore, hydrogen and methane concentrations exceeded 600 μmol/kg and 300 μmol/kg during the 200 °C experiment, and were one and two orders of magnitude higher, respectively, than the 150 °C experiment. Fe K-edge X-ray absorption near edge structure analyses of alteration minerals demonstrated Fe oxidation that occurred during the 200 °C experiment. Vibrating sample magnetometer measurements on post-experimental cores indicated little to no magnetite production, suggesting that the hydrogen was largely generated by the oxidation of iron as olivine was converted to ferric iron (Fe(III)) serpentine and/or saponite. Scanning electron microscopy images suggested secondary mineralization on the post-experimental core from the 200 °C experiment, portraying the formation of a secondary phase with a honeycomb-like texture as well as calcite and wollastonite. Scanning electron microscopy images also illustrated dissolution along linear bands through the interiors of olivine crystals, possibly along pathways with abundant fluid inclusions. Energy dispersive X-ray spectroscopy identified Cl uptake in serpentine, while Fourier transform-infrared spectroscopy suggested the formation of serpentine, saponite, and talc. However, no change was observed when comparing pre- and post-experimental X-ray computed tomography scans of the cores. Furthermore, (ultra) small angle neutron scattering datasets were collected to assess changes in porosity, surface area, and fractal characteristics of the samples over the ≈ 1 nm- to 10 μm-scale range. The results from the 200 °C post-experimental core generally fell within the range of values for the two pristine samples and the 150 °C post-experimental core that underwent negligible reaction, indicating that any change from reaction was smaller than the natural variability of the dunite. Even though there was little physical evidence of alteration, the initial stage of serpentinization at 200 °C was sufficiently significant to have a dramatic effect on flow fields in the core. Furthermore, this experiment generated significant dissolved hydrogen concentrations while simulating open system dynamics. Even though open systems prevent elevated hydrogen concentrations due to continual loss of hydrogen, we speculate that this process is responsible for stabilizing ferric Fe-rich serpentine in nature while also oxidizing more ferrous iron (Fe(II)) and cumulatively generating more hydrogen than would be possible in a closed system.

A chemically inert, insulating layered silicate (saponite; SP) and an iron(II)-based metallo-supramolecular complex polymer (polyFe) were combined via electrostatic attraction to improve the electrochromic properties of polyFe. Structural characterization indicated that polyFe was intercalated into the SP nanosheets. Interestingly, the redox potential of polyFe was lowered by combining it with SP, and the current was measurable despite the insulating nature of SP. X-ray photoelectron spectroscopy showed that the decrease in the redox potential observed in the SP-polyFe hybrid was caused by the electrostatic neutralization of the Fe cation in polyFe by the negative charge on SP. Electrochemical analyses indicated that electron transfer occurred through electron hopping across the SP-polyFe hybrid. Control experiments using a metal complex composed of Fe and two 2,2':6',2''-terpyridine ligands (terpyFe) showed that SP contributes to the effective electron hopping. This modulation of the electrochemical properties by the layered silicates could be applied to other electrochemical systems, including hybrids of the redox-active ionic species and ion-exchangeable adsorbents.

We propose a methodology for applying a pseudo uniaxial pressure to an organic molecule under ordinary temperature and pressure, namely by intercalation into smectites. The pseudo pressure on a biphenyl derivative (BP) was estimated from the averaged dihedral angle around the central bond of BP. In a high hydrostatic pressure field, biphenyl takes a planar conformation. In the interlayer space of synthetic saponite (SSA), the averaged dihedral angle of BP at a loading level of 27% versus the cation exchange capacity was ~26.3°, which indicates that the pseudo pressure applied to BP in the SSA interlayer space corresponds to 0.99 GPa. The high pseudo-pressure field in the interlayer space of SSA was also confirmed by absorption measurements. The dihedral angle around the central bond of the biphenyl moiety decreased to enhance the planarity of the molecule, mainly in response to the electrostatic force that operates between the negatively charged SSA layer and the interlayer cation. The pseudo pressure operating on BP in the smectite interlayer space could be controlled by varying the smectite layer charge density and/or the BP loading level. By using this methodology, controllable pseudo high-pressure properties of organic molecules can be obtained at ordinary temperatures and pressures.

Acid treatment of clay minerals is known to modify their properties such as increase their surface area and surface acidity, making them suitable as catalysts in many chemical processes. However, the role of these surface properties during biodegradation processes of polycyclic aromatic hydrocarbons (PAHs) is only known for mild acid (0.5 M Hydrochloric acid) treated clays. Four different clay minerals were used for this study: a montmorillonite, a saponite, a palygorskite and a kaolinite. They were treated with 3 M hydrochloric acid to produce acid activated clay minerals. The role of the acid activated montmorillonite, saponite, palygorskite and kaolinite in comparison with the unmodified clay minerals in the removal of PAHs during biodegradation was investigated in microcosm experiments. The microcosm experiments contained micro-organisms, oil, and clays in aqueous medium with a hydrocarbon degrading microorganism community predominantly composed of Alcanivorax spp. Obtained results indicated that acid activated clays and unmodified kaolinite did not enhance the biodegradation of the PAHs whereas unmodified montmorillonite, palygorskite and saponite enhanced their biodegradation. In addition, unmodified palygorskite adsorbed the PAHs significantly due to its unique channel structure.

The present study is primarily focused on the investigation of spectral properties of cationic cyanine dye (1,1′-diethyl-4, 4′-carbocyanine iodide, denoted as “NK5”) adsorbed into the structure of synthetic clay mineral (Sumecton SA, denoted as “SUM”) as a host matrix. The hybrid systems were investigated by means of absorption and fluorescence spectroscopy. Beside the solvent effect, the influence of dye/saponite ratio on the formation of specific dye species was studied in detail. It was found that used solvents have greatly affected the spectral properties of prepared hybrids. The NK5/saponite systems in ethanol and methanol were dominated by isolated dye cations. In the NK5/saponite systems in acetone and acetonitrile, the formation of higher aggregates was significantly suppressed. Moreover, the fluorescence spectra showed evidence of the formation of highly fluorescent J -aggregates. Finally, the fluorescence quantum yields of the NK5/saponite systems in various solvents were calculated. It was found that polar protic solvents as ethanol and methanol could stabilize the hybrid cyanine/saponite system with higher quantum yields as in case of used aprotic solvents.

Resonance energy transfer (RET) in hybrid polymer/inorganic/organic layers in saponite films, prepared using the ‘layer-by-layer’ (LBL) method, was studied. This method allows the fabrication of a multicomposite molecular assembly based on electrostatic and/or other intermolecular interactions between the interacting species. The LBL films were designed by sequential deposition including positively charged polycations ( poly(diallyldimethyl ammonium), PDDA) and negatively charged saponite dispersions with donor molecules (rhodamine 6G) and saponite dispersions with acceptor molecules (rhodamine 3B). In this sequence, the layer of saponite donor molecules was placed on an adjacent layer of saponite acceptor molecules, while the layers were separated by inserting a PDDA polycationic layer. The adsorption process was studied using absorption spectroscopy. The linear deposition regime was completed when ten layers had been deposited. The process of REF was studied by fluorescence spectroscopy. In this case the donor molecules – rhodamine 6G – play the role of lightharvesting antennae and transfer the energy to the next layer covered by energy acceptor, i.e. rhodamine 3B molecules. The insertion of polycation layers is rationalized by the adhesion of negatively charged underlying layers and the stabilization of multicomponent systems. The energy transfer efficiency was affected heavily by changing the distances between the adjacent layers.

In presented work dye assemblies with J-type intermolecular coupling, which are well recognized not only for their exciton transport but also for hole and electron transport properties were investigated. The use of materials consisting of J-type dye assemblies can be significantly enhanced if their photonic properties can be controlled by some external stimuli. For these reasons the switching abilities between J-type aggregated and non-aggregated states of a cationic cyanine dye, 1,1′-diethyl-2,2′-cyanine (pseudoisocyanine, PIC) intercalated in the interlayer space of synthetic saponite (Sap) were compared. The switching was performed by adding and removing of dimethyl sulfoxide (DMSO) from the interlayer space. The PIC/Sap hybrid film prepared at 70% CEC loading level has shown excellent stability within 20 cycles of photophysical response after adding and removing of DMSO from the interlayer space, indicating that presented experimental approach can be useful in the future development of artificial light harvesting or semiconductor systems with controllable properties.

DOI: 10.1016/j.apcata.2017.03.018 URL: http://www.sciencedirect.com/science/article/pii/S0926860X17301175 Filiació URV: SI This study explores the use of glycidol, as alternative to glycerol, to improve the selectively to 1,3-propanediol (PrD) by hydrogenolysis. The reaction was performed using Ni (with different Ni wt%) supported on an acid delaminated saponite catalysts which are cheaper compared to the expensive catalysts needed to favor the 1,3-PrD formation by glycerol hydrogenolysis. An increase in metallic area and a decrease in the catalyst acidity resulted in higher conversion and selectivity to propanediols (1,2- + 1,3-PrD). An acid activation of glycidol during hydrogenolysis promoted the 1,3-PrD formation and increased the 1,3-PrD/1,2-PrD ratio. For the catalyst prepared with 40 wt% Ni loading, an increase in the reaction temperature to 423 and 453 K led to higher 1,3-PrD/1,2-PrD ratio. The highest 1,3-PrD yield (29%) and 1,3-PrD/1,2-PrD ratio (0.97) at total conversion were obtained at 453 K, after 1 h. The overall 1,3-PrD yield from glycerol, assuming a two-step synthesis (Glycerol → Glycidol → 1,3-PrD) and a yield of 78% for the first step, should be around 23%. This value is comparable to that reported for the hydrogenolysis of glycerol using noble metal catalysts.

A natural pigment, anthocyanin, extracted from purple sweet potato was complexed with smectite group layered clay minerals, a synthetic saponite and a natural montmorillonite. The resulting biohybrid with the synthetic saponite exhibited a clear color change between blue and pink upon exposure to acidic (HCl) and basic (ammonia) vapors. The color change is similar to that of anthocyanin molecule in solution which is due to the change in the molecular structure of anthocyanin. The response for the color change was within 10 min upon exposure to the vapors and was reversible. The present biohybrid composed of environmentally benign chemically stable and non toxic components is regarded as a possible candidate of environmental sensors and smart pigments.