Interactions of Carbaryl with homoionic montmorillonite

Adsorption and catalytic degradation of the insecticide Carbaryl on montmorillonite self-supporting films (Upton, Wyoming) saturated with different cations (Al³⁺, Ca²⁺, Cu²⁺, Na⁺) was studied using thin-layer chromatography, X-ray diffraction, infrared and mass spectroscopy techniques. Carbaryl is adsorbed at room temperature by a coordination bond, through a water bridge, between the C=O group and the exchangeable cation. X-ray diffraction patterns showed that the molecule is always intercalated in the smectite layers except for Na-montmorillonite. On moderate heating (90°C for 30 h) the Carbaryl adsorbed on Cu- and Al-montmorillonite decomposes to CO₂, N-methylammonium cation, and 1-naphthol and polymerization products, di- and tri-condensate of 1-naphthol, are formed. By contrast for Ca- and Na-montmorillonite systems no degradation of Carbaryl was observed on heating at 90°C for 30 h. The Carbaryl decomposition can be ascribed to the concurrent effect, enhanced by dehydration, of the stronger polarizing power of Cu²⁺ and Al³⁺ ions and the acidity of the residual solvation water.     

Complexes of homoionic montmorillonite with thioamides

The adsorption and catalytic decomposition mechanisms of thioacetamide, thiobenzamide and 2,6-dichlorothiobenzamide (Chlorthiamid, used as herbicide) on Al- and Ca-montmorillonite (Upton, Wyoming) have been studied. According to the results of the infrared analysis, the 2,6-dichlorothiobenzamide is adsorbed on Al-montmorillonite by protonation of the CS roup; in contrast, with Ca-montmorillonite the molecule is adsorbed by a coordination bond to the exchangeable cation. Thiobenzamide is mainly adsorbed on Al-montmorillonite by a coordination bond between the CS group and the exchangeable cation: a small fraction of the molecule is, at the same time, decomposed to benzoic acid, NH₃ and H₂S. The presence of benzoic acid was confirmed by thin-layer chromatography. The same coordination bond is only observed when the molecule is adsorbed on Ca-montmorillonite. Thioacetamide, adsorbed on Al-montmorillonite, is partially decomposed to acetate ion, acetic acid, NH₃ and H₂S. The presence of acetic acid was confirmed by thin-layer chromatography. The remaining molecules of thioacetamide are adsorbed by coordination of the CS group to the exchangeable cation. On Ca-montmorillonite the hydrolytic decomposition to acetic acid is strongly reduced and the molecule is adsorbed by a coordination bond to the exchangeable cation.     

Characterization and properties of treated smectites

Two natural smectite clays named BC and AC were thermal and chemically treated. Apart from smectite, quartz and kaolinite, BC clay also contains calcite, whereas illite and higher quartz content is found in AC. Treatment at 823 K leads to a collapse of the smectite structure. Treating with H₂SO₄ or NaOH also leads to the elimination of calcite and Al and Si ions. The higher swelling capacity of BC clay is in accordance with its higher cation exchange capacity.${\gamma }_S^d$ values for both smectites decreases with the applied treatments. The surface acid–base constants determined for BC clay are higher than those obtained for AC independently of the applied treatment. This result together with the higher nanorugosity index, has been attributed to the higher quartz of the AC clay. Moreover, it has been observed that the cationic exchange capacity increases in both clays with the acidity of the surface.     

Influence of layer charge on swelling of smectites

Six separate processes control the swelling of smectites saturated with alkali and alkaline earth cations in aqueous systems. The basic mechanism and forces controlling each of the processes are different. Crystalline swelling occurs between smectite layers within quasicrystals and involves the intercalation of zero to four discrete layers of water molecules. A balance between strong electrostatic-attraction and hydration-repulsion forces controls crystalline swelling. The extent of crystalline swelling decreases with increasing layer charge. Double-layer swelling occurs between quasicrystals. An electrostatic repulsion force develops when the positively charged diffuse portions of double layers from two quasicrystals overlap in an aqueous suspension. Layer charge has little or no direct effect on double-layer swelling. The break up and formation of quasicrystals is a dynamic process that controls the average size of quasicrystals in an aqueous smectite suspension. As layer charge increases, quasicrystals tend to become larger and more stable. In smectite suspensions with more than one type of exchangeable cation, the cations can demix (e.g., Na and Ca may be segregated in different interlayer regions) due to a complex feed-back between cation exchange selectivity and crystalline swelling. Demixing influences the breakup and formation of quasicrystals because quasicrystals preferentially cleave along interlayers dominated by alkali cations. Increasing layer charge increases selectivity for alkaline earth cations relative to Na or Li, and hence reduces the breakup of quasicrystals. Co-volume swelling is an entropy driven process caused by restrictions on the rotational freedom of suspended quasicrystals. Brownian swelling is also an entropy driven process resulting from random thermal motion of suspended colloids. There is no reason to believe that layer charge directly influences either co-volume or Brownian swelling. Macroscopic measures of swelling (e.g., change in total volume or water content) necessarily measure the combined effect of all swelling processes occurring within the system.     

Requirements of organic gels for a successful ambient pressure drying preparation of carbon aerogels

In this paper, we investigated the requirements of organic gels for a successful ambient pressure drying by analyzing the role of the strength, the pore size and the surfactant of organic gels in decreasing the drying shrinkage of organic aerogels. Experimental results showed the effect of the decrease of the surface tension, resulting from the surfactant, on the drying shrinkage was very small and negligible. The drying shrinkage depended strongly on the strength and the pore size. Subsequently, the respective role of the strength and the pore size was evaluated. It can be found that the strength plays a greater role than the pore size.     

Modification of layer charge in smectites by microwaves

The layer charge reduction of two Li-saturated montmorillonites is referred to application of microwave radiation at 2.45 GHz for dispersions and 30.0 GHz for the solid powders. Efficiency of these treatments was compared to the same conditions applying conventional heating. The samples were heated in the temperature and time windows corresponding to 190–270 °C and 30–120 min, respectively. Changes in the mean layer charge were monitored by the determination of cation exchange capacity values using exchange of triethylene tetraamino copper ions. The charge reduction of the montmorillonites in aqueous dispersions was rather low (< 30%) despite the fact, that high Li⁺ concentration dissolved in solution was selected (1 mol L^− 1). This behaviour was attributed to the very high water content in used dispersions and high hydration enthalpy of Li⁺ cations. Nevertheless, the microwave heated dispersions (2.45 GHz) showed detectable layer charge reduction as compared to conventionally heated dispersions, where no significant changes were found.Solid powders with different content of exchangeable lithium ions were prepared with solutions having different molar fraction of Li⁺ and Na⁺ cations (0%, 20%, 40%, 60%, 80%, 100% of Li⁺). Final composition of interlayer cations was analysed with ICP-OES. In contrary to dispersions, the microwave treatment of the prepared powders revealed high layer charge reduction, which was much higher than for conventionally heated powders. The efficiency was enhanced with increasing interlayer lithium content but reached a limiting value depending on the montmorillonite used. Migration of the lithium into the structure of the montmorillonite supported with microwaves was extremely fast, finished probably within the few minutes of the treatments. The exchangeable Li⁺ cations are accelerated through alternating electric field of microwaves and highly efficient layer charge neutralisation occurs. Infrared spectroscopy showed that the products obtained with microwave treatments correspond to the materials heated conventionally for much longer periods of time. Hence, applying microwaves the time and energy requirement can be significantly reduced. The X-ray diffraction showed that montmorillonite layers were able to swell in ethyleneglycol upon charge reduction, if the cation exchange capacity was not reduced more than 20–40%.     

Interaction of Fluazifop-butyl and Fluazifop with smectites

Adsorption of the herbicides Fluazifop-butyl and Fluazifop by two smectites homoionic to Al, Fe(III), Ca, Mg, Na, K and Cs, has been studied by infrared spectroscopy, X-ray diffraction and thin-layer chromatography. At room temperature Fluazifop-butyl and Fluazifop were adsorbed on smectites by both direct coordination and indirect coordination (through a water bridge) between the CO group of the herbicide and the exchangeable cation. The extent and strength of this coordination depended on the nature of the cation saturating the clays. With Al- and Fe- smectites interactions also occurred between the pyridine and benzene rings of the molecules and the clay surface. The formation of the pyridinium ion suggested that on Al- and Fe-smectites the herbicides were also adsorbed by protonation of the pyridine nitrogen. X-ray diffraction analysis showed that Fluazifop-butyl and Fluazifop penetrated into the interlayer space of smectites. Further, adsorbed Fluazifop-butyl was partially decomposed at room temperature giving rise to a phenolic compound.     

Variability in water sorption and in particle thickness of standard smectites

Variability in sorbed water content was studied on several standard smectites, as dependent on the relative humidity (RH=0.5, 0.95 and 1.0), on temperature (constant 30 °C and variable room temperature) and on sorption time (t_s=1, 12 and 32 days). The particle thickness, δ was estimated, assuming a given number of molecular layers of sorbed water at the given RH. δ decreased with the increase in the factors mentioned above.The thickest particles in dry state were found in hectorite and in synthetic mica/smectite (SHCa-1 and Syn-1, δ=22 and 20 unit layers [u.l.], respectively), the thinnest ones-in Ca-smectite (SAz-1) and in nontronite (SWa-1, δ=5–6 u.l.) and the intermediate both in Na-smectite (SWy-1) and in Ca-smectite (STx-1), δ=12 and 8 u.l., respectively.On prolonged storage at RH=1.0, t_s=32 days, the smectite particles disintegrated gradually into separate crystallites, δ=3–5 u.l., thus close to the thickness measured by XRD. An exception was hectorite, SHCa-1, with δ=6–8 u.l. possibly due to “gluing” by calcium carbonate present.The decrease in δ (delamination) observed on increasing RH was partly reversible. The hysteresis between water sorption on its increasing (WS) and water retention on its lowering to RH=0.5 (WR) was especially pronounced in SHCa-1, SWy-1 and Syn-1 of initially thick particles. This was due either to a different number of the sorbed water layers, higher in WR, or to incomplete collapse in WR.     

Reversible collapse and Mg release of de- and rehydroxylated homoionic cis-vacant montmorillonites

Homoionic Na⁺, Ca²⁺, Sr²⁺, Li⁺, Cu²⁺ and Zn²⁺ samples of the <2 μm fraction of a cis-vacant montmorillonite from Linden (Bavaria) were steam treated at 200°C (≈1.5 MPa), 240°C (≈3.3 MPa) and 300°C (≈8.0 MPa) after dehydroxylation at temperatures up to 630°C. Cation exchange capacity (CEC) measurements, determination of exchangeable cations and X-ray diffraction (XRD), supplemented by thermoanalytical investigations of the evolved water in a thermobalance linked to a mass spectrometer, infrared (IR) and electron spin resonance (ESR) spectroscopy were employed to obtain information about the state of expandability and structural changes of swellable montmorillonite and the sites of interlayer and octahedral cations after heating and rehydroxylation.The XRD pattern of the initial samples showed a well-defined (001) reflection according to the interlayer cation and its hydration state under laboratory atmosphere. After dehydroxylation the pattern exhibited (001) reflections between 9.6 and 9.8 Å, corresponding to a collapsed structure for all samples. The Na⁺-, Ca²⁺- and Sr²⁺-rich montmorillonites regained partial expandability after rehydroxylation at 200°C and full expandability after rehydroxylation at 300°C if the dehydroxylation temperature was less than 630°C. Rehydroxylation at 300°C of the Cu²⁺- and Zn²⁺-rich montmorillonites did not cause reexpansion, whereas the Li⁺-rich samples recovered a partial swellability after rehydroxylation at 240°C and nearly the full swellability after rehydroxylation at 300°C.The Li⁺-, Cu²⁺- and Zn²⁺-rich samples underwent a strong CEC reduction due to migration of the interlayer cations into the 2:1 layer before dehydroxylation started. After rehydroxylation under water steam Cu²⁺- and Zn²⁺-rich samples released 16–30 meq/100 g of Mg²⁺ from the structure, increasing with the steam temperature. Mg²⁺ release was not observed for the Li⁺-rich montmorillonite.     

Hydrothermal synthesis and characterization of dioctahedral smectites: A montmorillonites series

The aim of this study is to synthesize and finely characterize montmorillonite samples, dioctahedral smectites without tetrahedral charges (structural formulae Na_x(Al_(2 − x)Mg_x)Si₄O₁₀(OH)₂), to allow their use as reference samples in clay science. The montmorillonites synthesis under hydrothermal conditions at different pressures and with various layer charge deficit has been attempted. The temperature was fixed at 320 °C, the pressure parameter values were 20 MPa, 80 MPa, 120 MPa and 200 MPa. The Mg content varied from 0.25 to 0.60 per half unit cell. The reaction products have been characterized with multi-technique analyses (ICP-AES, EMP, CEC, XRD, FTIR, NMR and TGA).Montmorillonite phase was only produced at 120 and 200 MPa.At 20 and 80 MPa, the results suggest that a 0.33 and 0.16-tetrahedral charge deficit exist in the formed samples. Moreover, the octahedral occupancies are higher than two (2.15 and 2.07 at 20 and 80 MPa respectively). In these experimental conditions, the synthetic smectites are mixtures between montmorillonite, beidellite and saponite.At 120 MPa and for a Mg content of 0.25 or higher than 0.33, the synthetic products were also mixtures of smectites. Tetrahedral charge deficits of 0.11, 0.11 and 0.15 were found for Mg contents of 0.25, 0.50 and 0.60 respectively. The octahedral occupancy was also higher than 2.00.A montmorillonite phase with only octahedral charges and an octahedral occupancy near 2.00 was synthesized for a Mg content of 0.33 and at pressures equal to or higher than 120 MPa. This low charge reference smectite shows a very low amount of accessory minerals and an octahedral charge deficit only created by the presence of magnesium in the structure. This montmorillonite can be compared structurally to the most studied natural one: the montmorillonite SWy-2 from Wyoming.     

Sorption of phosphates on Al-pillared smectites and mica at acidic to neutral pH

To investigate sorption behaviors and mechanisms of phosphates, phosphate sorption (hereafter, P sorption) experiments were carried out for synthetic montmorillonite, beidellite, saponite, and fluor-tetrasilicic expandable mica pillared with cationic, Keggin ion-like, Al clusters (Al_clst). The P sorption experiments were done in the final pH range of 3 to 7 at room temperature and at an initial concentration of 3.2 mmol/l P. The P sorption maxima for the Al_clst samples were 0.66–0.87 mmol/g, which are higher by about 2 orders of magnitude than those for smectites without Al_clst pillars. The sorption ability of the Al_clst samples is nearly as high as that of Al-bearing minerals and materials such as boehmite and amorphous Al hydroxide, which are regarded as effective absorbents to remove P from water. Examinations by X-ray diffraction analysis, infrared spectroscopy, scanning electron microscopy, and analytical transmission electron microscopy indicated that the P sorption is mostly related to the OH functional groups of the Al_clst pillars, but little to the P species in solution, the reactive sites on the edge surface of smectites and mica, or possible precipitates. The P sorption maxima increased with increasing an amount of Al_clst pillars in the Al_clst samples, suggesting that the P sorption maximum is determined by the number of the OH functional groups of the Al_clst pillars and is independent of the structures and chemical compositions of the host phases.     

Influence of layer charge and charge distribution of smectites on the flow behaviour and swelling of bentonites

The influence of layer charge and charge distribution of dioctahedral smectites on the rheological and swelling properties of bentonites is examined. Layer charge and charge distribution were determined by XRD using the LayerCharge program [Christidis, G.E., Eberl, D.D., 2003. Determination of layer charge characteristics of smectites. Clays Clay Miner. 51, 644–655.]. The rheological properties were determined, after sodium exchange using the optimum amount of Na₂CO₃, from free swelling tests. Rheological properties were determined using 6.42% suspensions according to industrial practice. In smectites with layer charges of − 0.425 to − 0.470 per half formula unit (phfu), layer charge is inversely correlated with free swelling, viscosity, gel strength, yield strength and thixotropic behaviour. In these smectites, the rheological properties are directly associated with the proportion of low charge layers. By contrast, in low charge and high charge smectites there is no systematic relation between layer charge or the proportion of low charge layers and rheological properties. However, low charge smectites yield more viscous suspensions and swell more than high charge smectites. The rheological properties of bentonites also are affected by the proportion of tetrahedral charge (i.e. beidellitic charge), by the existence of fine-grained minerals having clay size, such as opal-CT and to a lesser degree by the ionic strength and the pH of the suspension. A new method for classification of smectites according to the layer charge based on the XRD characteristics of smecites is proposed, that also is consistent with variations in rheological properties. In this classification scheme the term smectites with intermediate layer charge is proposed.     

Influence of layer charge and charge distribution of smectites on the flow behaviour and swelling of bentonites

The influence of layer charge and charge distribution of dioctahedral smectites on the rheological and swelling properties of bentonites is examined. Layer charge and charge distribution were determined by XRD using the LayerCharge program [Christidis, G.E., Eberl, D.D., 2003. Determination of layer charge characteristics of smectites. Clays Clay Miner. 51, 644–655.]. The rheological properties were determined, after sodium exchange using the optimum amount of Na₂CO₃, from free swelling tests. Rheological properties were determined using 6.42% suspensions according to industrial practice. In smectites with layer charges of − 0.425 to − 0.470 per half formula unit (phfu), layer charge is inversely correlated with free swelling, viscosity, gel strength, yield strength and thixotropic behaviour. In these smectites, the rheological properties are directly associated with the proportion of low charge layers. By contrast, in low charge and high charge smectites there is no systematic relation between layer charge or the proportion of low charge layers and rheological properties. However, low charge smectites yield more viscous suspensions and swell more than high charge smectites. The rheological properties of bentonites also are affected by the proportion of tetrahedral charge (i.e. beidellitic charge), by the existence of fine-grained minerals having clay size, such as opal-CT and to a lesser degree by the ionic strength and the pH of the suspension. A new method for classification of smectites according to the layer charge based on the XRD characteristics of smecites is proposed, that also is consistent with variations in rheological properties. In this classification scheme the term smectites with intermediate layer charge is proposed.     

Catalysts for the preparation of polybenzimidazoles

The single-stage preparation of poly[2,2′-(m-phenylene)-5,5′-bibenzimidazole] (PBI), from 3,3′,4,4′-tetraaminobiphenyl (TAB) with isophthalic acid (IPA) in the presence of a catalyst, was explored and developed. The effects of a variety of catalysts on the polymerization of TAB with IPA and/or diphenyl isophthalate were screened and evaluated. Many organo phosphorus and silicon compounds catalyzed the PBI condensation reactions, increased the molecular weight, and improved the quality of PBI polymers. Fiber and reverse osmosis membrane properties of PBI prepared from TAB and IPA were comparable to those for commercial standard PBI prepared from TAB and diphenyl isophthalate. © 1994 John Wiley & Sons, Inc.     

热固性树脂的制备工艺

本发明涉及了以热固性树脂作为基料的电泳漆。本发明叙述了采用水溶性或水分散性树脂A(每千克树脂A含有0．2～1mol的氢氧化季铵基团)，来控制质子化的热固性树脂B(带有叔氨基，分散在水性电泳槽中)在阴极电泳期间水性电泳槽的pH值。     

Stakeholder communications for successful water reuse operations

A well-organised, comprehensive communications program with stakeholders is essential to any modern water reuse project. To maximise trust between water reuse organisations and stakeholders, the communication process needs to begin long before project plans are drawn up and continue throughout the life of any project. It must begin with the decision to seriously consider the development of a scheme and remain highly visible throughout all of its stages, including planning, construction, implementation and operation. The communications program must also embrace any extensions of the project. This paper relates to a study that was undertaken in the preliminary preparation of a manual of best practice for water recycling operations. The purpose of the study was to provide an understanding of major communication issues to be addressed and successful means of addressing them. Ten key messages to stakeholders were established during the process and are presented here.     

青龙寺选煤厂优化设计

通过青龙寺矿区煤质特征分析、筛分和浮沉实验资料分析以及可选性评定,确定了选煤厂产品结构。选煤厂入洗上限为50mm,入洗下限为0.25mm,经粗煤泥分选和细煤泥干燥的研究,最终确定工艺流程为50～0mm原煤采用无压给料三产品重介旋流器分选;1.5～0.25mm的粗精煤和粗中矸煤分别回收后掺入精煤和中煤;-0.25mm细粒煤采用加压过滤机及压滤机联合脱水,脱水后细煤泥可直接掺入中煤或矸石,也可部分或全部进入干燥系统干燥,干燥后的煤泥掺入中煤。此优化设计工艺系统与原地面工艺系统方案相比优势显著。     

Japanese试剂的合成新方法

用二甲苯作溶剂来代替1,2,4－三氯苯使五硫化二磷和硫酚反应,制得的Japanese试剂产率由58％提高到72%。     

Evaluation of the phytomass source for composite preparation

The properties of lignocellulose materials from the trunk and bark of trees, and from agricultural sources were investigated by thermogravimetry (TG) and pyrolysis–gas chromatography/mass spectrometry (Py‐GC/MS). The goal was to learn which of the phytomass sources is the most accessible to dehydration and aldol reactions, and in this way could be considered suitable for composite preparation by the thermal pressing treatment. The bagasse second differential thermal analysis peak in air is at the highest temperature acceptable for intermolecular dehydration/crosslinking, and therefore we consider bagasse to be the most suitable candidate for composite preparation. From the TG results in air at 250°C, it follows that willow wood and bagasse are the most thermally resistant sources. The data obtained by Py‐GC/MS analysis showed glycolaldehyde and acetic acid as dominant markers related to adhesion properties via aldol condensation. The detected sum amount of glyceraldehyde and acetic acid decreases in the order: beech wood > bagasse > acacia wood > sugar beet pulp, whereas the remaining species produced much less of it. By comparing results run at above conditions with composite preparation using the pressing thermal treatment at a temperature of 150°C and pressures up to 800 kPa, the suggested evaluation was examined for application on sugar beet residue. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013