Structure and inhibition properties of a new amine-terminated hyperbranched oligomer shale inhibitor

To inhibit the hydration and dispersion of shale in drilling, a new amine-terminated hyperbranched oligomer (HBO-NH₂) shale inhibitor was synthesized. Compared with linear polymer inhibitors and inorganic salts, HBO-NH₂ possessed a unique hyperbranched structure and plenty of amine groups. The characterization of HBO-NH₂ was done through the aid of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance hydrogen spectroscopy, and time of flight mass spectrum. Upon thermogravimetric analysis, HBO-NH₂ demonstrated favorable thermal stability below 180 °C. As a shale inhibitor, the interlayer spacing of wet bentonite treated with HBO-NH₂ was significantly reduced from 1.9070 to 1.3422 nm in X-ray diffraction analysis. The recovery rate of shale cuttings reached the highest (76.85%) at 120 °C, when the concentration of HBO-NH₂ was 3 wt %. Due to the adsorption of protonated primary amine groups on bentonite particles, the zeta potential absolute value of bentonite base slurry was maintained in a relatively low range of 5–10 mV after HBO-NH₂ treatment. Also, FTIR analysis suggested that hydrogen bonds existed between bentonite and HBO-NH₂. In scanning electron microscope analysis, the inhibition of HBO-NH₂ was observed by the curl degree of bentonite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47573.     

Improved evidence for the existence of an intermediate phase during hydration of tricalcium silicate

Tricalcium silicate (Ca₃SiO₅) with a very small particle size of approximately 50 nm has been prepared and hydrated for a very short time (5 min) by two different modes in a paste experiment, using a water/solid-ratio of 1.20, and by hydration as a suspension employing a water/solid-ratio of 4000. A phase containing uncondensed silicate monomers close to hydrogen atoms (either hydroxyl groups or water molecules) was formed in both experiments. This phase is distinct from anhydrous tricalcium silicate and from the calcium-silicate-hydrate (C-S-H) phase, commonly identified as the hydration product of tricalcium silicate. In the paste experiment, approximately 79% of silicon atoms were present in the hydrated phase containing silicate monomers as determined from ²⁹Si{¹H} CP/MAS NMR. This result is used to show that the hydrated silicate monomers are part of a separate phase and that they cannot be attributed to a hydroxylated surface of tricalcium silicate after contact with water. The phase containing hydrated silicate monomers is metastable with respect to the C-S-H phase since it transforms into the latter in a half saturated calcium hydroxide solution. These data is used to emphasize that the hydration of tricalcium silicate proceeds in two consecutive steps. In the first reaction, an intermediate phase containing hydrated silicate monomers is formed which is subsequently transformed into C-S-H as the final hydration product in the second step. The introduction of an intermediate phase in calculations of the early hydration of tricalcium silicate can explain the presence of the induction period. It is shown that heterogeneous nucleation on appropriate crystal surfaces is able to reduce the length of the induction period and thus to accelerate the reaction of tricalcium silicate with water.     

Hydration mechanism and sintering characteristics of hydratable alumina with microsilica addition

Hydratable alumina is potential for the application in refractory industry as one of Ca-free binders, but it is greatly limited because of the excess hydration of rho-alumina (ρ-Al₂O₃). In this study, hydration mechanism and sintering characteristics of hydratable alumina with different microsilica addition are researched, via the rheological, hydration, and morphological characteristics of ρ-Al₂O₃–SiO₂–H₂O system during aging are analyzed using various techniques. Boehmite (AlOOH) initially appears and increases in content after 1 h aging at the setting temperature of 30 °C and relative humidity of 80%. As the addition of microsilica increases from 0 wt% to 8 wt%, the SiO₂ coating combines with the boehmite gel and efficiently suppresses the hydration reaction, resulting in decrease of relative hydrated densities from 5.42% to 4.27% and increase of zeta potential from −10.1 mV to −21.3 mV. Further, the thus-formed SiO₂-AlOOH gels cover the surface of hydratable alumina particles, connect with each other, and get distributed homogeneously around hydratable alumina particles to harden, thus inhibiting the further hydration. This is reflected by the high-temperature X-ray diffraction and the final sintering microstructures. Overall, these results indicate that the 6 wt% addition of microsilica makes hydratable alumina promising for application as a kind of controlled binders.     

The structure and application of amine‐terminated hyperbranched polymer shale inhibitor for water‐based drilling fluid

Amine‐terminated hyperbranched polymer (HBP‐NH₂), as an inhibitor in water‐based drilling fluid, is prepared by the polycondensation of diamine AB₂ monomers. The primary amine and secondary amide structures are confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy. Through time of flight mass spectrometry, the molecular weight of HBP‐NH₂ is mainly distributed in the range of 200–1400. Also, the quasi‐spherical shape and the high temperature resistance (200 °C) performance of HBP‐NH₂ are, respectively, certified through the environmental scanning electron microscope and the thermogravimetric analysis. In the inhibition performance test, the linear expansion rate of sodium bentonite in 3 wt % HBP‐NH₂ aqueous solution is only 11.42%, which is lower than other inhibitors (KCl, FA‐367, and HPAM). Zeta potential analysis shows that HBP‐NH₂ has a strong ability to inhibit the hydration and dispersion of sodium bentonite by protonated primary amine groups. Compared with the base slurry, the absolute value of zeta potential is reduced by 25.5 mV in the slurry containing 3 wt % HBP‐NH₂ at 180 rpm. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45466.     

A Preliminary Investigation of the ISG Glass Vapor Hydration

During the geological disposal of high-level waste, the nuclear glass is expected to be first hydrated in water vapor prior to liquid alteration. In the present work, we investigated the vapor hydration of the International simple glass (ISG) at 175°C and different relative humidities (60%, 80% and 98%). The glass hydration was investigated by nuclear reaction analysis (NRA) and Fourier transform infra-red spectroscopy. The chemical and mineralogical compositions of the alteration products were studied using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDS) and μ-Raman spectroscopy, respectively. The NRA results gave water diffusion coefficients of 2.31–7.34 × 10⁻²¹ m²/s_, in good agreement with the literature data on borosilicate glasses altered in aqueous media. The glass hydration increased with relative humidity percentage and the SEM-EDS analysis showed a slight enrichment in Si and loss of Na in the hydrated glass layer compared with the pristine glass. The hydration rate of the ISG glass was little higher than that of the French SON68 glass hydrated using water vapor. The corrosion products were analcime, tobermorite, and calcite, which were typical of the SON68 glass hydrated in similar conditions.     

Small-Molecule Inhibitors Targeting Sterol 14α-Demethylase (CYP51): Synthesis,Molecular Modelling and Evaluation Against Candida albicans

Fungal infections are a global issue affecting over 150 million people worldwide annually, with 750 000 of these caused by invasive Candida infections. Azole drugs are the frontline treatment against fungal infections; however, resistance to current azole antifungals in C. albicans poses a threat to public health. Two series of novel azole derivatives, short and extended derivatives, have been designed, synthesised and investigated for CYP51 inhibitory activity, binding affinity and minimum inhibitory concentration (MIC) against C. albicans strains. The short derivatives were more potent against the C. albicans strains (e. g., MIC 2-(4-chlorophenyl)-N-(2,4-dichlorobenzyl)-3-(1H-imidazol-1-yl)propanamide ( 5 f ) <0.03 μg/mL, N-(4-((4-chlorophenyl)sulfonamido)benzyl)-2-phenyl-3-(1H-1,2,4-triazol-1-yl)propanamide ( 12 c ), 1 μg/mL, fluconazole 0.125 μg/mL) but both displayed comparable enzyme binding and inhibition ( 5 f K_d 62±17 nM, IC₅₀ 0.46 μM; 12 c K_d 43±18 nM, IC₅₀ 0.33 μM, fluconazole K_d 41±13 nM, IC₅₀ 0.31 μM, posaconazole K_d 43±11 nM, IC₅₀ 0.2 μM). The short series had poor selectivity for CaCYP51 over the human homologue, whereas the selectivity of the extended series, for example, compound 12 c , was higher (21.5-fold) than posaconazole (4.7-fold) based on K_d values, although posaconazole was more selective (615-fold) than 12 c (461-fold) based on IC₅₀ values. Based on inhibitory activity and selectivity profile, the extended series are the better of the two series for further development.     

Hydrogen production in fluidized bed by chemical-looping cycle

To investigate the feasibility of a chemical-looping hydrogen generation system, we investigated the reduction and water splitting reaction characteristics for three mediators and two reducing gas in a bubbling fluidized bed reactor (0.02 m I.D.). For three oxygen carrier particles (NiO/bentonite, Fe₂O₃/bentonite, (NiO:Fe₂O₃)/bentonite), hydrogen was used as a reduction gas and water was used as an oxidation gas. For (NiO: Fe₂O₃)/bentonite particle, carbon monoxide, which is the main component in the syngas from coal or heavy residue, was used as a reducing gas to check reactivity for the carbon containing fuels and carbon deposition characteristics. Based on the reactivity tests, (NiO: Fe₂O₃)/bentonite particle was selected as the best mediator for the chemical-looping hydrogen generation system to achieve stable continuous operation. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Synergistic effect of iodide ions on inhibitive performance of 2,5-bis(4-methoxyphenyl)-1,3,4-thiadiazole during corrosion of mild steel in 0.5?M sulfuric acid solution

The synergistic effect of iodide ions on the corrosion inhibition of mild steel in 0.5 M H₂SO₄ solutions by 2,5-bis(4-methoxyphenyl)-1,3,4-thiadiazole (4-MTH) has been studied using electrochemical impedance spectroscopy (EIS) and the Tafel polarisation method. The results showed that the inhibition efficiency increased with 4-MTH concentration while the potential of desorption (E _d) remained unchanged. The addition of potassium iodide (KI) in the acid solution stabilized the adsorption of 4-MTH molecules on the metal surfaces and, therefore, enhanced the inhibition efficiency of 4-MTH and increased the value of E _d. The synergistic effect was observed between KI and 4-MTH with an optimum mass ratio of [4-MTH]/[KI] = 5/5. The calculated values of synergism parameter (S _θ) from the coverage of the surface were found to be more than unity in most cases. This clearly showed the synergistic influence of iodide ions on the corrosion inhibition of mild steel in 0.5 M H₂SO₄ by 4-MTH. The adsorption of this inhibitor alone and in combination with iodide ions followed Langmuir’s adsorption isotherm.     

A kinetic evaluation of the anaerobic digestion of two‐phase olive mill effluent in batch reactors

A comparative kinetic study was carried out on the anaerobic digestion of two‐phase olive mill effluent (TPOME) using three 1‐dm³ volume stirred tank reactors, one with freely suspended biomass (control), and the other two with biomass supported on polyvinyl chloride (PVC) and bentonite (aluminium silicate), respectively. The reactors were batch fed at mesophilic temperature (35 °C) using volumes of TPOME of between 50 and 600 cm³, corresponding to chemical oxygen demand (COD) loadings in the range of 1.02–14.22 g, respectively. The process followed first‐order kinetics and the specific rate constants, K₀, were calculated. The K₀ values decreased considerably from 2.59 to 0.14 d^?1, from 1.93 to 0.23 d^?1 and from 1.52 to 0.17 d^?1 for the reactors with suspended biomass (control) and biomass immobilized on PVC and bentonite, respectively, when the COD loadings increased from 1.02 to 14.22 g; this showed an inhibition phenomenon in the three reactors studied. The values of the critical inhibitory substrate concentration (S*), theoretical kinetic constant without inhibition (K_A) and the inhibition coefficient or inhibitory parameter for each reactor (n) were determined using the Levenspiel model. Copyright © 2004 Society of Chemical Industry     

Effect of iodide ions on corrosion inhibition of mild steel by 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole in sulfuric acid solution

The synergistic effect of iodide ions on the corrosion inhibition of mild steel in 0.5 M sulfuric acid (H₂SO₄) in the presence of 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole (4-MTHT) was investigated using weight loss measurements and different electrochemical techniques such as potentiostatic polarization curves and electrochemical impedance spectroscopy (EIS). The inhibition efficiency (E, %) increased with 4-MTHT concentration, but the desorption potential (E _d) remained unchanged with increasing 4-MTHT concentration. The addition of potassium iodide (KI) enhanced E considerably and increased the value of E _d. A synergistic effect was observed between KI and 4-MTHT with an optimum mass ratio of [4-MTHT]/[KI] = 4 × 10^–2. The synergism parameters (S ) calculated from surface coverage were found to be more than unity. This result clearly showed the synergistic influence of iodide ions on the corrosion inhibition of mild steel in 0.5 M H₂SO₄ by 4-MTHT. The adsorption of this inhibitor alone and in combination with iodide ions followed Langmuir's adsorption isotherm.     

Solid-state C NMR investigation of the structure and hydrogen bonding for stereoregular poly(vinyl alcohol) films in the hydrated state

The structure and hydrogen bonding of the hydrated stereoregular poly(vinyl alcohol) (PVA) films have been investigated by high-resolution solid-state ¹³C NMR spectroscopy. It is found by the ¹³C spin-lattice relaxation analysis that there exist three components with different T_1C values assigned to the crystalline, less mobile and mobile components for the hydrated syndiotactic PVA (S-PVA) and highly isotactic PVA (HI-PVA) films. The line shape analysis indicates that the probability of intramolecular hydrogen bonding is appreciably increased in the crystalline region for the S-PVA films by the hydration but a slightly helical structure, which is probably allowed by the formation of the successive intramolecular hydrogen bondings along the chains in the crystalline region, seems not to undergo any significant change by the hydration for HI-PVA. This fact indicates that intramolecular hydrogen bonding is more stable in the hydrated state in the crystalline region. As for the less mobile component, the line shape of the CH resonance line for the hydrated S-PVA or HI-PVA films is found to be very similar to that of the corresponding crystalline component, probably being due to the successive formation of intermolecular or intramolecular hydrogen bonding in the interfacial region, which mainly contributes to the less mobile component, for the S-PVA or HI-PVA films even in the hydrated state. The mole fractions of the mm, mr and rr sequences are also estimated for the mobile component that is produced in each stereoregular PVA sample by swelling with water and it is concluded that no prominent preferential partitioning of the mm, mr and rr sequences occurs in the crystalline and noncrystalline regions for the PVA films with different tacticities.     

Removal of 3—(3,4—dichlorophenyl)—1, 1 dimethylurea from aqueous solution by natural and activated bentonite

The adsorption of 3-(3,4-dichlorophenyl)-1,1 dimethylurea (diuron) on bentonite desiccated at 110°C untreated, and acid treated with H₂SO₄ solutions over a concentration range between 0.25 M and 5.00 M, from aqueous solution at 30°C has been studied. In addition, adsorption of diuron on combined acid/heat treated samples (0.50 M and 2.50 M H₂SO₄/200°C and 400°C) has also been studied. The experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K) of the samples; K values range from 0.92 μg g^?1 for the untreated bentonite up to 974.42 μg g^?1 for the 0.50 M H₂SO₄/400°C acid/heat treated bentonite. The removal efficiency (R) has also been calculated; R values ranging from 2.02% for the untreated bentonite up to 97.17% for the 0.50 M H₂SO₄/400°C acid/heat treated bentonite. The adsorption experiments show that bentonite heat treatment is more effective than bentonite acid treatment in relation to adsorption of diuron.     

An Extended Empirical Valence Bond Model for Describing Proton Mobility in Water

In order to study the microscopic nature of the hydrated proton and its transport mechanism, we have introduced a multistate empirical valence bond model, fitted to ab initio results. This model was applied to the study, at low computational cost, of the structure and dynamics of an excess proton in liquid water. The quantum character of the proton is included by means of an effective parametrization of the model using preliminary path-integral calculations. The mechanism of proton transfer is interpreted as the translocation of a special O–H⁺–O bond along the hydrogen network, i.e., a series of reactions of the form H₅O₂⁺ + H₂O ⇌ H₂O + H₅O₂⁺, rather than H₃O⁺ + H₂O → H₂O + H₃O⁺ as usually described. The translocation of the special bond can be described as a diffusion process with a jump time of 1 ps. A time-dependent correlation function analysis of the special pair relaxation yields two timescales, 0.3 and 3.5 ps. The first time is attributed to the interconversion between a delocalized (H₅O₂⁺-like) and a localized (H₉O₄⁺-like) form of the hydrated proton within a given special pair. The second one is the relaxation time of the special pair, including return trajectories. The computed diffusion constant, as well as the isotopic substitution effect, are in good agreement with experiment. The hydration structure around the excess proton is discussed in terms of various radial distribution functions around the water molecules involved in the special pair and those in the first solvation shell. The hydrogen-bond-dynamics which accompanies the translocation process is studied statistically. The “Moses mechanism” proposed by Noam Agmon for proton mobility in water is partially verified by our simulations.     

Influence of slag chemistry on the hydration of alkali-activated blast-furnace slag — Part II: Effect of Al2O3

The hydration and microstructural evolution of three alkali activated slags (AAS) with Al₂O₃ contents between 7 and 17% wt.% have been investigated. The slags were hydrated in the presence of two different alkaline activators, NaOH and Na₂SiO₃·5H₂O. The formation of C(A)–S–H and hydrotalcite was observed in all samples by X-ray diffraction, thermal analysis and scanning electron microscopy. Higher Al₂O₃ content of the slag decreased the Mg/Al ratio of hydrotalcite, increased the Al incorporation in the C(A)-S-H and led to the formation of strätlingite. Increasing Al₂O₃ content of the slag slowed down the early hydration and a lower compressive strength during the first days was observed. At 28 days and longer, no significant effects of slag Al₂O₃ content on the degree of hydration, the volume of the hydrates, the coarse porosity or on the compressive strengths were observed.     

Combined hydration of tricalcium silicate and β-dicalcium silicate

The mutual interaction of tricalcium silicate (C₃S) and β-dicalcium silicate (β-C₂S) in their combined hydration was studied. The rate of β-C₂S hydration was accelerated significantly in the presence of C₃S. The rate of C₃S hydration was retarded, but only in the presence of large amounts of β-C₂S. The stoichiometric composition and the pore structure of the hydrates formed was altered only unsignificantly when both compound hydrated simultaneously.     

An IR study on ion-specific and solvent-specific swelling of poly(N-vinyl-2-pyrrolidone) gel

Swelling degrees of poly(N-vinyl-2-pyrrolidone) (PVP) gel were measured in aqueous salt solutions and in water/organic solvent mixtures to find marked ion- and solvent-specificities. In order to investigate any correlation of those specificities with hydration or solvation of PVP, IR spectra band of the CO group was monitored by means of ATR method both for PVP gel and the relevant solution systems. Dependence of the peak frequency on the swelling ratio suggested that hydration of PVP carbonyl group in deswollen gel systems is different from that in the corresponding solution systems. In the solution systems, PVP carbonyl band showed a high-wavenumber shift for deswollen systems, which can be well correlated with changes in water proton charge through ionic hydration and with Gutmann's acceptor number of organic solvents. In the deswollen gel systems, the CO band showed a low-wavenumber shift, suggesting a strong hydration or doubly hydrated state. This unexpected behavior was interpreted by assuming an intermolecular hydrogen bond of two carbonyl groups intermediated by water molecules.     

Electronic-level interactions of tungsten oxide with unsupported Se/Ru electrocatalytic nanoparticles

Se/Ru nanoparticles - a potent non-platinum catalyst towards oxygen reduction reaction - were modified by hydrated WO₃ and investigated using the rotating disk/ring electrode methods and by synchrotron X-ray photoelectron spectroscopy. The modification resulted in an enhanced catalytic activity towards oxygen reduction reaction (ORR). Our data indicate that the oxygen reduction current starts ca. 70 mV more positive and formation of undesirable hydrogen peroxide has significantly decreased following the modification of Se/Ru with WO₃. X-ray photoelectron spectroscopy reveals that WO₃ interacts electronically with Se/Ru as the W 4f and Se 3d line-shapes change. We therefore conclude that the electronic interactions between Se/Ru and WO₃ are primarily responsible for the increase in activity and selectivity of the WO₃-modified Se/Ru towards ORR.     

Modified bentonites as adsorbents of hydrogen sulfide gases

Carbonate-rich bentonite was modified by iron and copper chlorides in order to synthesize effective and cheap adsorbents for neutralization of H₂S in low-concentrated exhaust gases. Bentonite and modified bentonite were analysed using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and BET surface area analysis. In addition, bentonite and modified bentonite were tested as hydrogen sulfide adsorbents. Iron-containing material showed a significant improvement in the capacity for H₂S removal. The longest time of effective protective action (before H₂S appears on the outlet of the column) was obtained for the bentonite modified with copper hydroxide. The results indicated that on the surface of modified samples hydrogen sulfide reacts with metal hydroxide forming sulfides. Sulfided iron-containing sample could be regenerated by exposing it to the air.     

Preparation of diatomite/Ca(OH)2 sorbents and modelling their sulphation reaction

Mixtures of Ca(OH)₂ and diatomite were hydrated at different conditions to produce reactive SO₂ sorbents. Two different hydration techniques were used; namely, atmospheric and pressure hydration. The effect of the hydration temperature, time and diatomite/Ca(OH)₂ weight ratio on the physical properties of the activated sorbents were investigated. In atmospheric hydration, it was found that increasing the temperature and hydration time caused an increase in the total surface area of the sorbents. However, surface area values of the sorbents prepared from mixtures which have different diatomite/Ca(OH)₂ weight ratio were generally not changed significantly. In pressure hydration, the surface area of the activated sorbents was positively affected from the hydration temperature and pressure. Finally, Ca(OH)₂ and two diatomite/Ca(OH)₂ sorbents were sulphated at constant temperature using a synthetic gaseous mixture consisting of 5% O₂, 10% CO₂, and the balance of nitrogen with a 55% relative humidity. The sulphation reaction of these sorbents were investigated and modelled. The unreacted shrinking core model was chosen to describe this non-catalytic solid/gas (hydrated sorbent/SO₂) reaction mechanism. The experimental results were found to be correlated successfully by this model.     

Molecular dynamics studies of a model polymer-catalyst-carbon interface

Classical molecular dynamics simulations are performed to obtain insights into structural and dynamical behavior of water and O₂ transport through a model polymer membrane, and at the interface of such hydrated polymer with graphite-supported nanocatalyst platinum particles. Water clustering is observed near the membrane hydrophilic sites constituted by sulfonic groups, which due to their affinity with platinum, are located near the metallic surface. It is found that the diffusion of water through the model hydrated polymer membrane depends strongly on the level of membrane hydration due to contribution from various mechanisms whose relative weights change with the degree of hydration. Possible scenarios for O₂ diffusion are also analyzed.