Gibbs Free Energy Values Research Articles

Ketoprofen-FA Co-crystal: In Vitro and In Vivo Investigation for the Solubility Enhancement of Drug by Design of Expert.

The present piece of research work is framed for improving the solubility of ketoprofen by forming co-crystal using fumaric acid as a coformer. Co-crystal of ketoprofen and fumaric acid was prepared by simple solvent-assisted grinding method, containing drug and coformer as independent variables and solubility and % drug release were assumed to be dependent variables. Differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, nuclear magnetic resonance and scanning electron microscopy techniques were used to characterize the preparation of optimized batch of co-crystal and further, evaluated for in vitro and in vivo anti-inflammatory and analgesic activities. Based on results of solubility and dissolution rate studies the formulation showed magnified improvement in both the properties on co-crystallization. The values of Gibbs free energy are negative at all levels of carrier demonstrating spontaneity of the drug solubilization process. The IC50 value of optimized batch of co-crystal formulation and the pure drug was observed as 327.33μg/ml and 556.11μg/ml, respectively, demonstrating that co-crystal formulation possesses more percentage protection against protein denaturation than the drug ketoprofen. In vivo (anti-inflammatory and analgesic) activities revealed that optimized batch of co-crystal formulation delivered a rapid pharmacological response in Wistar rats and albino mice when compared with standard drug.

Effect of Soybean Protein Isolate-7s on Delphinidin-3-O-Glucoside from Purple Corn Stability and Their Interactional Characterization.

Anthocyanins are abundant in purple corn and beneficial to human health. Soybean protein isolate-7s (SPI-7s) could enhance the stability of anthocyanins. The stable system of soybean protein isolate-7s and delphinidin-3-O-glucoside complex (SPI-7s-D3G) was optimized using the Box–Behnken design at pH 2.8 and pH 6.8. Under the condition of pH 2.8, SPI-7s effectively improved the sunlight-thermal stabilities of delphinidin-3-O-glucoside (D3G). The thermal degradation of D3G conformed to the first order kinetics within 100 min, the negative enthalpy value and positive entropy value indicated that interaction was caused by electrostatic interaction, and the negative Gibbs free energy value reflected a spontaneous interaction between SPI-7s and D3G. The interaction of SPI-7s-D3G was evaluated by ultraviolet visible spectroscopy, circular dichroism spectroscopy and fluorescence spectroscopy. The results showed that the maximum absorption peak was redshifted with increasing the α-helix content and decreasing the β-sheet contents, and D3G quenched the intrinsic fluorescence of SPI-7s by static quenching. There was one binding site in the SPI-7s and D3G stable system. The secondary structure of SPI-7s had changed and the complex was more stable. The stabilized SPI-7s-D3G will have broad application prospects in functional foods.

Optimization of Process Parameters for Adsorption of Hexavalent Chromium from Wastewater Using Response Surface Methodology

This study investigated the optimization of process parameters for adsorption of hexavalent chromium with activated carbons extracted from palm tree leaves of Nigerian origin. The effect of process parameters such as adsorbent dosage, initial chromium concentration, temperature, contact time, and adsorbent particle size was studied with the aid of Central Composite Design. The result showed that for the adsorbent dosage, initial concentration, temperature, contact time, and particle size, the optimum conditions were found to be 20 mg, 80 mg/l, 40° C, 40 minutes, and 1400µm, respectively. The actual and predicted values obtained were 72.96 % as well as 70.33 %, respectively, indicating a good correlation with a comparatively small variance of 2.66 %. The Langmuir isotherm showed an R2 of 0.981 and thereby showing better linearity when compared with the Freundlich isotherm. The result of the adsorption kinetics indicated that it was better described by the Pseudo-second order model. The overall adsorption process on the other hand showed an exothermic reaction with an enthalpy value of -18.707. The values of Gibbs free energy (∆G) at various temperatures also revealed a spontaneous reaction and a positive value of entropy. The results obtained showed that the adsorbent was effective in the adsorption of hexavalent chromium.

Thermodynamic analysis and modeling of water vapor adsorption isotherms of roasted specialty coffee (Coffee arabica L. cv. Colombia)

The experimental assessment and computer modeling of the water vapor adsorption isotherms of roasted specialty coffee is addressed in this study. Thus, both coffee beans and ground coffee of medium (850 μm) and fine (600 μm) particle sizes were analyzed over a range of water activities of between 0.1 and 0.9 and at temperatures of 25, 35, and 45 °C. The adsorption isotherms were determined using the dynamic dew point (DDI) method. The computer modeling of adsorption isotherms was addressed in order to describe the influence of the water activity and temperature on the equilibrium moisture content. Furthermore, the hygroscopic capacity of roasted coffee was analyzed by differential thermodynamic analysis. Experimental results and modeling showed that the high level of moisture adsorption found in the ground coffee was related to a large adsorption area, suggesting that specialty coffee should preferably be stored as beans. The Peleg empirical model was the most suitable at representing both type III upward concave adsorption behavior and the effect of temperature on the adsorption isotherms. Differential thermodynamic analysis revealed an increase in the water adsorption energy at low equilibrium moisture content, while negative Gibbs free energy values revealed the spontaneity of the adsorption process.

Adsorption of methyl violet dye from wastewater using poly(methacrylic acid-co-acrylamide)/bentonite nanocomposite hydrogels

In this study, nanocomposite hydrogels of poly(methacrylic acid-co-acrylamide) (Poly(MAA-co-AAm)) containing different weight percent bentonite clay nanoparticles (0, 5, 10, and 15 wt. %) were used to remove methyl violet (MV) dye. FTIR, SEM, TGA, and XRD were used to analyze the properties of adsorbents. Results showed that bentonite nanoparticles were successfully distributed in the hydrogel system. Bentonite nanoparticles at 10 wt. % gave the maximum MV dye adsorption efficiency. The highest adsorption was obtained at a pH of 5, an adsorbent dosage of 1.5 g/L, a temperature of 25 °C, a contact time of 60 min, and a pollutant concentration of 10 mg/L. In thermodynamics studies, a negative values of Gibbs free energy (ΔG°) indicating that the adsorption process was spontaneous. In addition, Poly(MAA-co-AAm) hydrogels and Poly(MAA-co-AAm)/bentonite nanocomposite hydrogels gave the adsorption enthalpy (ΔH°) of –61.24 and –36.14 kJ/mol witch shows that the adsorption process is exothermic in the temperature range 25–45 °C using both adsorbents. Langmuir isotherm model was successfully applied in describing the equilibrium behavior of the adsorption process. The kinetic study showed that the pseudo-second-order model was more successful in describing the kinetic behavior of the adsorption process than pseudo-first-order and Elovich models. Poly(methacrylic acid-co-acrylamide) and poly(methacrylic acid-co-acrylamide)/bentonite adsorbents gave the α parameter values of 0.4276 and 22.15 mg.(g.min)−1, respectively indicating the high adsorption capacity of these adsorbents.

Kinetics, thermodynamics, and thermal decomposition characteristics of co-pyrolysis of municipality solid waste residue hydrochar and

The solid residues obtained after subjecting Municipality Solid Waste Residue (MSWR) to hydrothermal treatment were blended (50:50) with the <1.5 g/cm3 density-separated fraction of discard coal. Co-pyrolysis experiments were conducted using a thermogravimetric analyser (TGA) in a temperature range of 25 °C to 900°C under N2 atmosphere. The pyrolysis tar yields at 520°C were 17.5%, 35.1% and 26.3% for the coal, MSWR and blended samples, respectively. The pyrolysis char yields were 77.0%, 56.6% and 67.55% for the coal, MSWR and blended sample, respectively at 520°C, and the rest of the distribution contributed to the gas yields. The kinetic and thermodynamic properties of the samples were investigated by TGA using four heating rates (10,20,30, and 40 °C/min). The TGA results were analysed using the model-free isoconversional Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO) and Starink methods. The blended samples showed lower activation energies and higher Gibbs free energy values than coal and MSWR.

Clouding and thermodynamic behavior of the triton X-100 + metformin hydrochloride drug mixture: Investigation of the impacts of potassium salts

The cloud point (CP) of aqueous triton X-100 (TX-100) and metformin hydrochloride (MNH) mixture was investigated in the attendance of various inorganic salts (KCl, KHSO4, K2SO4, and K3PO4) media. TX-100 concentration for CP measurement was chosen well above the critical micelle concentration value of TX-100. The values of CP decrease as the electrolyte’s concentration raises, turning the clear solution cloudy. The reason of the reducing CP is the enhanced aggregation. Thermodynamic variables of the clouding process (standard free energy (ΔG0c), standard enthalpy (ΔH0c), and standard entropy (ΔSco)) were determined at CP. The Gibbs free energy (ΔG0c) values were positive but dropped as the additive (inorganic electrolytes) concentrations increased. This result demonstrated that the TX-100 + MNH mixture's phase partition was thermodynamically unfavoured, and the percentage of its non-spontaneity reduced as the electrolytes concentration enhanced. The values of enthalpy (ΔH0c) and entropy (ΔSco) for the phase separation were achieved negative at lower electrolyte concentrations and positive at higher contents. The ΔH0c and ΔSco values suggest that hydrophobic and electrostatic interactions are the primary forces amongst TX-100 and MNH. Here, the intrinsic enthalpy gain (ΔH0*c) and the compensation temperature (Tc) are as well computed and explained.

Active catalytic species generated in situ in zirconia incorporated hydrogen storage material magnesium hydride

This study explores how zirconia additive interacts with MgH 2 to improve its hydrogen storage performance. Initially it is confirmed that the zirconia added MgH 2 powder releases hydrogen at a temperature of about 50 °C below that of the additive free MgH 2 . Subsequent tests by X ray diffraction (XRD) and infrared (IR) spectroscopy techniques reveal that the ZrO 2 mixed MgH 2 powder contains ZrH x (2 <x> 1.5) and MgO secondary phases. This observation is supported by the negative Gibbs free energy values obtained for the formation of ZrH 2 /MgO from ZrO 2 /MgH 2 powder samples. An X ray photoelectron spectroscopy (XPS) study reveals that apart from Zr 4+ cations, Zr 2+ and zero valent Zr exist in the powder. Atomic force microscopy (AFM) study reveals that the average grain size is 20 nm and the elemental line scan profiles further proves the existence of oxygen deficient Zr bearing phase(s). This study strengthens the belief that functional metal oxide additives in fact chemically interact with MgH 2 to make active in-situ catalysts in the MgH 2 system.

Effective adsorptive removal of dyes and heavy metal using graphene oxide based Pre-treated with NaOH / H2SO4 rubber seed shells synthetic graphite Precursor: Equilibrium Isotherm, kinetics and thermodynamic studies

Graphene oxide (GO) has excellent adsorption capacity as a promising adsorbent due to its large surface area consisting of large number of oxygen-functional groups. Nonetheless, the properties of GO are heavily influenced by the graphite sources and the type of pretreatment. This study aims to investigate the effect of pre-treatment of graphite sourced from agricultural wastes on the properties of the GO for the adsorption of dyes and heavy metal ion. Two sources of graphite (pre-treated with NaOH and H2SO4) were synthesised using biomass wastes (rubber seed shells) and were utlilized to produce high-efficiency GO for the adsorption of Methylene blue (MB), Congo red (CR) and Cadmium (II) from aqueous solutions. The effect of pre-treatment on the GO properties, behavior and performance was evaluated through batch adsorption studies which were conducted under operational condition of activation temperature (25–55 ○C), contact time (2–20 min), dosage (0.02–0.1 g), pH (2–12) using impregnation ratio of 1:4. The morphological analysis revealed that GO pretreated with NaOH (GO-N) graphite source exhibited more porous surface area compared to GO pretreated with H2SO4 (GO-H) graphite source, the surface properties was attributed to higher oxygen ratio as indicated in the EDX mapping and as demonstrated in the BET analysis. In general, both GO demonstrated excellent adsorption capacity due to their single-layered planes with noticeable functional groups which included hydroxyl, alkoxy, and carboxyl groups along with the π − π interactions and hydrogen bonds. Maximum monolayer adsorption capacities for the effective removal of CR, MB and Cd (II) was achieved as 299.38, 311.54, and 107.65 mg g−1 respectively onto GO-N compared to GO-H as illustrated by the Langmuir isotherms. Furthermore, the results showed that the experimental data were well-fitted to the pseudo-second-order model for both CR and MB including Cd (II) with GO-N with higher correlation coeficient R2 (R2 > 0.9) recorded. Thermodynamic study signified that the enthalpy (ΔH) and Gibbs free energy (ΔG) values of the adsorption process for both pollutants were negative indicating that adsorption of CR, MB and Cd were spontaneous and exothermic in nature which suggests that the adsorption of dyes and heavy metal from an aqueous solution was attributed to the presence of active sites and functional groups on the GO surface. However, the study revealed that GO–N proved to be a better adsorbent compared to GO-H under same operational condition and can be considered as a promising and cost-effective adsorbent for the removal of dyes and metal ions from industrial wastewater.

Influence of temperature, ultrasound, and variety on moisture diffusivity and thermodynamic properties of some durum wheat varieties during hydration

This study covers the effect of temperature, ultrasound, and variety on moisture diffusivity and thermodynamic properties of durum wheat varieties during hydration. The process was performed at hydration temperatures of 25, 35, 45, and 55°C during conventional and ultrasound-assisted soaking. The Fick’s diffusion model fitted the experimental data satisfactorily with average coefficient of determination of 0.9946, root mean square error (%, d.b) of 0.0296, Chi-square of 0.0013, and relative mean error (%) of 0.0205, respectively. Deff of wheat varieties during hydration process increased with the ultrasound treatment and temperature increase. Activation energy of wheat varieties decreased with the ultrasound (40 kHz, 200 W) treatment. Increase in Gibbs free energy and negative values of enthalpy and entropy changes with increasing temperature and ultrasonication process confirming the effect of temperature and ultrasound on Deff of wheat varieties during hydration process. Novelty impact statement The results of this investigation can assist wheat products industry in understanding heat and mass transfer phenomena during ultrasound-assisted hydration process of different wheat varieties in tempering, cooking, milling, fermentation, formulation of meals, and storage processes. The results of this study can also be useful in optimizing ultrasound-assisted hydration process and improving the thermodynamic properties of different wheat varieties. New derived generalized hydration equations can be useful for temperature and time-dependent moisture content detection during ultrasound-assisted and conventional hydration processes of wheat varieties.

Prediction of thermodynamic properties for sulfur dioxide

We report a novel formulation representation of the molar Gibbs free energy for sulfur dioxide (SO2), which depends only on experimental values of six molecular constants of SO2, whereas the conventional explicit representations contain many adjustable coefficients determined from fitting a great number of experimental spectroscopic data or calorimetric data. The formulation representation of the molar entropy for SO2 is also developed from the Gibbs free energy representation. The predicted reduced molar Gibbs free energy and entropy values yield the average absolute deviations of 0.0750 % and 0.228 % from the data reported in the National Institute of Standards and Technology database at the pressure of 0.1 MPa and in the temperature range from 298 to 6000 K, respectively. The proposed formulation representation of the Gibbs free energy for SO2 can be valuable in practical engineering applications.

Equilibrium, Kinetic and Thermodynamic Studies of Dyes in Aqueous Solution onto Iron Nanocomposite Stabilized by Irvingia gabonensis Leaf Extract

Elimination of dyes in contaminated water or wastewater has become a universal challenge because of their colouration, toxicity, mutagenicity and carcinogenicity when discharged into the recipient environment without treatment and several technologies have been developed to deal with this problem. This paper reports the potential of exploring the use and comparison of conventional iron zero-valent (nZVI) nanoparticle and Irvingia gabonensis stabilized iron nanocomposite (Ig-nZVI) for the elimination of methyl red (MR) and methyl orange (MO) dyes in aqueous solution under effect of different experimental conditions of adsorbent dosage, initial dye concentrations, pH, contact time and temperature. Data obtained show an increase in percent dye elimination as the amount of adsorbent increased. The optimal removal of MR and MO occurred in ˂ 60 min of the start of each experimentation, obtained at a maximum pH of 5.1 at 98.5% and 80.6% for adsorbent dosage of 0.3g/50 mL and 20 mg/L initial dye concentration at temperature of 27oC. The experimental data fitted the Lamgmuir isotherm with maximum adsorption capacity (qmax) of 166.7mg/g (Ig-nZVI) and 83.35 mg/g (nZVI) for MR while 128.21 mg/g (Ig-nZVI) and 40.02.5 mg/g (nZVI) were obtained for MO. Kinetics studies showed that the removal of MR and MO fitted the pseudo second-order model. The adsorption of MR and MO were endothermic and spontaneous with enthalpy values of 3.39kJ/mol (Ig-nZVI) and 776.26kJ/mol (nZVI) and standard Gibbs free energy values of -5.95kJ/mol (Ig-nZVI) and -12.00kJ/mol (nZVI). Thermodynamic studies (ΔG &lt; 0, ΔH &lt; 0, ΔS &gt; 0) implied a spontaneous and exothermic process in nature. The adsorption of MO was endothermic and spontaneous with enthalpy values of 31.70kJ/mol (Ig-nZVI) and 20.91kJ/mol (nZVI) and standard Gibbs free energy values of -5.92kJ/mol and -7.07kJ/mol for Ig-nZVI and nZVI respectively. Adsorbent produced from leaf extracts of African mango tree (Irvingia gabonensis) and stabilized by iron oxide could be an attractive option for elimination of dye from industrial effluents.

Application of aluminum nitride nanotubes as a promising nanocarriers for anticancer drug 5-aminosalicylic acid in drug delivery system

We investigated and discussed the adsorption of the anticancer drug 5-aminosalicylic acid (5-ASA) on the surface of aluminum nitride nano-tubes (AlNNTs) via density functional theory (DFT). The adsorption results using DFT showed the strong interactions of AlNNTs with the carbonyl (–NH2) group of 5-ASA with a higher adsorption energy of approximately − 31.58 kcal.mol−1, while the interaction of AlNNTs with 5-SAS with its –OH and –CO2H groups was weak, which is because of the negative energy of adsorption. Additionally, the values of Gibbs free energy showed the spontaneity of the adsorption of 5-ASA on the surfaces of AlNNTs. In addition, the NBO analysis confirmed the charge transport from the σ orbitals of N and H atoms of 5-ASA to the n* orbitals of N and Al atoms of AlNNTs with high energies. The results demonstrate that 5-ASA tends to interact with AlNNTs in a favorable manner. A significant change was observed in the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) during the adsorption of 5-ASA on AlNNTs, thereby decreasing the band gap (Eg) values that enhanced their electrical conductivity. The current work showed that AlNNTs can be considered suitable candidates for delivering 5-ASA in biological systems.

Behaviour of Impurities during Electron Beam Melting of Copper Technogenic Material.

The current study presents the electron beam melting (EBM) efficiency of copper technogenic material with high impurity content (Se, Te, Pb, Bi, Sn, As, Sb, Zn, Ni, Ag, etc.) by means of thermodynamic analysis and experimental tests. On the basis of the calculated values of Gibbs free energy and the physical state of the impurity (liquid and gaseous), a thermodynamic assessment of the possible chemical interactions occurring in the Cu-Cu2O-Mex system in vacuum in the temperature range 1460–1800 K was made. The impact of the kinetic parameters (temperature and refining time) on the behaviour and the degree of removal of impurities was evaluated. Chemical and metallographic analysis of the obtained ingots is also discussed.

Reliable estimate of minimum miscibility pressure from multiple possible EOS models for a reservoir oil under data constraint

Multiple Equation of State (EOS) models are possible for a reservoir oil if limited laboratory data is used in the EOS model development; each EOS model has its own predicted minimum miscibility pressure (MMP) value with unknown reliability. This article presents a novel approach to estimate a reliable MMP value using the multiple MMP values calculated from multiple EOS models developed with limited laboratory data such as bubble point and density at bubble point. MMP predicted using the proposed approach has better accuracy than the estimated MMP from an EOS model developed using a large set of data at the regression stage. Each possible EOS model for a reservoir oil has a specific set of values of total Gibbs free energy of mixing (g) at bubble point and predicted MMP for a given injection gas. The MMP estimate is developed using the trend of g versus MMP (predicted) from multiple EOS models in the proposed approach. The AARD in MMP prediction for 22 oils is 5.21% using SRK EOS and 6.65% using PR EOS, which is lower than the earlier approach (7.6%) that uses all PVT, swelling test, and multi-contact test data in EOS model development.

Evaluation of Asphaltene Adsorption Free Energy at the Oil–Water Interface: Effect of Oil Solvents

We investigated asphaltene adsorption behaviors at the oil–water interface, focusing on the effect of oil solvents, by molecular dynamics simulations. Heptane, toluene, and their mixtures with ratios of heptane to toluene of 25:75, 50:50, and 75:25 by volume (namely, heptol25, heptol50, and heptol75) were used as the oil models. Two asphaltene models with essentially the same structure were employed: one contains a basic pyridine-type nitrogen heteroatom; another contains no heteroatoms. The asphaltene adsorption Gibbs free energy at the oil–water interface was evaluated by potential of mean force (PMF) calculations using the umbrella sampling method. The results show that the oil solvent not only affects the adsorption Gibbs free energy but also the adsorption structure as revealed by PMF minimum numbers, locations, and asphaltene orientation angles. For nitrogen-containing asphaltene, the adsorption Gibbs free energy increases linearly with the heptane volume fraction. Noteworthily, the adsorption Gibbs free energy value of this nitrogen-containing asphaltene is high enough to adsorb at the toluene–water interface. It implies that solely adding solvent (such as toluene) may not be enough for solving the emulsion problems induced by interface-active asphaltenes. For the asphaltene without heteroatoms, the asphaltene prefers to be solvated in the oil phase, and there is no well-defined adsorption state when the heptane volume fraction is less than half. For heptol75–water and heptane–water interface systems, the asphaltene adsorption minima can be detected. This clearly indicates that the oil solvent can influence the surface activity of asphaltenes. The study highlights the importance of subtle balances of different noncovalent interactions between asphaltenes, water, and oil components in the oil solvent. The detailed understanding of the asphaltene adsorption behaviors presented in this study will be helpful to solve oil–water emulsion problems and understand the effect of water cut to asphaltene deposition in crude oil production.

Non linear regression analysis and response surface modeling for Cr (VI) removal from aqueous solution using poly-aniline coated sugarcane bagasse (PANI@SB) composites as an adsorbent

Hexavalent chromium has been found most hazardous pollutants being discharge from many industrial sectors like chromite mines, electroplating industries, leather and tanning industries etc. and need to be controlled before discharge to save natural water resources. Adsorption is one of the best and economic process for hexavalent chromium removal. In present investigation, agricultural waste sugarcane bagasse has been coated with polyaniline and PANI@SB composites were synthesized as an adsorbent for the removal of Cr (VI) from its aqueous solution by adsorption process. Batch adsorption was conducted to optimize the dose of adsorbent, pH, time and concentration. The optimum condition has been found are pH 2.0, 0.3 g adsorbent dose, 10 mgL−1 initial concentration at 303 K. Multilayer adsorption of Cr (VI) was found to occur on the heterogeneous surface of PANI@SB with maximum adsorption capacity of 35.2 mgg−1 at 303 K. It was observed that adsorption data fitted well to the Freundlich isotherm model and pseudo- second-order model with high R2, low chi square (χ2), low root mean square error (RMSE) and low standard deviation (SD) values by applying non linear regression method. Positive values of enthalpy and Gibbs free energy of adsorption suggest endothermic and spontaneous nature of adsorption occurs. FESEM, EDX, XRF, HR-TEM, FTIR, XRD, AFM, BET surface area and XPS analysis were conducted to understand the surface characteristics of PANI@SB before and after adsorption of Cr (VI). Response surface modeling (RSM), a statistical tool, was applied to experimental data to optimize the process parameters. A quadratic model equation was generated between the process parameters and response for Cr (VI) removal. The optimization study from RSM showed that pH and adsorbent dose has significant effect on removal of Cr (VI) due to higher lack of fit (F) value. The optimum conditions for maximum removal of 97% Cr (VI) are found at pH 2.0 with 0.3 g of adsorbent dose, time of 90 min at 303 K obtained by RSM. PANI@SB is regenerated with 0.2 N NaOH and can be reused up to two desorption-adsorption cycles (removal 92%) with slight decreases in its original sorption capacity. On the basis of this study it is found that PANI@SB is very efficient, stable, reusable and effective adsorbent for removal of Cr (VI) from aqueous medium and it can be used in industrial scale.

Thermodynamic study on the prevention of B30 biodiesel wax crystallization by γ-Al2O3 nanoparticles and sorbitan monooleate

This paper reports a thermodynamic investigation on the role of γ-Al2O3 nanoparticles and sorbitan monooleate (SMO) as cold-flow improver additives for B30 biodiesel blend. Here, the two additives were able to improve fuel’s cold-flow properties and responsible for reducing wax crystallization temperature as low as 6.42 °C. Based on DCS analysis, the addition of individual SMO or γ-Al2O3 nanoparticles gave rise to the increase in crystallization enthalpy and entropy. However, the opposite effect was observed when they were used in combination. This synergistic effect was found to be responsible for making them effective in the prohibiting the spontaneity of wax crystallization, which was proven by the increase in crystallization Gibbs free energy (ΔGxtal) value from −72.9 to −35.7 J/g. This is primarily due to that the ability of SMO to stabilize wax nuclei and the role of γ-Al2O3 nanoparticles as an additional nucleation site. Furthermore, DLVO analysis also revealed that γ-Al2O3 nanoparticles exhibited high colloidal stability, enabling them to facilitate stable Pickering emulsion formation. Finally, microscopic observations demonstrated that both additives could suppress the formation of insoluble paraffinic “house of cards” crystals.

Intrinsic Dependence of Groundwater Cation Hydraulic and Concentration Features on Negatively Charged Thin Composite Nanofiltration Membrane Rejection and Permeation Behavior.

Commercial nanofiltration membranes of different molecular weight cut-offs were tested on a pilot plant for the exploration of permeation nature of Ca, Mg, Mn, Fe, Na and ammonium ions. Correlation of transmembrane pressure and rejection quotient versus volumetric flux efficiency on nanofiltration membrane rejection and permeability behavior toward hydrated divalent and monovalent ions separation from the natural groundwater was observed. Membrane ion rejection affinity (MIRA) dimension was established as normalized TMP with regard to permeate solute moiety representing pressure value necessary for solute rejection change of 1%. Ion rejection coefficient (IRC) was introduced to evaluate the membrane rejection capability, and to indicate the prevailed nanofiltration partitioning mechanism near the membrane surface. Positive values of the IRC indicated satisfactory rejection efficiency of the membrane process and its negative values ensigned very low rejection affinity and high permeability of the membranes for the individual solutes. The TMP quotient and the efficiency of rejection for individual cations showed upward and downward trends along with flux utilization increase. Nanofiltration process was observed as an equilibrium. The higher the Gibbs free energy was, cation rejection was more exothermic and valuably enlarged. Low Gibbs free energy values circumferentially closer to endothermic zone indicated expressed ions permeation.

Mechanism of heteroatom-doped Cu5 catalysis for hydrogen evolution reaction

Developing high-performance hydrogen evolution reaction (HER) electrocatalysts is of great significance for solving the global energy crisis. Cluster has great application potential in the field of catalysis due to their unique quantum size effect and high specific surface area. Herein, the HER catalytic performance of Cu5 cluster were regulated and optimized by doping heteroatoms. The Gibbs free energy calculation shows that the catalytic activity of Cu5Ni and Cu5Pt is comparable to that of Pt-based catalysts, and the Gibbs free energy value of Cu5C can even reach 0.005 eV, indicating its much higher catalytic performance than that of other catalysts. Thus, the catalytic activity of Cu5 clusters is optimized by doping non-metal and transition metal atoms to regulate the geometric and electronic structure of Cu5. It was found that Cu5Ni, Cu5Pt and Cu5C are potential catalysts to replace Pt-based catalysts for reducing the cost and achieving large-scale hydrogen production. This work provides a new avenue to regulate the catalytic performance of clusters, which is helpful for the further development and application of clusters in the field of catalysis.