Microcalorimetric Experiments Research Articles

Improving separation of sphalerite and galena by surface oxidation behavior regulation using calcium lentisulfonate as depressant

BackgroundSphalerite and galena often exist in mixed form and are difficult to separate effectively. The effect of surface oxidation behavior regulation on the depression of calcium lentisulfonate (CLS) was studied in galena and sphalerite. MethodsFlotation experiment, contact angle experiment, X-ray photoelectron spectroscopy (XPS) analysis and microcalorimetric experiment were used to study the effect and mechanism of modulation of surface oxidation behaviour on CLS on the depression of galena flotation. Significant findingsThe results show that CLS can depress both galena and sphalerite. The oxidizing agent H2O2 oxidizes galena significantly faster than sphalerite. The treatment with H2O2 induces the formation of more oxidation products, such as PbSO4, on the surface of galena, enhances the adsorption of CLS and makes the surface of galena hydrophilic, thus reducing the recovery of galena in the flotation process. On the other hand, the treatment of the activator ethylenediaminetetraacetic acid (EDTA) reduces the amount of oxidation products ZnSO4 on the sphalerite surface, and CLS loses the active site that can be adsorbed on the galena surface, making the galena surface hydrophilic. In view of the huge hydrophobicity difference between sphalerite and galena, flotation separation is achieved.

Comparative analysis of thermal stability and electrochemical performance of NaNi1/3Fe1/3Mn1/3O2 cathode in different electrolytes for sodium ion batteries

The electrochemical compatibility and thermal stability of cathode and electrolyte guarantee the intrinsic safety of batteries. The NaNi1/3Fe1/3Mn1/3O2 (NaNFM) cathode for sodium ion batteries (SIBs) has not received, sufficient attention concerning its thermal safety compared to its electrochemical properties. Herein, we investigated the thermal stability of NaNFM, exothermic reaction and electrochemical performance of NaNFM with various electrolytes. The comprehensive electrochemical performance of NaNFM in different electrolytes followed this sequence: sodium hexafluorophosphate (NaPF6) > sodium bis(trifluoromethyl-sulfonyl)imide (NaTFSI) > sodium perchlorate (NaClO4)- based electrolytes. Additionally, ethylene carbonate (EC): propylene carbonate (PC)- type electrolytes displayed superior cycling stability compared to ethylene carbonate (EC): diethyl carbonate (DEC)- type electrolytes. Moreover, the heat flow profiles demonstrated that the thermal stability between NaNFM and various electrolytes could be ordered according to the total heat release as: NaClO4 < NaPF6 < NaTFSI-based electrolyte. X-ray diffractometer (XRD), scanning electron microscope (SEM) and x-ray photoelectron spectrometer (XPS) analyses were carried out to investigate the changes in crystal structure, morphology and valence state of thermal reaction products after microcalorimetric analysis experiments. These findings provide valuable insights for the safe application of the NaNFM cathode in SIBs.

Tailoring novel polymer/UTSA-16 hybrid aerogels for efficient CH4/CO2 separation

A significant number of industrially relevant separation processes involves the removal of carbon dioxide (CO2), as the purification of natural gas (CO2/CH4 separation). In this scenario, the development of new adsorbents with a real technological future for CO2 separation, i.e with a high separation efficiency, good mechanical properties and easy to handle, is of primary importance. In the present work, novel composite monolithic aerogels containing the UTSA-16 metal organic framework as the active phase and porous crystalline polymers (namely syndiotactic polystyrene and polyphenyloxide) as binders were successfully synthesized and fully characterized. The adsorption capacity of such novel aerogels towards CO2 and CH4 was tested at low pressure and variable temperature, allowing the evaluation of their CO2/CH4 selectivity. Microcalorimetric experiments provided the CO2 interaction energy and disclosed possible deformation-relaxation phenomena involving the polymeric matrix during gas adsorption. The new composites retain a very high CO2 adsorption capacity compared to the pristine UTSA-16 (around 75% at 298 K and 1 bar) and have excellent CO2 capture performances in comparison to other types of supported/printed MOFs reported in the literature. The outstanding adsorption properties and the possibility to obtain monoliths with the desired size and shape and good mechanical stability make these new composites very good candidates for efficient CO2/CH4 separation processes.

Synthesis of high-crystallinity MIL-125 with outstanding xylene isomer separation performance

MIL-125 is a metal-organic framework with great potential for the adsorption and separation of xylene isomers. However, MIL-125 is usually synthesized under anhydrous and anaerobic conditions. In this study, homogeneously shaped and highly crystalline MIL-125 was synthesized by introducing water-resistant titanium-containing oligomers into the synthesis process. With the assistance of the novel oligomers, MIL-125 can be synthesized in the presence of water, which meets batch-production requirements. The adsorption separation performance of the obtained highly crystalline MIL-125 was also significantly enhanced. The para-xylene/meta-xylene selectivity can reach 13.5 in mesitylene, which is higher than the selectivity values of most previously reported para-selective adsorbents. The MIL-125 xylene separation performance was verified using both batch adsorption and breakthrough experiments in the liquid phase. In addition, the influence of the solvent effect was evaluated through microcalorimetric experiments, liquid-phase adsorption experiments, and theoretical calculations.

Synergistic effect of mixed DDA/surfactants collectors on flotation of quartz

In this study, five types of surfactants including non-ionic lipophilic surfactant Span series surfactant, non-ionic hydrophilic surfactant Tween and OP series surfactant, characteristics of both anionic and hydrophilic surfactant NaOL and triethanolamine oleate (named as OL series for short), characteristics of both cationic and hydrophilic surfactant AC1201 and AC1205 (named as AC series for short) were chosen as research subjects to investigate the relationship between the structure and synergistic ability of surfactants, focusing on the adsorption of the typical cationic collector dodecylamine (DDA) and surfactant mixture at liquid/air and solid/liquid interface to investigate the application potential of structure in the development of an effective surfactant to apply for quartz flotation. Flotation experiments, surface tension measurements, microcalorimetric experiments, interaction parameter calculation and Fourier Transform Infrared Spectroscopy (FTIR) analysis were used to analyze the characteristics of different DDA/surfactant systems and the interaction mechanism between quartz and collector mixture. The flotation results indicated that the synergistic capacity of these surfactants was in the following ranking: AC > OP > Tween > Span > OL. AC1201 showed a stronger synergistic ability than the other surfactants, accompanying with a recovery promotion over 20% compared with pure DDA. The physicochemical properties including surface activity parameters, the micelles and interfacial compositions, and interaction parameters were evaluated according to the theory of regular solutions. The surface tension and critical micelle concentration of the mixture solution decreased with the addition of the surfactant. According to the basic Rubingh equations, the interaction parameter of these surfactants was in the following ranking: OL > Span > OP > Tween > AC, indicating that the flotation recovery of quartz was negatively correlated with the interaction parameters. While there was a positive correlation between the interaction heat changes obtained from microcalorimetry and the trend from the flotation experiments. The obtained results demonstrated that it should be chosen this type of surfactant, which can be able to intensify collector adsorption at the solid/liquid interface. AC1201 has a potential for industrial application in the flotation of quartz.

Syntheses, crystal structures, thermal stabilities, CT-DNA, and BSA binding characteristics of a new acylhydrazone and its Co(II), Cu(II), and Zn(II) complexes

A new acylhydrazone (C12H12N4OS, HL) and its three transition metal complexes [M(HL)2](NO3)2 (M = Co, I; Cu, II; Zn, III) have been synthesized. The structures of above four compounds were determined by single-crystal X-ray diffraction analyses. HL belonged to orthorhombic system and Pbca space group. I and II belonged to triclinic system and P-1 space group, whereas III belonged to monoclinic system and P21/C space group. The thermal stabilities of four compounds were investigated by thermogravimetric analyses, and their maximum thermal decomposition peak temperatures were all more than 240 °C, showing high thermal stabilities. The binding behaviors of four compounds with CT-DNA were determined by UV–vis absorption spectra, viscosity and microcalorimetric experiments, all presenting intercalative modes. The interactions of four compounds with BSA were determined by fluorescence spectra and microcalorimetric experiments, showing static quenching effects, and the binding constants K A are (8.32 ± 0.36) × 103 M−1, (1.44 ± 0.40) × 105 M−1, (7.59 ± 0.09) × 104 M−1, and (4.68 ± 0.45) × 105 M−1 for HL, I, II, and III, respectively. Microcalorimetric experiments explored that the interactions of four compounds with CT-DNA or BSA were exothermic processes and the interaction times were all less than 43 min.

Thermal Decomposition Characteristics and Thermal Safety of Dihydroxylammonium 5,5′-Bistetrazole-1,1′-diolate Based on Microcalorimetric Experiment and Decoupling Method

A microcalorimeter (C600) was used to conduct dynamic heating experiments on dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50), and the results were compared with those of differential sca...

Hydrogenotrophic methanogens of the mammalian gut: Functionally similar, thermodynamically different-A modelling approach.

Methanogenic archaea occupy a functionally important niche in the gut microbial ecosystem of mammals. Our purpose was to quantitatively characterize the dynamics of methanogenesis by integrating microbiology, thermodynamics and mathematical modelling. For that, in vitro growth experiments were performed with pure cultures of key methanogens from the human and ruminant gut, namely Methanobrevibacter smithii, Methanobrevibacter ruminantium and Methanobacterium formicium. Microcalorimetric experiments were performed to quantify the methanogenesis heat flux. We constructed an energetic-based mathematical model of methanogenesis. Our model captured efficiently the dynamics of methanogenesis with average concordance correlation coefficients of 0.95 for CO2, 0.98 for H2 and 0.97 for CH4. Together, experimental data and model enabled us to quantify metabolism kinetics and energetic patterns that were specific and distinct for each species despite their use of analogous methane-producing pathways. Then, we tested in silico the interactions between these methanogens under an in vivo simulation scenario using a theoretical modelling exercise. In silico simulations suggest that the classical competitive exclusion principle is inapplicable to gut ecosystems and that kinetic information alone cannot explain gut ecological aspects such as microbial coexistence. We suggest that ecological models of gut ecosystems require the integration of microbial kinetics with nonlinear behaviours related to spatial and temporal variations taking place in mammalian guts. Our work provides novel information on the thermodynamics and dynamics of methanogens. This understanding will be useful to construct new gut models with enhanced prediction capabilities and could have practical applications for promoting gut health in mammals and mitigating ruminant methane emissions.

Effect of natural and synthetic surfactants on crude oil biodegradation by indigenous strains

Hydrocarbon pollution is a worldwide problem. In this study, five surfactants containing SDS, LAS, Brij 30, Tween 80 and biosurfactant were used to evaluate their effect on crude oil biodegradation. Hydrocarbon degrading bacteria were isolated from oil production water. The biosurfactant used was a kind of cyclic lipopeptide produced by Bacillus subtilis strain WU-3. Solubilization test showed all the surfactants could apparently increase the water solubility of crude oil. The microbial adhesion to the hydrocarbon (MATH) test showed surfactants could change cell surface hydrophobicity (CSH) of microbiota, depending on their species and concentrations. Microcalorimetric experiments revealed these surfactants exhibited toxicity to microorganisms at high concentrations (above 1 CMC), except for SDS which showed low antibacterial activity. Surfactant supplementation (about 0.1 and 0.2 CMC) could improve degradation rate of crude oil slightly, while high surfactant concentration (above 1 CMC) may decrease the degradation rate from 50.5% to 28.9%. Those findings of this work could provide guidance for the application of surfactants in bioremediation of oil pollution.

The crystal structure of the tandem-PAS sensing domain of Campylobacter jejuni chemoreceptor Tlp1 suggests indirect mechanism of ligand recognition.

Chemotaxis and motility play an important role in the colonisation of avian and human hosts by Campylobacter jejuni. Chemotactic recognition of extracellular signals is mediated by the periplasmic sensing domain of methyl-accepting chemotactic proteins (membrane-embedded receptors). In this work, we report a high-resolution structure of the periplasmic sensing domain of transducer-like protein 1 (Tlp1), an aspartate receptor of C. jejuni. Crystallographic analysis revealed that it contains two Per-Arnt-Sim (PAS) subdomains. An acetate and chloride ions (both from the crystallisation buffer) were observed bound to the membrane-proximal and membrane-distal PAS subdomains, respectively. Surprisingly, despite being crystallised in the presence of aspartate, the structure did not show any electron density corresponding to this amino acid. Furthermore, no binding between the sensing domain of Tlp1 and aspartate was detected by microcalorimetric experiments. These structural and biophysical data suggest that Tlp1 does not sense aspartate directly; instead, ligand recognition is likely to occur indirectly via an as yet unidentified periplasmic binding protein.

Antibacterial effect of different extracts from Wikstroemia indica on Escherichia coli based on microcalorimetry coupled with agar dilution method

The root of Wikstroemia indica has been widely used in China as folk medicine for the treatment for arthritis, whooping cough, cancer, and bacillosis. However, the constituents which have antibacterial activity were not clarified yet. In this study, the antibacterial effect of five extracts from W. indica on Escherichia coli was evaluated by microcalorimetry coupled with agar dilution method. The ethanol extract of W. indica was isolated with organic solvents of different polarities including petroleum (P.E.) extract, chloroform (CHCl3) extract, ethyl acetate (EtOAc) extract, n-butylalcohol (nBuOH) extract, and residue extract. The metabolic profiles of E. coli growth at 37 °C were measured by microcalorimetry. According to the principal component analysis, k1, k2, and P1 were obtained from heat flow power–time (HFP–time) curve. The agar dilution method was performed to verify the results of thermodynamics. The results of microcalorimetric experiment indicated that EtOAc fraction demonstrated the strongest antibacterial activity with half-inhibitory concentration of 92.4 μg mL−1. Meanwhile, similar results were gained from the common method of agar diffusion, which suggested that EtOAc extract could be further developed as antibacterial bioactive fraction of W. indica. Altogether, microcalorimetry is a useful technique to provide sufficient quantitative information and evaluate the antimicrobial effect with its sensitive.

Removal of bacteria and yeast in water and beer by nylon nanofibrous membranes

This work explores the capability of nylon-6 nanofibrous membranes prepared by electrospinning to remove bacteria and yeast cells. Nanofibrous membranes have been widely used as affinity membranes to selectively capture molecules onto the membrane surface. However, their capacity to remove microbial cells in food beverages was not yet reported. Here, dead-end filtration experiments working under constant flow-rate were tested with beer samples fortified with yeasts (Saccharomycescerevisiae) and bacteria (Flavobacteriumjohnsoniae and Iodobacterfluviatilis) ranging from 1.0×104 to 5.1×108CFU/mL. The filtration experiments resulted in resistance to flow proportional to the cells dimensions. Yeasts formed soft cakes with the lowest resistance. Conversely, it could be assumed that bacteria formed a close-pack arrangements resulting in cakes with higher density, smaller interstitial space and, thus, higher resistance to flow. Microcalorimetric experiments and plate counts demonstrated that NFM were able to completely remove S. cerevisiae from water slurries. Instead, NFM reduced the concentration of F. johnsoniae and I. fluviatilis of only 5 and 3-log cycles, respectively. However, when the two bacteria strains were mixed together, the filtration resulted in the complete removal of the cells. These results were confirmed during the filtration of beer samples inoculated with S. cerevisiae, I. fluviatilis and F. johnsoniae.

Adsorption of probe molecules in pillared interlayered clays: experiment and computer simulation.

In this paper we investigate the adsorption of various probe molecules in order to characterize the porous structure of a series of pillared interlayered clays (PILC). To that aim, volumetric and microcalorimetric adsorption experiments were performed on various Zr PILC samples using nitrogen, toluene, and mesitylene as probe molecules. For one of the samples, neutron scattering experiments were also performed using toluene as adsorbate. Various structural models are proposed and tested by means of a comprehensive computer simulation study, using both geometric and percolation analysis in combination with Grand Canonical Monte Carlo simulations in order to model the volumetric and microcalorimetric isotherms. On the basis of this analysis, we propose a series of structural models that aim at accounting for the adsorption experimental behavior, and make possible a microscopic interpretation of the role played by the different interactions and steric effects in the adsorption processes in these rather complex disordered microporous systems.

English

The microcalorimetric method was applied to analyze the influences of successive reforestations with Eucalyptus granddis &times; E. uophylla, Pinus massoniana, and continuous sugarcane production on the soil microbial activities. 500 g of each refined representative sample was collected in rainy and dry seasons from four 100 m2 homogeneously and perfectly defined acrisol quadrats in subtropical China. Two of them were Eucalyptus plantations with 10 (E10) and 20 (E20) year&ndash;old stands. The other two were 10&ndash;year&ndash;old pine tree plantation (P10) and sugarcane land (SL10) correspondingly contiguous to E10 and E20 and used as references for E10 and E20, respectively. Blocks of E10/P10 were 1500 m away from that of E20/SL10. Microcalorimetric experiments were carried out using 1.2 g soil samples and 0.6 ml of solution containing 5.0 mg of glucose and 5.0 mg of ammonium sulphate at 28&deg;C. The effects of land management practice on soil quality were examined by measuring their physicochemical and biological properties. The results showed that: 1) zymogeneous bacteria were the dominated microbes in the land of continuous sugarcane production, but autochthonous floras were the ones for forest; 2) when compared with its control (SL10), land of eucalyptus (E20) had lower soil packing degree and inhibitory effect on microbial activities, but higher seasonal fluctuation in microbe constitution and activities under the same circumstance; 3) compared with its control P10, the land of eucalyptus E10 had alike soil packing degree and higher seasonal fluctuation degree of microbial activities, but lower inhabiting degree of soil microbial metabolism. &nbsp; Key words: Microcalorimetry, microbial activity, eucalyptus, pine tree, sugarcane.

Amino-Acid Adsorption in MFI-Type Zeolites Enabled by the pH-Dependent Ability to Displace Water

Downstream processing of biochemical products strongly depends on the interaction between biomolecules and material surfaces that can be influenced greatly by the pH level. In this study, the influence of the pH value on the adsorption of the amino acids glycine, alanine, and lysine in MFI-type zeolite was investigated using density functional theory (DFT) and microcalorimetric experiments. Different pH values were modeled by varying the amino acids protonation states. The investigated protonation states exhibit two different adsorption motifs in the pores, with the neutral α-C-amino group motifs being significantly less stable than the protonated ones. In the case of neutral glycine and alanine, the adsorption energy is insufficient to overcome the adsorption of the four water molecules usually present in the pores. This result explains the pH-dependent adsorption behavior that has also been observed experimentally and provides an avenue for designing efficient adsorption processes.

Thermal properties of holmium-implanted gold films for a neutrino mass experiment with cryogenic microcalorimeters

In a microcalorimetric neutrino mass experiment using the radioactive decay of (163)Ho, the radioactive material must be fully embedded in the microcalorimeter absorber. One option that is being investigated is to implant the radioactive isotope into a gold absorber, as gold is successfully used in other applications. However, knowing the thermal properties at the working temperature of microcalorimeters is critical for choosing the absorber material and for optimizing the detector performance. In particular, it is paramount to understand if implanting the radioactive material in gold changes its heat capacity. We used a bolometric technique to measure the heat capacity of gold films, implanted with various concentrations of holmium and erbium (a byproduct of the (163)Ho fabrication), in the temperature range 70 mK-300 mK. Our results show that the specific heat capacity of the gold films is not affected by the implant, making this a viable option for a future microcalorimeter holmium experiment.

Microcalorimetric study of the adsorption of native and mono-PEGylated bovine serum albumin on anion-exchangers

The adsorption of native bovine serum albumin (BSA) and 12kDa-PEG-BSA on 12 different commercially available strong and weak anion-exchange resins is studied at 25°C and pH 7. The resins differ in their base matrix material, their functional groups and the type of polymer modification. A combination of equilibrium measurements and microcalorimetric experiments is used to determine the specific enthalpy of adsorption of the proteins. From these data, the entropic contributions to the specific Gibbs energy of adsorption are determined. The results strongly differ for different resins. They also depend on the loadings. The adsorption of BSA on strong (Q) anion-exchangers is exothermic and enthalpy-driven. The adsorption of BSA on weak (DEAE) anion-exchangers is endothermic and entropy-driven. The adsorption of PEG-BSA on strong (Q) anion-exchangers is exothermic or endothermic, depending on the resin, while the adsorption of PEG-BSA on weak (DEAE) anion-exchangers is exothermic for all studied resins. The present study provides a large body of new experimental data that contribute to the understanding of the nature of protein adsorption on ion exchange resins and the influence of the resin properties and polymer modification of the proteins on this process.

Determination of Reduce of Arsenic (III) Toxicity to &lt;i&gt;Pseudomonas fluorescens&lt;/i&gt; Using Iron by Combined Methods

A series of microcalorimetric experiments were performed to evaluate the As(III), Fe(II), P and their joint effects by analyzing the thermodynamic parameters, microbial growth rate constant k, total heat evolution QT, inhibitory ratio I and highest heat flow Pmax. They were obtained from power-time curves of the growth of P. fluorescens. The effect of mixed As(III), Fe(II) and P were moderate, compared with control, single As(III) or Fe(II). In addition, FT-IR spectra of dry P. fluorescens after the adsoption of As(III) and Fe(II) and their mixture showed that Fe influenced the C-H bonds of the functional groups on the cellwall, the As(III) caused litter effect.

High Affinity Crown Ether Complexes in Water: Thermodynamic Analysis, Evidence of Crystallography and Binding of NAD+

Improving traditional crown ether to the water-soluble and high binding ability host molecule is critical to our efforts to model or mimic biological supramolecular systems. In this paper, we converted two traditional crown ethers, 1,5-dinaphtho-32-crown-8 and 1,5-dinaphtho-38-crown-10, into the water-soluble tetrasulfonated 1,5-dinaphtho-32-crown-8 and tetrasulfonated 1,5-dinaphtho-38-crown-10, evaluated their complexation with three dicationic bipyridiniums in aqueous solution by microcalorimetric titration, UV-vis, and NMR experiments, and then determined the crystal structures of three tetrasulfonatocrown ether-bipyridinium complexes. The equilibrium association constants of tetrasulfonated 1,5-dinaphtho-32-crown-8 with these bipyridiniums reach up to 10(7) M(-1), while those of tetrasulfonated 1,5-dinaphtho-38-crown-10 are just in the range of 10(5) M(-1) order of magnitude. The thermodynamic data obtained show that the complexation of two tetrasulfonatocrown ethers with dicationic bipyridiniums is absolutely enthalpy-driven in water with an accompanying little entropic gain, and each monocationic pyridinium moiety in guest molecules can provide about -10 to -15 kJ·mol(-1) enthalpy contribution irrespective of the size of ether crowns. Moreover, we also investigated the recognition capability of the two water-soluble crown ethers with NAD(+) and NADH by microcalorimetric titration and NMR experiments, indicating that tetrasulfonated 1,5-dinaphtho-32-crown-8 shows exclusive selectivity to NAD(+). The water-solubility and high affinity of this system as well as the flexible and non-preorganized characteristic of these crown ethers make it suitable to serve as a model for mimicking biological systems.

Anticancer peptide NK-2 targets cell surface sulphated glycans rather than sialic acids

Some antimicrobial peptides have emerged as potential anticancer agents. In contrast to chemotherapeutics, they act primarily by physical disruption of the cancer cell membrane. Selective targeting of these cationic peptides still remains elusive. We focus on the interaction of α-helical peptides NK-2, cathelicidin LL32, and melittin with PC-3 prostate cancer cells, and we provide strong evidence that, amongst the anionic glycans covering the cell surface, sulphated carbohydrates rather than sialic acids are the preferred interaction sites of the peptides. To test the significance of cell surface carbohydrates, a glycan microarray screen with fluorescently labelled peptides has been performed. Amongst 465 mammalian glycan structures on the chip, more than 20 different sulphated glycans were detected as the preferred binding partners of the peptide NK-2. The amount of peptide bound to sialic acid containing oligosaccharides was close to background level. These findings were consistent with microcalorimetric experiments revealing high and low binding enthalpies of peptides to sulphated carbohydrates and to sialic acid, respectively. Enzymatic desialylation of PC-3 cells did not affect peptide-mediated changes in cell metabolism, cell membrane permeabilisation, killing rate, and kinetics. Finally, the cytotoxicity of all peptides could be drastically impaired through the competitive inhibition by chondroitin sulphate, but not by sialic acid and sialylated fetuin.