Stages Of Dehydration Research Articles

Thermal studies on Zirconium hydroxide gel formed by aqueous gelation

Zirconium hydroxide gel has been prepared by a novel aqueous gelation process by the controlled hydrolysis of zirconium oxychloride in the presence of sodium acetate. The gel thus formed has been subjected to thermal analysis: TG, DTG, and DSC. Thermal analysis shows that the gel is continuously dehydrated in the temperature range between room temperature and 500 °C. The total mass loss relative to the initial mass is about 44.1%. Thermal analysis shows that the decomposition takes place in three stages. The gel contains absorbed and coordinated water. In the second stage of dehydration, dehydration of the Zr(OH)4 gel also takes place along with the removal of the coordinated water. The DSC analysis coupled with TG and structural information, indicate that the exothermic processes between 349 and 460 °C can be attributed to the nucleation process of the formation of tetragonal zirconia, with phase transformation at 460 °C.

Phenylbutazone의 란탄(III) 착물에 대한 합성, 스펙트럼 및 열적 연구

1,2-diphenyl-4-butyl-3,5-pyrazolidinedione(phenylbutazone, PB)의 란탄(III) 착물을 합성하여 원소분석, 몰전기전도도 측정, IR, UV-Vis. 및 NMR 스펙트럼으로 특성을 조사하였다. 스펙트럼 데이터로부터 PB가 pyrazolidinedione 고리의 두 카르보닐 산소를 통해 이배위 및 일이온화 리간드로 배위됨을 규명하였다. 몰전기전도도 데이터로부터 이들 착물이 비전해질임을 규명하였다. 이들 착물의 열적 행동을 공기 중에서 TG 및 DTG로 연구한 결과, 탈수화, 열적 안전성 및 열분해에 관한 정보를 얻을 수 있었다. 최종 생성물은 해당 금속의 산화물로 밝혀졌다. 탈수화 및 분해 단계에 대한 열역학 및 반응속도 파라메터를 구하였다. 분해 단계에 대한 음의 엔트로피 값은 반응물보다 활성화 착물이 더 질서있는 구조를 갖는다는 것을 의미하며, 이때 반응은 정상보다 느렸다. 이러한 연구를 바탕으로 착물의 분자식이 <TEX>$[Ln(PB)_3]{\cdot}5H_2O$</TEX>(Ln=La 및 Ce) 그리고 <TEX>$[Ln(PB)_3 (H_2O)_2]{\cdot}2H_2O$</TEX>(Ln=Pr, Nd 및 Sm)임을 규명하였다. Lanthanide(III) complexes of 1,2-diphenyl-4-butyl-3,5-pyrazolidinedione(phenylbutazone, PB) have been synthesized and characterized by elemental analyses, molar conductance measurements, IR, UV-Vis. and NMR spectra. The spectral data reveal that the PB acts as a bidentate and mono-ionic ligand coordinating through both the carbonyl oxygens of the pyrazolidinedione ring. The molar conductance data suggest that the complexes are non-electrolytes. The thermal behaviour of the complexes was studied by TG and DTG in air atmosphere and the results provide information about dehydration, thermal stability and thermal decomposition. The final products are found to be the corresponding metal oxides. The thermodynamic parameters and kinetic parameters were evaluated for the dehydration and decomposition stages. The negative entropy values of the decomposition stages indicate that the activated complexes have a more ordered structure than the reactants and that the reactions are slower than normal. Based on these studies, the complexes have been formulated as <TEX>$[Ln(PB)_3]{\cdot}5H_2O$</TEX>(Ln=La and Ce) and <TEX>$[Ln(PB)_3(H_2O)_2]{\cdot}2H_2O$</TEX>(Ln=Pr, Nd and Sm).

Dehydration of subducting serpentinite: Implications for halogen mobility in subduction zones and the deep halogen cycle

We investigated the halogen (Cl, F, Br, and I) chemistry of serpentinites that record progressive dehydration during subduction from shallow oceanic environments via increased pressure and temperature conditions to complete breakdown of antigorite. The aim is to evaluate the relevance of serpentinites for halogen recycling in subduction zones and for deep mantle recharge of these elements. The halogen compositions of the analyzed samples indicate input from seawater and sedimentary sources during initial serpentinization of either subducting lithospheric mantle during slab bending or forearc mantle by uprising slab fluids. During the first dehydration stage (antigorite + brucite → olivine + H 2O), fluids with high Br/Cl and I/Cl ratios are released resulting in residual serpentinites with lower Br/Cl and I/Cl ratios. Veins associated with this event and with the final antigorite breakdown (antigorite → olivine + orthopyroxene + H 2O) show higher halogen ratios compared to their adjacent wall rocks, and they are similar to those found in arc volcanoes (F/Cl and I/Cl between ca. 0.083–1.5, and ca. 0.00038–0.0013, respectively). All measured deserpentinization samples show a narrow range in δ 37Cl values (between − 0.42‰ and + 0.92‰) overlapping the δ 37Cl values of seafloor serpentinites and confirming that no significant Cl isotope fractionation occurs during subduction dehydration of serpentinites. Our findings document the conservative behavior of halogens during subduction. Mass balance constraints reveal that serpentinites strongly control the halogen chemistry of deep subduction zone fluids and that descent of rock residues after deserpentinization strongly affects the halogen budget of the mantle.

Influence of electrolytes on the hydration of methylcellulose in solution.

Abstract Light-scattering techniques were used to obtain weight-average molecular weights for three grades of methylcellulose in water. On addition of electrolyte to the polymer solutions the molecular weight was not found to alter but the root-mean-square end-to-end length decreased. This contrasts with the results of Neely (1963). The exponent α of the Mark-Houwink viscosity equation was also found to decrease in the presence of electrolyte. Two stages of polymer dehydration are suggested for non-ionic cellulose ether derivatives.

Protein Salting Out Observed at an Air−Water Interface

A protein salting-out process is directly observed at an air−water interface. By using time-resolved X-ray specular reflectivity and off-specular diffuse scattering, we identified several key stages in the adsorption of hen egg white lysozyme in a concentrated NaCl solution, (1) adsorption-induced unfolding, (2) monolayer formation with unfolded proteins, (3) protein refolding, and (4) island formation with the refolded proteins. Stages 3 and 4 are not observed either at the isoelectric point or in the salt-free solution, suggesting that they are induced by screening of the positive charges in the lysozyme by chloride ions. It is considered that the hydrated salt ions act to minimize the water-accessible surface area of the protein, not only enhancing protein dehydration (stages 1 and 2) but also assisting in protein refolding and association (stages 3 and 4). These results provide insight into the early stages of protein crystal nucleation.

Thermal behavior of residues (sludge) originating from the sugarcane industry

The Brazilian sugarcane industry shows a great amount of generated sludge which should be utilized adequately. Two sludge samples, aerobic and anaerobic, were collected. Both were evaluated by thermogravimetry and differential thermal analysis (DTA) as well as X-ray power diffraction. These compounds show variations of mass between 30 and 140 °C due to the dehydration stage. The DTA curves show that the compounds have an exothermic reaction between 450 and 550 °C, which indicates that this can be used as an energy source. Details concerning the kinetic parameters of the dehydration and thermal decomposition have also been described here. The kinetic study of these stages was evaluated in open crucibles under nitrogen atmosphere. The obtained data were evaluated with the isoconversional kinetic method. The results show that different activation energies were obtained for thermal decomposition.

A study of thermal and dielectric behavior of manganese malonate dihydrate single crystals

Thermal decomposition of manganese malonate dihydrate single crystals grown by gel method has been studied using the TG-DTA and DSC techniques. The presence of water molecules and the dehydration stages are discussed. Dielectric constant, dielectric loss, and AC conductivity have been estimated as a function of temperature in the range of 40–120 °C for four different frequencies. Thermal studies reveal that the material is thermally stable up to123 °C. The dielectric measurements indicate that the dielectric parameters increase with the increase in temperature. Also, the dielectric constant and dielectric loss factor values decrease whereas the electrical conductivities increase with the increase in frequency of the AC applied.

Preparation of Bauxite-Based Homogenized Mullite Grogs with Bauxite and Coal Gangue

The sintering behavior, physical properties and heat processing changes of bauxite-based homogenized grogs prepared by homogenization process and high temperature sintering using bauxite as starting material were investigated. Results show that the bauxite-based mullite can be synthesized by the method, sintering temperature with and without MgO/CeO2sintering aids are 1600°C and 1700°C separately, the mullite with apparent porosity of＜1.0% and 2.5%, bulk density of ≥2.87g•cm-3and 2.75g•cm-3, Refracteriness-Under-Load(RUL) 1600°C and 1620С; changes in the heat processing is divided into three stages: dehydration stage(400°С~900°С ), primary mullitization stage(1000°С ~1200°С) and secondary mullitization stage(&gt;1200°С).

Synthesis of high molecular weight poly(L‐lactic acid) via melt/solid polycondensation: Intensification of dehydration and oligomerization during melt polycondensation

AbstractMelt/solid state polycondensation (MP/SSP) is a cost‐effective route for synthesis of high molecular weight poly(L‐lactic acid) (PLLA). However, the reaction rates in its four stages need to be enhanced greatly and the reaction times to be shortened largely before the MP/SSP technology can be industrialized. In this study, a new catalyst addition policy, i.e., adding TSA at the dehydration stage and SnCl2·2H2O at the MP stage, and more appropriate temperature and pressure programs were presented and applied in the MP process of LLA. The presence of TSA from dehydration appeared very effective for speeding up the dehydration and oligomerization stages as well as depressing racemization in the whole MP process. The polymerization degree (Xn) of oligomer was clearly increased, and the reaction time was shortened to a great extent. Direct using reduced pressure was also very helpful for intensifying the dehydration stage, only leading to LLA loss as little as 2%. A PLLA with Mw of 44,000 and optical purity of 96.8% suitable for subsequent SSP was produced after dehydration for 2 h, oligomerization for 2 h and MP for 4 h under appropriate conditions. And an interesting strong dependence of the Mw of final PLLA product on the Xn of the oligomer was observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Immobilisation of yeast cells on the surface of hydroxyapatite ceramics

Hydroxyapatite (HAP) ceramics was tested for the first time for the possibility of being used as a new carrier for the immobilisation of yeast cells that are both model organisms for eukaryotic cell investigations and producers, which is important in classical and modern biotechnological processes. It was shown that under typical immobilisation conditions yeast (Saccharomyces cerevisiae) has no affinity to HAP ceramics. A novel method for yeast immobilisation was developed. This new method includes the joint incubation of a carrier with the cells, the sedimentation and adhesion of cells on the carrier and the dehydration of obtained preparations. It was shown that the sedimentation and adhesion stages strongly depend on the value of the electron work function of the HAP ceramics surface. An increase in this value, which corresponds to a higher negative charge on the ceramics surface, correlates with higher cell immobilisation. The dehydration stage strongly and stably fixes cells on the ceramics. Experiments with yeast cells immobilised on HAP ceramics have shown the efficiency of using these preparations in biotechnologies linked with the purification of wastewaters from heavy metals.

A Mutation in ArabidopsisSEEDLING PLASTID DEVELOPMENT1Affects Plastid Differentiation in Embryo-Derived Tissues during Seedling Growth

Oilseed plants like Arabidopsis (Arabidopsis thaliana) develop green photosynthetically active embryos. Upon seed maturation, the embryonic chloroplasts degenerate into a highly reduced plastid type called the eoplast. Upon germination, eoplasts redifferentiate into chloroplasts and other plastid types. Here, we describe seedling plastid development1 (spd1), an Arabidopsis seedling albino mutant capable of producing normal green vegetative tissues. Mutant seedlings also display defects in etioplast and amyloplast development. Precocious germination of spd1 embryos showed that the albino seedling phenotype of spd1 was dependent on the passage of developing embryos through the degreening and dehydration stages of seed maturation, suggesting that SPD1 is critical during eoplast development or early stages of eoplast redifferentiation. The SPD1 gene was found to encode a protein containing a putative chloroplast-targeting sequence in its amino terminus and also domains common to P-loop ATPases. Chloroplast localization of the SPD1 protein was confirmed by targeting assays in vivo and in vitro. Although the exact function of SPD1 remains to be defined, our findings reveal aspects of plastid development unique to embryo-derived cells.

EFFECTS OF POSTHARVEST PARTIAL DEHYDRATION AND PROLONGED TREATMENTS WITH ETHYLENE ON TRANSCRIPT PROFILING IN SKINS OF WINE GRAPE BERRIES

For certain food products, postharvest controlled stresses or treatments with specific elicitors are applied to induce desired physical/chemical changes and/or to positively affect phytochemical content. This is the case of wine grapes where both strategies, singularly applied or coupled, can be used to modulate berry composition and, as a consequence, affect wine quality traits. Since the knowledge of the effects of these postharvest treatments on berry metabolism and the regulation of gene expression is very limited, a large-scale transcriptome analysis has been carried out, using an oligo-based microarray (14,562 probes) on skins of wine grape (Vitis vinifera L.) berries subjected to dehydration, at different rates, up to 30% of weight loss or to ethylene treatment (500 ppm for 7 days) after harvest. A number of differentially expressed targets was detected following both treatments, indicating that grape berries are still reactive at advanced stages of postharvest dehydration and that ethylene induces marked changes in transcriptome after harvest also in non-climacteric fruit such as grape berries.

Scrutinizing Gypsum Board Thermal Performance at Dehydration Temperatures

This article investigates the thermal performance of gypsum boards in the dehydration temperature region, where pronounced chemical reactivity is anticipated. Gypsum board samples were gradually heated up to 300°C, using a low heating rate. Temperature measurements at pre-selected board locations indicated three distinct stages of gypsum dehydration; free moisture evaporation, transformation of calcium sulfate dihydrate to calcium sulfate hemi-hydrate and of calcium sulfate hemi-hydrate to calcium sulfate anhydrate. Physical properties of the gypsum board sample, that is density, specific heat, and thermal conductivity, were measured as a function of the dehydration temperature range. Results suggested that the thermal conductivity of the calcium anhydrate sulfate is higher than that of the hemi-hydrate, despite the fact that gypsum porosity increases during the dehydration process. Based on the experimental results, correlations for the thermal conductivity and the dehydration energy as a function of the mass loss during the dehydration process and the initial water content of the gypsum board, respectively, were obtained.

Effect of structure of the amino acids and amines on the rate and mechanism of their condensations with pyridoxal

Kinetics and mechanism of condensation of amino acids and amines of different structure and their derivatives with pyridoxal were studied. It was established that the amino acid with secondary amino group, proline, adds to pyridoxal with the formation of amino alcohol. α-Amino acids in the course of condensation with pyridoxal form amino alcohols which transform to Schiff bases. The latter compounds by elimination of the α-hydrogen atom or CO2 from the amino acid fragment and the subsequent hydrolysis of the quinoid structure form the final products. β- And ɛ-amino acids react with pyridoxal to form Schiff bases which are stable to chemical transformations. The possibility was shown of their conversion to the quinoid structure. It was established that the guanidine structure of the molecule of L-arginine unlike its α-NH2 group did not take part in the condensation with pyridoxal. The quantitative evaluation of the condensation rates of triptamine, Ltriptofane, and its methyl ester in the stage of dehydration of their amino alcohols was carried out.

Glycerol hydrogenolysis to 1, 2 propanediol over Ru/C catalyst

Optimal experimental conditions for catalytic conversion of glycerol to 1,2 propanediol over catalyst Ru/C are investigated. Results indicate that glycerol hydrogenolysis is the result of two reaction stages: dehydration to acetol and hydrogenation to 1,2 propanediol. Use of a cationic exchange resin improves the dehydration stage, providing higher conversion and selectivity to 1,2 propanediol. Division of the reaction time into a dehydration period (under a nitrogen atmospheric pressure) and a hydrogenation period (under a hydrogen atmosphere of 60 bar) is essayed. This sequential stage reaction process provides lower glycerol conversion but increases the selectivity ratio between 1,2 propanediol and the main liquid by-product, ethylenglycol. The influence of two relevant variables in this process, H2/glycerol ratio and initial glycerol concentration, is analysed. Increasing the H2/glycerol ratio increases glycerol conversion, although it also causes higher production of unfavourable ethylenglycol. Ethylenglycol production is reduced when the glycerol concentration increases. A balance between conversion and selectivity is necessary in order to select optimal reaction conditions.

Radial shrinkage and ultrasound acoustic emissions of fresh versus pre-dried Norway spruce sapwood

Acoustic emission (AE) and radial shrinkage were compared between fully saturated fresh and pre-dried Norway spruce sapwood during dehydration at ambient temperature. Hydraulic conductivity measurements, anatomical investigations on bordered pits and X-ray computed tomography (CT) scans were done to search for possible AE sources other than the breakage of the water columns inside the tracheids. Both fresh and pre-dried specimens showed radial shrinkage due to drying surface layers right from the beginning of dehydration, which induced almost no AE. Whereas no dimensional changes occurred in pre-dried wood thereafter, fresh wood showed a rapid shrinkage increase starting at 25% relative water loss. This dimensional change ceased when further moisture got lost and was even partially reversed. AE of fresh wood showed much higher activity and energy, which is a waveform feature that describes the strength of the acoustic signal. Extremely high single AE energy events were detected at this critical stage of dehydration. After partial recovery from shrinkage, neither dimensional changes nor AE activity showed differences between fresh and pre-dried wood after more than 80% relative moisture loss. Our results suggested that fresh sapwood is more prone to dehydration stresses than pre-dried sapwood. Differences in AE and shrinkage behavior might be due to the weakening or distortion of the pit membranes (cavitation fatigue), pit aspiration, structural changes of the cell walls and micro-checks, which occurred during the first dehydration cycle.

ChemInform Abstract: DTA, DSC and X-Ray Studies on Copper and Manganese Selenate Hydrates

Abstract The thermal dehydration of copper and manganese selenate hydrates has been studied by TG, DTA and DSC. The enthalpies of dehydration stages as well as the enthalpies of formation of CuSeO4·5H2O, CuSeO4·H2O, MnSeO4·5H2O, MnSeO4·2H2O and MnSeO4·H2O have been determined. The comparatively lower temperature of CuSeO4·H2O dehydration as compared to the kieserite-type compounds MeSeO4·H2O (Mg, Mn, Co, Ni, Zn) and the formation of CuSeO4·0.5H2O have been discussed in terms of the crystal structures. The dehydration of copper and manganese selenate hydrates has been studied in aqueous and aqueous-acid solutions. A crystallization field of MnSeO4·4H2O is observed in the ternary MnSeO4–H2SeO4–H2O system at 20°C. The strength of the hydrogen bonds in MnSeO4·2H2O and CuSeO4·H2O has been studied by FTIR spectroscopy. Two crystallographically unequivalent water molecules asymmetrically bonded to the metal ions are assumed to exist in MnSeO4·2H2O. The oxygen atoms from water molecules in an almost square planar structure of Cu(H2O)2(SeO4)2 complex form strong hydrogen bonds due to the strong Cu–H2O interaction (synergetic effect). Lattice parameters of CuSeO4·3H2O have been calculated: a = 5.720(2) A, b = 13.437(4) A, c = 7.475(2) A, β = 97.25(2)°, V = 570.0(2) A3, SG Cc.

Thermal Study in Solid State of Zn(II)‐Diclofenac Complex: Behavior Kinetic of the Dehydration, Transition Phase and Thermal Decomposition

AbstractThe dehydration, thermal decomposition and transition phase stage of Zn(II)‐diclofenac compound were studied by simultaneous TG‐DTA and DSC techniques. The TG and DSC curves of this compound were obtained with the mass of sample of 2 and 5 mg. Additionally, DSC curves were carried out in opened and closed α‐alumina pans under static and nitrogen atmosphere. The DTA and DSC curves show that this compound possesses exothermic transition phase between 170‐180 °C, which it is irreversible (monotropic reaction). The kinetics study of this transition phase stage was evaluated by DSC under non‐isothermal conditions. The obtained data were evaluated with the isoconversional method, where the values of activation energy (Ea / kJ mol−1) was plotted in function of the conversion degree (α). The results show that due to mass sample, different activation energies were obtained. From these curves a tendency can be seen where the plots maintain the same profile for closed lids and almost run parallel to each other.

Genotypic variation in drought stress response and subsequent recovery of wheat (Triticum aestivum L.)

Three wheat (Triticum aestivum L.) genotypes, Sadovo, Katya and Prelom, with different tolerance to drought were comparatively evaluated in terms of leaf respiratory responses to progressing dehydration and consecutive rewatering. Under drought stress, the respiration of all varieties gradually decreased, as the drought-tolerant Katya showed the most pronounced decline at earlier stages of dehydration. When water stress intensified, this genotype gave relatively stable respiration rates compared with the drought-sensitive varieties. Additionally, dehydrated Katya leaves displayed lower stomatal conductance and higher photosynthesis values, which resulted in greater water use efficiency during the dehydration period. Combination of drought stress and short-term changes in leaf temperature also induced genotype-specific response that differed from the response to drought only. Over the whole temperature range, the leaves of Katya exposed to dehydration for 14days, showed higher respiration rates compared to the drought-sensitive varieties. The sensitive varieties maintained higher respiration rates under control conditions and mild dehydration, and very low rates under severe drought. In Katya, respiration and photosynthesis were fully restored from the stress within the first day of rewatering. The drought-sensitive genotypes displayed a considerably slower recovering capacity. The results are discussed in terms of possible physiological mechanisms underlying plant tolerance to drought.

Preparation of the Ca–diclofenac complex in solid state

Abstract The Ca–diclofenac compound was prepared. Thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), X-ray diffraction powder patterns, and microscopy analysis were used to characterize this compound. Details concerning the stages of dehydration, transition phase, and thermal decomposition as well as data of the kinetic parameters of these stages have been described here. The kinetic study of these stages was evaluated from several heating rates with a sample mass of 2 and 5 mg in open crucibles under nitrogen atmosphere. The obtained data were evaluated with the isoconversional kinetic method, where the value of activation energy (Ea/kJ mol−1) was evaluated in function of the conversion degree (α). The results show that this compound is hygroscopic. The obtained data lead to a dependence on the sample mass, which results in two kinetic behavior patterns.