Hemihydrate Research Articles

The effect on the crystallization of calcium sulfate hemihydrate with the addition of magnesium in an MSMPR crystallizer

The effect of Mg2+ ions on the purity of calcium sulfate hemihydrate (HH) in concentrated phosphoric acid solution (wt% P2O5 39) was studied, using a continuously mixed suspension mixed product removal (MSMPR) crystallizer. Impurity distribution into crystals in the MSMPR crystallizer was considered by the population balance equation. The presence of Mg2+ ions make the crystals needle-like and agglomerated in large quantities, leading to more three-dimensional defects formation. This effect on crystals increases the uptake ratio (U) of phosphate and reduces HH purity and phosphorus yield. Through the scanning electron microscopy (SEM) and the focused beam reflectance measurement (FBRM), the effect of Mg2+ ions in inhibiting the radial growth of crystals and increasing the critical nuclear radius (rcrit) of crystals in solution was discovered. The influence of Mg2+ ions is crucial for the preparation of HH in the phosphoric acid hemihydrate process.

Enhancing the aluminate reaction during OPC hydration by combining increased sulfate content, triethanolamine and tartaric acid

Possibilities for enhancing the aluminate reaction were studied in a mix of OPC blended with 7.9 % hemihydrate (HH) or 7.4 % anhydrite (AH) in combination with different triethanolamine (TEA) dosages. Heat flow calorimetry and quantitative X-ray diffraction (XRD) were performed to study the hydration process. Using anhydrite as an additional sulfate carrier allowed a lower TEA dosage compared to hemihydrate systems to enhance the degree of hydration of C3A. High TEA dosages in hemihydrate systems were found to hinder C3S hydration. Nevertheless, it was possible to push the aluminate reaction ahead of the silicate reaction, thereby enhancing the degree of hydration of C3A. Additionally, the degree of hydration of C3S was not strongly affected when anhydrite and a well-balanced TEA dosage were used. The addition of tartaric acid to OPC-anhydrite-TEA systems retarded the subsequent aluminate reaction.

The influence of calcium formate on the hydration of calcium sulfate hemihydrate

In this study, the influence of calcium formate (CF) on the hydration of a synthesized calcium sulfate hemihydrate (HH) powder was investigated. Isothermal calorimetry measurements showed that CF retards the hydration reaction of HH. This was confirmed by XRD of stored samples and pore solution analysis. Two retardation mechanisms were identified. The combination of pore solution and laser granulometric experiments revealed that firstly, the initial dissolution of hemihydrate decelerates because of high Ca2+ ion concentrations, donated by the faster dissolving CF. Secondly, the HCOO− species of CF adsorb on surfaces of the gypsum crystals, as further pore solution measurements showed. This impedes their formation kinetic. The gypsum crystals exhibited anisotropic peak narrowing in XRD measurements when CF was added. This was caused by a morphology change, which could be verified using the anisotropic domain size morphology approach during Rietveld refinement analysis and SEM images. Gypsum crystals exhibit a blockier shape with CF addition compared to the usual acicular shape in pure water.

Quantum computational investigation into structural, spectroscopic, topological and electronic properties of L-histidinium-L-tartrate hemihydrate: Nonlinear optical organic single crystal

For the first time, a systematic investigation of optimization in the geometrical, vibrational, natural bonding orbital (NBO), electronic, linear and nonlinear optical properties, and Hirshfeld surface analysis for the L-histidinium-l-tartrate hemihydrate (HT) crystal is reported by employing the density functional theory (DFT). The geometrical parameters and vibrational frequencies obtained from the B3LYP/6–311++G(d,p) level of theory are in good agreement with the experimental values. The presence of strong hydrogen bonding interactions in the molecule causes an intense absorption peak in the infrared spectrum below 2000 cm−1. Quantum Theory of Atoms in Molecules (QTAIM) has been used to evaluate the topology of the electron density of a particular molecule to identify the critical points of the system using Multiwfn 3.8. These studies included ELF, LOL, and RDG studies. A time-dependent DFT approach is employed to obtain the excitation energies, oscillator strengths, and UV–Vis spectra for different solvents, such as methanol, ethanol, and water. The NBO analysis of the chosen compound, HT, is performed in terms of atom hybridization and electronic structure. The HOMO-LUMO energies and other associated electronic parameters are also computed. The nucleophilic sites are identified from MEP and Fukui functions analysis. The electrostatic potential and total density of states spectra of HT are discussed in detail. The theoretically obtained polarizability and first order hyperpolarizability values confirm that the grown material HT has NLO efficiency 15.771 times that of urea, and is proposed to be an exceptional nonlinear optical material. In addition, Hirshfeld surface analysis is performed to determine the inter-and intramolecular interactions in the title compound.

A study of the heat-mediated phase transformations of praziquantel hydrates. Evaluation of their impact on the dissolution rate

Comprehensive knowledge of the critical properties of the active pharmaceutical ingredients is a requirement within the modern concept of quality. Praziquantel hemihydrate (HH) and monohydrate (MH) are new solid forms of this antihelmintic agent, which have better solubility properties than the commercial anhydrous solid form (polymorph A). The thermal stability of the hydrates was evaluated, aiming to understand any possible transformation (amorphization, change to a less soluble form).Therefore, HH and MH were prepared along with the related anhydrous solid forms A and B, and characterized employing solid-state nuclear magnetic resonance, powder X-ray diffraction, mid and near infrared spectroscopy, thermal methods and the intrinsic dissolution rate.The transformations of HH and MH under thermal stress conditions were monitored through a variable temperature infrared spectroscopy approach, assisted by multivariate curve resolution with alternating least squares (MCR-ALS), finding that HH undergoes a two-step transformation (HH→B→A) to form A, whereas MH dehydrates directly into form A. This was further confirmed by conventional calorimetric methods (differential scanning calorimetry and thermogravimetry) and powder X-ray diffractometry.The impact of changes in the stressed solid forms and their dissolution rates was also assessed. Significant differences in dissolution performance were found regarding the solid forms produced as a consequence of thermally-induced dehydration.

The effect of additives on the hydration of CaSO4·0.5H2O: A synchrotron X-ray diffraction study

To modulate the rate of hydration of calcium sulfate hemihydrate (HH) to calcium sulfate dihydrate for industrial applications, additives (both accelerants and retardants) are added to the HH. Here we explore in detail the kinetics and mechanism of HH hydration in the presence of the accelerators K2SO4 or ZnSO4, and also when a retardant (citric acid or tartaric acid) is added. Retardants tend to lower the maximum temperature of the reaction and increase the time needed to reach 50% hydration, yet the total conversion percentage is similar to that when an accelerant is added. The reaction process is found to involve heterogenous nucleation regardless of the nature of the additive. More soluble accelerants act mainly though increasing the rate of crystal growth, while less soluble species have a more significant effect on the rate of nucleation.

PREPARATION OF CALCIUM SULFATE HEMIHYDRATE WHISKERS FROM COMPLEX JAROSITE WASTE

Complex jarosite waste was obtained from zinc metal hydrometallurgical process, which contained gypsum and ammonium jarosite (NH4Fe3(SO4)2(OH)6). The influence of impurity ions (Fe3+ and NH4+) on the calcium sulfate hemihydrate (HH) morphology was studied using pure gypsum as the raw material, respectively. HH crystals with a high aspect ratio were obtained without the impurity ions. The diameter increased and the aspect ratio of the HH decreased, while the addition of iron sulfate and ammonia sulfate increased. Ammonium iron (NH4+) can be removed by using calcium oxide to decompose the ammonium jarosite in the waste and then to wash the sediment with tap water. The sediment (calcified jarosite sediment) mainly contained CaSO4·2H2O and Fe(OH)3. The influence of cultivating time on HH crystals growth was researched by using the sediment as raw materials. The diameter of the whiskers increased, while the hydrothermal time increased. The whiskers were obtained, with high a aspect ratio (10–60), large diameter (1–4 µm) and smooth surface, after the sediment was treated at 140 °C for 6 h in pH = 5 solution.

Development of validated analytical methods and stability indicating studies for pharmaceutical formulation

A simple, accurate rapid and precise has been developed and validated for estimation of Canagliflozin hemihydrate in Pharmaceutical Tablet Formulation by VU-Spectrophotometer and RP-HPLC Method. The successful estimation was carried out of the drug product is developed on the Jasco V-630 and Shimadzu-UV-1700 for VU-Spectrophotometer method and for HPLC successful estimation was carried out of the drug product is developed on the ACE Column C18 (150mm x 4.6mm, 5μm or equivalent) at ambient temperature using Acetonitrile: Orthophosphoric acid (1%) (60: 40 v/v) as mobile phase composition. The flow rate was adjusted to 1.0mL/minute and the absorption maxima were observed on UV detector at 290nm. Retention time for Canagliflozin hemihyd rate 3.0±0.5 min. The linearity was obtained in the concentration range of 80%-120% for Canagliflozin hemihydrate. For the HPLC method injection volume should be 20μL.The method was robust with respect to change in flow rate, temperature and composition of mobile phase. The method was validated statistically and applied successfully for the determination of Canagliflozin hemihydrate by VU-Spectrophotometer and RP-HPLC method. Validation studies revealed that method is specific, rapid, reliable, and reproducible. The high recovery and low relative standard deviation confirm the suitability of the method for the routine determination of Canagliflozin hemihydratein pharmaceutical cream formulation.

A readily monitored and controllable hydrothermal system for the facile, cost-effective transformation of FGD gypsum to calcium sulfate hemihydrate whiskers

The controllable transformation of flue gas desulfurization (FGD) gypsum to calcium sulfate hemihydrate (HH) whiskers under facile, readily monitored, and cost-effective hydrothermal conditions could play a vital role in the preparation of high quality HH whiskers and improve our understanding of the transformation process. This work assessed the conversion of FGD gypsum to HH whiskers in 5×10–4 mol/L H2SO4 and 1.5 wt% CuCl2 at 120 °C while determining the effects of temperature as well as H2SO4 and CuCl2 concentrations on transformation kinetics. The preparation of HH whiskers was found to involve a solution-mediated transformation from the dihydrate (DH) to the α-HH. This transition was determined to proceed via a dissolution crystallization mechanism, the rate of which was controlled by nucleation and growth of the HH whiskers. An autocatalytic kinetic model was established based on variations in the HH whiskers mole fraction over time, and this model accurately fit the experimental data with R2 = 0.990. Increasing the temperature or H2SO4 concentration accelerated the transformation by modifying the super-saturation and water activity in the reaction solution, while increasing the CuCl2 concentration had the opposite effect. The hydrothermal conditions had an important effect on the transformation from FGD gypsum to HH whiskers.

Crystal structure of bis(3-bromo-N-(1-(3-methylpyrazin-2-yl)ethylidene)benzohydrazonato-κ3 O,N,N′)cadmium(II) hemihydrate, C28H25N8O2.5Br2Cd

Abstract C28H25N8O2.5Br2Cd, triclinic, P1̄ (no. 2), a = 8.7233(16) Å, b = 11.655(2) Å, c = 15.374(3) Å, α = 82.225(4)°, β = 86.125(3)°, γ = 76.300(3)°, V = 1503.6(5) Å3, Z = 2, R gt(F) = 0.0459, wR ref(F 2) = 0.1102, T = 296 K.

Repair of rabbit articular cartilage defect by a novel injectable bioactive glass scaffold

Objective By comparing different repairing effects of different methods on articular cartilage defects in rabbit model, the ability of a new bioactive glass scaffold to repair cartilage defect was studied. Methods We prepared the PSC/CS bone cement by mixing the bioactive glass (BG) powder composed of 10.8%P2O5-54.2%SiO2-35%CaO (PSC), chitosan solution (CS) and calcium sulfate hemihydrate (CSH), then the bone cement was sized by a mold to form cylindrical scaffold. In vivo experiment, 18 male rabbits were divided into three groups randomly, including blank group, BG group and TGF-β1 group, which was added TGF-β1 into BG scaffold. Both knees of each rabbit were made cartilage defect for the same group, and no intervention was applied in B group, then implanted scaffolds into defects in both experimental groups. At 6 and 12 weeks after surgery, observed the macroscopic growth, histologic staining and collagen II immunohistochemistry (IHC), and the International Cartilage Repair Society (ICRS) and Wakitani score were used to analyze the experimental results quantitatively. Results At 6 weeks after surgery, there was no obvious difference between blank group and BG groups, but the macroscopic result of TGF-β1 group was better than the other two groups and its ICRS score 4.67±0.52 points was statistically higher than BG group 2.83±0.75 points (t=-2.817, P=0.015). As to the comparison of histologic staining and Wakitani socre among three groups, no statistical difference was observed (blank group=13.67±0.52, BG group=13.83±0.41, TGF-β1 group=13.33±1.03). At 12 weeks after surgery, there was still no obvious difference between blank and BG groups, while the results of macroscopic observation and ICRS score in TGF-β1 group were significantly higher than them 9.01±0.63 points (blank group vs TGF-β1 group: t=-2.289, P=0.022; BG group vs TGF-β1 group: t=-2.326, P=0.020). More importantly, much deeper positive staining were observed in TGF-β1 group, and the Wakitani score was higher than the other two groups (blank group=9.83±1.33, BG group=9.51±1.05, TGF-β1 group=6.50±1.38, blank group vs TGF-β1 group: t=-2.771, P=0.007; BG group vs TGF-β1 group: t=-2.756, P=0.006). By comparing the degree of histologic staining and Col II expression with normal cartilage, the regenerated tissue in TGF-β1 group was similar. Conclusion Single PSC/CS scaffold doesn’t possess excellent ability to repair cartilage defect. When TGF-β1 was added into PSC/CS bioactive glass, the scaffold was able to promote cartilage defect repair, and the regenerated tissue was similar to normal cartilage. Key words: Tissue engineering; Glass; Tissue scaffolds; Chondrocytes

Product characteristics in simultaneous crystallization of NaCl and CaSO4 from aqueous solution under different evaporation rates

Knowledge about simultaneous crystallization in evaporative processes for water reuse is important for the promotion of particles with desirable characteristics. In this work, simultaneous crystallization of sodium chloride and calcium sulfate hemihydrate (HH) from aqueous solutions in unseeded batch mode is addressed. Both the crystallization mechanisms and the resulting particle morphological features have been identified. NaCl particles are generated by heterogeneous primary nucleation in solution, followed by growth and NaCl agglomeration. Calcium sulfate hemihydrate (HH) particles are also formed by heterogeneous primary nucleation in solution followed by crystal growth. HH crystals agglomerate with NaCl in all particle size ranges. Product particles are thus agglomerates with multimodal population densities in submillimetric size ranges, with HH widely dispersed throughout the size span of the particulate product. In comparison with NaCl binary solutions, simultaneous crystallization promotes the formation of larger, less polydisperse NaCl particles. Low supersaturations (low evaporation rates) inhibit HH agglomeration with NaCl. The submillimetric sized particles formed during simultaneous crystallization of NaCl and HH indicate ease in solid-liquid downstream separation.

Effects of AlCl3 on the Crystal Morphology of Calcium Sulfate Whisker Prepared from FGD Gypsum

Utilizing the purified flue gas desulfurization (FGD) gypsum as raw material and AlCl3 as crystal modifier to prepare calcium sulfate whiskers (CSWs) by hydrothermal method, the effects of the AlCl3 concentration and the pH of reaction slurry on the crystal morphology of CSW were discussed. The results show that the AlCl3 concentration and the pH of reaction slurry had a significant effect on the crystal morphology of CSWs. CSWs grown in the AlCl3-H2O slurry had diameters ranging from 2 to 6 um and aspect ratio above 80 μm, and their phase structure was calcium sulfate hemihydrate (HH).

L-aspartic acid: A crystal modifier for preparation of hemihydrate from phosphogypsum in CaCl2 solution

L-aspartic acid (L-Asp) was proposed as crystal modifier to regulate the morphology of hemihydrate (HH) prepared from phosphogypsum (PG) in CaCl2 solution. Effect of L-Asp on dehydration kinetics of PG, morphology and mechanical properties of HH as well as microstructure of hardened gypsum were investigated by crystal water content, strength and SEM measurements. The adsorption mechanism of L-Asp onto the HH crystals was explored by FTIR, XPS and zeta potential analyses. The results show that the L-Asp chemisorbs on the surfaces of HH by carboxyl (COO−) complexing with Ca atoms, and reduces the dehydration rate of PG to HH by extending the crystal growth period. The dehydration kinetics can be well described by the Boltzmann equation. With increasing L-Asp concentration from 0.00 to 2.50 mM, the HH crystals are shortened in length and enlarged in width with the aspect ratio decreasing from 5.74 to 1.21; meanwhile, the water requirement of normal consistency decreases from (41.5 ± 0.7)% to (31.2 ± 0.3)% and the corresponding bending/compressive strengths increase from (6.2 ± 0.6)/(13.1 ± 1.1) MPa to (10.7 ± 0.7)/(30.2 ± 1.4) MPa, respectively. Furthermore, the hardened gypsum presents a more compact microstructure with uniform in size and morphology in the presence of 2.50 mM L-Asp in comparison with blank test. Therefore, it can be concluded that the L-Asp is an effective crystal modifier for preparation of short columnar HH.

Mechanical Properties of Alpha-Calcium Sulfate Hemihydrate Replaced Concrete for Application to Box Culvert Power Transmission

Mechanical Properties of Alpha-Calcium Sulfate Hemihydrate Replaced Concrete for Application to Box Culvert Power Transmission

Effect of Al3+ on crystal morphology and size of calcium sulfate hemihydrate: Experimental and molecular dynamics simulation study

Changes of crystal morphology and size of calcium sulfate hemihydrate (HH) by Al3+ ions, synthesized by hydrothermal method, were carried out to understand the interaction mechanism between the metal ion and crystal surface. The preferential adsorption of Al3+ on the top crystal surface was confirmed by XPS and ICP-OES, and the interaction mechanism was evaluated by molecular dynamics (MD). It was observed that the Al3+ ions significantly inhibited the HH growth along c-axial. The shape of HH crystal with the increasing of Al3+ ions concentration (0 to 10 mM), changed from whiskers to short rod-like. The position of Al3+ ions into the structure by molecular dynamics simulation showed preferential adsorption on active sites of (0 0 2) face, which inhibited the growth rate and leaded to the formation of short rod-like HH. This provided a guide for the research of calcium sulfate whiskers preparation from industrial gypsum.

Morphology control of calcium sulfate hemihydrates and application in size screening iron/sulfur of jarosite sediment

To separate iron and sulfur in jarosite sediment by using the sieving method, firstly, the jarosite sediment is decomposed by adding calcium oxide to obtain iron hydroxide and calcium sulfate dihydrate mixed precipitation. Secondly, the calcium sulfate hemihydrate (HH) whiskers with a large diameter and iron (hydr)oxides with a small diameter are obtained by treating the mixed precipitation at 140 °C in a hydrothermal condition. Finally, the whiskers and iron (hydr)oxides can be separated by using the sieving method. The whiskers can be used as the reinforcing phase of composites and the (hydr)oxides can be used as raw materials of iron.The influence of the cultivating time, and the maleic acid and solid/solution ratio on the HH crystals morphology was detected in a 140 °C hydrothermal condition. The crystal diameter increased with cultivating time in the 1:20 ratio of solid/solution solution. The aspect ratio of the crystals increased and the diameter decreased, while the addition amount of maleic acid increased in the 1:20 ratio of solid/solution solution for a cultivating time of 6 h. The diameter of the crystal was not significantly changed, but the length became shorter while the ratio of solid/solution increased.The grain size of the iron (hydr)oxides did not significantly change in the hydrothermal condition, which was favorable for separation of iron (hydr)oxides and HH crystals with the sieving method. It was reasonable (economical) to treat the mixed precipitation in the 1:2.5 ratio of solid/solution solution at 140°Cfor 2 h.

Plaster of Paris: the orthopaedic surgeon heritage

Plastering is one of the most ancient of the building handicrafts. Plaster is the common name for calcium sulphate hemi hydrate made by heating the mineral gypsum, the common name for sulphate of lime. In the tenth century the Arabs used liquid plaster in orthopaedic treatment. At the beginning of the nineteenth century, patients with fractures of the lower extremities-and often of the upper extremities as well-were treated in bed with restriction of all activity for many weeks until the fractures united. It was the practice of surgeons to dress wounds and fractures at frequent intervals. The bandages, pads, and splints were removed, the fractures manipulated, and the dressings reapplied. The search for simpler, less cumbersome methods of treatment led to the development of occlusive dressings, stiffened at first with starch and later with plaster of Paris. The ambulatory treatment of fractures was the direct result of these innovations. Two military surgeons, Antonius Mathijsen of the Netherlands, and Nikolai Ivanovitch Pirogov of Russia, were responsible for the introduction of the new plaster bandage technique. At the beginning of the twentieth century the technique was improved by Jean-François Calot, a French surgeon, who invented the hand manufacture of plaster bandage as a roll. During the twentieth century, walking cast and ambulation for fresh fractures were developed with plaster and pin incorporated in plaster; the open fracture care concept was introduced with plaster of Paris by Trueta before the external fixation.

Effect of pulverization on dehydration behavior of crystals of GK-128, a serotonin3 receptor antagonist.

The effect of pulverization on the dehydration behavior of 2-[(2-methylimidazol-1-yl)methyl]benzo[i]thiochromen-1-one monohydrochloride hemihydrate (GK-128), a newly developed serotonin3 receptor antagonist, was studied using powder X-ray diffraction analysis, thermogravimetry (TG), and differential scanning calorimetry (DSC). The crystalline forms of GK-128 obtained by pulverizing with a jet mill and an agale mortar were each confirmed to be the same as that of intact GK-128, since the powder X-ray diffraction patterns of the two prepared samples were identical with that of intact GK-128. However, after pulverization by jet mill, the dehydration temperature of GK-128 was markedly lowered and the DSC endothermic peak due to dehydration disappeared. The activation energy for dehydration, calculated by the Ozawa method using TG data, decreased with decreasing particle size and/or crystallinity of GK-128 crystals, e.g., the activation energies for dehydration of intact and jet-milled GK-128 were 128.1 and 75.9 kj/mol, respectively. The results of comparison of powder X-ray diffraction patterns of pulverized GK-128 and intact GK-128 and of determination of the crystal structure of GK-128 suggested that water molecules could be removed easily along the c-axis of GK-128 crystals.

Synthesis and Characterization of Yellow Gypsum from LD Slag Fines Generated in a Steel Plant

We describe here a simple method for synthesis of a value-added product (yellow gypsum) from Linz-Donawitz slag (LD slag), which is an industrial waste product of the steel industry. XRD analysis of the product confirmed the presence of anhydrite and gypsum phases as well as the presence of iron, silica and titanium in the form of fayalite and illmenite phases. A weight loss of 17.26% was observed from the TG analysis, indicating the presence of mixture of the dihydrate, hemihydrate, soluble γ-anhydrite and insoluble β-anhydrite phases of gypsum in the product.