Calcium Sulfate Dehydrate Research Articles

Preparation of potassium salt with joint production of spherical calcium carbonate from sintering dust

Several physical and chemical detection methods were used to study the basic properties of sintering dust (ESP dust) collected from Baogang Steel Corporation. The result shows that the major constituents of the ESP dust are KCl, NaCl, Fe2O3 and Fe3O4. Water leaching experiment on the sintering dust shows that KCl in the ESP dust can be separated and recovered by water leaching and fractional crystallization. Component analysis of leaching solution indicates that the massive calcium sulfate in the leaching solution should be removed first in order to obtain the pure potassium salt. In order to provide theoretical guidance to inhibit the dissolution of calcium ions from the sintering dust, the water leaching experiment of ESP dust and the dissolution behavior of CaSO4 in the potassium chloride, sodium chloride, potassium sulfate and their mixed salt solution were studied. It is found that, a lower liquid–solid ratio should be chosen in the leaching process to inhibit the dissolution of calcium sulfate dehydrate. Using sodium carbonate solution as a precipitating agent, the influences of the concentration of sodium carbonate solution, reaction temperature, stirring speed and equilibrium time on the preparation of the spherical calcium carbonate were studied. Spherical calcium carbonate with good dispersing performance and grain size distribution in nanometer range of less than 10 μm was obtained. Furthermore, a potassium recovery process with joint production of spherical calcium carbonate was designed. This process is technically viable and considerable in economic benefit.

An in vivo swine study for xeno-grafts of calcium sulfate-based bone grafts with human dental pulp stem cells (hDPSCs).

The purpose of this in vivo study was to evaluate the effect of human dental pulp stem cells (hDPSCs) on various resorbable calcium sulfate/calcium phosphate bone grafts in bone regeneration. Granular particles of calcium sulfate dehydrate (CSD), α-calcium sulfate hemihydrate/amorphous calcium phosphate (α-CSH/ACP), and CSD/β-tricalcium phosphates (β-TCP) were prepared for in vitro dissolution and implantation test. The chemical compositions of specimen residues after dissolution test were characterized by XRD. The ratios of new bone formation for implanted grafts/hDPSCs were evaluated using mandible bony defect model of Lanyu pig. All the graft systems exhibited a similar two-stage dissolution behavior and phase transformation of poor crystalline HAp. Eight weeks post-operation, the addition of hDPSCs to various graft systems showed statistically significant increasing in the ratio of new bone formation (p<0.05). Null hypothesis of hDPSCs showing no scaffold dependence in bone regeneration was rejected. The results suggest that the addition of hDPSCs to calcium sulfate based xenografts could enhance the bone regeneration in the bony defect.

Anhydrite and Gypsum Compositions Modified with Ultrafine Man-Made Admixtures

The influence of technogenic ultrafine additives on structure and properties of binders based on calcium sulfate has been studied. The study of physical and mechanical properties of gypsum compositions modified with metallurgical dust has showed an increase in ultimate compressive strength up to 30%, ultimate bending strength – 15%, the value of water resistance of the binder did not change. 1% of metallurgical dust being added to natural anhydrite, there is a significant increase of the strength of the composition by 40%, and the water resistance of the material decreases slightly. The conducted X-ray analysis does not show the presence of any new products of hydration and intensification of hydration of calcium sulfate dehydrate. At the same time, the conducted studies of the structure of the compositions confirm significant changes in the morphology of new formations. Thus, adding ultrafine additives to natural anhydrite and gypsum leads to the formation of a dense matrix of the increased strength.

Preparation of Macroporous Ceramic Materials by Using Aluminium Powder as Foaming Agent

Aluminium powder was used as foaming agent in the production of macro-porous alumina ceramic. The porous ceramic material was developed by mixing an appropriate composition of cement, aluminium powder (Al), alumina (Al2O3), calcium oxide (CaO), gypsum (calcium sulphate dehydrate, CaSO4.2H2O), silica powder and deionized water. Different compositions of porous ceramic were produced at 2wt.%, 3wt.% and 4wt.% of aluminium powder. Their mechanical properties and macro-porosity structural of the porous ceramic material were analysed and compared. It is determined that the optimal properties of porous ceramic material were found at 3wt.% of aluminium powder and degraded drastically at 4wt.%. This phenomenon is due to the chemical reaction between the aluminium powder and DI water in which they form aluminium oxide that promotes the strength of the material but at the same time, more pores are created at higher reaction rate between these two fundamental materials.

Effect of calcium sulfate dehydrate and external electric field on the sedimentation of fine insoluble particles

Several reports show that calcium sulfate dehydrate can induce the sedimentation of insoluble substances in waste water. Silt, clay, and feldspar were selected in this study to settle with calcium sulfate dehydrate in water, and the parameters of particle interaction were calculated using the extended DLVO theory. Results indicate that the key to sedimentation is the electrostatic force between particles. Electrostatic force facilitates cosedimentation of calcium sulfate dehydrate with silt or clay, but not with feldspar, and their combination is weak. External electrical field can promote the sedimentation of silt, clay, and humic acid but not the cosedimentation of calcium sulfate dehydrate with insoluble substances. Moreover, an external electric field can facilitate the dispersion of clay and calcium sulfate dehydrate aggregates. Most of the electron charges after the cosedimentation of calcium sulfate dehydrate and silt was neutralized, but a certain amount of electron charge remained after the combination of clay and calcium sulfate dehydrate. Suspended particles in water continued to increase after the sedimentation of feldspar and calcium sulfate dehydrate, thereby implying that new nuclei must have been discharged by calcium sulfate dehydrate.

Investigation of influence of low phosphorous co-polymer antiscalant on calcium sulfate dihydrate crystal morphologies

Increasing environmental concerns and discharge limitations have imposed additional challenges in industrial cooling water treatment. Increasing research efforts have been directed towards finding economical and environmentally friendly inhibitors. In this study, a novel inhibitor of low phosphorus co-polymer was prepared. The inhibition performance of the novel low phosphorus co-polymer as calcium sulfate dihydrate scale inhibitors, the influence of phosphorus content and viscosity weighted average molecular weight on inhibition were evaluated in simulated cooling water. The results indicate that the optimal preparation conditions of the novel low phosphorus co-polymer for inhibiting calcium sulfate dihydrate were 2.103 of sodium ρ-styrene sulfonate/maleic anhydride ratio, 0.26 of the ratio of hypophosphorous to monomer, and 0.57 of the ratio of hydrogen peroxide to hypophosphorous. The novel low phosphorus co-polymer strongly affected the calcium sulfate dihydrate scale formation, the scale inhibition rate was 94%, and phosphorus content and viscosity weighted average molecular weight also evidently influence the scale inhibition rate to calcium sulfate dehydrate. Scanning electronic microscopy and powder X-ray diffraction investigations reveal that the crystal structure of the calcium sulfate dehydrate is highly modified in the presence of the novel low phosphorus co-polymer.

In vivo evaluation of resorbable bone graft substitutes in beagles: Histological properties

Calcium phosphate cement (CPC) is a promising material for use in minimally invasive surgery for bone defect repairs due to its bone-like apatitic final setting product, biocompatibility, bioactivity, self-setting characteristics, low setting temperature, adequate stiffness, and easy shaping into complicated geometrics. However, even though CPC is stable in vivo, the resorption rate of this bone cement is very slow and its long setting time poses difficulties for clinical use. Calcium sulfate dehydrate (CSD) has been used as a filler material and/or as a replacement for cancellous bone grafts due to its biocompatibility. However, it is resorbed too quickly to be optimal for bone regeneration. This study examines the invivo response of a hydroxyapatite (HA), [apatitic phase (AP)]/calcium sulfate (CSD) composite using different ratios in the mandibular premolar sockets of beagles. The HA (AP)/CSD composite materials were prepared in the ratios of 30/70, 50/50, and 70/30 and then implanted into the mandibular premolar sockets for terms of 5 and 10 weeks. The control socket was left empty. The study shows better new bone morphology and more new bone area in the histological and the histomorphometric study of the HA (AP)/CSD in the 50/50 ratio.

Bioactive glass incorporation in calcium phosphate cement-based injectable bone substitute for improved in vitro biocompatibility and in vivo bone regeneration

In this work, we fabricated injectable bone substitutes modified with the addition of bioactive glass powders synthesized via ultrasonic energy-assisted hydrothermal method to the calcium phosphate-based bone cement to improve its biocompatibility. The injectable bone substitutes was initially composed of a powder component (tetracalcium phosphate, dicalcium phosphate dihydrate and calcium sulfate dehydrate) and a liquid component (citric acid, chitosan and hydroxyl-propyl-methyl-cellulose) upon which various concentrations of bioactive glass were added: 0%, 10%, 20% and 30%. Setting time and compressive strength of the injectable bone substitutes were evaluated and observed to improve with the increase of bioactive glass content. Surface morphologies were observed via scanning electron microscope before and after submersion of the samples to simulated body fluid and increase in apatite formation was detected using x-ray diffraction machine. Invitro biocompatibility of the injectable bone substitutes was observed to improve with the addition of bioactive glass as the proliferation/adhesion behavior of cells on the material increased. Human gene markers were successfully expressed using real time-polymerase chain reaction and the samples were found to promote cell viability and be more biocompatible as the concentration of bioactive glass increases. Invivo biocompatibility of the samples containing 0% and 30% bioactive glass were evaluated using Micro-CT and histological staining after 3 months of implantation in male rabbits' femurs. No inflammatory reaction was observed and significant bone formation was promoted by the addition of bioactive glass to the injectable bone substitute system.

Performance of Composite Cements in the Repair of Porcine Thoracolumbar Burst Fracture &lt;i&gt;In Vitro&lt;/i&gt;

An ideal injectable bone cement should be able to fill fully the fractures gap and provide good mechanical support. In the present work, the mineralized collagen and calcium sulphate dehydrate (CSD) was incorporated into α-calcium sulphate hemihydrates (α-CSH) to explore an injectable composite cement. The injectability, the setting time and the biomechanics properties were investigated. A porcine thoracolumbar burst fracture model was used to evaluate the biomechanical performance of composite cements. The porcine thoracolumbar burst fracture models in vitro were prepared. A half of models was made by the vertebroplasty of the composite cements, the other half of models was used as control. Imaging analysis showed the composite cements distributed uniformly and solidified well. Biomechanical test showed the ability of the composite cements to repair spinal burst fractures was significant.

Preparation of calcium sulfate dihydrate and calcium sulfate hemihydrate with controllable crystal morphology by using ethanol additive

Abstract Calcium sulfate hemihydrate (CSH) with controlled crystal morphology has attracted broad interests due to its superior physical and chemical properties, as well as excellent biological performance. In this study, calcium sulfate dehydrate (CSD) was firstly synthesized via the reaction of H 2 SO 4 and Ca(OH) 2 using ethanol as morphology modifier. The prepared CSD was then converted to CSH through a hydrothermal method. It was found that the precipitation time of CSD powders was dramatically shortened and the morphology of CSD crystals was changed from thick tabular to short-rod with the increment in ethanol addition. The finally-obtained CSH crystals were found to have hexagonal prisms shape with smaller aspect ratios. The CSH powder with the desired crystal morphology would provide improved setting behavior and biological performance of the CSH bone cement.

In vivoevaluation of resorbable bone graft substitutes in mandibular sockets of the beagle

Hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2)), with its high biocompatibility and good bioaffinity, stimulates osteoconduction and is slowly replaced by the host bone after implantation. However, clinical use of HA as a bone substitute has proved problematic. It is difficult to prevent dispersion of the HA granules and to mold the granules into the desired shape. Calcium sulfate as a bone graft substitute is rapidly resorbed in vivo releasing calcium ions, but fails to provide a long-term, three-dimensional framework to support osteoconduction. The setting properties of calcium sulfate, however, allow it to be applied in a slurry form, making it easier to handle and apply in different situations. This study examines the in vivo response of a (Hydroxyapatite, apatitic phase)/calcium sulfate dehydrate (CSD) composite using different ratios in the mandibular premolar sockets of the beagle. The HA (AP)/CSD composite materials prepared in ratios of 30/70, 50/50, and 70/30 were implanted into the mandibular premolar sockets for 5 and 10 weeks. The control socket was empty. The authors compared the radiographic properties and the changes in height and width of the mandibular premolar sockets in the beagle. The composite graft in the 30/70 ratio had the best ability to form new bones.

A novel injectable and degradable calcium phosphate/calcium sulfate bone cement

The aim of this study was to obtain a composite material which not only has suitable workability but also has excellent degradability. A novel injectable and degradable bone cement consisting of a mixture of calcium phosphate (α-tricalcium phosphate; α-TCP) and calcium sulfate dihydrate (CaSO 4 . 2H 2 O; CSD) powders as the solid phase and an aqueous solution containing 2.5 weight percent of Na 2 HPO 4 as the liquid phase, was prepared. Seven groups with differing CSD content (0, 5, 10, 20, 30, 40 and 100%) were tested. The injectability of α-TCP increased with increasing proportions of CSD in the mixture; a small addition of CSD powder sharply decreased the setting time of the cement, but further addition caused the setting time of the mixture to increase again. Simultaneously, adding CSD to α-TCP had little effect on the setting temperature. The compressive strength of the cement decreased with increasing content of CSD except in the 5% group, because addition of a small amount of CSD to the cement induced the appearance of fiber-like crystallization; this was confirmed by scanning electron microscopy (SEM). Furthermore, the bone cement mixture had good degradability in simulated body fluid (SBF) when the content of CSD was increased. Key words: Calcium phosphate, calcium sulfate dehydrate, bone cement, injectability, degradability, bonerepair.

Fabrication of calcium phosphate–calcium sulfate injectable bone substitute using hydroxy-propyl-methyl-cellulose and citric acid

In this study, an injectable bone substitute (IBS) consisting of citric acid, chitosan, and hydroxyl propyl methyl cellulose (HPMC) as the liquid phase and tetra calcium phosphate (TTCP), dicalcium phosphate dihydrate (DCPD) and calcium sulfate dehydrate (CSD, CaSO4·2H2O) powders as the solid phase, were fabricated. Two groups were classified based on the percent of citric acid in the liquid phase (20, 40 wt%). In each groups, the HPMC percentage was 0, 2, and 4 wt%. An increase in compressive strength due to changes in morphology was confirmed by scanning electron microscopy images. A good conversion rate of HAp at 20% citric acid was observed in the XRD profiles. In addition, HPMC was not obviously affected by apatite formation. However, both HPMC and citric acid increased the compressive strength of IBS. The maximum compressive strength for IBS was with 40% citric acid and 4% HPMC after 14 days of incubation in 100% humidity at 37°C.

Fabrication of Injectable Calcium Sulfate Bone Graft Material

Calcium sulfate (CaSO4), as a commonly used implanting material, shows good biocompatibility, biodegradability, osteoconductivity and mechanical properties. Studies about using CaSO4 as bone filler for the treatment of bone defects are reported now and then, but the fabrication of injectable implant was hardly studied. In this study, calcium sulfate hemihydrate (CSH), as the basic material, was incorporated with a cellulose derivative, poly(ethylene glycol) (PEG), calcium sulfate dehydrate (CSD) crystal coated with PEG (P-CSD), and a certain amount of water to form injectable CaSO4 bone fillers. The structure of the bone fillers with different compositions was analyzed with scanning electron microscopy (SEM), infrared spectroscopy (IR) and X-ray diffraction (XRD). The effects of additives such as P-CSD, CSD, PEG and cellulose derivative on setting time, water absorption ability, mechanical properties and structure of the injectable bone fillers were studied. The in vitro degradation test showed that the injectable bone fillers have appropriate degradation time in phosphate-buffered solution (PBS), and they can maintain integrity throughout the degradation process. In vitro cell culture and preliminary animal model experiments demonstrated that the bone fillers do not exhibit a deleterious effect on cell viability and can hasten bone growth in bone defect model.

The thermal dehydration of synthetic gypsum

Mass losses vary between 13.7 and 16.5% and heat of dehydration values between 377 and 420 J g −1 for the dehydration of ground and mixed inhomogeneous gypsum samples. As for the dehydration of CaSO 4·2H 2O, the dehydration of synthetic gypsum proceeds via multi-step reactions. Using a heating rate of 5°C min −1, the very slow dehydration of CaSO 4·2H 2O and impurities in the gypsum samples start at temperatures lower than 95°C. The main dehydration of the calcium sulphate dehydrate part of synthetic gypsum occurs between 95 and 170°C (heating rate 5°C min −1) and seems to proceed via a process with an activation energy of 392 ± 100 kJ mol −1 for α-values between 0 and 0.1. For α-values between 0.1 and 0.7, the reaction can be described by a first-order process with autocatalysis with an activation energy value of 100.5 ± 1.2 kJ mol −1. The third part of the reaction (0.7 < α < 1), up to temperatures of 180°C, gives an activation energy value of 96 ± 15 kJ mol −1. Even at temperatures above 250°C, some CaSO 4·O.15H 2O was still observed. The dehydration of calcium hemihydrate seems to proceed via the formation of CaSO 4·0.15H 2O.

On the Hydration Mechanisms of Calcium Sulfate Hemihydrate

The hydration of calcium sulfate hemihydrate is studied mainly by the conduction calorimeter. The hydration process can be explaind by dissolution and recrystallization as follows; calcium sulfate hemihydrate dissolves into liquid phase and the nuclei of calcium sulfate dehydrate appear and grow into crystallites. As ‘gypsum gel’ is not found, the topochemical reaction is not considered to occur in the hydration of calcium sulfate hemihydrate.A small amount of calcium sulfate dihydrate is produced on the grain surface of plaster of Paris when it is exposed to moist air. The dehydrates thus produced play a very important role in the hydration process, because it acts as the nuclei. β hemihydrate has larger specific surface area, and dissolves faster than α hemihydrate. However, the production of dihydrate on the surface is retarded by the soluble anhydrite exist in the sample. Accordingly, induction period is, sometimes, longer than that of α hemihydrate.