Effect Of Demineralization Research Articles

The effects of demineralization and swelling in producing active carbon from Turkish lignites

In this study, active carbon was obtained through chemical activation methods using some pretreatment to Gölbaşı (Adıyaman) and Kangal (Sivas) lignites. For both lignites, pretreatment was carried out in three steps. In the first step, demineralization was achieved by applying HCl–HF pretreatment to raw lignites. In the second one, raw and demineralized lignites were swollen not only with benzene but also with THF (tetrahydrofurane). Later, these two samples at 85 °C were exposed to chemical activation by impregnation with ZnCl2. Chemical activation processes were carried out in a situation where samples on quartz board in a quartz tube in a cylindrical furnace were kept for 1 h at 500 °C, 100 ml/min N2 flow speed and 30 °C/min heating rate. The active carbons produced were washed with 10% HCl and later with demineralized water. BET surface area of the active carbon samples was generally higher than 1000 m2/g. The surface area value of the Gölbaşı lignite was relatively higher than that of Kangal lignites. Similarly, the surface area value of the active carbons produced at the end of pretreatment with THF was higher than that of active carbon produced through pre-swelling using benzene. For all active carbon samples, ash, total sulfur and iodine adsorption values were different.

Effect of chemical demineralization on thermal behavior of bituminous coals

Growing environmental concerns and the need for alternatives for oil and natural gas resulted in intensive researches on ultra clean coal (UCC). Therefore, the researches related to practice and application of various methods to produce UCC become more important. Thermal characterization of chemically demineralized coals by thermogravimetric analysis method is presented in this study. The aim of the study is to provide thermal data for HF–HNO3 leaching system used for the production of UCC. Coal samples were first physically enriched by density separation. Then the enriched portion was chemically demineralized by using HF and HNO3, respectively. Ash content of coal samples were reduced to a range of 0.12–0.41% by chemical demineralization process. The petrographic, ultimate and proximate analyses were carried out to determine main features of samples. Physically and chemically enriched coal samples were then analyzed in a TG by two different techniques separately. The first technique covered thermal characterization of samples under non-isothermal conditions. Characteristic temperatures for each sample were obtained from the TG and DTG data. The second technique involved the determination of reactivity of in situ produced chars of each sample.

Denaturation Temperatures of Dentin Matrices. I. Effect of Demineralization and Dehydration

The denaturation temperature (T d) of dentin collagen in mineralized versus demineralized teeth was examined as a function of dentin age and the extent of dehydration. Using differential scanning calorimetry, T d of mineralized dentin was shown to be between 160°C to 186°C, depending on whether it was from young or old dentin that was hydrated or dehydrated, respectively. Demineralized dentin exhibited a T d of 65.6°C that increased with dehydration to 176°C. The presence of apatite crystallites or interpeptide bonding increased the T d of demineralized matrices. Interpeptide hydrogen bonding seems to stabilize collagen to thermal challenge. Water breaks interpeptide hydrogen bonds making collagen more susceptible to thermal denaturation. Rises in intracanal temperature are unlikely to cause extensive denaturation of mineralized root dentin walls. However, hydrated or partially dehydrated root canal walls that have been partially demineralized with chelating agents or mild acids may be susceptible to thermal denaturation.

Effect of tumor therapeutic irradiation on the mechanical properties of teeth tissue

Tumor irradiation of the head-neck area is accompanied by the development of a so-called radiation caries in the treated patients. In spite of conservative therapeutic measures, the process results in tooth destruction. The present study investigated the effects of irradiation on the demineralization and remineralization of the dental tissue. For this purpose, retained third molars were prepared and assigned either to a test group, which was exposed to fractional irradiation up to 60 Gy, or to a non-irradiated control group. Irradiated and non-irradiated teeth were then demineralized using acidic hydroxyl-cellulose gel; afterwards the teeth were remineralized using either Bifluorid12® or elmex gelee®. The nanoindentation technique was used to measure the mechanical properties, hardness and elasticity, of the teeth in each of the conditions. The values were compared to the non-irradiated control group. Irradiation decreased dramatically the mechanical parameters of enamel and dentine. In non-irradiated teeth, demineralization had nearly the same effects of irradiation on the mechanical properties. In irradiated teeth, the effects of demineralization were negligible in comparison to non-irradiated teeth. Remineralization with Bifluorid12® or elmex gelee® led to a partial improvement of the mechanical properties of the teeth. The enamel was more positively affected by remineralization than the dentine.

05/01419 Effect of demineralization on yield and composition of the volatile products evolved from temperature-programmed pyrolysis of Beypazari (Turkey) oil shale: Ballice, L. Fuel Processing Technology, 2005, 86, (6), 673–690

05/01419 Effect of demineralization on yield and composition of the volatile products evolved from temperature-programmed pyrolysis of Beypazari (Turkey) oil shale: Ballice, L. Fuel Processing Technology, 2005, 86, (6), 673–690

Formation And Characterization Of Humic Acids From Low Rank Anatolian Coals By Air Oxidation

The results of this study are aimed at evaluating the effects of air oxidation time, temperature and demineralization on humic acid production from two low-rank Anatolian coals. Two Anatolian low rank coals were studied at 120 and 200°C up to 10 days with and without demineralization. The best results for humic acid formation were obtained at a high temperature for longer times. Demineralization effect is negligible for studied coals. The rate of humic acid formation increased at first with increase in oxidation time, reached a maximum, and then decreased at high oxidation time. Also, a detailed study of the elemental composition, the characterization by FTIR, and the acidity of humic acids are reported.

Effect of demineralization on yield and composition of the volatile products evolved from temperature-programmed pyrolysis of Beypazari (Turkey) Oil Shale

In this study, the effect of the mineral matter of Beypazari Oil Shale on the conversion of organic carbon of oil shale into volatile hydrocarbon, polycyclic aromatic hydrocarbons (asphaltenes, preasphaltenes) and carbon in solid residue was investigated. Kerogen was isolated by successive HCl, HNO 3 and HF treatments. A series of temperature-programmed pyrolysis operation was performed with raw Beypazari Oil Shale, and each product of every demineralization process. A carbon balance of the pyrolysis process was established by determination of the recovery of total organic carbon as organic products, and carbon remaining in the reactor because of the coking reactions. The removal of the material soluble in HCl washing affected the conversion of organic materials in the pyrolysis reactions. Alkali and alkaline earth metal cations affect the reactivity of oil shales and the leaching of these mineral matters with HCl caused a slightly decreases in the conversion to volatile hydrocarbons. The removal of pyrites with HNO 3 did not affect the reactivity of the organic material in pyrolysis. But, removal of the material soluble in HF increased the conversion in pyrolysis reactions. It can be explained by the inhibitive effect of the silicate minerals. Complete removal of mineral matrix and isolation of kerogen increased the driving force for heat transfer since more heat was transferred from outside towards the inside of the oil shale particles, thus pyrolysis reaction might have occurred with ease and diffusion limitation might have decreased due to absence of mineral matrix.

Evaluation of current techniques for isolation of chars as natural adsorbents.

Chars in soils or sediments may potentially influence the soil/sediment sorption behavior. Current techniques for the isolation of black carbon including chars rely often on acid demineralization, base extraction, and chemical oxidation to remove salts and minerals, humic acid, and refractory kerogen, respectively. Little is known about the potential effects of these chemical processes on the char surface and adsorptive properties. This study examined the effects of acid demineralization, base extraction, and acidic Cr2O7 2- oxidation on the surface areas, surface acidity, and benzene adsorption characteristics of laboratory-produced pinewood and wheat-residue chars, pure or mixed with soils, and a commercial activated carbon. Demineralization resulted in a small reduction in the char surface area, whereas base extraction showed no obvious effect. Neither demineralization nor base extraction caused an appreciable variation in benzene adsorption and presumably the char surface properties. By contrast, the Cr2O7 2- oxidation caused a >31% reduction in char surface area. The Boehm titration, supplemented by FTIR spectra, indicated that the surface acidity of oxidized chars increased by a factor between 2.3 and 12 compared to non-oxidized chars. Benzene adsorption with the oxidized chars was lower than that with the non-oxidized chars by a factor of >8.9; both the decrease in char surface area and the increase in char surface acidity contributed to the reduction in char adsorptive power. Although the Cr2O7 2-oxidation effectively removes resistant kerogen, it is not well suited for the isolation of chars as contaminant adsorbents because of its destructive nature. Alternative nondestructive techniques that preserve the char surface properties and effectively remove kerogen must be sought.

Effect of demineralization on hydrogen transfer of coal with tritiated gaseous hydrogen

Roles of mineral matters and oxygen functional groups of coal on hydrogen transfer reaction with gaseous hydrogen were investigated by using a tritium tracer technique in a fixed-bed reactor system. Mineral matters in coal were removed by HCl or HCl/HF treatments. Alkali metals and a part of pyrite were removed by HCl treatment. SiO 2 and Al 2O 3 were removed only by HCl/HF treatment. A large part of pyrite was removed by HCl/HF treatment but about 20% of them still remained even after the treatment. It was observed that the efficiency of hydrogen transfer of coal decreased to some extent when cations and mineral matters were removed by HCl treatment. Further decrease in hydrogen transfer was observed after HCl/HF treatment. These results suggested that iron species from pyrite may catalyze the hydrogen transfer reaction with H 2 gas. Mineral matters assist the H-transfer to the carbon network of coal but does not promote hydrogen transfer to hydroxy groups.

Fractionation of whey proteins by bipolar membrane electroacidification

Bipolar membrane electroacidification (BMEA) is a technology offering the coupled effect of demineralization and acidification by using the properties of bipolar membranes to dissociate water molecules at their interfaces and of cation exchange membranes (CEM) to demineralize by migration of low molecular weight ionic species. The aim of the present study was to demonstrate the feasability of BMEA to fractionate whey proteins and to study the effect of protein concentration on its performance in comparison with chemical acidification. These results demonstrated the feasability of BMEA for whey protein separation and the influence of the initial protein concentration on the purity and yield of the separated fraction. At 5% whey protein isolate (WPI) initial concentration, this technology allows the separation of 98% pure β-lactoglobulin (β-lg) fraction with a 44.0% recovery yield. At 10% WPI initial concentration, BMEA allows the production of a β-lg-enriched fraction containing 97.3 of β-lg and 2.7% α-lactalbumin (α-la), for a 98% total protein purity.

Effect of demineralization and catalyst addition on N 2 formation during coal pyrolysis and on char gasification

Six coals with different ranks and different ash contents have been used to study the effect of demineralization on N 2 formation during coal pyrolysis. Chars obtained after pyrolysis have been also gasified with carbon dioxide at 1000 °C to investigate the influence of the demineralization on char gasification reactivity. The pyrolysis results show that the demineralization by acid washing drastically changes N 2 formation profiles and decreases nitrogen conversion to N 2 for low rank coals; on the other hand, the demineralization has little effect on N 2 formation for high rank coals. Addition of 0.5 wt% Fe promotes N 2 formation from the demineralized coals, but the catalytic effect depends on the coal type. It is found that the Fe remarkably promotes N 2 formation from the demineralized low rank coals, but the effect is much smaller for high rank demineralized coals. These observations suggest that the existing state of Fe-containing minerals and added Fe catalyst is important for catalytic N 2 formation during coal pyrolysis. Gasification results show that the demineralization lowers char gasification reactivity not only for low rank coals but also for high rank coals.

Influence of abrasion in clinical manifestation of human dental erosion.

The influence of abrasion from oral soft tissues on softened enamel lesion remineralization and erosion development was investigated. Using orange juice, softened enamel lesions were produced on 20 human premolars assigned randomly to 10 volunteers. Sections used as control and two test slabs were cut from each tooth. One of the two slabs from each tooth had an appliance built on it, which protected the lesion from abrasion. The two slabs (with/without appliance) were bonded to the palatal surfaces of upper right and left lateral incisor teeth of the participants who chewed sugar-free gum four times daily. After 28-day intra-oral exposure, mineral loss (Delta Z) and lesion depth (ld) in both control and test samples were quantified using transverse microradiography, and the data was analysed by paired t-test. Delta Z was significantly lower in lesions with appliance (protected), but higher in lesions without appliance (unprotected) when compared with control (unexposed). Similar pattern was observed with lesion depth. In unprotected slabs the lesions were abraded resulting in eroded enamel lesions. It was concluded that erosion observed clinically is the combined effect of demineralization of the tooth surface by an erosive agent and abrasion of the demineralized surface by surrounding oral soft tissues and through food mastication. Abrasion from oral soft tissues can contribute to site-specificity of dental erosion.

1-27.石炭チャーのCO_2ガス化反応特性に及ぼす脱鉱物質の影響((6)液化・ガス化II,Session 1 石炭・重質油等)

1-27.石炭チャーのCO_2ガス化反応特性に及ぼす脱鉱物質の影響((6)液化・ガス化II,Session 1 石炭・重質油等)

Tissue response and osteoinduction of human bone grafts in vivo.

Freeze-dried human bone allograft is used clinically as an adjunct to autologous bone graft. When freeze-dried human bone allograft is demineralized, the allograft is osteoinductive, since it causes bone to form heterotopically. Both types of allograft are also used alone, such as in spinal fusions, critical size defects, and periodontal therapy. The purpose of this study was to determine the effect of demineralization on the osteoinductive potential of human bone grafts obtained from two different groups of patients. One group consisted of six patients younger than 42 years of age, while the other group consisted of six patients who were older than 70 years of age. The harvested material was lyophilized and divided into two portions, one of which was used directly while the other was demineralized. Osteoinductive ability was established using an in vivo assay for heterotopic bone formation. Activity in these bone grafts was compared with a batch of commercially prepared demineralized, freeze-dried human bone grafts that had been previously shown to be active and another batch that had been shown to display low ('inactive') osteoinductive ability. A bone induction score was determined for each group of grafts based on the number and size of any ossicles formed. In addition, the area of new bone formation and area of residual particles were determined histomorphometrically. Tissue response to the bone grafts varied with donor age and whether the samples had been demineralized or not. Only demineralized, freeze-dried bone graft from patients younger than 42 years of age was osteoinductive; all other batches displayed little or no osteoinductive activity. In the demineralized, freeze-dried bone from donors younger than 42 years of age, the bone induction score and new bone area were significantly higher than in the other batches of bone graft, and the area of residual particles was reduced. Both demineralized and nondemineralized bone graft from patients older than 70 years of age were encapsulated in dense, fibrous connective tissue. These results may help explain the observed differences in clinical outcome when demineralized, freeze-dried bone graft or nondemineralized, freeze-dried bone graft from different donors is used in bone regeneration applications.

Effectiveness of oxidative potential water as a root canal irrigant

The aim of this study was to evaluate the effectiveness of oxidative potential water (OPW) as an irrigant, based on its ability to remove the smear layer and/or debris from instrumented root canals. One hundred and twenty root canals from extracted human maxillary incisors were instrumented using a conventional step-back technique with irrigation from sodium hypochlorite (NaOCl) or oxidative potential water (OPW). After instrumentation, the canals were irrigated by syringe or ultrasound using 15% EDTA or OPW as an irrigant. The volume of each irrigant used for syringe irrigation was 10, 20, and 30 mL, respectively, whilst the duration for ultrasonic irrigation was 1, 3, and 5 min, respectively. After irrigation, each root was split longitudinally in two with cutting pliers, and the specimens were prepared for SEM observation. The presence of debris and smear layer on each canal wall was assessed using a three-point scale for each parameter. Smear layer was effectively removed with EDTA both introduced via syringe and via ultrasonic irrigation. A similar effect was observed with OPW via syringe irrigation following instrumentation with 5% NaOCl. The canal walls in any of these cases showed open and patent dentinal tubules following smear layer removal. Some specimens irrigated with EDTA exhibited the effect of demineralization on the dentine resulting in funnelling of tubule orifices. Syringe irrigation was more effective in smear layer removal, except for ultrasonic irrigation with 15% EDTA, whilst ultrasonic irrigation was more effective in debris removal including the use of OPW as irrigant following instrumentation with 5% NaOCl. Neither syringe nor ultrasonic irrigation with OPW following instrumentation with OPW removed smear layer or debris effectively. The most effective irrigation technique for smear removal was 15% EDTA irrigation by means of syringe following instrumentation with 5% NaOCl solution. However, the most effective irrigation technique for debris removal was ultrasonic irrigation regardless of irrigant used. OPW irrigation by means of syringe following instrumentation with 5% NaOCl showed a similar effect to that of 15% EDTA irrigation for removal of smear layer and debris.

Effect of demineralization on the reactivity of lignites

In this study, effect of demineralization on the combustion reactivity of 25 lignite samples, originating from different areas of Turkey, was investigated. Non-isothermal thermogravimetry, where the sample was heated in air where temperature increased at a linear rate of 40 K/min to 1273 K, has been used to investigate the combustion reactivities of the original and demineralized lignite samples. The activation energies calculated by two different methods and the burning profiles of the original and demineralized samples were compared and discussed. It was observed that the combustion reactivity of the samples was considerably influenced by the demineralization process applied.

99/01758 Effect of acid demineralization on the structure of organic matter of coals and inertinites and semicokes obtained from them: Matuszewska, A. Karbo-Energochem.-Ekol., 1998, 43, (7), 226–231. (In Polish)

The effect of the presence of limestone and dolomite in coal, and calcium in lignite, on atmospheric-pressure temperature-programmed reduction (AP-TPR) analysis was studied. AP-TPR experiments were carried out on a bituminous coal with added limestone and dolomite and on a demineralized lignite. The results showed that both calcium minerals captured the gaseous H2S formed under AP-TPR conditions and produced CaS. Consequently the sulfur recovery monitored was too low and the AP-TPR kinetograms were deformed. The study also showed that the influence of dolomite is greater than of limestone. AP-TPR analysis of lignite demineralized and then loaded with calcium ions again showed a clear lowering of sulfur comparable with that of dolomite, but starting at a higher temperature.

Improved osteoinduction of cortical bone allografts: a study of the effects of laser perforation and partial demineralization.

Massive cortical bone allografts have been found to incorporate slowly into host bone and thus are subject to complications such as nonunion, fatigue fracture, and infection. To better understand and improve the process of osteoinduction in these types of bone grafts, a new experimental model was developed with use of diaphyseal cortical bone grafts from rat tibiae that were prepared by partial demineralization and drilling of 0.33 mm diameter holes with a pulsed, 2.94 microns wavelength, erbium:yttrium-aluminum-garnet laser. Six types of grafts were analyzed: untreated (Type I), demineralized 25 microns deep (Type II), demineralized 150 microns deep (Type III), laser perforated (Type V), laser perforated and then demineralized 25 microns deep (Type V), and laser perforated and then demineralized 150 microns deep (Type VI). The graft was orthotopically transplanted in the tibia of an adult Sprague-Dawley rat and followed for as long as 4 months. Histologic evaluation at 1 and 4 months postoperatively with use of hematoxylin and eosin staining confirmed that there was new bone growth in Types II, III, V, and VI grafts. The amount of growth was estimated by comparing bone mineral density before implantation with values obtained after retrieval of the graft. These measurements were correlated to histomorphometric analysis of graft incorporation. The results show that the processes of partial demineralization (p < 0.000001) and laser perforation with partial demineralization (p < 0.000001) were both significant in enhancing bone growth in this model. New bone growth was significantly increased when the grafts were prepared with extensive demineralization (p < 0.015). This study demonstrates that osteogenesis in cortical bone grafts can be fostered through the process of partial demineralization and laser perforation. To the extent that minimal partial demineralization and laser perforation allow maintenance of structural integrity while altering the osteoinductive properties in such a way as to promote ingrowth of new bone, this experimental model represents an advance in understanding how osteogenesis in cortical bone grafts may be improved.

The modulatory role of cementum matrix on osteoblastic cells in vitro.

The formation of new cementum is an important issue in clinical periodontology, as cementum is required to provide attachment for newly formed periodontal tissues to the root surface. In this study a model of cementogenesis in vitro was used in order to test the effects of root surface demineralization on the migration, attachment and formation of a cementum-like tissue by osteoblastic cells cultured on cementum and to test the specificity of cementum matrix in modulating those effects by comparison of root co-cultures with bone co-cultures. It was demonstrated that root surface demineralization did not significantly alter the orientation, number and attachment of cells to the root co-cultures. The results also demonstrated that cementum and bone matrix appear to behave differently in culture, as seen by their distinct action on the morphological profile of the attached cells and the extracellular matrix deposited by these cells. These results demonstrate that although cementum matrix appears to stimulate the production of cementum-like tissue, this action is not confined to cementum matrix alone, since a similar material was also deposited on dentine and bone surfaces. Thus, these results do not support a specific action of cementum matrix on the modulation of the cementoblast phenotype. The use of co-cultures of neonatal rat calvaria cells with root slices represents a promising model of cementogenesis in vitro; however, studies should be undertaken towards the identification of markers to distinguish between cementoblast and osteoblast phenotypes in order to further validate this model.

OR 37 The effect of demineralization of resected root ends on cementogenesis

OR 37 The effect of demineralization of resected root ends on cementogenesis