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Use of surface modified natural zeolite (SMNZ) in pharmaceutical preparations. Part 2. A new approach for a fast functionalization of zeolite-rich carriers
No full textMain purpose of the research was to define an operative protocol, applicable at industrial scale, optimizing the functionalization of natural zeolites with surfactants, especially in pharmaceutical and environmental sphere. Three zeolite-rich samples from Italy (PHI_SAV), Slovakia (CLI_SK) and California (CLI_CA) were used for preparation of SMNZ. Two different protocols allowed to carry out surfactant adsorption equilibrium runs and surfactant sorption kinetics by varying different parameters: mixing speed (4000, 6000, and 8000 rpm); contact time (15 divided by 90 min) and initial surfactant concentration (from 25% to 200% of the external cation exchange capacity - ECEC) at a constant solid/liquid ratio (1 g/50 mL). Zeolite-rich materials were treated with solutions of cetylpiridinium chloride (CP-Cl). The functionalization of SMNZ was obtained by using a high-speed disperser. The amount of absorbed surfactant onto two carriers (CLI_SK and PHI_SAV) was evaluated through kinetic experiments under the following conditions: the initial CP-Cl concentration of 150% of the ECEC and a disperser speed of 8000 rpm. Results showed that after 15 min, equilibrium was attained with the adsorbed amount of about 0.14 meq/g of CP-Cl (equivalent to the ECEC of the investigated zeolitic support), confirming formation of monolayer (emi-micelle). The functionalization (micelle formation) of two samples occurred after 70 min of solid/liquid interaction with a total yield equal to 150% of the ECEC, thus indicating formation of a patchy bilayer. By contrast, CLI_CA behaves completely differently since the formation of emi-micelle was achieved only at much higher speed (18000 rpm) and not earlier than 90 min of mixing
Complex sulphide-barite ore leaching in ferric chloride solution
No full textThe results of research on the leaching process of complex sulphide- barite ore were presented in this paper. The leaching process was carried out in a laboratory autoclave by ferric chloride solution. Considering that those minerals are represented in complex structural-textural relationships, it is not possible to extract lead, zinc and copper minerals from ore by flotation methods. The obtained results confirmed possibility of the ore processing directly, by chemical methods. The effect of temperature, time and oxygen partial pressure on the lead, zinc and copper dissolution was studied. The maximal leaching degree was achieved at 100 degrees C and amount of 91.5 % for Pb, 96.1 % for Zn and 60.7 % for Cu). Leaching at temperatures above 100 degrees C is impractical
3D Bioactive phosphate glass-ceramic scaffolds prepared by the foam replica technique
No full textGlass-ceramic scaffolds similar to bone structure were obtained by the foam replica technique using a polyurethane (PU) foam and powdered polyphosphate glass containing strontium. The parent glass was prepared by the standard melt-quenching method. Polyurethane foam coated with glass particles (< 5μm) was thermally removed and the glass was sintered during 1h at 650 0C. The microstructure, morphology and phase composition of the as-prepared glass-ceramic scaffolds were investigated using the SEM and XRD methods. 3-D porous glass-ceramic scaffold containing bioactive β-Ca3(PO4)2 and β-Ca2P2O7 crystalline phases was fabricated
A review of Pb-Sb(As)-S, Cu(Ag)-Fe(Zn)-Sb(As)-S, Ag(Pb)-Bi(Sb)-S and Pb-Bi-S(Te) sulfosalt systems from the Boranja orefield, West Serbia
No full textRecent mineralogical, chemical, physical, and crystallographic investigations
of the Boranja orefield showed very complex mineral associations and
assemblages where sulfosalts have significant role. The sulfosalts of the
Boranja orefield can be divided in four main groups: (i) Pb-Sb(As)-S system
with ±Fe and ±Cu; (ii) Cu(Ag)-Fe(Zn)-Sb(As)-S system; (iii) Ag(Pb)-Bi(Sb)-S;
(iv) and Pb-Bi-S(Te) system. Spatially, these sulfosalts are widely spread,
however, they are the most abundant in the following polymetallic deposits
and ore zones: Cu(Bi)-FeS Kram-Mlakva; Pb(Ag)-Zn-FeS2 Veliki Majdan
(Kolarica-Centralni revir-Kojići); Sb-Zn-Pb-As Rujevac; and Pb-Zn-FeS2-BaSO4
Bobija. The multi stage formation of minerals, from skarnhydrothermal to
complex hydrothermal with various stages and sub-stages has been determined.
All hydrothermal stages and sub-stages of various polymetallic deposits and
ore zones within the Boranja orefield are followed by a variety of
sulfosalts. [Projekat Ministarstva nauke Republike Srbije, br. OI-176016:
Magmatism and geodynamics of the Balkan Peninsula from Mesozoic to present
day: Significance for the formation of metallic and non-metallic mineral
deposits
Effects of mechanical activation and two-step sintering on the structure and electrical properties of cordierite-based ceramics
No full textThe mechanical activation can help reduce production costs and modify cordierite-based materials. In this study, the structure and electrical properties of the mechanically activated MgO-Al2O3-SiO2 system have been analyzed. The mixtures of MgO-Al2O3-SiO2 powders were mechanically activated in a planetary ball mill for time periods ranging from 0 to 160 min. Structural investigations were performed on the obtained powders. The effects of activation and a two-step sintering process on the microstructure and crystal structure were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The thermal stability was analyzed using DTA. Electrical measurements showed variations of the dielectric constant (epsilon(r)) and loss tangent (tan delta) as a function of the time of mechanical treatment
Microstructural and Electrical Properties of Cordierite-based Ceramics Obtained After Two-step Sintering Technique
No full textCordierite-based ceramic materials are attracting much interest for their various applications in industry, for manufacturing multilayer circuit boards, catalytic converters, filters, thermal insulation, kiln furniture, components of portable electronic devices, etc. In order to reduce production costs and modify cordierite-based materials, mechanical activation can be used. In this study, microstructural and electrical properties of mechanically activated MgO-Al2O3-SiO2 system have been analyzed. The mixtures of MgO-Al2O3-SiO2 powders were mechanically activated in a planetary ball mill for the time periods from 0 to 160 min. Morphological investigations have been performed on the obtained powders. The effects of activation and two-step sintering process on microstructure were investigated by scanning electron microscopy (SEM). Electrical measurements showed variations of the dielectric constant (epsilon(r)) and loss tangent (tan delta) as a function of time of mechanical treatment
Ecological potential of Epilobium dodonaei Vill. for restoration of metalliferous mine wastes
No full textMetalliferous mine wastes represent one of the major sources of environmental contamination from mining activities. Bor region (Serbia) is one of the largest copper mine basins in Europe where long-term mining caused severe environmental deterioration and created one of the most degraded locations in Serbia and Europe. At the spontaneously colonized metalliferous mine wastes in Bor, plant species Epilobium dodonaei dominates in the mine slopes and mine waste surfaces. Epilobium dodonaei has the status of endangered and protected species in parts of European range (i. e. plant is included in the Red lists of the countries in the Carpathian mountains region), primarily due to losses of natural gravel habitats. The main focus of this research was physico-chemical characterization of mine waste, assessment of phytoremediation potential and plant metabolic stress response of Epilobium dodonaei at the hot spot metalliferous mine site in order to evaluate the possibility for application of endangered species in ecological restoration. The Bor mine wastes are characterized by coarse soil texture, various pH (4.58-8.30), and elevated concentrations of arsenic (44.5-271 mg kg(-1)) and copper (311-2820 mg kg(-1)) that exceed the Serbian limiting threshold and remediation values. Oxidation of metal-sulfide minerals on waste surface leads to increased acidity, followed by elevated metal mobility of the mine spoil solution. Content of arsenic, copper, lead and zinc in roots of E. dodonaei was correlated with pseudo-total and EDTA-available concentrations in Bor mine spoils. Furthermore, the content of arsenic, copper, lead and zinc in roots (3.98 mg kg(-1), 140 mg kg(-1), 3.19 mg kg(-1), and 72.8 mg kg(-1), respectively) and shoots (4.69 mg kg(-1),57.7 mg kg(-1), 1.17 mg kg(-1), and 59.3 mg kg(-1), respectively) of E. dodonaei reflected the multi-metal pollution at the investigated site. Epilobium dodonaei largely retains copper, lead and zinc in roots than in shoots and has the potential for phytoremediation of mine wastes. Epilobium dodonaei at Bor mine spoil had a high content of malondialdehyde in roots and leaves as well as reduced chlorophylls and carotenoids content in leaves, indicating great oxidative stress. However, elevated arsenic and copper content could promote biosynthesis of antioxidants in roots and leaves of E. dodonaei at mine spoil. Creation of an endangered species habitat on mine waste rocks of the Bor mining area and similar sites of Carpatho-Balkan metallogenic province could successfully contribute to the preservation of E. dodonaei. Development of practical procedures for the selection and application of endangered plant species in reclamation should create stronger link between ecological restoration and conservation biology. Finally, the application of endangered plant species should take a more prominent role in the restoration process and ecosystem design
Natural zeolites for pharmaceutical formulations: Preparation and evaluation of a clinoptilolite-based material
No full textAim of this work was the preparation, starting from a clinoptilolite-rich rock, of a material suitable for the development of pharmaceuticals. In particular, the purpose was to obtain a reproducible product that maximizes zeolite properties and minimizes any kind of interference chemical, mineralogical and microbiological. In evaluating the material for the planned use, the recommendations and procedures of European, US and Japanese Pharmacopoeias were taken as benchmark to the largest extent possible. A set of technological properties was also determined. The prepared material, containing approximate to 90 wt.% of Na-clinoptilolite, was obtained through a replicable process, and do not contains fibrous minerals classified as carcinogenic by the IARC. Chemical analyses evidenced contents of trace metals below the more restrictive limits established by Eur Ph., USP and JP for "bentonite" - taken as reference due to the similarities between smectites and zeolites, and because of the lack of a Monograph on clinoptilolite. The oral bioaccessibility of potential harmful elements, tested simulating the transit in the gastrointestinal tract according to Eur Ph., was three to six orders of magnitude lower than the permissible daily exposure established by USP. The microbiological quality of the material complied with the acceptance criteria of Eur Ph. The clinoptilolite structure was not significantly affected by sterilization process nor by simulated gastric juices. As concerns the characteristics determined, the prepared material is suitable for the development of systems exploiting clinoptilolite's properties as pharmaceutical excipient
Model systems for fluorescence of fluorapatite based on crystallographic and quantum-chemical data
No full textHidroksiapatit (HAp) i fluorapatit (FAp) su dobro poznati biomaterijali jer pred stavljaju glavne komponente kostiju i zuba. Sintetički HAp i FAp se smatraju potencijal nim biomaterijalima zbog svojih bioloških, biokompatibilnih i antibakterijskih aktivnosti. Razni metalni joni korišćeni su za dopiranje hidroksiapatitnih i fluorapatitnih biomateri jala, sa ciljem da se dobiju bolja svojstva [1]. HAp i FAp dopirani retkim zemljama (RE)
su potencijalni luminescentni biomarkeri. Još jedna veoma bitna karakteristika nanočestičnih bioapatita je mogućnost zamene jona metala, kao što su joni lantanida koji predstavljaju nove luminescentne centre. Da bi kreirali model sistem za kvantno-hemijske proračune koji mogu da reprodukuju fluorescentne spektre dopiranih fluorapatita, urađena je analiza kristalnih struktura. Ana liza kristalnih struktura dobijenih iz Baze kristalnih struktura časopisa „American Miner alogist“ (AMCSD) pokazala je da FAp imaju heksagonalnu simetriju (prostorna grupa P63/m ), koja je izgrađena od jona metala (Ca, Sr, NA, Ce, Mn, La, Nd, Cd, Di, U ili Th), trovalentne anjonske grupe (PO43−ili SiO43−), i monovalentnog anjona (F-, OH-, i Cl-). U ovim strukturama postoje dva simetrijski neekvivalentna položaja jona Ca2+: položaji I i II (vidi sliku dole). Ab initio proračuni fluorescentnih spektara su urađeni za tri geometrije, sa jonima metala u položajima I i II položaju, dok treći model sistem sadrži tri katjona matala, tri PO43− jona i F− jon u centru (luminiscentni centar). Treći model sistem pokazao je najbolje slaganje sa eksperimentalnim podacima.Hydroxiapatite (HAp) and fluorapatite (FAp) are well known biomaterials being the main components of bones and teeth. The synthetic HAp and FAp are considered as potential biomaterial due to bioactive and biocompatible and antibacterial activity. Various metal ions, have been used to doped hydroxyapatite and fluorapatite biomaterials with in order to get better activity [1]. The rare-earth (RE) doped HAp and FAp are prospective lumi nescent biomarkers. Another very important characteristic of nanosized bioapatite is its structural capacity to accept many ionic substitutions such as lanthanide ions as new lu minescent centers. To create a model system for quantum-chemical calculations that can reproduce the fluorescent spectra of doped fluorapatite analysis of crystal structure were done.The anal ysis of crystal structures extracted from American Mineralogist Crystal Structure Database
shown that FAp has a hexagonal symmetry (space group P63/m), with metal cation (Ca, Sr, Na, Ce, Mn, La, Nd, Cd, Dy, U or Th), trivalent anionic group (PO4 or SiO4), and monovalent anion (F−, OH−, and Cl−). In these structures there are two non equivalent Ca2+ positions: position I and position II (see figure below). Ab initio calculations of fluores cence spectra were done on three geometries with metal ion in positions I and II, while the third model system contains three metal cations, three PO43− anions and F− ion in the center
(luminescence center). The third model system showed the best agreement with the exper imental data
Characterization of microstructural and thermal properties of the steatite powders applied as fillers in the ceramic coatings
No full textSteatite is a magnesium silicate multi-componential composite that can be synthesized from natural raw materials, and eventually produced via standard ceramic processing methods and readily machined or sintered into a variety of forms. Due to its excellent electrical properties, high mechanical resistance, low dielectric loss and high temperature resistance, steatite is widely utilized as a material for thermal insulation and heath protection. The raw materials used in steatite powder synthesis are: talc mixture for calcination, clay minerals as bonding agent, and feldspar or BaCO3 as melting agents. The synthesis is usually conducted at approximately 1400°C, and its product is a crystalline phase of magnesium metasilicate (MgSiO3 ) obtained from talc, while melting agent forms a vitreous phase which melts and surrounds the crystalline phase. Steatite ceramics’ fillers were fabricated via combined method of high-energy ball milling, cold pressing and sintering. The powder blends containing same amounts of components in all 4 mixtures were dry-pulverized for 30 min a laboratory mill, with ceramic vial and ceramic balls. After milling, the powders were compacted to cylindrical tablets with a diameter of 25 mm by uniaxial compression at 4 tons/cm2 . The green compacts were sintered at 1000-1400°C (10°C/min) for 2 h in an air atmosphere. The effect of dry grinding on phase, microstructural and thermal properties of the sintered tablets were carried out by using X-ray diffraction technique (XRD), thermogravimetry/differential thermal analyzer (TG/DTA) and scanning electron microscope (SEM). The effects of grinding on the change of the particle diameter, crystallinity and the phase transformations, and reactivity of the powders were studied. The powders that were pulverized for 30 min showed properties which positively influenced on the decrease of sintering temperature and the increase of the sintering rate of steatite fillers