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Foreign molecules and ions in beryl obtained by infrared and visible spectroscopy
No full textBeryl minerals of Serbia were slightly studied in the last century and despite that there is some obtainable data about main characteristics there is a limited amount of information about foreign molecules in the mineral structure. Two beryl samples from different locations in Serbia were examined in detail but infrared spectroscopy (IR) and spectrophotometry (VIS) was used for determination of foreign molecules and ions in the structure and the obtained data is shown in this paper. The infrared (IR) and visible spectra (VIS) of two natural beryl samples indicate the presence of two types of water molecule, Fe2+, Fe3+ ions and CO 3. The spectra of two types of water molecules can be recognized with molecular fundamental vibrations at 3687 cm-1 (asymmetric stretching) for type I, at 3574 cm-1 and 3585 cm-1 both symmetric stretching, and with deformation vibrations at 1627 cm-1 and 1632 cm-1 for type II. In range of symmetric stretching there is broad vibrational band which can be explained by presence of water molecules type II near alkali ions. Overtones and combinations of these fundamental vibrations have been identified. The type I molecules have their C2 symmetry axes perpendicular to the crystal C6 axis, while the type II molecules are rotated by 90 degrees and have their C2 symmetry axes parallel to the crystal C6 axis. Vibrational absorption frequency of 1425 cm-1 indicate the presence of CO 3. Pale blue beryl is colored according to the relative intensities of two spectral features attributable to iron ions: a) a broad band in the extraordinary ray (Er) at 16000 cm-1 due to Fe2+ in a channel site and b) a broad band in range of 22500-31400 cm-1 in both ordinary ray (Or) and Er due to octahedral Fe3+ in the Al3+ site. Two other features, also attributable to iron, do not produce any visible coloration: a) an absorption edge at 12350 cm-1 in Or is due to Fe2+ in the octahedral site and b) a broad band in Er and Or, centered around 12350 cm-1, is due to Fe2+ in channel site. These spectral features are interpreted on the basis of the crystal field theory. Infrared and visible spectroscopy data of two natural beryl minerals from Serbia has shown that water molecules, carbonates and iron ions represent the main impurities in the crystal structure. Nature of the fluid inclusions and quantitative content of Fe2+ and Fe3+ ions remain to be examined in the future
Adsorption of ochratoxin A by surfactant modified phillipsite
No full textTwo different surfactants, cetylpyridinum chloride (CP) and
hexadecyltrimethylammonium bromide (HDTMA) were used to modify the surface of a natural
zeolite - phillipsite (PHI) and adsorption of ochratoxin A (OCHRA) was investigated.
Adsorption experiments were done with different amounts of adsorbents and with different
initial OCHRA concentrations at pH 3 and pH 7. Results showed that modification of phillipsite
surface with CP and HDTMA significantly improved adsorption of OCHRA in comparison to
unmodified phillipsite. CP modified phillipsite showed similar adsorption behavior as HDTMA
modified phillipsite. The highest adsorption capacity for OCHRA was obtained with CP
modified phillipsite at pH 3
Biokompatibilna prevlaka hidroksiapatit/hitozan/gentamicin dobijena postupkom elektroforetskog taloženja na titanu iz vodene suspenzije
No full textElectrophoretic deposition is an effective method for obtaining uniform coatings of precisely
controlled thickness and morphology. In this research, a single step electophoretic deposition
process for obtaining nanocomposite coating on titanium from a three-component aqueous
hydroxyapatite/chitosan/ gentamicin (HAP/CHI/Gent) suspension was investigated. The deposition
was carried out at a constant voltage, after the metal surface pretreatment. Characterization of the
coating was performed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR),
field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy
(XPS). Obtained results confirm the formation of a new composite coating HAP/CHI/Gent which
exhibits strong antibacterial activity and has the potential to be used as an orthopedic and dental
bone tissue implant or as a drug carrier.Elektroforetsko taloženje predstavlja efikasan postupak za dobijanje uniformnih keramičkih biokompatibilnih prevlaka kontrolisane debljine i morfologije. U ovom radu je ispitano elektroforetsko taloženje u jednom stupnju kompozitnih prevlaka na titanu iz trokomponentne vodene suspenzije hidroksiapatit/hitozan/gentamicin (HAP/CHI/Gent). Taloženje je izvedeno pri konstatnom naponu i uz prethodnu pripremu površine metala. Karakterizacija prevlaka je izvršena rendgenskom difrakcionom analizom (XRD), infracrvenom spektroskopijom sa Furijeovom transformacijom (FTIR), skenirajućom emisionom mikroskopijom (FE-SEM) i spektroskopijom fotoelektrona izazvanih X-zračenjem (XPS). Dobijeni rezultati potvrđuju formiranje nove kompozitne prevlake HAP/CHI/Gent koja pokazuje jaku antibakterijsku aktivnost i ima potencijal da se koristi kao ortopedski i dentalni implantat koštanog tkiva ili kao nosač lekova
Exergy concept and its implementation in the recycling of metals
No full textDizajn modernih industrijskih proizvoda je takav da oni predstavljaju kompleksne spojeve različitih materijala. Zbog toga se u postupku reciklaže materijala primenjuju procesi usitnjavanja i razdvajanja. Međutim materijali se ne mogu u potpunosti razdvojiti i zbog toga dolazi do kontaminacija u reciklažnim tokovima. Zbog toga se kvalitet materijala može smanjivati u svakom narednom reciklažnom koraku. Ovakvi kvalitativni gubici ne mogu se opisati masenim bilansom, i u radu je prikazan eksergijski koncept kao merilo gubitaka kvaliteta, odnosno dat je metod za izračunavanje eksergijskog sadržaja i eksergijskog gubitka. Gubici pripisani reciklaži ili tačnije materijalni gubici, gubici usled kontaminacije drugim metalima i posledično potreba za razblaživanjem, mogu se koristiti kao indikatori gubitka kvaliteta materijala i efikasnosti korišćenja resursa u proizvodnim sistemima. U radu je dat primer proračuna na čeličnom otpadu.Modern industrial product design implies presence of many different materials. Consequently, in the recycling process, shredding and separation procedures are applied. However, all materials cannot be completely separated; therefore, there is a contamination in the recycling streams. The quality of the materials streams can be reduced in each of the following recycling steps. These qualitative losses cannot be described by material balance. This paper presents the concept of exergy as a measure of quality losses, and gives the methods for the calculation of the exergy content and the exergy loss. Losses attributed to the recycling or material losses, material contamination losses and dilution requirements can be used as indicators for the materials quality loss as well as for the resource efficiency in the production systems. In this paper, the example of calculations on the steel scrap is presented
A Kinetic Study of Limestone Dry Micronization in an Ultra-Centrifugal Mill with Peripheral Comminuting Path
No full textBecause of its physico-mechanical and physico-chemical characteristics, fine-ground (i.e. micronized) limestone is widely applied in the production of new materials. Limestone can be used as a filler, coating and/or powder in ceramic composites. The effect of its fine micronization depends on the type of equipment used and on the disintegration process. In this study, the emphasis was placed on investigation of the kinetics of the dry micronization milling of limestone in a state-of-the-art ultra-centrifugal mill with a peripheral comminuting path. The efficiency of the ultra-centrifugal mill with a peripheral comminuting path was determined based on a detailed investigation of the limestone dry micronization, which satisfied all the requirements for technological parameters as well as for micronized product parameters. On the basis of the investigation of these parameters and theory of dry micronization conducted in a state-of-the-art mill with use of advanced instrumental techniques for determination and observation of the most significant physical and chemical characteristics, a kinetics model was developed to serve as the basis for quick and effective determination of micronization quality and efficiency. In this paper, the results of grinding in a Retsch ZM-1 ultra-centrifugal mill were analyzed in order to optimize and automate the process of ultrafine micronization
Dissolution behavior of a polyphosphate glass in simulated body fluid
No full textIn this work, the dissolution behavior of a polyphosphate glass, with the composition 45P(2)O(5) center dot 3SiO(2) center dot 25K(2)O center dot 15CaO center dot 10MgO center dot ZnO center dot MnO (mol %), in simulated body fluid (SBF) at a temperature of 37 degrees C for different times was studied. Two powder sizes of the glass (granulation: 0.1-0.3 and 0.3-0.65 mm) and the bulk glass were investigated. The dissolution experiments were conducted under stationary conditions. Changes in the normalized mass release, normalized concentration of ions, pH values, and surface morphology were determined as a function of the dissolution time. The initial rates of glass powder dissolution and leaching of ions, as well as the diffusion coefficient of cations and the releasing rate of ions, during the hydrolysis process of glass were determined. It was shown that the investigated phosphate glass dissolves in SBF incongruently, with neither precipitation nor the formation of newly potentially toxic compounds, in a dissolution period 720 h
Leaching behaviour of natural “low cost” sorbents saturated with zinc and copper
No full textThe leachability of zinc and copper from natural low-cost sorbents through saturation and
leaching study was examined in order to investigate their possible application as materials for
permeable reactive barrier (PRB). Examined low cost sorbents were natural and iron-modified
zeolite (IMZ), apatite, concentrated apatite, kaolin and raw bentonite. The highest saturation
ability towards zinc and copper was detected with raw bentonite and IMZ. Leaching of zinc and
copper has been confirmed from all saturated sorbents at pH=2.94, while at pH=6.46 was not
detected. This indicates that among investigated sorbents, raw bentonite and IMZ are the most
promising materials for removal of zinc and copper in PRB
Effect of micronized grinding on the quality of the fillers based on cordierite, mullite and zircon
No full textThis study presents the results of an investigation of high temperature materials – refractory filler based on cordierite, mullite and zircon for the synthesis of new refractory pattern coating and application in foundry. In order to obtain better properties of refractory fillers, special attention in the research was devoted to the preparation of fillers by grinding and mechanical activation. The application of the fillers for the synthesis of refractory pattern coatings and use in the new EPC casting process for obtained aluminum alloys and steel casting was shown positive results
The choice of high gradient magnetic separation processes for removal of Fe2O3 carriers from quartz raw material
No full textThis review article surveys the subject of choice of high gradient magnetic separation processes for removal of Fe2 O3 carriers from quartz raw material by electromagnetic separator with magnetic field intensity of 1.4 T. The review is based on current experience of authors during research phase, as well as project development phase and initial operation of facilities in several locations. Quartz mineral raw material in those locations appeared as sandstone or as loose material. In addition to that, quartz raw material from those locations contained various impurities, i.e. Fe2 O3 carriers. The choice of this process for Fe2 O3 removal depended on mineralogical composition, shape and the content of minerals, and Fe2O3 removal rate after this process was from 29 to 65%. Magnetic separation is magnetic induction of 1.4 T. It is applied on commercial assortments which were previously subjected to washing and classification processes. It is always the assortment which has to have the lowest Fe2 O3 content. The choice of „dry“ or „wet“ magnetic separation (with water flush) also depends on the fact whether this desired assortment is intended for market as dry or wet, as well as on the composition of magnetic impurities. In most cases, the process applied is the wet one
Sorption properties and thermal behaviour of Prunus persica L. waste biomass
No full textRastuća industrijalizacija i smanjivanje energetskih rezervi uslovilo je istraživanja u pravcu razvoja novih tehnologija koje bi primenile obnovljive, lako dostupne i ekonomski isplative otpadne materijale.Poslednjih nekoliko decenija otpadna agroindustrijska lignocelulozna (LC) biomasa predstavlja predmet brojnih istraživanja širom sveta usled velike rasprostranjenosti, niske cene, obnovljivosti i strukturnih karakteristika...Growing industrialization and resource depletion induced the research of new clean up technologies that provide implementation of renewable, low cost waste materials. In the last few decades, agro industrial lignocellulosic waste biomass (LCW) appeared as an attractive feedstock worldwide. LCW’s abundance, multi functionality and low cost have influenced many investigationsin the field of its renewable potential..