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Optimal conditions of vacuum distillation process for obtaining the high grade pure magnesium
No full textU ovom radu opisana je procedura dobijanja metalnog magnezijuma visoke čistoće, korišćenjem tehnologije vakumske destilacije. Ispitivan je uticaj različitih parametra temperature i vremena vakuumske destilacije, kao i uticaj niskog i visokog vakuma na proces dobijanja magnezijuma visoke čistoće. Takođe, struktura kondezatora, u opremi za vakuumsku destilaciju, je podešavana na takav način da se dobijaju optimalni uslovi procesa vakuumske destilacije. Na osnovu eksperimentalnih ispitivanja, određeni su optimalni parametri procesa vakuumske destilacije, koji opravdavaju ekonomiju i tehnlogiju procesa.In this paper the procedure of obtaining of high purity magnesium by using the vacuum distillation process has been shown. Vacuum distillation process has been conducted under low and high vacuum at different operating temperatures and times. Also, the condenser structure in vacuum equipment is set up in such a way to get the optimal conditions for obtaining of high purity magnesium. Based on experimental results, optimal process parameters were determined which justify the economy and technology of the process
Semi-empirical software for the aluminothermic and carbothermic reactions
No full textUnderstanding the reaction thermochemistry as well as formatting the empirical data about element distribution in gas-metal-slag phases is essential for creating a good model for aluminothermic and carbothermic reaction. In this paper modeling of material and energy balance of these reactions is described with the algorithm. The software, based on this model is basically made for production of high purity ferro alloys through aluminothermic process and then extended for some carbothermic process. Model validation is demonstrated with production of FeTi, FeW, FeB and FeMo in aluminothermic and reduction of mill scale, pyrite cinders and magnetite fines in carbothermic process
Application of lime in the polyvinyl chloride industry
No full textU radu je prikazan značaj krečnjaka u različitim industrijskim granama sa posebnim osvrtom na upotrebu krečnjaka kao punioca u industriji polivinil-hlorida (PVC). Od svih punilaca koja se koriste u industriji prerade PVC-a, 80 % su punioci tipa kalcijum karbonata. Punioci se koriste sa ciljem da se poboljšaju različite mehaničke osobine polimera kao što su: zatezna i prekidna svojstva, gustina, tvrdoća, toplotna postojanost, viskozitet i drugo. Najnoviji pravci industrijskog razvoja kao i zahtevi prerađivačke industrije za što kvalitetnijim karbonatnim puniocima uticali su na uvođenje postupka površinskog modifikovanja krečnjaka odnosno kalcita, koji je osnovni konstituent fino mikroniziranog krečnjaka kako bi se poboljšale njegove osobine.This paper presents the importance of limestone in a variety of industries with a special focus on the use of limestone as filler in the industry of polyvinyl chloride (PVC). Of Out of all fillers, used in the industry of PVC processing, calcium carbonate type of fillers are 80%. Fillers are used in order to improve various mechanical properties of polymer such as tensile and breaking properties, density, bending strength, hardness, thermal stability, viscosity and more. Latest trends of industrial development and demands of the processing industry for high quality carbonate fillers influenced the implementation process of surface modification limestone and calcite, which is the main constituent of fine micronized limestone in order to enhance its performance
Compost of Aquatic Weed Myriophyllum spicatum as Low-Cost Biosorbent for Selected Heavy Metal Ions
No full textAquatic weed Myriophyllum spicatum L. is one of the most invasive water plants known. In many countries, it is usually harvested and landfilled, where aerobic and anaerobic decomposition takes place. In this research, the kinetic, equilibrium, and desorption studies of biosorption of Pb(II), Cu(II), Cd(II), Ni(II), and Zn(II) ions onto compost of M. spicatum were investigated in batch experiments. Biosorbent was characterized by scaning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). SEM analysis showed that ion exchange between divalent cations Ca(II) and selected metals takes place. The results of FTIR exposed that carbonyl, carboxyl, hydroxyl, and phenyl groups are main binding sites for those heavy metal ions. The rate of adsorption of the five heavy metals was fast, which achieved equilibrium in 40 min, and followed the pseudo-second-order model well. Langmuir, Freundlich, and Sips equilibrium adsorption models were studied, and Sips isotherm gave the best fit for experimental data. Desorption by 0.1 M HNO3 did not fully recover the metals sorbed onto the compost, indicating that reusing this material as biosorbent is not possible. Furthermore, the use of spent biosorbent as a soil fertilizer is proposed
An investigation of diclofenac sodium release from cetylpyridinium chloride-modified natural zeolite as a pharmaceutical excipient
No full textIn this paper, investigations of zeolite - cationic surfactant - drug composites as drug carriers were performed. For that purpose, after adsorption of the model drug - diclofenac sodium (DS) onto composites obtained by the modification of natural zeolite (NZ) with cetylpyridinium chloride (CPC) at the three different levels, i.e., 10, 20 and 30 mmol/100 g (ZCPC-10, ZCPC-20 and ZCPC-30, respectively), the release of the drug, at pH 6.8, was studied. The results of DS release from ZCPC-10 composite (DS/ZCPC-10) were compared with the DS release from corresponding physical mixture, as well as from physical mixture of NZ and DS. Characterization of the composites after adsorption of DS and the physical mixtures was realized by zeta potential measurements and by thermal analysis. Results showed that the prolonged release of DS from all the three composites, as well as from physical mixture containing ZCPC-10 and DS was achieved over a period of 8 h. The drug release from both DS/ZCPC-10 (max 55%) and corresponding physical mixture (max 38%) was remarkably lower than that from the physical mixture of NZ and DS (max 85%). The kinetic analysis for all the three composites, as well as for the physical mixture of ZCPC-10 and DS, showed that drug release profiles were best fitted with the Korsmeyer-Peppas and Bhaskar release models, indicating a combination of drug diffusion and ion exchange as the predominant release mechanisms in the dissolution medium
Mechanism of stearic acid adsorption to calcite
No full textThis paper presents the interpretation of binding mechanism of stearic acid for calcite surface in two modification methods. In the "dry" method, a surface dissociation of stearic acid is assumed where H+ ion goes to a surface carbonate ion and stearic ion is chemisorbed on primary surface center of -Ca+ ion which is only available for chemisorption. The structure of adsorbed layer indicates chemisorption of stearate, but due to steric effects, and the oblique or gauche conformation of hydrocarbon chains. A part of surface -Ca+ centers can be blocked, which is explained by the result that physical adsorption dominates over 1.5%. In the "wet" method, by adding stearic acid, at concentration above the critical concentration of micelle formation in base solution, micelles are formed, and on the other side free stearic acid molecules or molecules from developed micelle dissociate. The resulting stearic ions can be chemisorbed on primary centers of -Ca+ ions or participate in ion exchange with OH- ions from secondary surface centers. With increasing adsorption density, the adsorbed ions and molecules, due to interactions of hydrocarbon chains, and thickness of double electrical layer, achieve a vertical orientation and keep the trans-conformation of hydrocarbon chains
Influence of prolonged sintering time on density and electrical properties of isothermally sintered cordierite-based ceramics
No full textMehanička aktivacija je brza i jeftina procedura koja se obično koristi za pripremanje uzoraka pre procesa sinterovanja. Kordijerit, stehiometrijska mešavina tri različita oksida (2MgO⋅2Al2O3⋅5SiO2) je veoma atraktivan, i široko korišćen visokotemperaturni keramički materijal. Početna smeša sa 5.00 masenih % TiO2 je mehanički aktivirana u visokoenergetskom mlinu sa kuglicama u vremenskom intervalu od 10- 80 minuta. Pre procesa sinterovanja uzorci su ispresovani pod pritiskom od 2t/cm2, bazirano na našem pređašnjem istraživanju. Uzorci su sinterovani na temperaturi od 1350°C u periodu od 2 i 4 sata u atmosferi vazduha. Difrakcijom H zraka je ustanovljena faza neaktiviranih i uzoraka aktiviranih 80 minuta, sinterovanih 2 i 4 sata, respektivno. Skenirajućom elektronskom mikroskopijom je analizirana mikrostruktura oba sinterovana uzorka. Mikroskopom atomskih sila smo analizirali površinu oba uzorka. Ovaj rad ispituje uticaj produženog vremena sinterovanja na gustinu sinterovanih uzoraka, kao i električne osobine.Mechanical activation is a commonly used and relatively fast and inexpensive procedure for sample preparation before the sintering process. Cordierite, a stoichiometric mixture of three different oxides (2MgO⋅2Al2O3⋅5SiO2) is a very attractive, widely used high-temperature ceramic material. The mechanical activation of the starting mixtures with 5.00 mass% TiO2 was performed in a high energy ball mill during 10-80 min. The applied compaction pressure before the sintering process was 2t/cm2, based on our recent investigation. The sintering process was performed at 1350°C for 2h and 4h in air atmosphere. X-ray diffraction was used to analyze the phase composition of non-activated and 80 min activated samples, sintered for 2 and 4h, respectively. Scanning electron microscopy was performed to analyze the microstructure of both compacted and sintered samples. Atomic force microscope was used to investigate the surface of the sintered samples. This paper investigates the influence of prolonged sintering time on the densities of the sintered samples, along with electrical properties
Investigation of adsorption and release of diclofenac sodium by modified zeolites composites
No full textResults on adsorption of diclofenac sodium (DS) by modified natural zeolite composites at three levels (10,20 and 30 mmol/100 g) of cationic surfactant-hexadecyltrimethylammonium bromide (HB), in a buffer solution, were compared. Characterization of composites before and after drug adsorption was performed by determination of electrokinetic mobility, FTIR and thermal analysis. The results indicated interactions between drug and carriers. The pharmaceutical performance of cationic surfactant-modified zeolites as drug formulation excipients was evaluated by in vitro dissolution experiments. The results were compared with the drug release from corresponding physical mixtures. Prolonged drug release over a period of 8 h (up to 30%) was achieved with both groups of samples. Furthermore, DS release reached up to 85% from physical mixtures containing drug amount closer to a therapeutic dose
High-temperature concrete binders based on fly ash
No full textHigh-temperature concrete binders in which fly ash, as environmentally harmful secondary raw material, is combined with masonry and refractory cement is a new option for reapplication of this coal combustion by-product. In this study, the design of the bonding agents was based on the fly ash from lignite coal combustion process and two types of cement: Portland cement and aluminate cement. Fly ash was applied without any further mechanical or thermal treatment. Mechanical properties of the binders were investigated and subsequently correlated with changes which occurred in the phase composition and microstructure of the agents. Scanning electron microscopy was used in investigation of microstructural changes caused by temperature. X-ray diffraction method was used in monitoring of the mineral phase changes also induced by increasing temperature. The investigations conducted on the bonding agents highlighted presence of good refractory properties and temperature-resistance, and also showed high values of compressive strength. The investigated bonding agents, thus, can be applied in refractory concretes, but also in various types of thermo-insulations
Polymetallic mineralization of the Boranja orefield, Podrinje Metallogenic District, Serbia: zonality, mineral associations and genetic features
No full textThe Serbo-Macedonian Metallogenetic Province, part of the Alpine metallogenic belt, hosts several ore deposits in mainly three geotectonic units: the Vardar Zone, the Serbo-Macedonian massif, and to a lesser extend the Dinarides. This metallogenic province includes the most significant Pb-Zn and Sb deposits in Serbia, as well as smaller Bi, Mo, Cu, Fe, Sn, Au and minor U, Wand Hg deposits, which are genetically related to emplacement of granitoids. The Podrinje Metallogenic District belongs to the Serbo-Macedonian Metallogenetic Province and incorporates several smaller orefields: Cer (Northwest Serbia), Boranja (West Serbia), and Srebrenica (East Bosnia and Herzegovina). Polymetallic deposits in the Boranja orefield are genetically related to the emplacement of the Tertiary Boranja granodiorite complex. The orefield contains a large number of sulfide deposits with Pb-Zn, and Sb with subordinate Cu, As, Bi and Ag. Small magnetite deposits connected to pyrometasomatic (skarn) stage are also significant. Skarns are of calcic type, and were formed along contacts of Triassic limestones and quartz diorites. Ore minerals are similar among the various types of orebodies in the Boranja orefield and consist of sulfides, sulfosalts [Pb-Bi-(Ag)-Te-Cu, Pb-Sb-(As), Sb-Cu-(Ag, Fe, Zn)], tellurides, native metals and alloys, oxides and complex-oxides, and gangue minerals. Minerals of the Boranja orefield were formed in several successive stages, which together correspond to a single regional-scale mineralization event that is genetically related to the subvulcanic-plutonic intrusion of the Neogene-aged magmatic Boranja complex. This can be best demonstrated by the zonal arrangement of several metallic mineral associations [Fe-Cu(Bi) -> Pb(Ag)-Zn -> Sb(As) -> CaF2(Pb-Zn)], with increasing distance from the Boranja granodiorite. Silver occurs as a minor metal principally as Ag-tetrahedrite, with subordinate native silver, Ag-bearing gold and pyrargyrite. Significant quantities of Ag can also be accommodated in galena as it is found to contain varied amounts of Ag, Bi and Sb (0.001-0.936, 0-3.345, and 0.012-0.510 wt%, respectively). The presence of both Ag and Bi in significant amounts in a Pb-rich sulfide system is essential for development of galena [solid solution alpha-(Pb-2, AgSb, AgBi)S-2]. This study demonstrates that silver, the most economic metal in Boranja orefield, is mainly accommodated in the galena structure, with lesser amounts present in the form of visible and/or invisible Pb-Bi-(Ag) sulfosalts