ritnms
Not a member yet
1551 research outputs found
Sort by
The SEM/EDS analysis of zeolite minerals
No full textThe SEM/EDS analysis is one of the most important methods for characterizing and determining the morphology of minerals.In scanning electron microscopy (SEM), a highly energetic and focused electron beam scans the sample and normally provides an extremely enlarged image of the morphology of the sample, as well as information on its chemical composition using an energy dispersive spectrometer (EDS) detector. In this paper are presented the SEM/EDS investigation of natural zeolit deposit Igros and Zlatokop
Thermal properties of lithium germanate phosphate glass studied by DTA
No full textThe DTA data collected for 22.5Li2O·10Al2O3∙30GeO2∙37.5P2O5 (mol%) glass sample was reported and discussed. The ease of glass formation has been studied. It was determined that the DTA exothermal temperature peaks revealed the crystallization of LiGe2(PO4)3 and GeO2 phases. The activation energy of crystallization and viscous flow was determined. The value of the Avrami exponent and reduced glass transition temperature indicates that the LiGe2(PO4)3 phase has three-dimensional growth
Fabrication and characterization of manganese ferrite/expanded vermiculite as a magnetic adsorbent of nickel ions
No full textAdsorbents based on magnetic materials are the subject of numerous researches. Beside good magnetism and functional surface, manganese ferrite is unstable and prone to form low mechanical strength agglomerates, which necessitate its deposition on the substrate surface. Expanded vermiculite outer surfac, is a useful medium for the deposition of nanoparticles whereas intercation layer is suitable for holding cation species (distance of 2:1 layers may be greater than 10 Å). Due to its relatively high surface area, cation exchange capacity and natural abundance of vermiculite, this mica mineral and its composites could be valorized as potentially low-cost adsorbents. In this study, manganese ferrite/expanded vermiculite (MnFe2O4/EV) composite was prepared by in-situ method. Deposited manganese ferrite particles on the surface of EV were formed in the solvothermal reaction using suitable reagents. Both composite and base material are characterized by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area (SSA), cation exchange capacity (CEC) and pH point of zero charge (pHPZC) determination. The adsorption properties of MnFe2O4/EV and EV have been investigated in a batch system at pH close to the pHPZC for the removal of Ni (II) from water. Considering process parameters such as contact time, adsorbent dosage and temperature: adsorption type, isotherm parameters (Langmuir and Freundlich) and rate of adsorption parameters were determined. Results of the kinetic studies gave fine correlations with pseudo – second order and Weber – Morris model. Taking into consideration fact that EV had low CEC values and SSA, obtained composite have high adsorption capacity (more than 30 mg Ni g-1). Also, X-ray diffractograms showed alteration of biotite vermiculite (formed during solvothermal action) into phlogopite (formed after adsorption process and aging). The methodology applied in this work may be utilized for the fabrication of other ferrite spinels, perovskites and other oxide systems
Imobilizacija celulaza na polimetakrilatne nosače
No full textCelulaze su vrlo značajna grupa industrijskih enzima koja se primenjuje u industriji hrane,
tekstilnoj industriji, proizvodnji papira i deterdženata. U novije vreme mnogobrojna istraživanja su
fokusirana na izolovanje novih celulaza iz mikrobnih procesa i optimizaciju njihove primene u
razgradnji lignocelulozne frakcije biljne biomase. Posle tretmana ovih sirovina celulazama povećava
se njihova svarljivost i fermentabilnost što ih čini pogodnijim za primenu u proizvodnji hrane za
životinje. U ovom radu ispitana je imobilizacija celulaze iz Aspergillus niger na novu seriju
biokompatibilnih polimetakrilatnih nosača za primenu u prehrambenoj i farmaceutskoj industriji.
Primenjeni su nosači sa različitim funkcionalnim grupama i različitim dužinama akrilnih lanaca koji
ih povezuju sa površinom nosača. Najefikasnija imobilizacija celulaze se postigla primenom umereno
poroznog nosača sa amino-grupama - LifetechTM ECR8409F. Nakon izbora nosača, optimizovani
su uslovi imobilizacije. Utvrđeno je da se pri pH 6 i početnoj koncentraciji proteina od 23,3 mg/g
nosača i 28 mg/g nosača dobija imobilisani enzimski preparat najveće aktivnosti (400 IU/g nosača i
450 IU/g nosača). Imobilisana i slobodna celulaza primenjene su na hidrolizu lignocelulozne frakcije
suncokretove sačme pri čemu su hidrolizati analizirani tečnom hromatografijom visokih performansi
sa kolonom (Hyper REZ XP Carbohydrate Ca2+) za razdvajanje sećera. Detektovane su niže
koncentracije redukujućih šećera sa imobilisanim enzimom
Influence of sintering time on density properties and SEM analysis of cordierite-based ceramics
No full textThe mechanical activation of the starting mixtures of cordierite (2MgO*2Al2O3*5SiO2) 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. The sintering process was performed at 1350°C
for 2h and 4h in air atmosphere. 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
The influence of high compaction pressure on cordierite-based ceramics
No full textCordierite, 2MgO⋅2Al2O3⋅5SiO2 is a high-temperature ceramic material. In order to improve its properties, titanium oxide was added to the starting mixture in an amount of 5%. Mechanical activation of samples was performed in a high-energy ball mill for 10 minutes. The compaction pressure was unusually high, 6 t cm-2 (588 MPa) in order to compare to previous research. Cordierite was sintered at the temperature of 1375°C. The phase composition of the activated and sintered samples was analyzed using X-ray diffraction. Scanning electron microscopy was used to analyze the microstructure of both compacted and sintered samples
A review of coal demineralization and desulphurization by chemical leaching
No full textCoal is a well-known fossil fuel. It was used as a non-renewable energy source for several centuries. Nowadays it is mainly used for electricity generation in power plants or heat generation for industrial and home utilization.
There are many types of coal that differ in composition and calorific value, as well as in the amounts of undesired hazard substances produced by combustion. Depending on the coal composition, environmental impact can be reduced by its treatment before combustion. One of the cheap and effective methods is the chemical leaching of coal that reduces sulfur content and the amount of mineral matter (ash). Lowering the ash amount increases the calorific value of coal, reduces its transportation cost, and reduces the negative environmental impact of toxic elements, which are usually present in ash. Another benefit of coal leaching, that results from lowering the sulfur content is reduced emission of toxic gases (SO2 and SO3) during combustion. In order to determine the optimal leaching conditions for the treatment of different types of coal, numerous studies have been done, investigating various chemical reagents, including inorganic and organic acids, alkalis, oxidative reagents, and their combinations [1, 2]. The key parameters that effect leaching efficiency are type and concentration of reagent, reaction temperature, the mass ratio between coal and leaching reagent, coal particle size, and reaction time. The degree of leaching efficiency is measured by the level of demineralization and desulphurization [3]. The current review summarises recent results and further plans for the development of an efficient and environmentally friendly method for the chemical leaching of Serbian sub-bituminous coal
Invasive Acer negundo L. biomass as lead sorbent from aqueous solution
No full textAcer negundo L. is recognized as an invasive deciduous tree species that tends to grow and spread out of its natural range posing a threat to the biodiversity of the impacted areas. Although invasive plant species are considered to negatively affect ecosystems, their biomass can be used for environmental benefits. In order to find abundant and inexpensive sorbent for wastewater purification and metal pollution minimization, A. negundo leaf biomass was selected and investigated for that purpose. Since lead is well known as a common pollutant occurring in various industrial effluents with harmful effects on biota, it was selected for the sorption experiments. Acer negundo L. (AN) samples were collected at the unpolluted area in Mountain Avala, Serbia. After milling and sieving, the prepared sorbent was used in batch system sorption experiments. Experiments were conducted under isothermal conditions, by adding a precise amount of sorbent in the lead solution of known initial concentration. The adsorption performance of the obtained biomass-derived material (AN) was evaluated by testing several operational parameters: initial pH value, initial sorbent dosage, contact time, and initial lead concentration. The experimental parameters were optimized in order to determine the most appropriate conditions for Pb(II) removal. Maximum lead uptake occurs at pH 5, with 2g/L of sorbent dosage. The kinetic study revealed very fast adsorption, with equilibrium occurring after an initial 15 min of contact between sorbent (A. negundo leaf biomass) and sorbate (1mmol/L of lead solution). After this contact time, the residual metal concentration started to increase indicating the desorption process. Data obtained from sorption experiments were subjected to equilibrium modeling: they were fitted by two-parameter models (Langmuir and Freundlich). Results showed that the maximal adsorption capacity of a sorbent is 109 mg/g. Obtained results suggest that Acer negundo leaf biomass can be successfully applied as a lead sorbent upon the optimization of the operating parameters. Studies of this type provide valuable information for future water remediation technology development
Novi biomedicinski materijali na bazi metal dopiranih fluorapatita
No full textIn this paper, metal substitutions in the fluorapatite crystal matrix will be presented in order to obtain a new type of biomedical material. Fluorapatite has been intensively tested in recent decades as a building material for luminescent materials for many applications, from fluorescent lamps, through LEDs, to nanomaterials for high-tech biomedical applications. Fluorapatite has been shown to be non-toxic, extremely chemically stable and corrosion-resistant, as well as biocompatible, bioactive and osteoconductive. Also, fluorapatite proved to be a great host material for doping luminescent centers in the form of trivalent ions of rare earth and transition metals. Thanks to the position of the fluorine atom in the structure of the crystal lattice of fluorapatite, in the center of the Ca2 triangle (6h position) in the mirror planes at z = 1/4 and z = 3/4, this structure is extremely stable and stable. Also, the fluorine atom is responsible for the fact that fluorapatite, unlike hydroxyapatite, shows antibacterial properties. By touching different metals
into this low phonon energy matrix, luminescent materials can be constructed that will emit light in the ultraviolet, visible or infrared region of the electromagnetic spectrum. If all these properties of fluorapatite are taken into account, their combination can lead to new materials for a wide range of
biomedical applications.U ovom radu biće prikazane supstitucije metala u kristalnom matriksu fluorapatita s ciljem dobijanja nove vrste biomedicinskih materijala. Fluorapatit se poslednjih decenija intenzivno ispituje kao materijal za izgradnju luminiscentnih materijala za široki spektar primena, od fluorescentnih lampi, preko LED dioda, do nanomaterijala za biomedicinske aplikacije visoke tehnologije. Fluorapatit se pokazao kao netoksičan, izuzetno hemijski stabilan i otporan na koroziju, a uz to i biokompatibilan, bioaktivan i osteokonduktivan. Takođe, fluorapatit se pokazao i kao sjajan materijal domaćin za dopiranje luminiscentnih centara u vidu trovalentnih jona retkih zemalja i prelaznih metala. Zahvaljujući položaju atoma fluora u strukturi kristalne rešetke fluprapatita, u centru Ca2 trougla (6h položaj) u ogledalskim ravnima na z = 1/4 i z = 3/4, ovakva struktura je izuzetno stabilna i postojana. Takođe, atom fluora je odgovoran što fluorapatit, za razliku od hidroksiapatita, pokazuje i antibakterijska svojstva. Dopiranjem različitih metala u ovu matricu niske fononske energije, mogu se konstruisati luminiscentni materijali koji će emitovati svetlost u ultravioletnoj, vidljivoj ili infracrvenoj oblasti elektromagnetnog spektra. Ako se uzmu u obzir sve ove osobine fluorapatita, njihovom kombinacijom mogu se dobiti novi materijali za široki
spektar biomedicinskih primena
Upgrading of a fuel potential of waste biomass via hydrothermal carbonization
No full text"
In recent decades, the massive exploitation of fossil fuels, with a detrimental impact on the environment, caused a growing demand for the production of energies from renewable sources. One of the researchers' solutions was the application of waste biomass, but there are many disadvantages of its direct utilization, that include high moisture content, low energy content, high volatiles content, etc. In order to overcome these disadvantages, attention has been focused toward development of technologies for conversion of biomass into a multi-functional products. Hydrothermal carbonization (HTC) has recognized as highly effective technology for production of carbon rich material, hydrochar, from wet and waste biomass. Hydrochar possess a great potential for application as an energy source, for environmental protection, in agriculture. In this paper, three selected biomasses (corn cob (CC), Paulownia leafs (PL) and olive pomace (OP)) were hydrothermally carbonized at different temperatures (180, 220 and 260°C). The main goal of this study was to examine the influence of temperature on the structure and fuel characteristics of the obtained products and to compare it with the precursor. The results showed that the solid yiels decreases significantly with increasing temperature in all samples. On the other hand, C content increase upon temperature increment and reach the highest values in hydrochars obtained at 260°C (69.30% for CC, 64.54% for PL and 70.97% for OP). Also, a decrease in O/C and H/C atomic ratios with increasing temperature was observed. The results are shown in the Van Krevelen diagram, which reveals the transformation of precursors during carbonization from the biomass to the lignite region. Furthermore, with decrease of O/C and H/C ratio, higher heating value (HHV) was increasing and reaches the maximum values for hydrochars prepared at 260°C (27.33 MJ/kg for CC, 28.06 MJ/kg for PL and 30.55 MJ/kg for OP). The same trend is noticeable with ED contents. Also, the content of volatile matter (VM) was determined in all samples. VM decreases (from 90.45 to 55.42% for CC, from 76.70 to 62.10% for PL, from 82.86 to 66.77% for OP) with temperature contributes to less evaporation and pollutant emission during direct combustion. According to results, can be concluded that temperature has a great influence on the structure and characteristics of the obtained products, that dehydration and decarboxylation during HTC provoke intensive biomass carbonization and that hydrochars obtained at higher temperatures have significantly enhanced fuel properties and less volatiles compared to the biomass.