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Influence of mechanochemical activation on components on synthesis of cordierite ceramics for application in electronics
No full textThe properties of cordierite, 2MgO·2Al2O3·5SiO2, makes this ceramics nowadays an attractive
material, which can be used for various applications in electronics. As the sintering temperature of
cordierite is very high (1375 °C), any decrease in the temperature at which cordierite is formed leads
to economic benefits. Therefore, in this study, the mechanochemical activation of the initial components
mixture for the synthesis of cordierite was applied with the aim to lower its sintering temperature.
The effects of mechanochemical activation on the cordierite mixture were investigated. Changes
in the specific surface area of the activated components were determined by the BET method. The TG
method and mass loss were used to monitor the temperature- induced changes in the analyzed threecomponent
system. Based on the obtained results, increase in specific surface area and weight loss
with increasing activation time, a decrease in cordierite sintering temperature is expected.Kordijerit, 2MgO·2Al2O3·5SiO2, zbog svojih svojstava predstavlja izuzetno atraktivan
keramički materijal koji se može primeniti u elektronici za različite namene. Kako je temperatura
sinterovanja kordijerita veoma visoka (1375 °C), svako sniženje temperature na kojoj se formira
kordijerit donosi ekonomski benefit. Zbog toga je u ovom radu primenjena metoda mehanohemijske
aktivacije smeše polaznih komponenti za sintezu kordijerita sa ciljem sniženja njegove temperature
sinterovanja. Ispitivani su efekti mehanohemijske aktivacije na kordijeritnu smešu. Povećanje
specifične površine aktiviranih polaznih komponenti je praćeno BET metodom. TG metoda i gubitak
mase primenjeni su za praćenje promena uslovljenih temperaturom u analiziranom trokomponentnom
sistemu. Na osnovu dobijenih rezultata, povećanja specifične površine i gubitka mase sa povećanjem
vremena aktivacije, očekuje se sniženje temperature sinterovanja kordijerita
Removal of fluoride ions from water solutions by hydroxyapatite loaded aluminium gelled alginate particles
No full textFluoride ions (F-)might be found in drinking or wastewaters in too high concentrations either due to the
anthropogenic activity or some natural sources. Due to their negative effects on human health, allowed concentrations
for F- content in drinking water have been decreased. Therefore, in the last decade, investigations into researches in
new materials/techniques for fluoride removal from water streams have been intensified. This paper examines the
potential of hydroxyapatite loaded aluminum gelled alginate particles as an efficient and cheap sorbent for F- removal.
The adsorbent characterization before and after F- adsorption was performed using FT-IR technique. Adsorption
experiments were conducted in a stirring batch mode, varying concentration of adsorbate. Obtained results indicate
good adsorption capacity and removal efficiency, while FTIR spectra analysis point to the increased stability of
investigated adsorbent compared to Al-alginate without HAP
Removal cadmium ions from aqueous solution by biosorbent - immobilized aquatic weed M. spicatum
No full textThe lack of clean water and waste generation are problems that exist in many parts all over the world. Different industries: electroplating, smelting and alloying could discharge cadmium pollutants into water body. Cadmium as toxic metal must be properly removed from wastewaters because it may lead to: kidney damage, respiratory insufficiency, hypertension, cancer, gastrointestinal disorder and osteoporosis.
Globally depletion of natural and nonrenewable resources has induced need for application of renewable sources in environment protection practices; such as renewable biomass. Biosorption has emerged as an economically feasible alternative for the environment cleanup using naturally occurring, abundant, waste biomass. Application of biosorbents in the form of powder have difficulties associated with their powder properties, indicating need for suitable form with adequate mechanical strength (e.g. beads) for easily manipulation and further use in flow systems.
The waste biomass which is tested as biosorbent of cadmium is cosmopolitan invasive aquatic weed - waste Myriophyllum spicatum immobilized as beads in natural polymer matrix-alginate – (MsA-B). M.spicatum grows on five continents and based on its widely negative effects on the environment in the whole world, this weed has been categorized as Category 1 Weed. M.spicatum used for preparation of beads originates from Sava Lake (Belgrade, Serbia) where it is regularly harvested by public company "Ada Ciganlija”. Ratio M. spicatum and alginate in beads is 2:1.
This biosorbent (MsA-B) was characterized by Scanning-Electron-Microscopy-EnergyDispersive-X-Ray-Spectroscopy (SEM-EDX). EDX spectra showed: Ca, Mg, Na, K and Cl. Large amount of calcium originate from the water environment in which this aquatic weed lives. The surface of (MsA-B) is different from the surface of aquatic weed because the alginate covered the characteristic rectangular openings. The beads are not spherical, but more ovoid shape. The surface is wrinkled and clearly layered. After Cd(II) sorption, reduced peaks of Ca as well as a new peak of Cd(II) are observed
The effect of the Cd(II) concentration on adsorption was studied at pH 5.0 in the concentration range from 20 to 750 mg/L as batch biosorption tests with 2 g/L MsA-B. Experimental results were fitted by six isotherm models: Langmuir, Freundlich, Sips, Redlich and Peterson, Toth, Temkin. After biosorption experiments, beads didn’t change its shape, size or colour. They have been easily separated from the solution by decanting. Comparison of models was made on the basis of the coefficients of determination R2 and comparison value of biosorption capacities experimented and calculated by models. Order of best fit isotherm models: RP>L>S>Th>T>F. MsA-B showed high capacity for Cd(II) removal q=82,5 mg/g which is 33% higher capacity then capacity of dry biomass M.spicatum. During the biosorption experiments with MsA-B, changes of pH were insignificant. That is very important because there is no need to control pH, no demand for chemicals which greatly simplifies the process and makes it cheaper. Easy application and manipulation, much easier than other biosorbents simplify further investigations and applications of this aquatic weed beads – MsA-B in industrial wastewaters and also in the next step of the biosorption processes: flow systems and reactors
Orchid species Anacamptis morio as a potential bioremediator of As, Cd and Pb
No full textIn this study concentration of toxic elements As, Cd, and Pb was determined in
different soil types and belonging orchid species Anacamptis morio vital parts, in order to
examine accumulation patterns and provide new insights about potential use of this
orchidin bioremediation technology. The soils developed on limestone, serpentine, and the
chert were subjected to the BCR sequential extraction. Samples of orchid root and tuber,
as underground parts, and stem, leaves, and inflorescence, as above-ground organs, were
also analyzed for content of As, Cd and Pb. During this research, it was observed that metal
content in soil is directly proportional to its content in the plant, more specifically in roots,
which suggest that A. morio can potentially be used in phytostabilization of contaminated
sites. Values for BCF factors showed Cd immobilization in roots regardless of the soil type.
Certain level of arsenic was trasfered from root to leaves indicating potential for
accumulation of this element into aboveground organs. Assessment of the
phytoremediation potential of this orchid or another plant species from diverse
environments is important as it provides information about possibility of their future
application in environmental remediation programs
Postupak solidifikacije i stabilizacije teških metala iz otpadnih rudničkih voda adsorbovanih na peletama letećeg pepela u ekološki prihvatljiv građevinski materijal
No full textStabilizacija teških metala, posebno bakra, iz kiselih otpadnih rudničkih voda izvodi se njihovom solidifikacijom u sumpor polimerni beton kao ekološki prihvatljiv građevinski materijal. Postupak se izvodi tako što se u reakcionom sudu agregat u količini od 56 mas. % zagreva na 160 °C. Zatim se dodaje 5 mas. % letećegpepela iz termoelektrane kao filera i 6 mas. % peleta letećeg pepela sa adsorbovanim teškim metalima iz rudničkih voda. Homogenizovanoj čvrstoj mešavini dodaje se 33 mas. % rastopa elementarnog i modifikovanog sumpora, tzv. sumpor modifikovanog veziva u masenom odnosu 98,2 % elementarnog sumpora i 1,8 % modifikovanog sumpora. Modifikovani sumpor dobijen je mešanjem elementarnog sumpora kao nus-proizvoda iz rafinacije nafte sa diciklopentadienom, na temperaturi od 132-141 °C. Nakon homogenizacije u trajanju od 2 do 5 minuta, dobijena mešavina izliva se u kalupe prethodno zagrejane na 120 °C i vibrira 10 sekundi. Površina ovako dobijene sumpor polimerne betonske mešavine se izravna i ostavi da očvrsne u kalupu na sobnoj temperaturi. Nakon 3 časa očvršćavanja uzorci se vade iz kalupa i neguju na sobnoj temperaturi tokom 24 časa. Dobijeni materijal je nakon ispitivanja pokazao zadovoljavajuće karakteristike potrebne za sve oblasti primene konvencionalnih betona. Ovim postupkom eliminisani su teški metali iz otpadnih rudničkih voda, korišćeni su industrijski nus-proizvodi (leteći pepeo i sumpor), čime su smanjene njihove deponije dok dobijeni materijal ne dovodi do sekundarnog zagađenja životne i stoga se smatra ekološki prihvatljivim
Removal of Copper from Mining Wastewater Using Natural Raw Material-Comparative Study between the Synthetic and Natural Wastewater Samples
No full textThe intent in this paper is to define how the batch equilibrium results of copper removal from a synthetic solution on natural zeolite can be used for prediction of the breakthrough curves in the fixed-bed system for both a synthetic solution and wastewater. Natural zeolite from the Vranjska Banja deposit, Serbia, has been fully characterized (XRD, chemical composition, DTA/TG, SEM/EDS) as a clinoptilolite with cation exchange capacity of 146 meq/100 g. The maximum adsorption capacity (q(m)) in the batch of the mono-component system (synthetic copper solution) obtained using the Langmuir isotherm model was 7.30 and 6.10 mg/g for particle size below 0.043 and 0.6-0.8 mm, respectively. Using the flow-through system with the 0.6-0.8 mm zeolite fixed-bed, almost double the adsorption capacity (11.2-12.2 mg/g) has been achieved in a saturation point for the copper removal from the synthetic solution, compared to the batch. Better results are attributed to the constant high concentration gradient in flow-through systems compared to the batch. The complex composition of wastewater and large amounts of earth alkaline metals disturb free adsorption sights on the zeolite surface. This results in a less effective adsorption in flow-through systems with adsorption capacity in breakthrough point of 5.84 mg/g (similar to 0.95 x qm) and in a saturation point of 7.10 mg/g (similar to 1.15 x qm)
Accumulation of Potentially Toxic Elements in Invasive Ambrosia artemisiifolia on Sites with Different Levels of Anthropogenic Pollution
No full textThis study investigated invasive Ambrosia artemisiifolia from five localities with different levels of anthropogenic pollution in order to determine the potential for accumulation of trace metals and metaloids. Physical characteristics of the soil are presented, together with concentrations of As, B, Ba, Ca, Cd, Co, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sb, Sr, and Zn in both plant and soil. The tested samples displayed considerable differences in element concentrations, depending on the level of anthropogenic activities, with the highest concentrations of elements observed in samples from Stolice and Piskanja, the sites with most intensive human influence. A trend of shoot accumulation can be observed in A. artemisiifolia, but without hyperaccumulation, along with lower root concentrations in almost all analyzed samples. This may pose an additional environmental risk, as accumulated elements can spread to other components of the ecosystem. While A. artemisiifolia acumulates a high and even toxic rate of B in shoots regardless of boron concentration in soil, there is a high correlation of Ba, Pb, and Zn concentrations in species shoots with their respective concentration in the soil. Successful colonization of both natural and anthropogenically polluted habitats indicates high tolerance of A. artemisiifolia, which complements its wide environmental amplitude
Krečnjak-ekološka mineralna sirovina
No full textMonografija pruža sveobuhvatnu analizu krečnjaka sa stanovišta njegovog nastanka, mineralnog sastava, načina pripreme i primene. Prikazani su i novi trendovi korišćenja ove sirovine na globalnom nivou. Takođe, dat je odgovor na pitanje zašto je ova sirovina aktuelna i čega je to posledica. U monografiji su prikazana najvažnija ležišta i pojave ove sirovine na teritoriji Republike Srbije.
Smatram da će monografija biti od koristi svima onima koji imaju određenu ulogu u eksploataciji krečnjaka, postupcima pripreme i njegovoj primeni u različitim industrijskim granama.
Takođe, monografija je namenjena i svim studentima koji na fakultetu, u okviru predviđenih akademskih programa, izučavaju karbonatne mineralne sirovine, zatim istraživačima, investitorima, preduzetnicima, konsultantima i svima koji daju svoj stručni doprinos u izradi poslovnih strategija vezanih za ovu mineralnu sirovinu
Antibacterial graphene-based hydroxyapatite/chitosan coating with gentamicin for potential applications in bone tissue engineering
No full textElectrophoretic deposition process (EPD) was successfully used for obtaining
graphene (Gr)-reinforced composite coating based on hydroxyapatite (HAP), chitosan
(CS), and antibiotic gentamicin (Gent), from aqueous suspension. The deposition process
was performed as a single step process at a constant voltage (5 V, deposition
time 12 min) on pure titanium foils. The influence of graphene was examined through
detailed physicochemical and biological characterization. Fourier transform infrared
spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis,
X-ray diffraction, Raman, and X-ray photoelectron analyses confirmed the formation
of composite HAP/CS/Gr and HAP/CS/Gr/Gent coatings on Ti. Obtained
coatings had porous, uniform, fracture-free surfaces, suggesting strong interfacial
interaction between HAP, CS, and Gr. Large specific area of graphene enabled strong
bonding with chitosan, acting as nanofiller throughout the polymer matrix. Gentamicin
addition strongly improved the antibacterial activity of HAP/CS/Gr/Gent coating
that was confirmed by antibacterial activity kinetics in suspension and agar diffusion
testing, while results indicated more pronounced antibacterial effect against Staphylococcus
aureus (bactericidal, viable cells number reduction >3 logarithmic units) compared
to Escherichia coli (bacteriostatic, <3 logarithmic units). MTT assay indicated
low cytotoxicity (75% cell viability) against MRC-5 and L929 (70% cell viability)
tested cell lines, indicating good biocompatibility of HAP/CS/Gr/Gent coating.
Therefore, electrodeposited HAP/CS/Gr/Gent coating on Ti can be considered as a
prospective material for bone tissue engineering as a hard tissue implant
Impact of relaxation time of activated mixture on ceramics synthesis for electronic purposes
No full textDue to its properties, cordierite, 2MgO·2Al2O3·5SiO2, is nowadays an attractive ceramic material
for various applications but with very high sintering temperature. Mechanochemical activation
of the initial components mixture was performed in order to decrease the sintering temperature. DTA
method was used to monitor the temperature induced changes in the analyzed three-component system.
Since previous research has pointed out that the relaxation time can influence the activated
components in terms of chemical changes and the activation degree, it was important to determine
whether it has an impact on the observed activated system. The influence of the relaxation time on
the activated components mixture was analyzed by FT IR spectroscopy of both the initial components
and the activated mixture after 24h and 24 months relaxation periods.Zahvaljujući svojim svojstvima, kordijerit, 2MgO·2Al2O3·5SiO2, danas je atraktivan keramički
materijal za razne primene, ali sa vrlo visokom temperaturom sinterovanja. Mehanohemijska aktivacija
smeše početnih komponenti izvedena je da bi se snizila temperatura sinterovanja. DTA metoda
je korišćena za praćenje temperaturnih promena u analiziranom trokomponentnom sistemu. Kako je
ranijim istraživanjima utvrđeno da vreme relaksacije može da utiče na aktivirane komponente u
smislu hemijskih promena i stepena aktiviranosti, bilo je značajno utvrditi ima li uticaj i na
posmatrani aktivirani system. Uticaj vremena relaksacije na smešu aktiviranih komponenata analiziran
je FT IR spektroskopijom i početnih komponenti i aktivirane smeše nakon 24h i 24 meseca
perioda relaksacije