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FTIR spectroscopy analysis of mechanochemically activated Na2CO3 during relaxation time
No full textSodium carbonate was mechanically activated for 7 minutes in a vibro mill at a frequency of 3000 oscillations per
minute. Activated samples were stored in the air at room conditions for 31 days. To monitor the kinetics of the
transformation process of sodium carbonate to bicarbonate, Fourier-transform infrared (FTIR) spectroscopy
analysis was used and was performed as a function of relaxation time for characteristic groups observed: CO3
2–,
HCO3
– and OH–. The obtained results provided kinetics parameters for the transformation of carbonate into
bicarbonate as a result of chemisorption of moisture and carbon dioxide from the atmosphere
SEM and X-ray analyses of sintered MgO/Bi2O3 binary system
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
"Chemical leaching of subbituminous coal from the Bogovina - East field (Bogovina basin, Serbia) using hydrochloric acid"
No full textAll over the world, huge amounts of coal are available and it is utilized in large quantities for different
purposes. The coal combustion causes environmental problems, such as the release of toxic metals
and other pollutants into wastewaters, emission of noxious gases, produce of ash dumps, etc. One of
the solutions for the reduction of environment pollution, caused by coal combustion, is
demineralization and desulphurization of coal. In that sense, treatment of coal by different chemical
reagents becomes important. A subbituminous coal, used in this study was taken from the Bogovina -
East field (Lower Miocene » 20-16 Ma) of the Bogovina Basin, which is located in Eastern Serbia. The
sample was selected based on the previous studies of Bogovina - East field which indicated a high
amount of sulphur, relatively high percent of mineral matter and considerably amount of liptinites
for humic coal, which represent the most reactive maceral group. The aim of the study was an
attempt to reduce the amount of ash and sulphur in coal, keeping the organic matter unaltered as
possible, using simple and cheap method e.g. treatment with hydrochloric acid (HCl). Ash and total
sulphur content was determined before and after HCl leaching. In addition characteristics of initial
and treated coal were tracked by X-ray diffraction (XRD) analysis and Fourier-transform infrared
(FTIR) spectroscopy. The obtained results showed that the high percentage of deashing (» 80 %) was
achieved with cheap hydrochloric acid. XRD analysis of ash before and after sample treatment
provides more information about mineral phases in coal and effects of chemical leaching. FTIR
analysis indicates almost no changes in structure of coal organic matter after treatment by HCl,
which is important for further coal usage (e.g. combustion). On the other hand, the applied chemical
leaching with HCl had low impact on the sulphur content in Bogovina coal (desulphurization
percentage » 8 %). Therefore, in future research other reagents for efficient desulphurization should
be investigated
Influence of surface coverage of kaolin with surfactant ions on adsorption of ochratoxin A and zearalenone
No full textA natural kaolin from Serbia was modified with different amounts of octadecyldimethylbenzyl ammonium (ODMBA) - (25, 50 and 90% of kaolin cation exchange capacity). Samples were denoted as OKR-25, OKR-50 and OKR-90. Several methods (FTIR spectroscopy, thermal analysis, zeta potential measurements, and N2 physisorption) were used for characterization of the organokaolinites. Adsorption of the common mycotoxins ochratoxin A (OCHRA) and zearalenone (ZEN) by the organokaolinites was investigated at different levels of solid phase in suspension, different initial mycotoxin concentrations and different pH values. The natural kaolin was not effective in binding OCHRA or ZEN. Adsorption of both mycotoxins by organokaolinites increased with increasing amounts of solid phase as well as with increasing levels of surfactant on the kaolin surface. OCHRA and ZEN adsorption by all organokaolinites followed non-linear adsorption isotherms, at pH 3, 7 and 9. The maximum adsorption capacity for OCHRA adsorption was at pH 3 (4.8 mg/g for OKR-25, 26.7 mg/g for OKR-50 and 39.2 mg/g for OKR-90) that was calculated from the Langmuir model. Much lower OCHRA adsorption capacities were found at pH 7 and 9 (from 0.8 mg/g to 6.9 mg/g at pH 7 and from 1.1 mg/g to 4.6 mg/g at pH 9). The following adsorption capacities for ZEN were obtained from the Langmuir isotherms, at pH 3: 4.5 mg/g for OKR-25, 12.0 mg/g for OKR-50 and 13.5 mg/g for OKR-90. At pH 7, adsorption of ZEN was 5.7 mg/g for OKR25, 15.3 mg/g for OKR-90 and 14. 4 mg/g for OKR-90. At pH 9, ZEN adsorption capacities were 2.4, 14.1 and 8.1 mg/g for OKR-25, OKR-50 and OKR-90, respectively. Thus, at the lowest amount of ODMBA at the kaolin surface, adsorption of ZEN was similar at pH 3 and 7, while a slightly lower value was obtained for its adsorption at pH 9. With increasing amounts of organic phase at the kaolin surface, the adsorption of ZEN was practically independent of pH. Adsorption of both mycotoxins was dependent on the amount of ODMBA ions at the kaolin surface as well as on their forms in solution
Testing the effects of the presence of uranium in drinking water from individual wells in the village of Dubravica in the Braničevo district on public health
No full textSelo Dubravica se delimično nalazi iznad zapadnog lignitskog ležišta Kostolačkog basena. Ispitivanjem suvog ostatka dobijenog iz vode za piće iz dva individualna bunara rendgenskom difrakcionom analizom, na osnovu karakterističnih pikova, utvrđeno je prisustvo urana u vodi za piće. Indirektnom metodom Rajkovića i saradnika pouzdano je dokazano da je u prvom uzorku koncentracija urana u vodi za piće za 85,8% viša (3,71 mg/L), dok je u drugom uzorku koncentracija urana svega 22% niža (1.56 mg/L) od vrednosti MDK predviđene Pravilnikom (2 mg/L). Analiza posledica unošenja urana u čovekov organizam ukazala je na to da se na ovaj način unosi 0,84-2 mg urana u čovekov organizam na godišnjem nivou, odnosno 0,09-0,22 mg deponuje na godišnjem nivou u bubreg. Procena potencijalnog zdravstvenog rizika usled prisustva urana u vodi za piće ukazala je na to da je stanovništvo koje koristi vodu za piće iz prvog bunara i u kratkom vremenskom intervalu ugroženo od urana. Što se tiče dugoročnog rizika, proračun je ukazao da su u slučaju prvog uzorka vode za piće ugroženo oko 25, a u slučaju drugog uzorka vode za piće 10 stanovnika od 1000 stanovnika. Kako je bubreg organ u kome se uran deponuje u najvećoj meri u čovekovom organizmu, a dejstvo urana dugotrajno, slabljenje i otkazivanje funkcije bubrega može biti toliko da je čak 75% funkcije bubrega uništeno da bi se pokazali prvi klinički simptomi. Ova pojava se zapaža među stanovništvom duž reka Kolubare, Drine, Save i Morave i naziva se endemska nefropatija. Kao mogući uzročnici ističu se elementi koji se nalaze u tragovima (Pb, Cd, Si), živi agensi (bakterije i virusi), gljivični i biljni toksini, genetski faktori i imuni mehanizam, ali ne i uran u vodi za piće. Ispitivanja izvršena u ovom radu jasno ukazuju i na ulogu urana u epidemiji endemske nefropatije koja je u porastu i koja nema akutnu fazu već bolest progredira ka bubrežnoj insuficijenciji i terminalnom stadijumu bolesti bubrega. Zvanični podaci koji govore o porastu endemske nefropatije i šećerne bolesti i porastu njihovog udela u bolestima, kao i stope opšteg mortaliteta koja iznosi 18,19%, nedvosmisleno ukazuju na to da se uloga urana u životnoj sredini Braničevskog okruga ni na koji način ne sme zanemarivati. Zbog konfiguracije terena na kojima se nalaze naselja mora se pratiti uran i njegova migracija kroz životnu sredinu, za čije kretanje postoje, nažalost, svi uslovi.The village of Dubravica is partially located over the western lignite deposits of the Kostolac basin. The examination of the dry residue obtained from drinking water from two individual wells by X-ray diffraction analysis, based on a typical peak, showed the presence of uranium in drinking water. The indirect method by Rajković and associates showed that, in sample I, the concentration of uranium in drinking water was 85.5 percent higher (3.71 mg/L) and that the concentration of uranium in sample II was only 22 percent lower (1.56 mg/L) than the Maximum Allowable Concentration (MAC) values required by the Regulations (2 mg/L). Analysis of the result of the introduction of uranium in the human body has shown that this way brings 0.84 to 2 mg of uranium in the human organism per annum or 0.09 to 0.22 mg of uranium is deposited annually in the kidney. Assessment of the potential health risk due to the presence of uranium in drinking water indicated that the population using drinking water from wells will be threatened by uranium in a short time interval. Regarding the long-term risk, the calculation has indicated that in the first sample of drinking water, about 25 inhabitants, and in the case of the second sample of drinking water, 10 inhabitants out of 1000 inhabitants are endangered. As the kidney is the organ in which uranium is deposited (accumulated) to the greatest extent, its presence causes weakening and failure of kidney function, which can destroy 75 percent of kidney function until the manifestation of the first clinical symptoms. This phenomenon is observed among the population along the rivers the Kolubara, the Drina, the Sava and the Morava and is called endemic nephropathy. The elements found in trace amounts (Pb, Cd, Si), live agents (bacteria and viruses), fungal plant toxins, genetic factors and immune mechanism can be listed as possible causes. However, uranium in drinking water has not been listed so far. The tests performed in this study clearly show the role of uranium in the epidemic, endemic nephropathy, which is growing and which is not at the acute phase of the disease but has already progressed to renal failure and end-stage kidney disease. Official data on the rise of endemic nephropathy and diabetes and increasing their share in diseases, as well as overall mortality rates, which amount to 18.19%, clearly indicate that the role of uranium in the Braničevo district environment should not be ignored. Since there are settlements on the terrain to be investigated, uranium and its migration through the environment must be monitored as all conditions for its migration are unfortunately favourable
Phytoremediation of Mine Waste Disposal Sites: Current State of Knowledge and Examples of Good Practice
No full textMining activities are considered to be one of the main sources of environmental pollution, and lead to the production of vast amounts of waste materials. Mining leads to soil degradation, loss of biodiversity, and pollution of soil, water, and air. The disposal of mine waste is a global problem, and its composition depends on ore characteristics. In addition to high concentrations of metal/metalloids, mine tailings and spoils of abandoned mines are characterized by unfavorable physicochemical characteristics, such as extremely low or high pH, low nutrient status, and water retention capacity. Various remediation technologies could be applied to improve the environmental characteristics of mine waste disposal sites, reduce the amount of pollutants, and prevent their mobilization to the surrounding soil and waterbodies. One of the most cost-effective, and environmentally friendly technologies is phytoremediation, with phytostabilization, phytovolatization, phytofiltration, and phytoextraction as main techniques. An overview of the past experiences is discussed together with future trends in phytoremediation
DTA/TG analysis of mechanochemicaly activated sodium carbonate
No full textSodium carbonate is a material that is very good sorbent of carbon dioxide from the atmosphere, and it is a reason of it is increasing importance in environmental protection. In order to improve it is sorption characteristics, activation of Na2CO3 was performed by mechanochemical procedure and monitoring of changes during the relaxation time. This research is based on differential thermal analysis with thermogravimetry, in order to determine the changes that occurred on the activated samples during the relaxation period under controlled conditions. Sodium carbonate was activated for 2 and 7 minutes in a vibro mill, and then the activated samples were deposited in at room temperature and atmosphere of carbon dioxide at a humidity of 95% for 96h
XRD analysis of activated four-component ceramics
No full textThe aim of the presented research was to analyze ceramic material based on cordierite as a function of activation time and sintering temperature. Three-component oxide mixture was prepared (MgO + Al2O3 + SiO2 in the ratio 2:2:5). To decrease the sintering temperature, 10 mass % Bi2O3 was added to this mixture. The mixtures were mechanically activated for 5 and 240 minutes in a ceramic ball mill. Activated mixtures were sintered at temperatures of 1173-1573K. XRD method was used to determine the structural transformations of the obtained products
Bioaktivne kompozitne prevlake na titanu koje otpuštaju gentamicin / Bioactive Gentamicin-Eluting Composite Coatings on Titanium
No full textTrenutni trendovi u nauci o biomaterijalima favorizuju dizajniranje multifunkcionalnih prevlaka za
implantate koji služe kao nosači antibakterijskih sredstava sa primarnom namerom da inhibiraju rast
bakterija na površini kontakta implantata i tkiva, a da istovremeno promovišu osteointegraciju.
Elektroforetskim taloženjem (EPD) u jednom koraku pri konstantnom naponu, uspešno je dobijena
kompozitna prevlaka na bazi hidroksiapatita (HAP), hitozana (CS) i gentamicina (Gent) iz vodene
suspenzije na titanu. Kinetika otpuštanja leka ispitivana je u dejonizovanoj vodi na 37 °C tečnom
hromatografijom visokih performansi u kombinaciji sa masenom spektrometrijom. Sposobnost
osteointegracije dalje je potvrđena merenjem aktivnosti alkalne fosfataze (ALP), što ukazuje na
povoljne osteopromotivne osobine taloženih prevlaka. Kada su testirane na humane i mišje
fibroblastne ćelijske linije (MRC-5 i L929), kompozitna prevlaka pokazala je necitotoksični efekat.
HAP/CS/Gent prevlaka je pokazala dobru antibakterijsku aktivnost prema Staphylococcus aureus i
Escherichia coli, što ukazuje na visok potencijal za biomedicinske primene.Current trends in biomaterials science favor designing multifunctional implant coatings that serve as
carriers of antibacterial agents with the primary intention of inhibiting bacterial growth on the
implant-tissue interface, while still promoting osseointegration. Electrophoretic deposition (EPD) in
a single step at the constant voltage was successfully used to obtain composite coating based on
hydroxyapatite (HAP), chitosan (CS) and gentamicin (Gent) from an aqueous suspension on titanium.
Drug-release kinetics was investigated in deionized water at 37 °C by liquid chromatography coupled
with mass spectrometry. The osseointegration ability was further validated by measuring the alkaline
phosphatase activity (ALP) indicating the favorable osseopromotive properties of deposited coatings.
When tested against human and mice fibroblast cells lines (MRC-5 and L929), composite coatings
showed a noncytotoxic effect. HAP/CS/Gent coating exhibited good antibacterial activity against
Staphylococcus aureus and Escherichia coli, indicating the high potential for biomedical applications
Bioceramic coatings synthesized using electrophoretic deposition
No full textUvod: Regenerativna medicina poslednjih decenija postaje jedna od najbrže rastućih oblasti
zdravstva, sa posebnim fokusom na razvoj biomaterijala namenjenih primeni u ortopediji.
Cilj: Optimizacija uslova formiranja biokeramičkih kompozitnih prevlaka iz suspenzije na
bazi hidroksiapatita (HAP), hitozana (CS) i polivinil-alkohola (PVA) sa dodatkom antibiotika
gentamicina (Gent), na titanskom supstratu metodom elekroforetskog taloženja (EPD). Ispitivanje
bioaktivnosti i procena antibakerijskih svojstava prevlake HAP/CS/PVA/Gent.
Materijal i metode: Hidroksiapatit (HAP), hitozan (CS), polivinil-alkohol (PVA) i gentamicin
(Gent) korišćeni su za sintezu suspenzije iz koje su taložene biokeramičke prevlake na titanskim
pločicama (Ti). Za EDP je korišćen instrument Electrophoresis Power Supply EV231 (Peqlab,
Erlangen, Germany). Biokeramičke prevlake na Ti supstratu dobijene su metodom elektroforetskog
taloženja pri konstantnom naponu od 7 V. Pri ovom postupku Ti pločica kao radna katoda postavljena
je između dve platinske (Pt) pločice-anode i elektrode su uronjene u suspenziju HAP/CS/PVA/
Gent (vršena je optimizacija vremena taloženja u rasponu od 5 do 12 min). Radi karakterizacije
dobijenih prevlaka nakon potapanja u simuliranoj telesnoj tečnosti (SBF) na 37°C, nakon perioda
od 7 i 14 dana, korišćena je metoda rendgenske difrakcije (XRD), infracrvena spektroskopija sa
Furijeovom transformacijom (FTIR) i skenirajuća elektronska mikroskopija (SEM). Procena antibakterijske
aktivnosti prema dva bakterijska soja Echerichia coli i Staphylococcus aureus kvalitativno
je određena agar difuzionom metodom.
Rezultati: Dokazana je pretpostavljena bioaktivnost prevlake HAP/CS/PVA/Gent metodama
karakterizacije koje su pokazale rast nove hidroksiapatitne faze, dobru umreženost polimera i
homogenost sintetisane prevlake. Merenjem inhibicionih zona dobijenih agar difuzionom metodom
pokazana je jaka antibakterijska aktivnost prevlake prema oba bakterijska soja.
Zaključak: Biokeramičke prevlake dobijene elektroforetskim taloženjem, iz suspenzije HAP/
CS/PVA/Gent, pokazuju dobru mogućnost primene u regenerativnoj ortopediji.Introduction: In recent decades, regenerative medicine has become one of the fastest growing
areas of health care, with an emphasis on developing biomaterials to be used in orthopedics.
Aim: Optimization of deposition conditions of bioceramic composite coatings from suspension
based on hydroxyapatite (HAP), chitosan (CS) and polyvinyl alcohol (PVA) with the addition of
gentamicin (Gent), on titanium substrate by electrophoretic deposition process (EPD). Investigation
of coating bioactivity and antibacterial activity.
Material and Methods: Hydroxyapatite (HAP), chitosan (CS), polyvinyl alcohol (PVA) and
gentamicin (Gent) were used to synthesize a suspension from which bioceramic coatings were
deposited on titanium plates (Ti). Electrophoretic deposition was performed using Electrophoresis
Power Supply EV231 (Peqlab, Erlangen, Germany). The bioceramic coatings on the Ti substrate
were obtained by electrophoretic deposition at the constant voltage of 7 V. During this process, Ti
plate was used as a cathode placed between two platinum (Pt) plates – anodes and the electrodes
were immersed in a HAP/CS/PVA/Gent suspension (the deposition time was optimized in the
range from 5 to 12 min). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR)
and scanning electron microscopy (SEM) methods were employed for the characterization of the
obtained coatings after 7 and 14 days of immersion in a simulated body fluid (SBF) at 37°C. The
antibacterial activity against two bacterial strains Escherichia coli and Staphylococcus aureus was
evaluated using the agar diffusion method.
Results: The assumed bioactivity of the HAP/CS/PVA/Gent coating has been proven by characterization
methods that showed the growth of a new hydroxyapatite phase, good crosslinking
of the polymer and homogeneity of the synthesized coating. Measurement of inhibition zones
obtained by the agar diffusion method showed strong antibacterial activity of the coating against
both bacterial strains.
Conclusion: Bioceramic coatings obtained by electrophoretic deposition from a HAP/CS/PVA/
Gent suspension can be considered for application in regenerative orthopedics