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Electrophoretically deposited nanosized hydroxyapatite coatings on 316LVM stainless steel for orthopaedic implants
No full textHidroksiapatit se široko koristi kao keramički biomaterijal zbog svoje bioaktivnosti koju ispoljava kada se u vidu prevlake nanese na metalni implantat, kao i zbog kompatibilnosti sa sastavom ljudskih kostiju. Prevlake hidroksiapatitnog nano-praha elektroforetski su istaložene na peskiranu površinu uzoraka od nerđajućeg 316LVM čelika, pri konstantnom naponu i za različito vreme taloženja, a potom sinterovane u vakuumu na 1040°C i u atmosferi argona na 1000°C. Premda visoke temperature sinterovanja, koje su neophodne kako bi se dobile kompaktne prevlake velike gustine, mogu da dovedu do faznih promena kod hidroksiapatita, u ovom radu je pokazano da je na supsrtatu od 316LVM čelika moguće dobiti bioaktivne prevlake u kojima nije došlo do fazne promene zahvaljujući prirodi korišćenog hidroskiapatitnog nano-praha stehiometrijskog sastava. Visokotemperaturna stabilnost korišćenog HAp praha potvrđena je DTA-TG analizom u temperaturnom opsegu 23-1000°C, tj. na temperaturama na kojima su rađeni eksperimenti sinterovanja. Mikrostrukturna karakterizacija nanetih prevlaka urađena je korišćenjem SEM, dok je za određivanje faznog sastava korišćena XRD analiza.Hydroxyapatite is a widely used bioceramic material in implant coatings research because of its bioactive behavior when being deposited onto the metallic implant and compatibility with the human bones composition. The coating of nanosized hydroxyapatite was electrophoretically deposited on a blasted surface of stainless steel 316LVM samples at constant voltage, for different deposition times and subsequently sintered in both, vacuum and argon atmosphere, at 1040 and 1000°C, respectively. Although sintering temperatures needed to achieve highly dense coatings can cause HAp coating phase changes, the possibility to obtain a bioactive coating on 316LVM substrate, without the coatings phase changes due to the nature of the used stoichiometric nanostructured hydroxyapatite is presented in this work. The thermal stability of the used HAp powder was assessed by DTA-TG analyses over the temperature range of 23-1000°C, i.e., at the or nearby experimental sintering temperature. The microstructure characterization was accomplished using SEM, while phase composition was determined using XRD
Microbial leaching of ore dumps by Acidithiobacillus ferrooxidans in purpose of metal recovery
No full textLitotrofne bakterije učestvuju u transformacijama i kruženju elemenata u prirodi, sa veoma značajnom ulogom u bio-geohemijskim ciklusima sumpora i gvožđa, a u manjoj meri azota i drugih elemenata. One su litotrofni mikroorganizmi, što u doslovnom prevodu sa starogrčkog jezika znači 'mikroorganizmi koji se hrane kamenom'. Uloga ovih mikroorganizama u prirodi upotrebljena je za njihovu primenu u dobijanju metala, zapravo prevođenje u rastvor (ili koncentrovanje) njihovih teško rastvornih jedinjenja (prvenstveno sulfida). Dakle, procesi koji u prirodi teku spontano, usmereni su i pojačani kako bi se dobili korisni metali, prvenstveno iz metalom siromašnih ruda i otpadnih materijala (vanbilansne rude, raskrivke, jalovine itd.). U cilju valorizacije korisnih komponenata jalovine (raskrivke starog kopa u Boru) vršeno je mikrobiološko luženje u laboratorijskim uslovima, korišćenjem kulture Acidithiobacillus ferrooxidans. U eksperimentima su luženi uzorci, tačkasto uzeti sa 12 lokacija. Laboratorijskim istraživanjima su definisani sledeći parametri: fizičko-hemijske karakteristike jalovine, odnos tečne i čvrste faze, broj bakterija, vreme luženja, kao i broj recikliranja. Dobijeni rezultati pokazuju da je procenat izluženja bakra pet puta veći u suspenziji sa Acidithiobacillus ferrooxidans, nego u kontrolnoj suspenziji. Mikrobiološki postupci luženja siromašnih ruda i jalovina, imaju značajnu ulogu kako za dobijanje 'dopunskih' količina metala, tako i u konceptu zaštite okoline, jer se jednostavnom tehnologijom, stavljaju pod kontrolu i usmeravaju, a time i sprečavaju nekontrolisani odlivi metala u vodotokove i zemljište (koji u ovoj sredini predstavljaju polutante).Lithotrophs are involved in many transforming and cyclic reactions of elements in nature, having an important role in biochemical cycles of sulfur and iron, as well of nitrogen and other elements. The term 'lithotroph' is created from the terms 'lithos' (rock) and 'troph' (consumer), meaning the 'eaters of rock. The role of these microorganisms in nature has been widely used by man in processes of metal exploitation. More precise, main goal is converting low-soluble metal compounds, mostly sulfides, into solutions. Practically, naturally occurring reactions have been directed and enhanced, in such a way to get useful metals, mostly from low-grade metal ores and waste materials. The objective of our study was to investigate recovery of useful components from low-grade ores. The microorganism used in leaching was Acidithiobacillus ferrooxidans. Experiments were performed with samples taken from 12 different locations on Bor ore dumps in order to establish recovery conditions. Parameters, like solid-liquid ratio, number of bacteria, rate of leaching, physical and chemical characteristics of ore, rate of watering and number cycles, were determined. The results obtained show 5-fold higher copper leaching efficiency in the suspension with Acidithiobacillus ferrooxidans, then in control suspension. Microbiological leaching of low-grade ores and mine tailings is used nowadays as a method of supplying additional quantities of metal as well as protection of the environment. Natural processes of microbiological leaching, by use of relatively simple technology, are controlled and focused so that uncontrolled loss of useful components (pollutants in this environment) into streams and rivers is stopped
Properties of diclofenac sodium sorption onto natural zeolite modified with cetylpyridinium chloride
No full textIn this study an investigation of a model drug sorption onto cationic surfactant-modified natural zeolites as a drug formulation excipient was performed. Natural zeolite was modified with cetylpyridinium chloride in amounts equivalent to 100, 200 and 300% of its external cation-exchange capacity. The starting material and obtained organozeolites were characterized by Fourier transform infrared spectroscopy, zeta potential measurements and thermal analysis. In vitro sorption of diclofenac sodium as a model drug was studied for all surfactant/zeolite composites by means of sorption isotherm measurements in aqueous solutions (pH 7.4). The modified zeolites with three levels of surfactant coverage within the short activation time were prepared. Zeta potential measurements and thermal analysis showed that when the surfactant loading level was equal to external cation-exchange value, almost monolayer of organic phase were present at the zeolitic surface while higher amounts of surfactant produced less extended bilayers, ordered bilayers or admicelles at the zeolitic surface. Modified zeolites, obtained in this manner, were effective in diclofenac sodium sorption and the organic phase derived from adsorbed cetylpyridinium chloride was the primary sorption phase for the model drug. The Langmuir isotherm was found to describe the equilibrium sorption data well over the entire concentration range. The separate contributions of the adsorption and partition to the total sorption of DS were analyzed mathematically. Results revealed that that adsorption and partitioning of the model drug take place simultaneously
Phytoremediation of uranium contaminated soils
No full textEnvironmental uranium contamination based on human activity is a serious problem worldwide. Soil contaminated with uranium poses a long-term radiation hazard to human health through exposure via the food-chain and other pathways. This chapter is an overview of processes and modern techniques for remediation of soils contaminated with uranium, with special attention on phytoremediation. Phytoremediation takes advantage of plant to extract, sequester pollutants in soil, water, and air with an aim of pollutant removal and transformation into harmless forms.The objective of this chapter is to develop a better understanding of plants behavior and the degree of affinity towards the adoption of uranium for hyperaccumulators plants based on review of international research. To understand the mechanism of uranium uptake in plants and accumulation, a necessary prerequisite is the application of radiophytoremediation on the "real" scale. For this purpose, we investigated these processes using three different aspects with selected cultivated plants: 1. Vegetative tests in pots of fully controlled conditions, with corn plants that were grown on two types of soil, pseudogley and chernozem, together with its phytotoxic effect on the plant development, height, yield, and seed germination.2. Greenhouse experiments with tailings from the closed uranium mine Kalna on the southeast of Serbia. Three series of experiments were conducted in plastic-house. First, three plant species (corn, sunflower, and green peas) were grown in pots on the four substrate variants, tailings in mixture with sand. The substrate was irrigated with drinking water and "uranium water", which issues out from the mine. Another experiment was conducted in order to investigate the uptake of U in several kinds of roots-crops, bulbous, and tuberous plants: carrot, onion, potatoes, radish, red beet, and sugar beet. Content of uranium was found in leaves and roots (surface root layer and edible parts were peeled). Also we investigated uranium adoption in four genotypes of com, sunflower, and soy bean.3. Vegetation test on real, native conditions on tailings, from the closed uranium mine Kalna. The experiment was carried out on the elementary plots one square meter in size, with bean, cabbage, lettuce, com, onion, potatoes, spinach, and sunflower.Well-organized use of phytotechnology means an integrated management strategy for contaminated sites which include proper selection of plants (uranium hyperaccumulators), improving mobility of uranium with amendments (organic agents), and application sequestering agents for immobilization and transformation of excess uranium, which the plants didn't accept
The copper biosorption using unmodified agricultural waste materials
No full textProblem zagađenja životne sredine usled tehno-ekonomskog i urbanog razvoja zahteva integralan pristup održivog upravljanja i zaštite biodiverziteta. Poseban akcenat usmeren je na teške metale, zbog njihove visoke toksičnosti, postojanosti i tendenciji ka bioakumulaciji. Savremeni trend u rešavanju ovog problema je primena otpadne biomase agroindustrije kao efikasnih biosorbenta polutanata čime se ujedno produžava njihov životni ciklus i rešava problem deponovanja. Biosorpcijaja je ekološki i ekonomski prihvatljivija tehnologija u odnosu na konvencionalne metode, a biosorbenti, zahvaljujući svojim funkcionalnim grupama, poseduju širi spektar dejstva u odnosu monofunkcionalne jonoizmenjivače. Predmet rada je istraživanje mogućnosti primene otpadne biomase (koštice breskve i višnje) iz fabrike 'Vino Župa' Aleksandrovac, kao potencijalnog biosorbenta za uklanjanje bakra iz vodenih rastvora. Cilj urađenih istraživanja je bio sticanje fundamentalnih osnova fizičkih i hemijskih fenomena adsorpcije bakra na netretiranoj biomasi. Preliminarni rezultati prikazani u ovom radu i pionirska istraživanja te vrste u Srbiji, pokazali su da se ovaj tip netretiranog otpadnog materijala može koristiti za uklanjanje jona bakra, ali takođe, i da je neophodno ispitati mogućnost njihove hemijske ili fizičke modifikacije kako bi im se povećao biosorpcioni kapacitet.The rapid increase in global industrial activities has lead to the serious environmental pollution that requires systematic and sustainable approach in order to protect environment and biodiversity. Special concern is accented on heavy metal pollution because of their high toxicity, persistence and bioaccumulation tendency. The conventional methods for their removing are often either too expensive or create a large quantities of toxic sludge, so the other technologies, cheaper and more effective should be employed. Biosorption is one of the recently employed promising technologies that use biomaterials as sorbents for different type of pollution. Thanks to their active surface groups, biosorbents pose wider operational spectrum than mono functional ion exchangers. Agricultural waste materials have proved to be highly efficient, low cost and renewable source of biomass that can be exploited for heavy metal remediation, which leads to increase of their life cycle and also solve their disposal problem. The purpose of this paper is investigation of possible application of wasted untreated biomass from 'Vino Župa' Company as potential biosorbent that can be used for copper removal from water solutions. For this purpose, several type of biomass have been examined and the preliminary results presented in this paper have showed that this wasted untreated materials can bee used as promising and cheap adsorbents for copper removal from water solutions, but also that further physical and chemical modifications should be done in order to increase their biosorption capacity
Measures and methods for NOx reduction from glass-melting furnaces
No full textRazvojem tehnike i tehnologije javlja se potreba za većom proizvodnjom energije. Iako se danas uvode u upotrebu i drugi izvori energije, još uvek je najzastupljenije dobijanje energije u procesu sagorevanja goriva. Zbog visokih temperatura koje nastaju pri sagorevanje dolazi do velike emisije NOx oksida. U ovom radu opisane su mere i metode kojima je moguće smanjiti emisiju NOx u procesima dobijanja stakla.The nitrogen oxides emitted to atmosphere effect significantly on formation of photochemical smog, acidic rains and destroying of ozone shell of the earth. Therefore, the regulations for limited emission of nitrogen oxides to atmosphere become very strict. Glass manufacturing is a high-temperature, energy-intensive activity, because of the high temperature NOx emissions are extremely high. NOx emissions could be reduced by primary process modifications measures end secondary post-combustion measures. Primary process modifications are usually based on the following techniques: stoichiometric combustion and advanced burners systems, staged combustion (air- or fuelstaged), recircylation of flue gasses
Kinetics of mechanochemical synthesis of barium-titanate
No full textU ovom radu ispitivan je uticaj mehaničke aktivacije na sistem barijum oksid-titan dioksid. Mehanička aktivacija je vršena u vibro-mlinu u vremenskom intervalu od 30 do 440 minuta. Tokom aktivacije došlo je do reakcije polaznih komponenti u čvrstoj fazi, pri čemu je kao krajnji produkt dobijen barijum-titanat. Metode rendgenske difrakcije i spektrofotometrijske analize su korišćene radi identifikacije faznog sastava i kvantitativnog sadržaja komponenti tokom reakcije. Predložen je mehanizam sinteze barijum-titanata i utvrđeni su kinetički parametri.In this paper the influence of mechanical activation on the system barium oxide - titan dioxide has been investigated. Also, the theoretic model of mechanochemical reaction has been introduced. Process of mechanical activation was conducted in vibro-mill in the 30 to 440 minutes interval. Solid state reaction has been noticed during the activation process. X-ray diffraction method has been employed in order to determine phase composition of mechanically activated mixtures. The process of milling could be divided into three stages: first stage-progressive destruction of reactant's crystal structure; second phase-nanocrystal structure formation as a consequence of defects introduction within crystal structure; third phase-obvious formation of a new phase and peak's intensities growth caused by crystal phase arranging. It was noticed that barium titanate was obtained successfully at the end of the milling process. Method of spectrofotometry has been chosen for determining the quantitative ratio of starting components during the reaction. The authors suggested the synthesis mechanism of barium-titanate and established the kinetic parameters. Also, it was notices that the reaction between barium oxide and titan dioxide represents 'two-stages' reaction, which includes the formation of intermediate compound BaO*TiO2. Having in mind that the constant of reaction velocity of the process of intermediate compound formation is greater than constant of barium titanate formation, we can conclude that activation energy of first stage is less than activation energy of second process. Analysis of kinetics showed that the half-time synthesis of mentioned compound is 77.7 minutes, while at the end of milling process the reaction between starting reactants was complete
Crystallization behaviour of Li2O·Nb2O5·SiO2 glass containing TiO2
No full textThis paper deals with the crystallization of glass 30Li2O·15Nb2O5·50SiO2·5TiO2 (mol%). The crystallization behavior was studied under isothermal and non-isothermal conditions. XRD and SEM methods were employed for determination of phase composition and microstructure of crystallized glass. It was detected that this glass crystallizes by the surface crystallization mechanism. SEM micrographs of the crystallized samples revealed that the crystals grow in the form of dendrites. The glass-ceramics with complex phase composition was obtained. Three crystalline phases were detected where LiNbO3 has grown as primary phase and a secondary ones Li2Si2O5 and SiO2 appeared. The calculated average crystallite sizes are: 27 nm for LiNbO3 , 115 nm for Li2Si2O5 and 45 nm for SiO2 . From the experimental data an activation energy of crystals growth, calculated using the Kissinger relation, is Ea = 275 ±10 KJ / mol
Electrokinetic properties of hydroxyapatite under flotation conditions
No full textThe effect of calcite supernatant, calcium, and carbonate ions on the hydroxyapatite (HA) zeta potential without and in the presence of sodium oleate (1 x 10(-4) mol L-1) was examined within the pH range from 4 to 12. The interpretation of results was based on the HA Surface and oleate solution chemistry, and on some floatability tests. HA, with different positive and negative Surface sites formed depending on its solubility and pH, had a negative zeta potential over the whole pH range. This mineral is not naturally floatable (flotation recovery, 5% LT R LT 18%). The oleate ions (OI-), present in a very low concentration in an acidic medium (pH from 4.8 to 6), chemisorb individually on HA surface centers Ca+, HPO4Ca+, and OH2+, increasing the negative zeta potential of the mineral. Within the pH range from 7 to 9, the dominant oleate species OI- ion and ion-molecule complex, H(OI)(2)(+), adsorbed on HA by head groups toward the solid and associated due to chain-chain interaction in hemimicelles, made the HA surf ace with zeta potential about -22/-23 mV, and more floatable (R = 80-100%) than in 4 LT pH LT 7 (R = 15-35%) or in pH > 9.3. The HA surface is less negatively charged in calcite supernatant than in water from pH 6.6 to 9.2 due to the adsorption on HA negative surface active centers ( HPO4- and PO42+) of the Ca2+, CaHCO3+, and CaOH+ ions (present in the calcite supernatant), producing m re surface sites PO4Ca, HPO4CaOH, and PO4- CaOH, and new centers HPO4CaHCO3 and PO4- CaHCO3. In the presence of 1 x 10(-3) mol L-1 CaCl2, the HA sample has positive zeta potential, the same as calcite from the same deposit, up to IEP at pH 11.25. Carbonate ions (1 x 10(-3) mol L-1 Na2CO3) do not affect the HA zeta potential. However, a possible process can be the ion-exchange reaction between bicarbonate (or carbonate) and some anion from the surface sites formed on HA. The obtained values of the HA zeta potential with the collector (1 x 10(-4) mol L-1 Na-oleate) added into hydroxyapatite/calcite Supernatant suspensions corroborate the weak chemisorption of OI- and H(OI)(2)(-). The likely processes in this system also are the ion-exchange reactions on HPO4CaOH and PO4- CaOH, HPO4CaHCO3 and PO4- CaHCO3 between oleate ion and surface hydroxyl and bicarbonate ions, Surface and bulk precipitations of calcium oleate. Ca(OI)(2), and the Surface and bulk precipitations of Ca[H(OI)(2)(-)](2) over the pH range from 7 to 9. Calcite Supernatant does not influence natural floatability of the mineral. However, calcite Supernatant depresses the hydroxyapatite flotation in the presence of 1 x 10(-4) mol L-1 Na-oleate (pH 9, R similar to 50%), a likely result of the weak chemisorption due to the steric effect of heterogeneous HA surface formed in calcite supernatant, Ca(OI)(2) and Ca[H(OI)(2)(-)](2) surface and bulk precipitations
Influence of natural zeolitic tuff and organozeolites surface charge on sorption of ionizable fumonisin B-1
No full textNatural Zeolitic tuff was modified with 2, 5 and 10 mmol M+/100 g of octadecyldimethylbenzyl ammonium (ODMBA) ions and the products were denoted as OZ-2, OZ-5 and OZ-10. The starting material and organozeolites were characterized by determination of the point of zero charge (pH(pzc)) and by thermal analysis. in vitro sorption of fumonisin B-1 (FB1) was studied for all sorbents at pH 3, 7 and 9. The pH(pzc) for the zeolitic tuff was 6.8 +/- 0.1, while the pH(pzc) for OZ-2, OZ-5 and OZ-10 pH(pzc) was 7.0 +/- 0.1. The curves pH(final) = f(pH(initial)) suggest that the surfaces of all sorbents are positively charged at pH 3 and uncharged at pH 7 and 9. High sorption of FB1 by the zeolitic tuff in acidic solution Suggests electrostatic Interactions between the anionic FB1 and the positively charged surface. At pH 7 and 9, adsorption of FB1 is prevented because anionic FB1 cannot be adsorbed at the uncharged surface. From the pH(pzc) for the organozeolites, it is possible that with lower amounts of ODMBA (OZ-2 and OZ-5), at pH 3, beside interactions between head groups of ODMBA and its alkyl chains and anionic FB1, electrostatic interactions between positive uncovered surface and anionic FB1 contribute to the sorption, while at pH 7 and 9 there is only the possibility for interactions between FB1 and ODMBA. When the zeolitic surface was completely covered with ODMBA (OZ-10), FB1 sorption was independent of the form of FB1 suggesting only interactions between ODMBA and FB1