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Sustainable mining towards accomplishing circular economy principles
No full textToday human society is already witnessing rapid depletion of non-renewable ore resources. As the distribution of raw material resources globally is very off-balance, and preassure on environment as the consequence of ore exploatation is not negligible, re-utilization and recycling of industrial side-streams gaining on importance. Finding new potentially anthropogenic resources of material (at first place critical raw materials) are inline with sustainable waste management goals, and in correlation with boundaries given by the circular economy principles. Side-streams from mines can become source for recovery of these materials. The aim of this paper was to analyze position of mining waste in correlation with circular economy principles, as well potential for implementation of them within extraction industry in the Republic of Serbia
Impact of hydrochar and biochar amendments on sorption and biodegradation of organophosphorus pesticides during transport through Danube alluvial sediment
No full textThis work investigates the transport behaviour of selected organophosphorus pesticides, OPPs (chlorpyrifos, CP; chlorpyrifos-methyl, CPM; chlorfenvinphos, CF) through Danube alluvial sediment in the presence of hydrochars and biochars. The investigated hydrochar, obtained at three different temperatures (180 degrees C, 200 degrees Cand 220 degrees C), originated from sugar beet shreds (SBS) and Miscanthusxgiganteus (MIS). Results are described by conventional advective-dispersive equation (ADE). Retardation coefficients (R d ) for all OPPs were in the range 6.2-16. Biodegradation was 4.15 and 1.80 for CPM and CP, respectively, while for CF biodegradation did not occur. The addition of carbon rich materials increases retardation of all OPPs in the range from 4 to 18 times depending on the material. Column experiment results indicated that biodegradation of OPPs occurred (up to lambda = 13). In order to confirm that biodegradation occurred in the column experiments, we isolated OPPs degrading microorganisms for the first time from the alluvial sediment. A strain capable of degrading CP and CPM was isolated and identified as Bacillus megaterium BD5 based on biochemical properties, MALDI TOF and 16S rRNA analysis (99.54% identity). The results demonstrate that hydmchars, biochars and isolated degrading bacteria may be effective agents for reducing the mobility of or removing OPPs in contaminated soils or sediments
Chalcopyrite leaching in acid media: a review
No full textIn the modern practice of copper production, more attention is increasingly being given to the possibility of treating low-percentage sulphide ores that cannot be treated with conventional procedures (crushing, grinding, flotation). In addition, the processes of obtaining copper from complex sulphide concentrates, which cannot undergo pyrometallurgical processing, are increasingly being investigated. In most cases, the extraction of copper from such raw materials is achieved by applying the leaching procedures. Since chalcopyrite (CuFeS2) is the most abundant copper sulphide mineral, a great part of the research is focused on studying the behaviour of chalcopyrite in the leaching process, because processes of copper extraction from increasingly poor raw materials may be created using results of these studies. In addition, the main goal of these researches is to investigate the kinetics and mechanism of oxidation of chalcopyrite under the influence of various oxidants (O-2, Fe3-, H2O2, chlorate ions, etc.) and in the same time obtaining data necessary for the development of copper production process that could satisfy increasingly technological, economic and environmental stringent criteria. This paper presents the existing knowledge of chalcopyrite leaching and phenomena that follow chalcopyrite oxidation in acidic sulphate and chloride solutions
Sintering, crystallization and foaming of La2O3 center dot SrO center dot 5B(2)O(3) glass powders: effect of the holding time
No full textSintering, crystallization and foaming of nano glass powders with composition La2O3 center dot SrO center dot 5B(2)O(3) were studied by hot stage microscopy (HSM) and simultaneous thermal analysis (DTA-TG) under non-isothermal regime at 10 degrees C/min and by optical contactless dilatometer under isothermal conditions at 700 degrees C up to 10 hours for different times. After the thermal treatments, specimens were characterized by gas pycnometry, X-ray Powder Diffraction (XRD) and Field Emission Scanning Electron Microscopes (FE-SEM). The results demonstrate that the densification completed before the crystallization process, thus forming well sintered samples. Then, during the phase formation gas is released, which leads to foaming process. After holding of 160 minutes at 700 degrees C the degree of crystallization reached about 0.8 and the foaming stopped. The obtained sample had high closed porosity and quite intriguing structure composed of two fairly different crystal arrangements. The first was "sponge-like", while the second was denser and consisted of "sheets", 10-30 nm thick. The subsequent holding led to re-crystallization, formation of larger denser zones that reached even 10-15 mu m and an increase in open porosity. These results highlight that in the case of sinter crystallization of nano powders, some intriguing features can be expected
Postupak dobijanja ekspandirajućeg materijala otpornog na gorenje poboljšanih mehaničkih svojstava
No full textTehničko rešenje predstavlja novi protivpožarni materijal koji se koristi za izradu prstenova za cevi kao pasivne zaštite od širenja požara. Tehnološki postupak se sastoji iz dve faze. Prva faza se odnosi na mešanje kopolimera poli(vinilhlorid–co– vinilacetata) (VC–co–VAc) ili modifikovanog kopolimer poli(vinilhlorid–co–vinilacetata) (VC–co–VAc) sa ekspandovanim grafitom i plastifikatorima/modfikatorima kao što su: diizononil ftalat – DINP, dioktil adipat – DOA, 1-heksadecen ili metil estri masnih kiselina sojinog ulja (MES), azodikarbonamid (ADC), tri(p-krezil fosfat), tri(m-krezil)fosfat, epoksidovano sojino ulje (ESU) i akrilatna emulzija (DH50, Ecrylic, ili Flexryl, itd.). Druga faza se odnosi na oblikovanje dobijene smeše u presi sa kontrolisanom temperaturom da bi se napravili različiti uzorci koji su dalje testirani. Uzorci su imali različite dimenzije od 4 - 6 mm debljine, 70 - 400 mm širine i 240 - 500 mm dužine
Investigation of Bi2S3 oxidation process at elevated temperatures in the air atmosphere
No full textBizmut (III) sulfid je poslednjih godina naširoko istraživan zbog svoje primene, ali je malo akcenta dato na istraživanja u pogledu njegovog ponašanja na povišenim temperaturama. Ovo je od velike važnosti, uzevši u obzir da se bizmut, u obliku Bi2S3 nalazi u sulfidnim koncentratima bakra i važi za jednu od najštetnijih komponenti, zajedno sa olovom, arsenom i antimonom. Uklanjanje ovih supstanci jedan je od osnovnih zadataka u procesima pirometalurške ekstrakcija bakra, kako bi se na kraju proizvodnog procesa dobio metal visoke čistoće. U cilju boljeg razumevanja ponašanja bizmut (III) sulfida pri oksidaciji na povišenim temperaturama, u ovom radu je izvršena karakterizacija sintetisanog uzoraka Bi2S3 na sobnoj temperaturi i produkata oksidacije na 500°C metodom rentgenske difrakcije (XRD), kao i termodinamička, termijska i kinetička analiza procesa oksidacije Bi2S3 na povišenim temperaturama. Da bi se razumelo ponašanje Bi2S3 tokom oksidacije i raspodela produkata oksidacije, konstruisani su dijagrami stabilnosti faza u sistemu Bi-S-O na različitim temperaturama i proračunate su vrednosti promene Gibbsove slobodne energije na 400°C i 1000°C. Kinetička analiza procesa oksidacije Bi2S3, urađena po metodi Kissingera u neizotermskim uslovima, pokazala je da je oksidacija bizmutinita hemijski kontrolisani proces.Bismuth (III) sulfide has been widely researched in recent years due to its application, but little emphasis has been placed on research regarding its behavior at elevated temperatures. This is of great importance, considering that bismuth, in the form of Bi2S3, is found in copper sulfide concentrates and is considered one of the most harmful components, along with lead, arsenic and antimony. The removal of these substances is one of the basic tasks in the processes of pyrometallurgical extraction of copper, in order to obtain a high purity metal. In order to better understand the behavior of bismuth (III) sulfide during oxidation at elevated temperatures, this paper characterized the synthesized sample of Bi2S3 at room temperature and the oxidation products at 500 °C by X-Ray diffraction (XRD), as well as thermodynamic, thermal and kinetic analysis of the oxidation process of Bi2S3 at elevated temperatures. In order to understand the behavior of Bi2S3 during oxidation and the distribution of oxidation products, phase stability diagrams in the Bi-S-O system were constructed at different temperatures and the values of the Gibbs free energy change at 400 °C and 1000 °C were calculated. Kinetic analysis of Bi2S3 oxidation process was performed by Kissingers method in non-isothermal conditions
Functionality of chitosan-halloysite nanocomposite films for sustained delivery of antibiotics: The effect of chitosan molar mass
No full textThis study was designed to investigate functionality of tetracycline-loaded chitosan-halloysite nanocomposite films, with focus on evaluating the influence of chitosan molar mass on films applicability for sustained local antibiotic delivery. The films were prepared by casting and solvent evaporation using low, medium, and high molar mass chitosan. SEM analysis revealed compact, nonporous and rough surface of the nanocomposite films due to the presence of halloysite agglomerates and tetracycline crystals. Increasing chitosan molar mass led to higher values of elongation at break (from 21.65 +/- 2.65 to 34.48 +/- 2.34%), tensile strength (from 134.8 +/- 13.21 to 246.36 +/- 14.69 MPa), and elastic modulus (from 633.79 +/- 128.37 to 716.55 +/- 60.76 MPa) of the nanocomposite films. FT-IR, XRPD, and thermal analyses confirmed molar mass dependent chitosan-halloysite interactions and improved thermal stability of the nanocomposite films in comparison with chitosan films. The nanocomposite films released tetracycline in a sustained manner, with the slowest release achieved from the films consisting of low molar mass chitosan. Chitosan molar mass was confirmed to be a functionality-related characteristic of chitosan-halloysite nanocomposite films as potential sustained-release carriers for topical delivery of antibiotics
Enhancing properties of concrete by addition of fly ash from a thermal power plant for application in geothermal systems
No full textElectric power in Serbia is predominantly provided by thermal power plants. All of eleven existing
thermal power plants in Serbia use coal, mainly lignite in the electricity production process
thus generating about 6 million tons of fly ash per year. The estimated amount of fly ash from thermal
power plants accumulated in Serbian landfills exceeds 200 million tons. On the other hand, during
the last decades, respecting the principles of ecologically sustainable development has been imposed
on industries, and one of them is the construction industry. Due to the presence of amorphous SiO2
and Al2O3, fly ash as pozzolanic material is convenient for the production of concrete and mortar.
Consequently, multiple positive effects can be expected by the proper consumption of fly ash- reducing
landfills and improving concrete properties. The idea of this study is to analyze the possibility of
recycling fly ash from a thermal power plant by replacing a part of common mineral filler- limestone
in the production of self-compacting concrete (SCC). Properties of conventional SCC with limestone
and compositions with different fly ash content were compared. Considering that requirements for SCC should be satisfied and all properties remain or enhance in the case of fly ash addition, this
study proved that all designed concretes can be used for structural applications.Električnu energiju u Srbiji pretežno obezbeđuju termoelektrane. Svih jedanaest termoelektrana
u Srbiji koriste ugalj, uglavnom lignit u procesu proizvodnje električne energije, čime se
godišnje generiše oko 6 miliona tona letećeg pepela. Procenjena količina letećeg pepela iz termoelektrana
akumulirana na deponijama u Srbiji prelazi 200 miliona tona. S druge strane, poslednjih
decenija poštovanje principa ekološki održivog razvoja nametnuto je industrijama, a jedna od njih je
i građevinska. Zahvaljujući prisustvu amorfnog SiO2 i Al2O3, pepeo kao pucolanski materijal pogodan
je za proizvodnju betona i maltera. Zbog toga se pravilnom upotrebom letećeg pepela mogu
očekivati višestruki pozitivni efekti- smanjenje deponija i poboljšanje svojstava betona. Ideja ovog
istraživanja je analiziranje mogućnosti recikliranja letećeg pepela iz termoelektrane tako što će delimično
zameniti uobičajeni mineralni punioc- krečnjak u proizvodnji samozbijajućeg betona (SCC).
Upoređena su svojstva konvencionalnog SCC sa krečnjakom i kompozicija sa različitim sadržajem
pepela. S obzirom da je u slučaju dodatka letećeg pepela potrebno da budu zadovoljeni zahtevi za
SCC, kao i da svojstva betona ostanu ista ili poboljšana, ova studija je pokazala da se sve dizajnirane
smeše mogu koristiti za konstrukcijske primene
Effect of corn straw pretreatment on efficiency of biogas production process: Computer simulation
No full textAnaerobic digestion is a natural process of organic material degradation by different kinds of microorganisms in the absence of oxygen. This process is used for industrial purpose to manage waste streams or to produce biogas. It gives a major contribution in reduction of harmful effects of organic waste disposal to the environment. The aim of agricultural waste pretreatment in biogas production is to decrease the retention time, improve utilization of raw material and improve the overall productivity and energy efficiency of the production process. In this paper the effects of combined chemical and mechanical pretreatment of corn straw biomass on biogas yield during anaerobic digestion of the feedstock were analyzed. The impact of pretreatment and process parameters in biogas production was analyzed by process simulation using the software SuperPro Designer. Using this tool, it was shown that alkaline pretreatment leads to an decrease of degradation time along with an increase in biogas yield
The application of Calamagrostis epigejos (L.) Roth. in phytoremediation technologies
No full textPerennial grass, Calamagrostis epigejos, is native to Euro-Asian region and introduced to North America. Species has wide ecological amplitude and tolerance to abiotic stresses. Growth strategy and the significant abiotic stress tolerance of C. epigejos, enabled by a higher water and nitrogen use efficiency, are responsible for its competitiveness and ongoing spreading in certain natural and anthropogenic habitats. C. epigejos is colonizer of post-mining lands where it shows range of adaptation mechanisms to the stressful environments. The species pose multiple tolerance to metal(oids), retaining elements such as Cu, Zn, Pb, Cd Zn, Mn, As, and Mo in roots, and showing potential for phytoremediation primarily in the field of phytostabilization. Additionally, species has been proven to reduce erosion and heavy metal leakage from polluted sites, and contributes to the natural remediation of contaminated marginal lands. Chemical composition of C. epigejos paired with high calorific value of its biomass makes this species a potential source of bioenergy