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The effect of sieve loading and particles shape on the results of polymer sieve kinetics
No full textAn experimental investigation has been made into the effects of different factors on the results of screening efficiency of polymer samples. The used polyvinyl chloride (PVC) samples have equal content of `small`, `large` and `small-to large` particles and filled the whole area of the sieve in one, two and four characteristic layers during the screening. Visual examination showed that the particle shape was similar in whole particle size distribution in the one sample tested. In addition to the aforementioned variable, the other factors studied included samples shape, vibrating amplitude and the duration of screening. Analysis of the obtained results of the screening rate in laboratory conditions was performed by applying the classical and modified model of the first order screening kinetics. The results showed that high loading of the sieve requires a larger vibrating amplitude for good classification and that the high layer reduction of sample is a more effective remedy for good efficiency than prolongation of sieving time. It has also been shown that the particles shape has a significant impact on the screening rate. The modified kinetics model (Magdalinović–Trumić) of the first order describes polymer screening kinetics with very good correlation coefficient in all cases. The application of the classical model is not adequate for determining a screening rate constant since the correlation coefficients are smaller than the minimum correlation coefficient
Nemetalične mineralne sirovine kao osnov dugoročnog razvoja privrede Srbije
No full textU Srbiji radi oko 200 rudnika u eksploataciji nemetaličnih mineralnih sirovina. Nemetalične mineralne sirovine su zastupljene u svim područjima Srbije i zauzimaju značajno mesto u privrednom razvoju, bilo da služe kao finalni proizvodi ili kao sirovine kod proizvodnje u prerađivačkoj i drugim industrijskim granama. Po raspoloživim količinama, kao i raznovrsnosti, ove sirovine su jedan od najznačajnijih domaćih prirodnih resursa. Skoro da ne postoje privredne grane koje ne koriste nemetalične mineralne sirovine.
Osnovni cilj ovog referata je da se kroz sintezu raspoloživih podataka i dosadašnjih saznanja prikaže dostignuti nivo i potencijalne mogućnosti domaćih ležišta nemetaličnih mineralnih sirovina. Takođe, osnovni cilj je, da se sa raspoloživim podacima korišćenim u ovom tekstu dokumentuje određena zapostavljenost sirovinske baze nemetaličnih mineralnih sirovina u privrednom razvoju Srbije
Optimization of the process of Cu(II) sorption by mechanically treated Prunus persica L. - Contribution to sustainability in food processing industry
No full textThis paper presents an eco-friendly approach for minimizing heavy metal pollution, offering food waste valorization and energy source at the same time. It focuses on Cu(II) sorption by low cost sorbent developed by mechanical treatment of Prunus persica L. stones, a food industry waste biomass. Removal of Cu(II) was studied at different operating parameters in a batch sorption system, with special attention on temperature effect on sorption process. The pseudo-first order, pseudo-second order and Elovich model were applied to test kinetic experimental data. Equilibrium experimental results were fitted to Langmuir, Freundlich, Sips, Toth and Dubinin-Radushkevich isotherms to elucidate the type and sorption performance. Characteristic functional groups responsible for Cu(II) binding and thermal behavior of PS have been investigated using FT-IR and TGA analyses. The activation parameters were calculated using Arrhenius and Eyring equations. Using equilibrium data at different temperatures, thermodynamic parameters Delta G degrees, Delta H degrees and Delta S degrees were calculated, suggesting that the sorption of Cu(II) on PS is spontaneous and endothermic process with increased randomness during the sorption. The isosteric heat of adsorption (Delta H-iso) was determined, suggesting the non -uniformity of PS surface and lateral interactions among ions sorbed. Desorption experiments performed with different chemicals have confirmed the reusability of PS for five cycles, without losing and even improving its sorption capacity. Results presented in this paper might help in appropriate design of purification systems using this type of lignocellulosic waste
The extraction of aggregates in Serbia, 1973 - 2015: A statistical exploration
No full textWe contribute to the fields of mineral economics, environmental and economic history in two respects: first, we construct a novel time series data set for the levels of aggregates extraction in Serbia between 1973 and 2015; the second, we estimate a change point ordinary least squares regression to model the dynamics of aggregates extraction in the aforementioned period. Our cliometric estimates are in great accordance with the major business cycle facts of the Serbian economy in the last 40 years. The most important policy implication of our results pertains to the potential slowdown of aggregates extraction from the onset of the Great Recession
Sintering of Fly Ash Based Composites with Zeolite and Bentonite Addition for Application in Construction Materials
No full textDue to pozzolanic characteristics, fly ash is commonly used as a cement replacement in construction composites. Addition of natural clays with sorption ability (i.e. zeolite and bentonite) in to the fly ash based construction materials is of both scientific and industrial interest. Namely, due to the application of sorptive clay minerals, it is possible to immobilize toxic heavy metals from the composite structure. The thermal compatibility of fly ash and zeolite, as well as fly ash and bentonite, within the composite was observed during sintering procedure. The starting components were used in 1: 1 ratio and they were applied without additional mechanical treatment. The used compaction pressure for the tablets was 2 t.cm(-2). The sintering process was conducted at 1000 degrees C and 1200 degrees C for two hours in the air atmosphere. The mineralogical phase composition of the non-treated and sintered samples was analyzed using X-ray diffraction method. Scanning electron microscopy was applied in the analysis of the microstructure of starting and sintered samples. The thermal behavior was observed via DTA method. The influence of temperature on the properties of fly ash-zeolite and fly ash-bentonite composites was investigated
Heat balance calculation for freeze lining smelting process
No full textSimulating the furnace processes can lead to the minimal energy loses and optimal temperature distribution through the system. Freeze lining is a result of balance between the heat input from liquid bath and heat removal from outer layer. In that manner, solid slag crust is formed with good mechanical properties. At this paper freeze lining for the plasma smelting process was simulated using COMSOL software package. For smelting material corundum with the addition of other materials was used. Smelting is possible if the heat balance is properly calculated. Colling rate will control the layer thickness and inner temperature
Mineralogy and crystallochemical characteristics of HEU-type minerals from zeolitic tuff deposits of Serbia
No full textVeliki broj pojava i ležišta prirodnih zeolita piroklastičnog porekla široko rasprostranjenih u
miocenskim sedimentima Srbije, su predmet detaljnih istraživanja. Najznačajnija srpska
ležišta zeolitskih tufova su: Zlatokop (Vranjski basen), Igroš (Kopaonik), Beočin (Fruška
Gora), Toponica i Slanci (Dunavski ključ kod Beograda). Ležišta ovih zeolitskih tufova, prostorno
i genetski vezana su za vulkanske i vulkanoklastične stene marinskih sredina senonske
i neogenske starosti i jezerskih sedimenata neogene starosti. U procesima devitrifikacije
i dijageneze vulkanskog stakla kod zeolitskih tufova došlo je do obrazovanje hipokristalasto
porfirske odnosno vitroklastične strukture. Sami zeolitski tufovi u najvećem delu
sastavljeni su od hojlandita, koji je prisutan u obliku malih igličastih do pločastih kristala
dimenzija od 0,1 do 100 μm (u asocijaciji sa drugim silikatnim i alumosilikatnim fazama
približno sličnih specifičnih gustina). U zavisnosti od vrste i sadržaja izmenljivog katjona,
kao i termičke stabilnosti ispitivanog zeolitskog tufa razlikujemo Ca-klinoptilolite i Ca-hojlandite.
Kapaciteti katjonske izmene zeolitskih tufova imaju vrednosti od 96 do 166
meq/100 g, a spoljašnji kapaciteti se kreću od 8,0 do 10,5 meq/100 g. Ovaj rad se bavi
detaljnom karakterizacijom prirodnih zeolita najznačajnijih srpskih ležišta, gde je kristalohemijski
sastav zeolita u direktnoj vezi sa genetskim i paragenetskim karakteristikama
njihovih ležišta.The results of perennial research of several Serbian zeolitic tuffs enriched with
HEU-type minerals are presented in this paper. There are several recognized zeo-
litic tuff deposits containing HEU-type minerals: Zlatokop, Igroš, Beočin, Toponica
and Slanci, but their comparative mineralogical and crystallochemical features
have not been studied in detail so far. These zeolitic tuff deposits are spatially and
genetically connected to volcanic and pyroclastic rocks of marine and lake envi-
ronments of Senonian and Eocene, and Neogene age, respectively. As a result of
devitrification and diagenesis process of volcanic glass within zeolitic tuffs hypo-
crystalline porphiry and vitroclastic textures occur. The studied zeolitic tuffs are
mainly composed of heulandite occuring in a form of needle- to plate-like crystals
of 0.1 do 100 μm in length, associated with other silicates. Depending on the type
and content of exchangeable cations as well as the thermal stability of these raw
materials, clinoptilolite-Ca and heulandite-Ca can be distinguished. The values of
cation exchange capacity and surface area capacity range from 96 to 166
meq/100 g, and from 8.0 to 10.5 meq/100 g, respectively. HEU-type minerals can
be distinguished either by a Si/Al ratio or arrangement of extra framework cations
within the crystal structure of these minerals
Reclamation methods and their outcomes in Serbian mining basins
No full textThe reclamation plan is introduced in the early planning phase of exploitation of mineral deposits by
the national Law on mining and geological research. This way the reclamation practice is joint and
adapted to the excavation and ore processing technology in order to achieve more efficient, low cost
and sustainable solutions. However, reclamation activities in Serbian mining basins are still considered
poorly applied in practice. Non-selective deposition of overburden material, sporadically coupled with
improper technical reclamation, aggravates and slows down the process of biological reclamation and
the improvement of physical, chemical and biological characteristic of underlying Technosols. Besides,
management of reclaimed land and further maintaining of reclaimed surfaces often remains
questionable. During previous decades, although interrupted with periods of economic crisis, certain
efforts have been made towards improving the reclamation practice. Short and long-termed outcomes
of reclamation activities are achieved so that some examples of good practice may be displayed. This
is particularly reflected in the development of ecosystem processes in artificially created ecosystems,
including the development of the soil cover and the increase of biodiversity. The objective of this paper
is to give a review of the reclamation methods used in practice and the outcomes of biological
reclamation activities in some of the most important mining basins in Serbia, on base of which the
basic guidelines and directions for the adequate management measures can be given in order to
enhance the successful outcomes in future reclamation activities.
Identification of relevant publications, technical reports and unpublished sources was undertaken prior
to their systematic review. The results and the conclusions of relevant studies are summarized and
interpreted in order to answer the research questions.
Methods of reclamation in large mining basins in Serbia are described within context of ground
preparation, use of artificial covers or topsoil cover, prevailing type of biological reclamation, and
additional scientific researches. Agricultural and silvicultural approach to biological reclamation of
mining sites largely dominates in Serbia, often being coupled with ameliorative approach. As a
consequence of reclamation measures, content of nitrogen and organic matter in Technosols overly
increased in reclaimed areas, and their biogenity has generally been improved. Systematic monitoring
of reclaimed areas may provide information on soil and vegetation development that could significantly
contribute to the quality of future reclamation activities
Pharmaceutical waste managment
No full textPharmaceutical waste is hazardous waste generated in the production and trade of medicines and medical supplies (including pharmaceuticals, drugs and chemicals that are scattered prepared and unused or have expired expiration date or be rejected for any reason, as well as organic pollutants), as well as equipment used in handling. The pharmaceutical waste include medicines (finished, galenical and main medicines and pharmaceutical substances) which is out of date. Herbal, traditional and homeopathic remedies can also be considered as pharmaceutical waste, depending on their composition. Producer and owner of pharmaceutical waste shall be treated with pharmaceutical waste as hazardous waste. Waste Management aims to protect human health and the environment with handling and disposal of waste
Mineralogy and thermal properties of clay from Slatina (Ub, Serbia)
No full textThe " Slatina " deposit, Ub, Serbia was opened in 1965 and represents one of few deposits exploited by " Kopovi " a.d., Ub, company. Deposit is composed of clay layers belonging to Neogene sediments that are widespread transgressive over granitoid rocks of Cer mountain and Paleozoic and Mesozoic sediments. Clay is mostly of illite-montmorillonite-kaolinite type and they are generally used as ceramic materials while some of the layers are used as fire-resistant materials. In this study we present mineralogical and thermal characterization of two samples to determine their application as industrial materials. Chemical and mineral composition was determined using inductively coupled plasma optical emission spec-troscopy (ICP-OES), X-ray diffraction (XRD) on powder and oriented samples, infrared spectroscopy (IR) and granulometry. Cationic exchange capacity (CEC) and specific surface area (SSA) was determined using spectrophotometry and methylene blue (MB). Thermal properties where determined by gravimetry (120, 350, 600 and 1000 oC) and differential thermal analysis (DTA). Quantitative mineral composition obtained by Rietveld refinement of combined chemical and XRD data shows that the sample 1(SC) is mainly smectite-illite (45%) and kaolinite (14%) clay with 19% of quartz, 10% feldspars and 7% of limonite, while sample 2(SV) is smectite-illite (43%) and kaolinite (11%) clay with 10% of quartz, 15% feldspars and 7% of limonite. Both samples have low content of impurities (carbonate minerals). Medium grain size (µm) goes from 1.02 (SSA = 104 m2/g) for sample 1(SC) to 0.71 (SSA = 117 m2/g) for sample 2(SV) while their CEC is 12.7 and 14.9 mmol/100g for 1(SC) and 2(SV) respectively. IR spectra of the samples shows larger amount of smectite clays with quartz and carbonate minerals for both samples which is in accordance with XRD data. DTA data shows couple of events that are endothermic. First one (100-200 oC) is associated with loss of moisture and constitutive water, second (300-400 oC) with iron hydroxide minerals, third (500-600 oC) with smectite clay content with smaller separate bands of kaolinite clays while events between 800-900 oC correspond to carbonate minerals. Loss of mass after gravimetry measurement at given temperatures shows that the samples have significant amount of water in their structure (≈3 wt% (120 oC)) with larger weight loss at 600 oC (3.06 and 3.37 wt%) while total weight loss is 9.12 and 9.08 wt% for 1(SC) and 2(SV) respectively. The studied clays from " Slatina " deposit have a medium content of smectite-illite minerals with smaller amount of kaolinite mineral together with quartz and feldspars. Based on their mineral composition and characteristics, possible application should be in different types of ceramic and construction industries. REFERENCES-M. Miloševi´cMiloševi´c, M. Logar, B. Dojčinovi´Dojčinovi´c, A. Rosi´cRosi´c and S. Eri´cEri´c, 2016, Diffuse reflectance spectra of methylene blue adsorbed on different types of clay samples, Clay Minerals, (2016) 5, 1–1