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Modeli otpuštanja leka iz hidrogela poli(vinil alkohol)/hitozan/gentamicin (PVA/CHI/Gent)
No full textHidrogel poli(vinil alkohol)/hitozan/gentamicin (PVA/CHI/Gent) pripremljen je fizičkim umrežavanjem disperzije poli(vinil alkohola)/hitozana i namenjen je za upotrebu kao materijal za medicinske obloge dubokih nekrotičnih rana kao što su dekubitusi. Ispitivane su fizičko-hemijske (FTIR, SEM), mehaničke i biološke (citotoksičnost, antibakterijska aktivnost) osobine. Mehanizam difuzije gentamicina iz hidrogela PVA/CHI/Gent proučavan je upoređivanjem novog dvo-kompartmentskog modela sa opštim frakcionim izvodima (GFD) i Korsmajer-Pepas, Makoid-Banakar i Kopča difuzionih modela. GFD model bolje se poklapao sa eksperimentalnim podacima od drugih modela i takođe je omogućio određivanje koeficijenta difuzije gentamicina tokom celog proučavanog vremenskog perioda
Hydrophobized limestone as filler in polymer materials
No full textThe article shows changes in certain mechanical properties of polyvinyl
chloride (PVC) depending on the quality of added limestone as a filler. Natural
limestone and limestone hydrophobicized with stearic acid were added.
Modification experiments were carried out with “wet” and “dry” processes in order
to find out the required amount of stearic acid for a complete surface coating of
limestone - degree of coating 99.90%. Coating of the limestone surface was
achieved in the “wet” process with 1.5% stearic acid, while in the “dry” process
the same degree of coating was achieved with 3% stearic acid. A significant
amount of both “wet” and “dry” modified limestone was prepared. Such a product
was added to PVC mixture in order to investigate mechanical properties of the
obtained PVC product. Research into the mechanical properties of PVC has shown
that PVC containing limestone modified by the “wet” process exhibits better
mechanical properties than that containing limestone modified by the “dry”
process. For example, PVC obtained from a mixture containing limestone modified
by the “wet” process with 1.5% stearic acid shows a better tensile strength of 54.20
MPa, while limestone modified by the “dry” process with 3% stearic acid shows a
tensile strength 53.20 MPa
Comparative Study of Activation Energy and Desulfurization Efficiency of Coal in Graphite and Dimensionally Stable Anode (DSA) Electrodes
No full textThis study investigates the electrochemical desulfurization of sulfur-rich subbituminous coal (6.96 wt.%) from the Bogovina Basin using graphite and dimensionally stable anode (DSA) electrodes. The objective was to evaluate and compare the efficacy of these electrodes under varying thermal conditions to determine the optimal operational parameters that balance desulfurization efficiency with energy consumption. Electrochemical assessments were conducted through linear sweep voltammetry (LSV) to derive polarization curves and calculate activation energies, reflecting the intrinsic energy barriers of the desulfurization reactions. These tests were performed across a temperature range from 30°C to 70°C, providing insight into the thermally activated nature of these processes. The results demonstrated that the DSA electrodes outperformed the graphite electrodes in several key areas. Notably, DSA electrodes exhibited higher current densities at equivalent temperatures and potentials, indicating a more robust electrochemical activity conducive to higher desulfurization rates. Moreover, activation energy analysis revealed that DSA electrodes operate with significantly lower energy barriers, facilitating easier and more efficient reaction initiations. Energy consumption metrics were critical in evaluating the operational costs associated with each electrode type. The DSA electrodes were found to consume less energy per kilogram of sulfur removed, particularly at an optimal temperature of 50°C, which was identified as the most energy-efficient operational point. At this temperature, the DSA electrodes achieved peak desulfurization efficiency with the most favorable balance between energy input and desulfurization output. The study substantiates the superiority of DSA electrodes over traditional graphite electrodes for coal desulfurization processes, particularly at the optimal operational temperature of 50°C. The findings highlight significant potential for enhancing the sustainability and cost-effectiveness of coal desulfurization technologies, suggesting a paradigm shift towards the adoption of DSA electrodes in industrial applications to achieve more efficient and environmentally friendly outcomes
Morphology and structure of electrolytically produced zinc dendrites from the alkaline electrolyte
No full textThe alkaline electrolytes of zinc are widely used in a Zn-air secondary batteries which represent promising candidate for energy storage with many advantages relative to the other types, such as Li-air, Al-air, and Mg-air batteries. These advantages are related with an abundance of Zn, low toxicity, and low cost, as well as by the fact that Zn possess a relatively high specific energy density. One of the largest problems in a development of Zn-air batteries is dendritic growth caused by the uneven deposition of zinc in the charging process. The solving of this problem implies the good knowledge of all phenomena related with Zn deposition, and regarding it, this study aims to establish a correlation between morphology and structure of electrolytically produced Zn irregular forms, especially Zn dendrites. Zinc was electrodeposited potentiostatically from the concentrated electrolyte (0.35 M ZnO in 6.0 M KOH) at overpotentials belonging to the end of the plateau of the limiting diffusion current density (η = 160 mV), and to the zone of the fast growth of the current density after the end of the plateau of the limiting diffusion current density (η = 220 and 280 mV). Morphology and structure of Zn particles were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively.
Morphology of Zn electrodeposits changed with the increase of overpotential of the electrodeposition from regular hexagonal and other regular crystal forms to the mixture of 2D (two dimensional) and 3D (three dimensional) dendrites. The increase of overpotential of the electrodeposition led to an appearing and then intensification of hydrogen evolution reaction as a parallel reaction during Zn electrodeposition at the high overpotentials.
In spite of various shapes, Zn particles electrodeposited at all three overpotentials exhibited the strong (002) preferred orientation. The explanation for this predominant preferred orientation can be found in an analogy with a electrolytic growth of lead dendrites from the concentrated electrolyte. Although these two metals belong to different types of crystal lattice (Pb - face-cantered cubic type, and Zn - hexagonal close packed type), the common characteristic of dendritic growth is the preferred orientation in a crystal plane with the lowest surface energy. Namely, during growth of dendrites, this plane survives, while other crystal planes with the higher surface energy values disappear, causing the predominant orientation of Zn disperse forms in (002) crystal plane. In this way, interior of the Zn dendrites is constructed from (002) crystal plane, while tips and edges of Zn dendrites and other types of particles are from other crystal planes
Natural minerals and its influence on pH values of contaminated solutions
No full textRadionuclides such as lead, zinc, uranium and cadmium are major pollutants of agricultural
areas. In order to ensure the cultivation of healthy food, it is necessary to controle the mobility of
these heavy metals. The elimination of this elements with natural mineral raw materials such as
zeolite and apatite is extremely important from the aspect of health protection and healthy food production. Aim of this research was to determining the possibility of apsorption of mineral raw
materials of heavy metals. The investigation was performed in columns under constant pressure
with two pH values (5.0 and 7.0). The concentration of heavy metals was 300 mg/l. The
absorption monitoring time was 30, 60, 90, 120 and 180 min. Results showed a significant
change pH value of the filtrate as a function of the absorption time. It was found that both apatite
and zeolite significantly immobilized lead at both filtrate pH values. Uranium immobilization
was better performed in columns with apatite, zeolite showed better properties in cadmium
immobilization, and tests on a solution contaminated with zinc showed that both apatite and
zeolite show similar affinity. The obtained results were statistically processed using the method
of two-factor analysis of variance with repeated measurements
Carbonization of Invasive Plant Species—Novel Route for Removal of Active Pharmaceutical Ingredients via Adsorption
No full textThe development of efficient adsorbents for sustainable adsorption processes is required in environmental studies. Here, we propose using carbonized Ailanthus altissima leaves as a novel adsorbent, derived from invasive species that threaten biodiversity. Biochar was prepared by pyrolysis at 500 °C, activated with ZnCl2 and tested for the target adsorbates—active pharmaceutical ingredients (APIs). A range of characterization techniques were employed—FTIR, SEM, XPS and Raman spectroscopy—and the adsorption of representative APIs was analyzed. The adsorption kinetics revealed that the adsorbent reached equilibrium within a 3 h period. The adsorption capacities for the selected model substances ranged from 59 mg g−1 for atenolol to 112 mg g−1 for paracetamol, while the highest values were recorded for ketorolac and tetracycline at over 130 mg g−1. The excellent retention is ascribed to the developed surface area, the availability of oxygen surface functional groups and the aromatization of the biochar. The proposed biochar, which is obtained in a sustainable process, proves to be a highly efficient adsorbent for selected pharmaceuticals
Mogućnost dobijanja koncentrata bentonita iz ležišta „Bijelo Polje“bar postupcima klasiranja
No full textU ovom radu je prikazan deo tehnoloških ispitivanja, koncentracije rovne bentonitske rude iz ležišta „Bijelo Polje“-Bar koja su u ITNMS-u obavljena na 3 uzorka. Posle određivanja granulometrijskog i mineraloškog sastava polaznih uzoraka bentonita, ispitivana je mogućnost njihove koncentracije primenom postupaka mokrog klasiranja, Postupcima mokrog klasiranja dobijene su dve vrste koncentrata klase krupnoće -0,075+0,00mm I 0,037+0,00mm za sva tri ispitivana uzorka. Dobijeni koncentrati su ispitivani rendgenskom difrakcionom analizom da bi se utvrdio njihov mineralni sastav, i laserskom difrakcionom analizom radi utvrđivanja njihovog granulometrijskog sastava. Na osnovu dobijenih rezultata obavljenih analiza vršena je validacija dobijenih koncentrata bentonita i samog postupka mokrog klasiranja
Reapplication Potential of Historic Pb–Zn Slag with Regard to Zero Waste Principles
No full textThe presented work offers an innovative process scheme for valorizing Pb-Zn slag, which involves crushing, grinding, and separation techniques to concentrate valuable components (non- ferrous metals). This methodology could have a significant impact on the global beneficiation of metallurgical slags since it is significantly more simple, environmentally friendly, and cost-effective than standard pyro- and hydrometallurgical procedures. According to previous physicochemical and mineralogical studies, Pb-Zn slag is a valuable secondary raw material. This inhomogeneous technogenic resource contains substantial amounts of non-ferrous metals (Pb, Zn, Cu, and Ag). However, laboratory tests have indicated that the Pb-Zn slag contains highly uneven amounts of valuable metals, ranging from several g/ton to tens of g/ton. The main issue is that traditional metallurgical procedures for releasing beneficial elements are not commercially viable since the elements are “trapped” within the amorphous aluminosilicates or intergrowths of alloy grains and glassy phases. Gravity concentration (Wilfley 13 shaking table) and magnetic separation (Davis separator and disk separator) were used to obtain the final concentrate following comminution and grindability testing. The gravity concentration proved more effective. Namely, magnetic separators could not process nor adequately separate beneficial non-ferrous elements because they were merged together with iron-bearing minerals and aluminosilicates in amorphous Pb-Zn slag grains. With the gravity concentration approach, 12.99% of the processed slag belonged to ∆T fraction (concentration of non-ferrous metal alloys), while remaining 87% corresponded to the tailings fraction (∆L). The total amounts of recovered Pb, Zn, Cu, and Ag from ∆T and ∆L fractions were 5.28%, 6.69%, 0.58%, and 76.12 ppm and 1.22%, 6.05%, 0.43%, and 15.26 ppm, respectively. This streamlined approach to valorizing Pb-Zn slag can reduce the need for hazardous chemicals used in hydrometallurgical refinement operations, as well as the extremely high temperatures required for pyrometallurgical processing. This is the first study to investigate the viability of this novel methodology, which involves the direct examinations of the Pb-Zn slag feed with various alternative technologies for separation and concentration. After extracting the valuable metals, the amorphous aluminosilicate part of the Pb-Zn slag can be reapplied as an alternative raw material in the building sector, adding to the circularity of the suggested approach
Procedures for obtaining products based on zeolite minerals
No full textThere are several zeolite surface modifiers. For example, modification of the zeolite surface with primary amines and quaternary ammonium ions [1]. The organomineral complex is created by the activation of minerals with surface-active substances [2,3] . The Institute for Technology of Nuclear and Other Mineral Raw Materials (ITNMS) in Belgrade started several years ago the development of new modern technologies and new materials for agriculture as well as materials for fertilization and melioration of degraded and contaminated soils. This paper gives a brief description of the preparation of surface-modified zeolite minerals. Also a schematic representation of the technological process of obtaining the assortment of zeolites (Minazel and Minazel Plus) [4]
Preliminary study of nickel extraction from wild Odontarrhena muralis from Serbia
No full textThe industrial development will influence the demand and price of nickel in the coming years
which opens the possibility for the use of innovative ways for its exploitation from secondary
resources. Phytomining of nickel is a prospective in situ technology that uses plants with natural
hyperaccumulating capabilities for this element. This study represents application of currently
established and developed hydrometallurgical methods on wild populations of nickel
hyperaccumulator from Serbia and explores the impact of recrystallization on the purity of the
final product. The study confirms that nickel salts (ammonium nickel sulfate hexahydrate) can be
synthesized from the wild Odontarrhena muralis that is naturally occurring on the ultramafic
sites in West Serbia. Due to the small starting mass for the harvested biomass the preliminary
experiments were separated into two series, which yielded 7,3 g and 5,2 g nickel salts of 60%
and 73% purity, before recrystallization. However, after recrystallization their mass was reduced
to 5,45 g and 3,89 g respectively, but both their purities were maximized to 99,9%. More
comprehensive studies with larger biomass and proper cultivation on ultramafic soil are needed
in future to fully explore the potential for the development of Ni phytomining in Serbia