Технолошки факултет [Научни радови] / Faculty of Technology [Scientific papers]
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- СтавкаComparison of the Bacterial Inactivation Efficiency ofWater Activated by a Plasma Jet Source and a Pin-to-Pin Electrode Configuration Source(MDPI, 2023) Čobanović, Radovan; Maletić, Dejan; Kocić-Tanackov, Sunčica; Čabarkapa, Ivana; Kokić, Bojana; Kojić, Predrag; Milošević, Slobodan; Stulić, Višnja; Vukušić Pavičić, Tomislava; Vukić, MilanIn this comparative study, the bacterial inactivation efficiency of plasma-activated water (PAW) generated by two distinct plasma reactors, one utilizing a nitrogen plasma jet electrode and the other a hybrid argon plasma reactor, was explored. The present study involved the assessment of antimicrobial activity against suspensions of three Gram-positive and three Gram-negative bacterial strains in their planktonic cell state. Bacterial suspensions were introduced into PAW five days after generation. Subsequently, the viability of the bacteria was assessed at various time intervals, specifically at 0.5, 1, 3, 5, 10, and 24 h, in order to evaluate the effect of inactivation. Structural changes in bacteria after PAW treatment were assessed using a scanning electron microscope (SEM). The physicochemical properties of PAW, including pH, conductivity, and concentrations of H2O2, NO2 -, and NO3 - during aging were measured. The present study demonstrated the effective inactivation of the tested bacterial strains by PAW. Gram-positive bacteria displayed greater resistance compared to Gram-negative species, with the lowest reductions in bacterial counts observed for B. cereus, and the highest for Escherichia coli O157:H7. Morphological damage was evident across all bacterial species examined. Physicochemical measurements showed slow decay of the reactive species in the aging process. This study illustrated the potential utility of PAW as an alternative disinfectant.
- СтавкаExperimental and modeling studies of mass transfer and hydrodynamics in a packed bed absorption column for CO2 – water system(Association of the Chemical Engineers of Serbia, 2023) Balaban, Dario D.; Nikolovski, Branislava G.; Perušić, Mitar D.; Tadić, Goran S.This paper presents research on hydrodynamics and mass transfer in a packed absorption column. Experimental data on dry column pressure drop, flooding point, and efficiency of absorption of CO2 in water is obtained on a lab-scale absorption column packed with Raschig rings. Auxiliary parts of equipment together with chemical analyses provide simple monitor-ing and collecting the data. All obtained data were used to test different mathematical models for a given problem, i.e. for determination of the dry column pressure drop, flooding point and the overall gas transfer unit height. For dry column pressure drop, models developed primarily for packed columns described the data the best, with the Billet model generating a 6.54 % mean error, followed by Mackowiak and Stichlmair models. In flooding point calculations, empirical models were tested and models of Lobo, Leva and Takahshi gave the best results. Mass transfer (absorption) experiments gave expected results, since absorption efficiency increased with the increase in the liquid/gas flow rate ratio, i.e. with approaching the flooding point. The Onda’s model was used to calculate partial mass transfer coefficients in liquid and gas phases based on which the height of the overall gas transfer unit was estimated and subsequently compared with the experimental data. Deviation of calculated and experimental results for the height of the overall gas transfer unit is in the expected range of 0-20 %, with mean value of 15.5 %. In conclusion, the available models for determination of the investigated hydrodynamics and mass transfer parameters in packed absorption columns gave adequate results in comparison to the experimental values.
- СтавкаGliadin Proteins in Muffins with Quinoa Flour(2024) Gojković Cvjetković, Vesna S.; Škuletić, Dragana M.; Marjanović-Balaban, Željka R.; Vujadinović, Dragan P.; Rajić, Danijela Z.; Tomović, Vladimir M.Partial replacement of wheat flour in foodstuffs is of great importance in the food industry. Muffins are a type of semi-sweet cake that is traditionally made from wheat flour. They are especially favored by children and senior citizens. Muffins have a long shelf life, which also contributes to their popularity. However, gluten, the main protein in wheat flour, is commonly associated with celiac disease. Gluten consists of two fractions: gliadins and glutenins. In this experiment, the original muffins contained 100% wheat flour. Then, we replaced a portion of wheat flour with 25, 50, and 75% quinoa flour. The samples were stored for 0, 2, and 4 weeks. After that, gliadin proteins were extracted with 70% (v/v) ethanol. We separated gliadin using a high-performance liquid chromatograph (Agilent Technologies 1260 Infinity, USA) and measured the total amount of gliadin protein and the amount of gliadin proteins per fraction. The absorbance tests were conducted at 210 nm. The gliadin protein content was significantly reduced to the wheat vs. quinoa ratio of 50:50 because quinoa is gluten-free, even though it is rich in protein. During the storage time of 0, 2, and 4 weeks, the protein content fell down in the samples with the wheat vs. quinoa ratios of 100:0, 75:25, and 50:50. However, the muffins with 25% wheat flour and 75% quinoa demonstrated an increase in gliadin content. The results obtained could be a good starting point for the development of high-fiber, gluten-free, and more nutritionally valuable muffins.
- СтавкаCeria Particles as Efficient Dopant in the Electrodeposition of Zn-Co-CeO2 Composite Coatings with Enhanced Corrosion Resistance: The Effect of Current Density and Particle Concentration(MDPI, 2021) Riđošić, Marija; Bučko, Mihael; Salicio-Paz, Asier; García-Lecina, Eva; Živkovic, Ljiljana S.; Bajat, Jelena B.Novel Zn-Co-CeO2 protective composite coatings were deposited successfully from chloride plating solutions. Two different types of ceria sources were used and compared: commercial ceria powder and home-made ceria sol. Electrodeposition was performed by a direct current in the range of 1–8 A dm2. Two different agitation modes were used and compared, magnetic stirring and ultrasound-assisted stirring (US). The influence of magnetic stirring on the stability of the related plating baths was evaluated via a dynamic scattering method. The results pointed to better stability of the prepared ceria sol. The morphology of the composite coatings was examined by scanning electron microscopy (SEM), and particle content was determined by energy-dispersive X-ray spectroscopy (EDS). The results showed that the increase in the deposition current density was not beneficial to the coating morphology and particle content. The corrosion behavior of the Zn-Co-CeO2 composite coatings was analyzed and compared by electrochemical impedance spectroscopy and polarization resistance. The ultrasound-assisted electrodeposition at small current densities was favorable for obtaining composite coatings with enhanced corrosion stability. The protection was more effective when US was applied and, additionally, upon utilization of ceria sol as a particle source, which was revealed by higher polarization resistance and greater low-frequency impedance modulus values for sol-derived composite coatings deposited under ultrasound.
- СтавкаMorphology and growth of electrodeposited silver powder particles(Elsevier, 2007) Maksimović, V. M.; Pavlović, Lj. J.; Tomić, M. V.; Jović, V. D.The effect of overpotential pulsing and periodic current reversal on the morphology of silver powders was investigated using a scanning electron microscope (SEM). It is shown that the profile of pulses or current reversal determines the micromorphology of the electrodeposited silver particles. Generally, three forms of silver were detected: (1) dendrites, (2) equiaxial crystals (independent and/or agglomerates) and (3) rods. The shape of particle seems to be the result of an interplay between the surface energy and growth kinetics.