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A simplified method for enhanced accuracy in calculating adsorption thermodynamic parameters
No full textThis study investigates the thermodynamic parameters of phosphate adsorption on activated carbon using the Pitzer ion-interaction model. The adsorption data were analyzed using the Langmuir and Sips models, both providing satisfactory fits. Maximum adsorption (plateau) occurred at an equilibrium phosphate concentration of 60.8 mmol⋅ dm−3 (pH = 5.1), with an adsorption capacity of 7.03 mmol⋅g−1. The Pitzer model was used to calculate the activity coefficient of phosphates, considering the influence of all ions in the solution on the adsorption plateau. The maximum degree of dissociation of H₂PO₄-(aq) ions was determined to be xd(2) = 0.0026, taking hydrolysis into account. The activity coefficient of KH₂PO₄ in the mixed solution {K₂HPO₄ + KH₂PO₄ + H₃PO₄}(aq) was found to be γ± = 0.7788, while in a pure KH₂PO₄ solution at the same ionic strength corresponding to the plateau, it is γ± = 0.7790. Given the minor difference in activity coefficient, the mixed solution could be approximated as a pure KH₂PO₄(aq) for thermodynamic analysis, which greatly simplified the calculations. The Gibbs free energy was ΔGL = − 8.6200 ± 0.0004 (kJ⋅mol−1) using the Langmuir equilibrium constant shifting to ΔGa = − 9.240 ± 0.006 (kJ⋅mol−1) when accounting for activity coefficient and the thermodynamic equilibrium constant. With the Sips model, the Gibbs free energy was ΔGS = − 9.620 ± 0.004 (kJ⋅mol−1) and further refinement using phosphate activity coefficient gave ΔGa = −10.235 ± 0.007 (kJ⋅mol−1). The absolute differences in adsorption energy were approximately 7 % (Langmuir) and 6 % (Sips), highlighting the importance of considering ionic activities
Predicting the Fate of Bisphenol A During Electrochemical Oxidation: A Simple Semiempirical Method Based on the Concentration Profile of Hydroxyl Radicals
No full textThe efficiency of electrochemical advanced oxidation processes (EAOPs) is fundamentally governed by hydroxyl-radical (•OH) generation. While direct experimental measurements of these transient species remain complex and impractical, robust computational methods for predicting their temporal profiles are notably scarce. This work presents a semi-empirical methodology based on H2O2 measuring experiments that enables indirect •OH quantification. We employed a recently developed carbon-based electrode and the priority pollutant bisphenol A (BPA) as the model system. The system achieved 92.3% BPA degradation with 84% mineralization efficiency during 5-h electrooxidation at 15 mA/cm2. Gas chromatography/mass spectrometry (GC/MS) was used for tracking BPA and detection of intermediates. On this basis, we developed a computational model that successfully predicts temporal concentration profiles of all reactive species interacting with •OH, along with degradation kinetics across current densities (10–20 mA/cm2). By incorporating predictions from the Toxicity Estimation Software Tool (T.E.S.T.), the developed model accurately simulates time-dependent evolution of relative toxicity throughout the treatment process. The presented approach has a general character and requires rather simple experimental input to predict and optimize degradation outcome in terms of input concentration, degradation time, current density, and final toxicity. Further modifications of the model would enable widening to other EAOPs systems
Cu-Sn-Pb Bimetals: Prediction of Brinell Hardness
No full textThis paper presents the results of defining the mathematical model which describes the dependence of Brinell hardness (HB) from the most influential input parameters in industrial conditions of conducting the production process of the bi-metal elements which work in oil systems of axial-piston pumps of high-pressure. Mathematical model is defined using the methods of Multiple Linear Regression Analysis (MLRA), with R2=0.726 and significant statistical reliability –VIF<2 and p<0.05, on the one-year statistical sample. Validation of the acquired model was performed using the data from the following year, collected from the process conducted under industrial conditions, rendering the same statistical reliability, with R² = 0.759
Electrochemical Recovery of Nickel from Spent Ni-Cd Batteries
No full textNi-Cd battery electrodes contain heavy metals such as Ni, Cd and Co, which must be recycled due to environmental problems. The paper presents the research results of the process of recycling Ni-Cd batteries in order to obtain electrolytic nickel by a combination of hydro and electrometallurgical processes. The optimal degree of Ni leaching (93.85%) was achieved by leaching with 2.5 M H2SO4 at a temperature of 80 °C at a ratio of solid to liquid ratio of 1:15 (S:L = 1:15) and leaching time of 5 h. 1 M DEHPA was used to remove cadmium from the leach solution. Electrolytic Ni with a purity of 99.98% was obtained from the purified solution
Synthesis and Characterization of Unsaturated Polyester Resin Using Aromatic and Aliphatic Bio-Based Monomers
No full textIntroduction: Unsaturated polyester resins are among the most widely used
polymer materials, valued for their versatile properties and broad
applicability in industries such as automotive manufacturing, plastics, and
biomedical engineering. However, the increasing environmental concerns
associated with petroleum-based polymers have prompted research into
sustainable alternatives. In this study, a bio-based unsaturated polyester resin
was synthesized using renewable monomers to reduce dependency on fossilderived materials while maintaining the desired performance characteristics. ..
Uticaj predtretmana, parametara liofilizacije, korišćenja različitih krioprotektanata na preživljavanje imobilisanih probiotika tokom postupka liofilizacije
No full textLyophilization is an excellent process to increase the shelf life of food products or preserve probiotics. Living cells prefer mild conditions, and any deviation (vacuum, high or low temperatures) leads to cell damage. This paper examined the influence of different freeze-drying process parameters on the survival of probiotic Lactobacillus plantarum immobilized on the activated charcoal pad. In specific, the process included several phases in which different pretreatments, freezing temperatures, cryoprotectants and phase durations were investigated. Activation of L. plantarum in De Man, Rogosa and Sharpe (MRS) broth before freezing, resulted in the increased initial number of living cells, but also positively affected the cell survival after the lyophilization process. Freezing the culture in liquid nitrogen did not significantly affect cell viability after lyophilization compared to deep freezing at -80 °C, while incubation of the culture in a refrigerator for 2 h before lyophilization increased the probiotic viability. Also, the prolonged duration of lyophilization from 5 to 48 h had a slight impact on probiotic viability. The use of milk showed a significant increase in culture survival, while sucrose, maltose, and trehalose showed cryoprotectant ability, but significantly lower than that of milk. The best lyophilization protocol resulting in the highest viability of L. plantarum included the culture activation by MRS incubation, followed by either deep freezing in liquid nitrogen or by precooling for 2 h at 7 °C and then deep freezing at -80 °C in milk, and ending with lyophilization for 5 h.Liofilizacija je odlična metoda koja omogućavo produženje roka trajanja prehrambenih proizvoda kao i očuvanje probiotskih kultura. Žive ćelije preferiraju blage uslove i svako
odstupanje (npr. vakuum, visoka ili niska temperatura) dovodi do oštećenja ćelija. U ovom
radu je ispitan uticaj različitih parametara kao što su predtretmani, trajanje liofilizacije, tip
smrzavanja, primena krioprotektanata na preživljavanje probiotika imobilisanih na tkaninu
od aktivnog uglja tokom procesa liofilizacije. Aktivacija L. plantarum u De Man, Rogosa and
Sharpe (MRS) bujonu pre imobilizacije značajno povećava broj živih ćelija, ali i njihovo
preživljavanje tokom liofilizacije. Zamrzavanje imobilisanih ćelija tečnim azotom nije dalo
željeno povećanje procenta preživelih probiotskih ćelija nakon liofilizacije u poređenju sa
dubokim smrzavanjem na -80 °C, dok je inkubacija ćelija 2 h u frizideru pre dubokog smrzavanja doprinela povećanju broja ćelija koje prežive liofilizaciju. Dužina trajanja (5 i 48 h)
samog procesa sušenja imala je blagi uticaj na stepen preživljavanja probiotika. Upotreba
mleka kao krioprotektanta značajno je povećala stepen preživljavanja, dok su saharoza,
maltoza i trehaloza pokazale dobru zaštitnu moć, ali znatno manju u poređenju sa mlekom.
Najviši stepen preživljavanja L. plantarum obezbeđuje procedura koja podrazumeva inkubaciju ćelija u MRS bujonu, korišćenje mleka kao krioprotektanta, inkubaciju 2h u frizideru,
duboko smrzavanje i liofilizaciju u trajanju od 5 h
Uticaji sastava i termičke obrade na tvrdoću i zatezna svojstva Hadfildovog čelika
No full textIn this paper the effect of composition and heat treatment on strength and hardness of Hadfield steel is investigated. Two different compositions of Mn12 and Mn16 steels are used with two different heat treatments: water quenching and water quenching with additional aging. Hardness, tensile strength and microstructure are analysed in 8 samples used in this research. It is concluded that effects of composition and heat treatment reflect through the microstructure in complexity. The investigation shows that these effects are much more pronounced in hardness than in the strength.U ovom radu se istražuje uticaj sastava i termičke obrade
na čvrstoću i tvrdoću Hadfildovog čelika. Koriste se dve
različite kompozicije čelika Mn12 i Mn16 sa dve različite
termičke obrade: gašenje vodom i gašenje vodom sa dodatnim starenjem. Tvrdoća, zatezna čvrstoća i mikrostruktura
analizirani su na 8 uzoraka korišćenih u ovom istraživanju.
Zaključuje se da se uticaj sastava i termičke obrade odražava kroz mikrostrukturu i da je kompleksan. Ispitivanja su
pokazala da su navedeni uticaji znatno veći na tvrdoću nego
na čvrstoću
Evaluation of the potential of Ganoderma lucidum extract for dyeing and imparting protective properties to fabrics of various chemical compositions
No full textThis study tested the potential of Ganoderma lucidum ethanol extract for dyeing and imparting protective properties to diacetate (DA), viscose (CV), cotton (CO), polyester (PES), polyamide (PA), polyacrylonitrile (PAN), silk (SILK), and wool (WO) fabrics. The extract demonstrated an half-maximal inhibitory concentration (IC50) of 298.2 μg/mL, as determined using the DPPH antioxidant assay. Ultrahigh-performance liquid chromatography-electrospray ionisation-tandem mass spectrometry (UHPLC-ESI-MS/MS) identified 35 compounds, of which seven were coloured and contributed to dyeing PA, SILK, and WO fabrics (at pH 2–6) in light to dark brown shades with yellowish tones. Dyeing experiments pointed out that SILK and WO fabrics dyed at pH 4 and 6 exhibited excellent colour fastness to washing (ΔE < 1.6), indicating strong fixation of coloured compounds from Ganoderma lucidum extract. Regardless of the dyebath pH values, PA, SILK, and WO exhibited consistently high colour strength values (K/S), ranging between 17.5 to 20.7, 14.2 to 18.5, and 18.8 to 20.2, respectively. Besides coloration properties, antioxidant activity and ultraviolet protection factor (UPF) of dyed PA, SILK, and WO were evaluated. PA fabrics dyed at pH of 2 and 4 showed higher antioxidant activity (25.4% and 27.3%, respectively) than SILK fabrics dyed under the same conditions (20.0% and 21.0%, respectively), providing slight skin protection by mitigating free radical damage. SILK dyed at pH 2 has UPF greater than 30, qualifying as ultraviolet (UV)-protective, with minimal loss of UV-blocking ability after washing. These findings demonstrate the dual functionality of Ganoderma lucidum ethanol extract for dyeing and imparting protective properties to PA and SILK fabrics
Photodegradation mechanism of Reactive Orange 16 by recyclable green Ag/ZnO
No full textTo determine the mechanism of photodegradation of the textile dye Reactive Orange16 (RO16), an Ag/ZnO nanocomposite containing 1.5 wt.% of Ag was synthesizedusing a green precipitation method from zinc acetate, silver nitrat, ethylen glycol andchitosan.Based on XRPD and HRTEM/SAED, the ZnO was obtained in wurzite form withcrystallites of 24 nm, while the formed Ag crystallized in the face-centered-cubicstructure with crystallites of 22 nm. The UV-VIS DRS analysis revealed that the bandgap of Ag/ZnO is redshifted to 3.06 eV, indicating that the Ag surface plasmonresonance (SPR) enhances the absorption of visible light. The Ag/ZnO completelydegraded RO16 within 105 minutes under simulated solar light with a rate constantof 0.047(4) min−1. PSD analysis showed that the presence of silver prevented ZnOagglomeration in suspension and also led to decreasing of the ZnO particles, whichcontributed to the better photocatalytic activity of Ag/ZnO compared to ZnO. Adetailed analysis of the mechanism revealed that the activity of the Ag/ZnOphotocatalyst was improved due to two simultaneous mechanisms: excitation by UVradiation through the Schottky junction and excitation by VIS radiation through theSPR effect.The reusability, repeatability, and reproducibility of the Ag/ZnO were tested due toits practical application. This sample showed an improvement in photocatalyticactivity after four cycles due to the enhancement in light absorption and thedecrease in agglomerate concentration. The errors for repeatability andreproducibility were 2.1 and 5.6 %, respectively.The Ag/ZnO showed an excellent photocatalytic activity, high repeatability,reproducibility, and reusability in degrading RO16, which opens the chance of itsfuture application in wastewater treatment
Fungicide residues in apples: Analysis and health risk assessment
No full textFungicides are widely used in apple cultivation to prevent fungal diseases during the
growing season and in post-harvest treatments to reduce fruit decay and minimize economic losses.
Since washing apples is often insufficient to remove fungicide residues, their ingestion may raise
health concerns, particularly for children. In this study, an LC–MS/MS method was developed for the
determination of 10 commonly used fungicides in apples available on the market in the Republic of
Serbia. The QuEChERS method was used for extraction and purification. The method showed good
linearity, repeatability, and sensitivity, with limits of quantification well below the maximum residue
limits set by relevant regulations, ensuring suitability for regulatory monitoring. Recoveries were
within the range 75%–120%. Analysis of apple samples revealed that difenoconazole and fludioxonil
were the most frequently detected fungicides, while boscalid was found at the highest concentration
(1449 μg/kg). Health risk was assessed by calculating acute, chronic, and cumulative hazard indices
to account for combined exposure to multiple fungicides. The acute/short-term dietary intake risk
assessment showed a %ARfD value > 100% for pyraclostrobin in one apple sample, indicating
potential health risk for children. Chronic and cumulative risk assessment showed that there were no long-term hazards for consumers