Search

In the proposed study, agro-waste biomass oat straw (OS) was considered a potential adsorbent for Cu(II), Zn(II), and Se(IV) removal from aqueous solutions. In order to obtain material with better adsorption abilities, the OS was modified by a deep eutectic solvent (DES). Structural changes caused by the applied modification route were considered by pHpzc, SEM, FTIR, and DSC/TG analysis. These methods discovered that lignocellulosic biomass degradation and material functionalization were achieved by DES treatment. Preliminary adsorption tests showed an over fourfold increase in capacity upon modification. The kinetic parameters implied that adsorption on modified material followed the pseudo-second-order kinetic model. Different isotherm models were applied to experimental data, while the Sips isotherm model best describes the equilibrium of the adsorption process on the tested modified material. According to this isotherm model, the maximum achieved adsorption capacities of Cu(II), Zn(II), and Se(IV) were 48.21, 55.06, and 87.85 mg/g, respectively. The summarized experimental results revealed that the adsorption process of selected cations on modified OS was predominantly caused by chemisorption, while, in addition to chemisorption, electrostatic forces were also responsible for Se(IV) removal. Desorption test showed that the prepared material could be reused for at least 3 cycles, with minimal efficiency loss. Briefly, this study reinforces that DES-modified agro-waste biomass could be used as a promising adsorbent for cations and oxyanions from wastewater.

Research background. In the recent years, considerable attention has been given to selenium status since its deficiency is linked with various disorders and affects at least 13% of world population. Additionally, mushrooms are known to possess pronounced capacity for absorption of various micronutrients, including Se, from soil/substrate. Here, we investigate the possibility of using Se-rich zeolitic tuff as a supplement for production of selenized mushroom. Furthermore, the impact of the enrichment on the activity of antioxidant enzymes and biological potential of Coriolus versicolor medicinal mushroom is studied. Experimental approach. Se(IV)- and Se(VI)-modified natural zeolitic tuff from the Serbian deposit Zlatokop was used as supplement for mushroom cultivation. To examine the effectiveness of selenium enrichment, we determined total selenium with inductively coupled plasma mass spectrometry (ICP-MS), together with the activity of antioxidant enzymes in fresh fruiting bodies and biological potential of methanolic extracts. Antioxidant activity was evaluated using the appropriate tests for: inhibition of lipid peroxidation, DPPH free radical scavenging assay, Fe(III)-reducing antioxidant power assay and ability of chelating Fe2+ ions. The antibacterial activity against foodborne pathogens was measured by broth microdilution assay. Additionally, chemical composition of the prepared extracts was studied using UV-Vis and Fourier transform infrared (FTIR) spectroscopy. Results and conclusions. Content of selenium detected in biofortified C. versicolor was even 470 times higher than in control on dry mass basis ((140.7±3.8) vs (0.3±0.1) µg/g), proving that Se-rich zeolitic tuff is an excellent supplement for mushroom production. Furthermore, the results of monitoring the activity of antioxidant enzymes revealed that most of the Se-enriched mushrooms exhibited higher superoxide dismutase (SOD) and catalase (CAT) and lower glutathione peroxidase (GSH-Px) activities than control. Due to higher amounts of enzymes, which can quickly catalyze the reduction of superoxide radicals, the quality of selenium-enriched mushrooms is preserved for a longer period of time. Investigation of biological potential indicated that Se-enriched mushroom methanolic extracts, generally, expressed enhanced antioxidant properties. Additionally, extracts showed antibacterial activity against all tested pathogenic microorganisms. Novelty and scientific contribution. Cultivation of mushrooms on Se-enriched zeolitic tuff is a new technological approach for obtaining Se-fortified food/supplements with enhanced antioxidant and antibacterial activities., Pozadina istraživanja. Posljednjih se godina sve veća pažnja posvećuje udjelu selena u organizmu, s obzirom na to da se nedostatak ovog elementa u prehrani povezuje s pojavom mnogih bolesti koje pogađaju najmanje 13 % svjetske populacije. Prethodna su istraživanja pokazala da gljive uspješno apsorbiraju različita mikrohranjiva iz tla odnosno supstrata, uključujući i selen. Svrha je ovog rada bila ispitati mogućnost primjene zeolitnog tufa bogatog selenom kao dodatka u proizvodnji gljiva obogaćenih selenom. Uz to, ispitan je utjecaj obogaćivanja na aktivnost antioksidacijskih enzima i biološki potencijal medicinske gljive Coriolus versicolor. Eksperimentalni pristup. Prirodni zeolit bogat Se(IV) i Se(VI) iz rudnika Zlatokop (Srbija) upotrijebljen je kao izvor selena u proizvodnji gljiva na čvrstom supstratu. Za utvrđivanje uspješnosti obogaćivanja gljive selenom ispitani su sljedeći parametri: ukupni udjel selena, i to masenom spektrometrijom s induktivno spregnutom plazmom (ICP-MS), aktivnost antioksidacijskih enzima u svježim plodištima gljiva, te biološki potencijal metanolnih ekstrakata. Antioksidacijska aktivnost ispitana je sljedećim metodama: inhibicijom lipidne peroksidacije, mjerenjem sposobnosti hvatanja slobodnih DPPH radikala, metodom FRAP i određivanjem sposobnosti keliranja iona željeza. Antibakterijski učinak ekstrakata na patogene iz hrane ispitan je mikrodilucijskom metodom. Nadalje, kemijski je sastav ekstrakata ispitan pomoću UV-Vis i Fourier transformirane infracrvene spektroskopije (FTIR). Rezultati i zaključci. Udjel selena u gljivi Coriolus versicolor obogaćenoj selenom bio je i do 470 puta veći nego u kontrolnom uzorku ((140.7±3.8) naspram (0.3±0.1) µg po g suhe tvari), što potvrđuje da se zeolitni tuf bogat selenom može uspješno primjeniti za obogaćivanje gljiva selenom. Praćenjem aktivnosti antioksidacijskih enzima utvrđeno je da većina uzoraka gljiva obogaćenih selenom ima veću aktivnost superoksid dismutaze (SOD) i katalaze (CAT) te manju glutation peroksidaze (GSH-Px) od kontrolnog uzorka. Zbog veće aktivnosti enzima koji mogu brže katalizirati dismutaciju superoksid radikala, gljive obogaćene selenom mogle bi dulje zadržati svoju kakvoću. Ispitivanjem biološkog potencijala utvrđeno je da metanolni ekstrakti gljiva obogaćenih selenom imaju izraženija antioksidacijska svojstva. Osim toga, ekstrakti su inhibirali rast svih ispitanih patogenih mikroorganizama. Novina i znanstveni doprinos. Uzgoj gljiva na zeolitnom tufu bogatom selenom predstavlja novi tehnološki pristup proizvodnji hrane odnosno suplemenata obogaćenih selenom s pojačanom antioksidacijskom i antibakterijskom aktivnošću.

The goal of this research is to investigate the effect of SrO and La2O3 addition on the crystallization characteristics and sintering behavior of polyphosphate glasses. Differential scanning calorimetry (DSC), hot stage microscopy (HSM), X-ray diffraction (XRD), and scanning electron microscopy (SEM) methods were used to investigate the crystallization and sintering behaviors of glasses. The addition of SrO and La2O3 (1 or 5%), at the expense of phosphate mole fraction in polyphosphate bioactive glass, raises the characteristic temperature of glasses, and resistance to crystallization. Furthermore, the temperature of maximal shrinkage increases with the addition of SrO and La2O3. Surface crystallization is the dominant mechanism of crystallization in all samples. All glasses show complex crystallization leading to the formation of several crystalline phases. Sintered phosphate glass–ceramic containing bioactive β-CaP2O6, α-Ca3(PO4)2, and β-Ca3(PO4)2 phases were successfully prepared.

– The maintenance and reliability of the signaling system are one of the key factors when it comes to the safety of rail transport. The objectives of this paper are to define a prediction model for the failure of railway signaling devices. The obtained results can significantly help in maintaining. Keywords – Maintenance, Railway signalling, Failure, Artificial neural network.

Modern problems of the Earth’s population are increasing in the areas related to the basic concepts of survival of living beings, but also with opposite views, if parallels are made between energy and ecology. Many new technologies are searching for their way towards development and must be viewed from several points of view. In this paper, the issue is addressed through modern laser techniques in terms of obtaining energy for various purposes concerning selected roles in medicine, as well as the impact on flora, fauna and as a support to other technologies both classical and modern. Contemporary attributes of lasers and other quantum generators in terms of coherence, power and intensity densities have significantly increased, although some predictions from the time of the first quantum generator masers, like gammarasers (and X raser) are still relatively far from commercial concepts. Some of the possible contemporary implementations of quantum generators in measurements control and processing schemes, along with other possible applications of various laser types, have been estimated. The paper focuses on the characterization of today’s problems with Covid-19 virus, only from the engineering point of view. The lexical side of the issue is also included, as well as the social management needs with the application of modern technologies, including help from natural sciences.

By-products from zinc hydrometallurgy are classified as hazardous waste with strong leaching toxicities. Even though numerous research papers are dedicated to valorizing valuable metals in it, the primary management route is still disposal or partial reuse, such as the Waelz process. Presented experimental research investigates possibilities of sulfidization and further processing as a technologically sustainable route for valuable metals valorization from non-standard jarosite-PbAg sludge. The comprehensive thermodynamic analysis was done by HSC Chemistry®, through optimizing process parameters, i.e., temperature, sulfur addition, and selection of possible additives. Technological possibility of magnetic separation, flotation, and smelting of sulfidized material was also investigated, the results were below the values that allow practical application, due to the obtained texture of sulfidized jarosite, which does not allow the liberation of minerals. Smelting tests were performed on sulfidized jarosite with sulfur and without and with carbon as additive. By smelting sulfidized jarosite-PbAg sludge with added carbon in sulfidization stage at 1375 °C, obtained products were matte, slag, raw lead, and dust in which base, critical, and slag forming components were valorized. Valuable metals were concentrated in smelting products so as to enable further processing, which also could be interesting in the case of treatment of complex, polymetallic, and refractory primary materials, which represent a significant contribution to the circular economy.

This paper presents an experimentally-proved hydrometallurgical process for selective metals recovery from the waste-printed circuit boards (WPCBs) using a combination of conventional and time-saving methods: leaching, cementation, precipitation, reduction and electrowinning. According to the results obtained in the laboratory tests, 92.4% Cu, 98.5% Pb, 96.8% Ag and over 99% Au could be selectively leached and recovered using mineral acids: sulfuric, nitric and aqua regia. Problematic tin recovery was addressed with comprehensive theoretical and experimental work, so 55.4% of Sn could be recovered through the novel physical method, which consists of two-step phase separation. Based on the results, an integral hydrometallurgical route for selective base and precious metals recovery though consecutive steps, (i) Cu, (ii) Sn, (iii) Pb and Ag, and (iv) Au, was developed. The route was tested at scaled-up laboratory level, confirming feasibility of the process and efficiencies of metals recovery. According to the obtained results, the proposed hydrometallurgical route represents an innovative and promising method for selective metals recovery from WPCBs, particularly applicable in small scale hydrometallurgical environments, focused on medium and high grade WPCBs recycling.