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The microstructure–property relationship in poly(methyl methacrylate) PMMA composites is very important for understanding interface phenomena and the future prediction of properties that further help in designing improved materials. In this research, field emission scanning electron microscopy (FESEM) images of denture PMMA composites with SrTiO3, MnO2 and SrTiO3/MnO2 were used for fractal reconstructions of particle agglomerates in the polymer matrix. Fractal analysis represents a valuable mathematical tool for the characterization of the microstructure and finding correlation between microstructural features and mechanical properties. Utilizing the mathematical affine fractal regression model, the Fractal Real Finder software was employed to reconstruct agglomerate shapes and estimate the Hausdorff dimensions (HD). Controlled energy impact and tensile tests were used to evaluate the mechanical performance of PMMA-MnO2, PMMA-SrTiO3 and PMMA-SrTiO3/MnO2 composites. It was determined that PMMA-SrTiO3/MnO2 had the highest total absorbed energy value (Etot), corresponding to the lowest HD value of 1.03637 calculated for SrTiO3/MnO2 agglomerates. On the other hand, the highest HD value of 1.21521 was calculated for MnO2 agglomerates, while the PMMA-MnO2 showed the lowest Etot. The linear correlation between the total absorbed impact energy of composites and the HD of the corresponding agglomerates was determined, with an R2 value of 0.99486, showing the potential use of this approach in the optimization of composite materials’ microstructure–property relationship.

Predloženo tehničko rešenje opisuje tehnološki postupak za dobijanje aerogelova skroba velike poroznosti. Ovim tehničkim rešenjem prevazilaze se ekološki problemistvaranja i akumulacije otpada. Aerogelovi su proizvedeni od biokompatibilnih materijalaiz obnovljivih izvora upotrebom zelenog medujuma (natkritičnog ugljen(IV)-oksida). Zeleni medijum se u potpunosti uklanja iz finalnog proizvoda i može da se reciklira nakon proizvodnje materijala.Predloženim tehnološkim postupkom proizvodnje omogućava se ušteda vremena i energije za proizvodnju polisaharidnih aerogelova koji imaju poroznost do 82%.Dobijeni aerogelovi se mogu upotrebiti u medicini za tretiranje vlažnih rana jer apsorbuju do 420% okolne tečnosti.Vlažne rane proizvode značajnu količinu eksudata ili tečnosti i njihov tretman je ključan za promovisanje pravilnog zarastanja i sprečavanje infekcija. Dodatno,usled biodegradabilnosti skroba korišćenjem proizvedenih aerogelova izbegava se akumulacija otpada nakon upotrebe istog.

Aerogels are materials with high specific surface area and high porosity, which can be produced from polysaccharides such as starch [1,2]. Starch is an abundant and low-cost polymer with versatility in processing. Aerogel properties are influenced by the process parameters including starch-to-water ratio, gelatinization temperature (T), selection of non-solvent for water replacement in hydrogels, selection of drying method, drying pressure (P) and T, etc. [1,2]. Supercritical drying, which employs supercritical carbon dioxide (scCO2), is an environmentally friendly process that allows relatively fast production of aerogels. Despite the superior properties of starch aerogels, they do not express biological activity. This can be overcome by the incorporation of bioactive compounds (BCs) into aerogels using the supercritical impregnation (SCI) process [3,4]. SCI implies the dissolution of BCs in scCO2, diffusion of BC-scCO2 solution into a polymer matrix, possible chemical or physical interaction of BC with polymer, and complete removal of scCO2 from the BC-polymer after a decrease of P and T to atmospheric. This process allows one-step production of solvent-free added value materials at relatively low T and the incorporation of high amounts of BC with various biological activities. Aerogels can be impregnated with pharmaceutical drugs but also with natural BCs (single or mixture) such as plant extracts [3,4]. To produce aerogels, 10 g of cornstarch (amylose content 20−30%, HeMoss, Serbia) was mixed with 100 mL of distilled water, gelatinization T was changed from 70 to 100 °C, water contained in hydrogels was replaced with acetone or ethanol during 1 or 5 days, drying P was varied from 8 to 20 MPa while drying T was 35 or 40 °C. Drying of gels was performed in a 25 mL high-pressure view cell while impregnation of aerogels with BCs was performed in a 280 mL high-pressure unit (Eurotechnica GmbH, Germany). Developed aerogels were tested as possible carriers of hemp and

The possibility of using waste tailings produced by flotation in the lead and zinc mine of Grot, Serbia as a potential source of secondary mineral raw materials was examined. The aim of the research was primarily to carry out a detailed characterization in order to determine the dominant minerals, and, for the first time, to trace the changes occurring in the unit cells of the minerals present in that deposit. There was also a need to determine the exact proportions of the present mineral phases for their further application and utilization as natural resources in environmental protection. Samples were taken from three different sections of tailings: the crest of dam (JKB), outlet pipe of the flotation facility (JOF) and hydrocyclone overflow (JHC). Granulometric separation was performed to facilitate the extraction of certain minerals from waste. The results showed that all samples mainly contained quartz, clinochlore, calcite, albite, pyrite and biotite, but their ratios in each sample varied significantly. After characterization, samples were separated into different fractions and their mineralogical compositions were determined. Depending on the fraction, the mineralogical compositions also changed. Mineralogy and geochemical analysis indicate that waste tailings can be used as a secondary mineral raw materials source applicable in various industries.

This study presents the characterization of waste vitreous enamel generated during the production process of heating devices in a factory in Southeast Europe. The sample was analyzed for chemical composition and concentrations of heavy metals using inductively coupled plasma optical emission spectroscopy (ICP-OES), while the mineralogical composition was determined using X-ray diffraction (XRD). The functional groups were recorded using DRIFT spectroscopy, and the morphological and microstructural properties were investigated using FESEM measurements. The results showed that the sample waste vitreous enamel contains high levels of heavy metals and must be classified as hazardous waste. Quartz was found to be the most represented mineral in the sample, while oxides of metals Sb, Fe, Ti, and Cu appeared in the form of supporting minerals. The DRIFT spectra showed the presence of silicates, organic materials, and OH groups in Ti(IV)-OH crystal structure. The FESEM analysis revealed different sizes of particles mainly with polygonal forms and pronounced edges corresponding mostly to the silica and the alumina. These findings can contribute to the development of strategies for the safe and sustainable management of waste vitreous enamel.

The sepiolite/ZrO2 composites were prepared by sepiolite (Sep) modification with zirconium propoxide in toluene at room temperature for 24 h (Sep–ZrI) or 95 °C for 4 h (sample Sep–ZrII). The efficiency of the obtained composites for the removal of phosphate from aqueous solutions at initial pH = 4 and pH = 8 was investigated. Characterization of the samples shows that synthesis at a higher temperature for a shorter time provides a slightly higher content of amorphous Zr phase, which is deposited on the sepiolite fibers as a thin layer and agglomerated nanoparticles. Compared to Sep, the composites have a lower point of zero charge and higher specific surface area and pore volume. The adsorption kinetics follow the pseudo second-order model. The adsorption capacities of the composites are approximately the same at both initial pH and higher at initial pH = 4 than at pH = 8. The XPS and ATR-FTIR of Sep–ZrI before and after adsorption identifies the formation of inner-sphere complexes as the mechanism of phosphate adsorption. The slow release during desorption with NaOH solution confirms the strong bonds of the phosphates with the surface of the composites.

Waste vitreous enamels from the heating device production process were used for partial replacement of cement in the mortar and concrete production industry. This waste, due to the high content of heavy metals, is classified as hazardous waste. At the same time, waste vitreous enamels possess pozzolanic activity and belong to class 15 (WEP—generated during the production process of heating devices, premix technology), that is 5 (WETM—generated during the production process of heating devices, classic technology) of pozzolanic materials. The purpose of this research was to develop new composites from these wastes to reduce the deposition of the toxic compounds and reduce their environmental impact. The chemical and physical-chemical characterization and pozzolanic activity of the raw waste materials were studied by a mixture of complementary methods, as well as physical-mechanical characterization and a leaching test of mortar and concrete composites. The results indicate that the replacement of cement with WEP up to 30%, or with WETM up to 20% does not significantly affect the quality of concrete in comparison to the quality of the reference concrete prepared with 100% cement. The leaching test showed no significant release of toxic elements for both obtained composites.

Nanomaterials based on metal–doped fluorapatite (FAP) have attracted considerable interest as potential next–generation antimicrobial agents. In this study, Cu2+–doped FAP nanocrystals have been successfully synthesized by a neutralization method at room temperature. Their structural, optical, antimicrobial, and hemcompatible properties have been investigated. XRD, FTIR, FESEM, and N2 adsorption–desorption studies indicate the formation of single–phase FAP mesoporous nanopowders, composed of rod–like particles. TEM images confirmed the formation of nanorodes with a length of 60 nm and a width of about 18 nm. Rietveld analysis shows that the Cu2+ ions preferentially substitute Ca2 (6 h) sites in the hexagonal fluorapatite crystal structure. Fluorescence spectroscopy accompanied by MCR–ALS method confirms substitution of Cu2+ ions in FAP crystal lattice with extracting additional d–d band transition at green color from FAP broadband self–activated luminescence in violet–blue color. Antimicrobial studies conducted on Staphylococcus aureus, Escherichia coli and Micrococcus lysodeikticus showed that FAP nanopowder with the highest Cu2+ content have strong bacteriostatic action on Staphylococcus aureus bacterial strain in mediums containing nutrition matters. In addition, this sample in comparison to pure FAP achieved a high percentage of relative reduction of bacterial population for all three species, being >90% in most cases. Fungistatic action is noticed too, throwgh the slowing down mycelium growth of fungus Aspergillus niger, Aspergillus flavus and Penicillium roqueforti and reduction of sporulation of Aspergillus niger species. Cu2+–doped FAP nanocrystals shows a synergistic antimicrobial effect with Cu2+ and F− ions. Concerning the potential biomedical applications, the hemolysis ratios of the Cu2+–doped FAP samples were below 5%. The obtained results pointed out the possible use of the synthesized nanocrystals as broad–spectrum antimicrobial agents for various

Kaolinite/illite (KUb) and sepiolite (SEP) clays were used to study Cr(III) adsorption removal from aqueous solutions so that they could be utilized after saturation for ceramic manufacturing. SEP had a larger specific surface area and a higher PZC than KUb. The removal of Cr(III) was evaluated using a batch equilibration procedure at pHi = 4 and pHi = 6. Fast removal kinetics were observed for both clays. Maximum removal capacity was determined by changing the concentration of Cr(III) while keeping the concentration of clay constant and by altering the amount of clay while keeping the concentration of Cr(III) constant. In all situations, SEP had greater capacity than KUb, and capacity was greater for both clays at higher pHi. Not only did the pHi impact the removal capacity and efficiency, but so did the pH during adsorption and the initial concentration of Cr(III). Because of the higher PZC, the pHf for SEP was higher for the same pHi. The higher the pH and Cr(III) concentration, the higher the probability of Cr(OH)3 precipitation and the higher the removal capacity. Dried saturated clays were uniaxially pressed and sintered at 1000 °C for 2 h. The densities of the sintered materials were nearly identical to those of pure clay-based materials, but the compressive strengths were higher, which is significant for the use of saturated clays as raw materials in ceramic manufacturing. Leaching of Cr from SEP-based material was significantly higher than from KUb-based material probably due to the presence of CaCO3 in the SEP.

The sepiolite/ZrO2 composites were prepared in toluene using sepiolite and zirconium propoxide by two different procedures. The efficiency of the obtained adsorbents for the removal of phosphate from water solutions was investigated. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive analysis (EDS). Fourier transform infrared (FTIR) spectroscopy, DTA/TG thermal analyses, specific surface area determination and determination of the point of zero charge were used to characterize the obtained composites, Sep-Zrl and Sep-ZrII. The results indicate that ZrO, in the form of fine nanoparticles was successfully loaded onto the surface of sepiolite fibers. Adsorption kinetics and equilibrium isotherms were investigated to establish the adsorption rates, maximum capacities and possible mechanisms of the adsorption of phosphate from water onto Sep-Zrl and Sep-Zrll composites at a pH of 4. The adsorption kinetics and isotherm follow the pseudo second-order equation and Freundlich adsorption model, respectively.

Tehničko rešenje se odnosi na unapređenje postupka prečišćavanja otpadnih voda koje sadrže trovalentni hrom, kao što su otpadne vode iz površinske zaštite metala, štavljenja kože, zaštite drvenih proizvoda i dr. U konvencionalnim postupcima joni trovalentnog hroma se talože u obliku Cr(OH)3, čime nastaje talog kao sekundarni opasni otpad koji se uglavnom odlaže na deponije, što dovodi do dodatnih troškova i negativnog uticaja na životnu sredinu. U ovom tehničkom rešenju joni trovalentnog hroma se uklanjaju iz vode adsorpcijom na jeftinim glinama iz lokalnih ležišta, jednoj kaolinitsko-ilitskog tipa i jednoj na bazi sepiolita, koje su komercijalno dostupne kao sirovine za proizvodnju tradicionalne keramike. Utvrđen je adsorpcioni kapacitet ovih glina, pri različitim pH vrednostima, variranjem početne koncentracije jona hroma pri konstantnoj koncentraciji adsorbenta, kao i variranjem koncentracije adsorbenta pri konstantnoj koncentraciji jona hroma, u cilju optimizacije procesa prečišćavanja. Imajući u vidu da regeneracijom zasićenih adsorbenata nastaju nove otpadne vode, ovim tehničkim rešenjem je predviđeno da se zasićeni adsorbenti koriste kao sirovine za proizvodnju keramike umesto čistih glinenih minerala. Određivanje pritisne čvrstoće sinterovanih materijala dobijenih od zasićenih adsorbenata je pokazalo da adsorbovani joni hroma ne pogoršavaju mehanička svojstva u poređenju sa materijalima koji su dobijeni od čistih glina, već naprotiv dovode do povećanja pritisne čvrstoće i to u većoj meri u slučaju materijala na bazi sepiolitske gline, čiji je kapacitet adsorpcije veći. Ispitivanja izluživanja hroma iz sinterovanih materijala na bazi zasićenih adsorbenata su pokazala da je izluživanje u slučaju materijala na bazi sepiolitske gline veće od vrednosti koja je definisana odgovarajućim standardom, verovatno zbog prisustva kalcijum-karbonata kao primese ove gline. Ovaj problem se može prevazići povišenjem temperature sinterovanja. Hrom je efikasno imobilisan u mate

An emerging technology of active packaging enables prolongation of food shelf life by limiting the oxygen transfer and the reactivity of free radicals, which both destruct food freshness. In this work, Fe2TiO5 nanoparticles were synthesized using a modified sol–gel method and evaluated as an enforcement of alginate food packaging film. Pure phase Fe2TiO5 nanoparticles had an average particle size of 44 nm and rhombohedral morphology. Fe2TiO5 nanoparticles induce no cell damage of human Caco-2 epithelial cells and show no inhibitory effect towards growth of a panel of bacterial strains, suggesting good biocompatibility. Films obtained by incorporation of Fe2TiO5 nanoparticles into alginate using the solvent casting method show no migration of iron or titanium ions from films to food simulants again suggesting their safety as a packaging material. Fe2TiO5 nanoparticles also showed strong antioxidant efficiency as determined using the DPPḢ assay, and confirmed further in a preservation test on fresh fruit.

In this paper, the capillary rise and sorption ability of hemp fibers oxidized with hydrogen peroxide and potassium permanganate were studied, with the aim to get more insight into the changes in the structure of hemp fibers caused by oxidation, and to compare the influence of applied oxidative agents on hemp fibers. Capillary rise was presented as a function of a liquid rise height vs times, with determined all three capillary coefficients, while sorption ability was determined as water retention values and moisture sorption. For structural analysis of the samples the ATR-FTIR technique was used. Also, the amount of aldehyde and carboxyl groups and the lignin content in oxidized fibers were determined. The surface fibers morphology was observed by FESEM. In all oxidized hemp fibers an increase in capillarity was obtained for both oxidizing agents (33-75 mm for H2O2, and 40-114 mm for KMnO4), compared to 31 mm for unmodified fibers, but decreased sorption ability. Application of both oxidative agents, were successful for introduction of functional groups into oxidized fibers, for reduction of the amount of non-cellulosic substances, as well as moisture sorption. Simultaneously, the fibers became finer, cleaner, whiter, softer and more suitable for further processing, while, generally, higher influence on changes into oxidized hemp fibers was achieved by oxidation with KMnO4, compared to oxidation with H2O2.

Carbon materials of different structural and textural properties (multi-walled carbon nanotubes, carbon cryogel, and carbonized hydrothermal carbon) were used as adsorbents for the removal of estrone, 17 beta-estradiol, and 17 alpha-ethinylestradiol from aqueous solutions. Chemical modification and/or activation were applied to alter surface characteristics and to increase the adsorption and desorption efficiency of carbon materials. Surfaces of treated and untreated carbon materials were characterized through the examination of the textural properties, the nature of surface functional groups, and surface acidity. It was found that the adsorption capacity of tested carbon materials is not directly proportional to the specific surface area and the content of surface oxygen groups. However, a high ratio of surface mesoporosity affected the adsorption process most prominently, by increasing adsorption capacity and the rate of the adsorption process. Adsorption of estrone, 17 beta-estradiol, and 17 alpha-ethinylestradiol followed pseudo-second-order kinetic model, while the equilibrium adsorption data were best fitted with the Langmuir isotherm model. Calculated mean adsorption energy values, along with the thermodynamic parameters, indicated that removal of selected hormones was dominated by the physisorption mechanism. High values of adsorption efficiency (88-100 %) and Langmuir adsorption capacities (29.45-194.7 mg/g) imply that examined materials, especially mesoporous carbon cryogel and multi-walled carbon nanotubes, can be used as powerful adsorbents for relatively fast removal of estrogen hormones from water.

Ciprofloxacin (CIP) as a broad-spectrum quinolone antibiotic is extensively used in daily life and can be detected in municipal and pharmaceutical wastewaters, as well as natural waters. In this study, natural mineral sepiolite (SEP), SEP modified with hexadecyltrimethylammonium-bromide (HDAB) and SEP composites with graphene oxide (GO) were used as adsorbents for the removal of CIP from aqueous solutions. The composites were prepared at a mass ratio SEP to GO of 2 : 1, using SEP and SEP modified by [3-(2-aminoethylamino)propyl]trimethoxy-silane (APT). Thermogravimetric analysis, X-ray diffraction and nitrogen adsorption-desorption were used to characterize the obtained adsorbents. The adsorption of CIP was investigated at the pH value close to pH of natural waters. The concentration of CIP in aqueous solution was determined by UV-Vis spectroscopy. GO showed the highest adsorption capacity (~ 150 mg/g). The capacity of SEP was about 60 mg/g, while the SEP modification with HDAB has led to a decrease in the adsorption capacity (~ 35 mg/g). The composite SEP/GO showed the higher adsorption capacity (~ 110 mg/g) than the composite SEP-APT/GO (~ 40 mg/g). The capacity of the composite SEP/GO was higher than of mixture of SEP and GO, which indicated a certain degree of GO exfoliation and intecalation of sepiolie particles, as it was shown by X-ray diffraction. Equilibrium data for all adsorbents, except for HDAB modified sepiolite, fitted well to the Langmuir isotherm model.

Alkali activated slag (AAS) is an environmentally friendly material which were extensively investigated in a pass two decade. Currently, these materials are considering as an effective alternative for cement binder. Process of slag alkali activation involves a chemical reaction between solid calcium aluminosilicate materials and a highly alkaline activator. The alkali activation mechanism of slag consists of the slag dissolution in a highly alkaline which is followed by the condensation and hardening processes yielding formation of calcium (alumina) silicate hydrate C– (A)–S–H gel as a reaction product of slag alkali activation. Properties of these materials primarily depends on the choice of solid row materials. Primarily, granulated blast furnace slag, by product of iron production) is considering as a precursor for AAS synthesis. However, an important shift towards the use of steelmaking slag is also observed. Although electric arc furnace slag has already found its application mainly in civil engineering, this investigation has aimed to investigate properties of AAS prepared using the electric arc furnace slag (EAFS) with an emphasize with different possibilities of its application. Characterization of AAS involved XRDP, SEM/EDS and pore size analysis with the aim to build up a detailed illustration of AAS from the stand point of different application.