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Dental composite materials based on Zn/Al-layered double hydroxide and their physical mechanical properties
No full textDental materials' demands can be answered using composite materials, ascomposite properties are suitable for tailoring the material's behavior. Poly(methyl methacrylate) (PMMA) is usually a material of choice in dental applica-tions, and its mechanical properties can be improved in terms of modulus,strength, and hardness. The chosen reinforcement in this publication wasZn/Al-layered double hydroxide (LDH), as this material has functional propertymodification possibilities. The reinforcement was synthesized using the coprecipi-tation process on a laboratory scale. The dispersion of the reinforcement was donewith ultrasonication, and the composites prepared contained 1, 3, and 5 wt% ofreinforcement, and the so-prepared composites were compared to the matrix.Improvements were observed in terms of the elastic modulus and tensile strength,and the best performance was observed in the composite with 3 wt% of particles.Hardness increased with the addition of particles and the higher the particle con-tent, the better the hardness. Materials were tested using dynamic mechanicaltechniques, and it was proven that the addition of particles lowers the Tg of thecomposite compared to the pure matrix. The addition of particles diminished theaffinity of the material for polar liquids such as water
Developing thermal insulation cement-based mortars with recycled aggregate in accordance with Net Zero principles
No full textThe performance of thermo-insulation rendering mortars with alternarions in ratios of powdered cordierite and talc was examined. The goal was to confirm that recycled kilnware cordierite can be reapplied in the mortar design without significant deterioration in performance in comparison with OPC mortar. Differential thermal analysis was employed for examining thermally induced reactions. The cavitation erosion, in testing sequences ranging from 30 to 120 minutes, was used to assess the compactness of the mortar structure. The physico-mechanical properties of experimental mortars were investigated. The morphologies of the mortar tablets upon cavitation were studied using a scanning electron microscope. It was established that cordierite and talc filler in amounts up to 20% enhance microstructural packing and mechanical strengths due to improved cementation and therefore contribute to cavitation erosion resistance. Higher amounts of talc cause structural degradation and mass loss during cavitation tests. Reducing manufacturing costs, energy consumption, and greenhouse gas emissions are the main objectives of the production of this waste-based construction composite, as the reuse of waste materials can help achieve a number of Sustainable Development Goals
Application of Fly Ash-Based Geopolymers for the Removal of Pesticides from Water
No full textHarmful effects of pesticides on human health have been observed even at very low concentrations. These chemicals are used in large quantities in agriculture to suppress the adverse impacts caused by various types of insects, bacteria, fungi, and algae [1]. Their extensive use has led to their penetration into natural ecosystems. On the other hand, modern societal development has resulted in an ever-increasing demand for electrical energy, which inevitably generates large amounts of waste originating from thermal power plants - fly ash [2]. The main aim of this study is to address the problem of environmental pollution by pesticides through the valorization of waste via the synthesis of a new type of inorganic polymeric material—geopolymers. In this work, geopolymers based on fly ash modified with chitosan and polyvinyl alcohol were synthesized. The obtained materials were characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRPD), and point of zero charge determination (pHPZC). The adsorption capacity of the synthesized materials was examined for eight commercial pesticides: acephate, monocrotophos, dimethoate, carbofuran, carbaryl, linuron, malathion, and tebufenozide. The results showed that the adsorption efficiency depends on the type of pesticide and ranged from 19.1 % for acephate to 99.9 % for carbofuran, carbaryl, and malathion. These findings indicate that modified fly ash-based geopolymers have the potential to serve as an efficient and sustainable adsorbent for the removal of pesticides from contaminated water
Sustainable Integrated Approach to Waste Treatment in Automotive Industry: Solidification/Stabilization, Valorization, and Techno-Economic Assessment
No full textAn integrated approach to waste management is based on efficient and safe methods for
waste prevention, recycling, and safe waste treatment. In accordance with these principles,
in this study, non-hazardous aluminosilicate waste (dust and sand) was used in the solidification/stabilization (S/S) treatment of hazardous waste (coating, emulsion, and sludge)
from the automotive industry. Also, the oily component of the waste was valorized and
investigated for energy recovery through co-incineration. The two S/S processes were proposed and their sustainability was assessed by utilizing all types of waste generated in the
same plant, obtaining stabilized material suitable for safe disposal and oil phases for further
valorization, and by techno-economic analysis. The efficiency of the S/S processes was
evaluated by measuring unconfined compressive strength, hydraulic conductivity, density,
and the EN 12457-4 standard leaching test of S/S products, along with XRD, SEM-EDS, and
TG-DTG analyses. The possibility of using the oil phase was assessed based on its calorific
value. The techno-economic assessment compared the investments, operating costs, and
potential savings of both treatment scenarios. The results show that an integrated approach
enables safe waste immobilization and resource recovery, contributing to environmental
protection and economic benefits
Modeling Mass Release From Nanofibers – Theory and Application
No full textThis study investigates the drug release performance of electrospun composite nanofiber mats,
which hold significant promise as drug carriers for site-specific delivery in therapeutic
applications such as cancer therapy. Predicting drug release rates from poly(D,L-lactic-coglycolic acid) (PLGA) nanofibers produced via emulsion electrospinning is challenging due to
the system's inherent complexity. To address this, two distinct implants were fabricated at the
Faculty of Technology and Metallurgy, University of Belgrade: a PLGA implant and a
composite scaffold consisting of a PLGA fibrous structure enclosed between two layers of
poly(ε-caprolactone) (PCL), prepared via emulsion-based and sequential electrospinning
techniques. Computational modeling was employed to evaluate the continuous drug release
from these nanofibers. The study utilized the PAK software program and a CAD user interface
to create nano-implant models, with post-processing by the PAK finite element (FE) solution.
Two models were developed to simulate diffusive drug release from nanofibers into a threedimensional (3D) surrounding medium: (1) a one-dimensional (1D) finite elements with axial
and radial diffusion representing the fibers, and (2) a 3D continuum discretized using composite
smeared finite elements (CSFEs); with coupling of these models two models. Both models
account for polymer degradation and drug hydrophobicity as partitioning at the
fiber/surrounding interface. Experimental drug release rates from the scaffold were compared
with computational predictions from the FE models. The results demonstrate the effectiveness
of the proposed models in capturing the complex dynamics of drug release, providing valuable
insights into the design and optimization of electrospun nanofiber-based drug delivery systems. This work highlights the potential of integrating experimental and computational approaches to
advance the development of controlled drug release platforms for biomedical applications
Toward Zero Waste Mining: Circular Economy of Copper Slags
No full textOnly 8.6% of the global economy follows the principles of the circular economy. Mining and metal extraction processes generate over 90% of global waste, with slags being the major contributor to waste accumulation. Copper slags mostly consist of stable compounds that are safe for the environment, the main concern being the leaching of heavy metals into the ground. The market for using waste copper slags to produce value-added products is established in the last century and grown to an 800 million dollar market in 2024, with a predicted compound annual growth rate of 5.5% in the following years. However, only 15% of the generated copper slags worldwide are used for commercial purposes. In order to attain complete reusability of copper slags, industrial techniques must be adopted to eliminate threats from heavy metals and other possibly harmful elements. Additionally, it is essential to establish a market that can sustainably handle all quantities of generated slag. This review highlights the properties that make copper slags suitable for producing value-added products. With the rapid increase in population and urbanization, there is a potential to utilize copper slags for a-large-scale construction purposes such as earthworks and buildings. The demand for geotechnical applications and construction materials constantly increases and can absorb the entire quantity of copper slags generated. If this happens, it would mean an achievement of 100% reusability of copper slags in compliance with circular economy principles
Synchronous Measurement of Optical Transmission and Viscoelastic Properties of Polymer Optical Fibers
No full textIn this paper, synchronous mechanical and optical measurements are proposed using the dual cantilever mode of dynamic mechanical analysis (DMA). It was demonstrated that this mode enables the detection of phase transitions in both the core and cladding materials of polymer optical fibers (POFs), with corresponding changes in optical signal intensity observed across different light wavelengths. In dual cantilever mode DMA, an increase in optical transmission was recorded between the two detected glass transition temperatures. The initial increase in transmission is attributed to cladding softening and the consequent reduction in internal stresses in the POF, while the maximum in optical transmission coincides with the beginning of the phase transition in the core material. To compare and interpret the optical and thermo-mechanical results, Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) measurements were carried out on POF pieces, as well as separately on the core and cladding materials. This integrated technique yields quantitative data on a material’s viscoelasticity and light-transmission changes, making it valuable for quality control and for predicting the long-term behavior of advanced POFs in various applications
Probiotic immobilization on flaxseed
No full textLactobacillus gasseri has gained considerable attention for its potential roles in modulating gut
microbiota and enhancing host immune function. To exert health-promoting effects, probiotics must retain
high viability, which can be improved by incorporating them into protective delivery matrices [1]. Flaxseed
cake, a byproduct of cold-pressed oil production, is rich in fiber, protein, and bioactive compounds, making it
a promising substrate for probiotic immobilization.
In this study, the flaxseed cake was ground, sieved to a particle size below 600 µm, sterilized, and
suspended in distilled water at 10 % (w/v). Following L. gasseri inoculation, one sample underwent
fermentation, incubation at 4 °C for 1 h, freezing, and subsequent freeze-drying, while the other was processed
identically without fermentation. The resulting lyophilized powders were evaluated for probiotic survival and
antioxidant activity.
High viability of L. gasseri was maintained in both preparations. Fermentation prior to lyophilization
decreased survival by approximately 5 %, yet significantly enhanced the antioxidant capacity of the probiotic
powder. These findings demonstrate that flaxseed cake is an effective carrier matrix for L. gasseri, supporting
both microbial stability and functional bioactivity
Kavitaciona erozija - Proces i razvoj metoda za ispitivanje
No full textThe paper presents an ultrasonic vibration method for laboratory testing of the resistance of materials to the effect of cavitation. The description of the test method and device, the test procedure, and the interpretation of test results are given in accordance with ASTM G32 standard. A compara-tive overview of the test results of different types of materi-als is presented: metal (steel, aluminium alloys); ceramics (based on pure and mixed refractory fillers); composite mate-rials with a polymer base; refractory castings and protective coatings. Based on the test results, the correlation of struc-tural characteristics, mechanical properties of materials are determined as a basis for quick selection of materials in hydrodynamic conditions of application.U radu je prikazana ultrazvučna vibraciona metoda za
laboratorijsko ispitivanje otpornosti materijala na dejstvo
kavitacije. Opis metode i uređaj za ispitivanje, procedura
ispitivanja, kao i interpretacija rezultata ispitivanja dati su
u skladu sa standardom ASTM G32. Prezentiran je uporedni pregled rezultata ispitivanja različitih vrsta materijala:
metalni (čelik, legure aluminijuma); keramika (na bazi čistih
i mešavine vatrostalnih punioca); kompozitni materijali sa
polimernom osnovom; vatrostalni livački i zaštitni premazi.
Na osnovu rezultata ispitivanja određena je korelacija strukturnih karakteristika, mehaničkih svojstava materijala i svojstava kavitacione otpornosti materijala kao osnova za brz
izbor materijala u hidrodinamičkim uslovima primene
Prirodne eutektičke smeše za delignifikaciju i valorizaciju agro-industrijskog otpada
No full textLignocellulosic biorefineries are recognised as a sustainable way to produce a wide range of valuable bio-based products while simultaneously addressing the environmental challenge related to waste disposal and the emission of greenhouse gases. Despite huge advancements in the field of lignocellulosic biorefineries in recent years, the pretreatment of lignocellulose remains a major challenge that limits the implementation of the biorefinery processes at the industrial level. Natural deep eutectic solvents (NADES) have emerged as a promising alternative to traditional treatment technologies based on corrosive acids or alkalis due to the environmentally friendly properties of NADES and their ability to fractionate lignocellulose under relatively mild treatment conditions. In this study, we evaluated the treatment of corncob biomass using NADES based on choline chloride and lactic acid, aiming to achieve efficient biomass delignification and improve the susceptibility of the corncob polysaccharide fraction to enzymatic hydrolysis.
Sun-dried corncob was kindly obtained from a local farm in South Banat, Serbia. The corncob was ground in a hammer mill grinder and a particle fraction between 0.5 mm and 1 mm was collected by sieving and further used in this study. The biomass was treated in a microwave reactor (MonowaveTM 300, Anton Paar, Austria) at a constant temperature of 60 ℃, 90 ℃ and 120 ℃ for 30 min or 60 min, while the molar ratio of choline chloride and lactic acid was 1:1, 1:2, 1:5 and 1:10. After treatment, the solid biomass was separated by filtration, thoroughly washed with distilled water and dried to a constant weight. Treated biomass was analyzed for the lignin content by applying the spectrophotometric acetyl-bromide method. Additionally, the biomass was subjected to enzymatic hydrolysis using commercial cellulase enzymes (Cellic® CTec2, Novozyme, Denmark) and the reducing sugars were determined by the spectrophotometric DNS method.
The results of the present study showed that the highest delignification of corncob can be obtained at temperature of 90 ℃ and using the NADES based on choline chloride and lactic acid at the molar ratio of 1:10. By treating the biomass for 60 min, delignification of 51.98% was obtained, while shorter treatment also resulted in significant lignin removal, achieving delignification rate of 47.54%. The treatment improved susceptibility of corncob polysaccharide fraction to cellulase enzymes leading to significantly higher yield of reducing sugars in enzymatic hydrolysis, compared with untreated biomass. These fermentable sugars can be further fermented by microorganisms to a variety of bio-based products, including bioethanol and different commodity and platform chemicals. The results obtained in this study indicate that the treatment of corncob using NADES could be attractive option for development of „greener“ and more sustainable biorefinery processes.Lignocelulozne biorafinerije su prepoznate kao održiv način za dobijanje širokog spektra vrednih bio-proizvoda,
dok istovremeno nude rešenje za globalne ekološke izazove koji se odnose na skladištenje otpada i emisiju
gasova staklene baste. Uprkos velikom napretku u oblasti lignoceluloznih biorafinerija poslednjih godina,
predtretman lignoceluloze i dalje predstavlja veliki izazov koji ograničava primenu ovih procesa na
industrijskom nivou. Upotreba prirodnih eutektičkih smeša u tretmanu biomase predstavlja alternativni pristup
tradicionalnim tehnologijama koje se zansivaju na upotrebi korozivnih kiselina ili baza zbog ekološki
prihvatljivih osobina prirodnih eutektičkih smeša i njihove sposobnosti da frakcionišu lignoceluloznu biomasu
pri relativno blagim uslovima tretmana. U ovom radu je ispitivan predtretman kukuruznog oklaska primenom
prirodne eutektičke smeše na bazi holin hlorida i mlečne kiseline u cilju postizanja efikasne delignifikacije i
poboljšanja enzimske hidrolize tretirane biomase.
Suvi kukuruzni oklasak je dobijen od lokalnog poljoprivrednog gazdinstva u južnom Banatu, Srbija. Za
usitnjavanje oklaska je korišćen mlin čekićar, a frakcija veličine čestica u opsegu od 0.5 mm do 1 mm je
sakupljena prosejavanjem i dalje korišćena u ovom istraživanju. Biomasa je tretirana u mikrotalasnom reaktoru
(MonowaveTM 300, Anton Paar, Austrija) pri konstantnoj temperaturi od 60 ℃, 90 ℃ i 120 ℃ tokom 30 min ili
60 min, dok je odnos molova holin hlorida i mlečne kiseline iznosio 1:1, 1:2, 1:5 i 1:10. Nakon predtretmana,
tretirana biomasa je odvojena filtracijom, temeljno isprana destilovanom vodom i osušena do konstantne mase.
U uzorcima je određen sadržaj lignina primenom spektrofotometrijske metode sa acetil-bromidom. Takođe,
tretirana biomasa je podvrgnuta enzimskoj hidrolizi pomoću komercijalne celulaze (Cellic® CTec2, Novozyme,
Denmark), a koncentracija redukujućih šećera je određena primenom spektrofotometrijske DNS metode.
Rezultati ovog istraživanja su pokazali da se najveća delignifikacija kukuruznog oklaska može postići pri
temperaturi od 90 ℃ i upotrebom prirodne eutektičke smeše za čiju sintezu su korišćeni holin hlorid i mlečna
kiselina u molarnom odnosu 1:10. Tretmanom biomase u trajanju od 60 minuta je ostvarena delignifikacija od
51,98%, dok je tretman u trajanju od 30 minuta takođe doveo do značajnog smanjenja sadržaja lignina čime je
postignuta delignifikacija od 47,54%. Tretman je poboljšao efikasnost enzimske hidrolize kukuruznog oklaska i
doveo do značajno većih prinosa redukujućih šećera u poređenju sa netretiranom biomasom. Dobijeni
fermentabilni šećeri se mogu dalje koristiti u različitim fermentacionim procesima za proizvodnju bio-proizvoda
kao što su bioetanol i biohemikalije. Rezultati dobijeni u ovom radu ukazuju da tretman kukuruznog oklaska
pomoću prirodnih eutektičkih smeša može biti atraktivna opcija u razvoju „zelenih“ i održivih biorafinerijskih
procesa