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Development of sustainable method for metal recovery from old flotation tailings (Majdanpek, Serbia) using Aspergillus niger fungus
No full textThe accumulation of mine tailings in the mining area of Majdanpek represents a serious environmental problem. A strong impetus for the development of sustainable methods for the recovery of metals from mine tailings is given by the importance of heavy metal recovery and the economic benefits of precious and base metals. Currently, researchers are working to develop metals recovery from tailings through bioleaching, which is a more sustainable method compared to traditional metallurgical methods. Biotechnologies for leaching heavy metals from old flotation tailings (Majdanpek, Serbia) with fungus Aspergillus niger (A. niger) are discussed in this paper. The subject of this research is iron ions, since the tailings are the richest in this metal. With a simple bioleaching process, which is based on the cultivation of A. niger in the basic growth medium and then challenging it with tailings, 5% iron was released in 35 days. The transformation of mine tailings morphology was also confirmed by optical microscopy. Processes by which A. niger extracts metals from
tailings include acidolysis, complexation, alkaloysis and biosorption. Also, in addition to metabolites, these fungi produce spores and mycelium that can destroy material and transform it to the soil. Given that Serbia is abundant with agricultural
waste, as well as waste from the food industry, in future studies cheap waste should be used as an energy input source for A. niger and transformation of tailings
"Predicting the modulus of elasticity for biocompatible titanium alloys"
No full textTitanium alloys have been present for decades as the main components for the production of various orthopedic and dental elements. However, modern times require titanium alloys of different composition, with lower modulus of elasticity, without the presence of toxic alloying elements such as Al and V [1]. Traditional methods used to detect dependencies between parameters, as well as alloy design, are often not particularly effective and usually require large investments of time and resources. The study introduces the machine learning technique Extra Tree Regression, which, through the analysis of data from 246 biocompatible titanium alloys, identifies factors associated with reduced elastic modulus [2]. The three most influential were: specific heat and mass fraction of titanium and mass fraction of titanium silicon. Using data on the most influential factors, four-component diagrams were designed where certain alloy compositions reach a modulus of up to 54 GPa. In addition, Monte Carlo simulations were used to demonstrate the feasibility of modeling multicomponent alloys with elastic modulus below 70 GPa
Determining the role of acicular ferrite carbides in cleavage fracture crack Initiation for two medium carbon microalloyed steels
No full textTwo medium-carbon microalloyed steels with a predominant acicular ferrite microstructure were investigated in this study in order to determine the initial micro-crack formation mechanism and the role of acicular ferrite structure in cleavage fracture. In order to ensure cleavage fracture, samples were investigated at −196 ◦C for uniaxial tension and four point bending fracture. Previous investigations have shown that cleavage fracture for steels with a predominant acicular ferrite microstructure has not been initiated by the fracture of coarse TiN particles as in ferrite-pearlite,
bainite, or martensitic microalloyed steels. The average maximal thickness of cementite plates measured in this work is 0.798 µm and 0.966 µm, for V and TiV steel, respectively. The corresponding stress values required for their fracture according to Griffith’s equation are 1970 MPa and 1791 MPa,
respectively. Estimated values of the effective surface energy for the V steel with an average cementite volume fraction of 3.8% range from 40 Jm−2 to 86 Jm−2, and for the TiV steel with an average cementite volume fraction of 18.3% range from 55 Jm−2 to 82 Jm−2. The fracture of coarse cementite plates was found to not to be responsible for the cleavage fracture initiation in case of both steels
Reciklaža i ponovna upotreba flotacijske jalovine rudnika „Rudnik“ u cilju osvajanja tehnoloških postupaka prerade sekundarnih sirovina u srbiji – projekat iz programa prizma (2024-2026) - REASONING
No full textVelike količine flotacijske jalovine stvaraju se u Srbiji (preko 20 Mt), kao i u svetu (20.000-25.000 Mt). Zbog zaostalih teških metala (Pb, Cu, Fe i Zn...) ona predstavlja potencijalno opasni otpad koji bi trebalo zbog vrednosti plemenitih i obojenih metala u njoj reciklirati. Na Rudniku „Rudnik“ svake godine se generiše oko 250.000 t, flotacijske jalovine, od 1953. god. oko 11 Mt. Naučno istraživačkim radom i obavljenim ispitivanjima u okviru Projekta-REASONING (2024.-2026.) dobiće se rezultati i osvojiće se nova inovativna rešenja i znanja čija će implementacija omogućiti osvajanje tehnoloških postupaka reciklaže i prerade flotacijske jalovine Rudnika “Rudnik”
The effect of particle size on the crystallization LiGe2(PO4)3 phase from glass
No full textThe glass was prepared by the standard melt-quenching technique. The crystallization of powder glass from the system Li2O-Al2O3-GeO2-P2O5 was studied. The investigations were performed under non-isothermal and isothermal conditions using the AAS, DTA, XRD and FTIR methods. The aim of this research was to study the ease of glass formation, crystallization and crystal structure of obtained phases. The results showed that the glass crystallizes by primary crystallization. LiGe2(PO4)3 was formed as the primary phase, until detectable traces of GeO2 were formed as secondary. The influence of particle size of the glass powder samples in the range 0-1 mm on the temperature of the DTA crystallization peak, Tp, the peak height (T)p and the parameter Tp2/(T)p was studied. It was demonstrated that for the particle size in the range of 0.05-0.35 mm surface and volume crystallization were significant, while the particle size >0.35 mm according to the volume crystallization was dominant
Hydrochar and Its Composites for Highly Efficient Pollutant Removal
No full textWater pollution caused by industrial effluents without prior purification treatment represents one of the serious environmental concerns in contemporary times. Lately, due to its surface characteristics, pronounced chemical reactivity, and efficient regeneration ability, hydrochar obtained by hydrothermal carbonization of waste biomass has been explored as sustainable adsorbents for the removal of different pollutants. Besides, potential disadvantages of this material, such as low specific surface area and porosity, are easily overcome by surface modifications and composites synthesis. Previous reported studies have shown that chemical methods that include hydrogen peroxide or alkalis treatment, and incorporation of metals onto hydrochar surface can significantly improve its adsorption performances. Within this study, the potential application of hydrochars from different precursors and its composites as efficient sorbents of organic dyes and heavy metals from aqueous solutions will be discussed. Special attention will be directed towards structural changes caused by modification, achieved adsorption capacities and potential adsorption mechanisms. In general, the valorisation of hydrochar as a polluter sorbent solves the problems of sustainable and efficient material for purification and disposal of waste with permanent consequences to the environment
Challenges, Opportunities, Valorization and Green Advancements for Food and Agricultural Waste
No full textSynthesis and characterization of luminescent Cu2+–doped fluorapatite nanocrystals as potential broad–spectrum antimicrobial agents
No full textNanomaterials 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 biomedical and health care preparations
Hydroxyapatite/poly(vinyl alcohol)/chitosan coating with gentamicin for orthopedic implants
No full textElectrophoretic deposition (EPD) was employed to fabricate composite coatings aimed for orthopedic implants.
Hydroxyapatite (HAP), poly(vinyl alcohol) (PVA) and chitosan (CS) coatings, with or without antibiotic gentamicin
(Gent) were deposited in a single-step process from aqueous suspension, using EPD. Polymer/mineral
composite coatings were formed with the aim to mimic the natural composition of bone tissue, along with
improved coatings antibacterial properties, at the same time serving as a drug carrier, allowing local administration
of antibiotic. Structural and morphological characterization of HAP/PVA/CS and HAP/PVA/CS/Gent
coatings was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric
analysis (TG/DTG), and scanning electron microscopy (SEM) proving carbonate-substituted HAP.
The presence of gentamicin contributed to the bactericidal activity of composite HAP/PVA/CS/Gent coating
against Staphylococcus aureus and Escherichia coli. Cytotoxicity studies were performed towards human MRC-5
and mice L929 fibroblast cell lines, and both investigated samples (HAP/PVA/CS and HAP/PVA/CS/Gent)
expressed good biocompatibility, without causing toxic effect on tested cells. Biomineralization potential was
investigated by measuring the alkaline phosphatase activity, demonstrating high potential of HAP/PVA/CS/Gent
to induce the growth of new HAP layer. Therefore, the present investigation proposes the production of nents,
along with antibiotic gentamicin, improving the antibacterial coatings’ properties
Application of pyrophyllite in high-temperature treated building materials
No full textPhyllosilicate mineral pyrophyllite is predominantly used in the ceramic industry because it exhibits high refractoriness. Due to its thermal transformation into mullite, pyrophyllite is stable at elevated temperatures, making it a suitable mineral additive for refractory non-shaped materials and various ceramic shaped products. In this study, pyrophyllite is employed as 50 % clay replacement in the ceramics and up to 30 % cement replacement in mortars. Physico-mechanical properties were investigated. The firing shrinkage in the ceramics treated at 1200 °C was reduced by pyrophyllite addition. Pyrophyllite acted as additional pozzolana during cement hydration. Within the microstructure, it formed micro-reinforcement in the shape of crystalline folia, which improves the mechanical properties of ordinary Portland cement, high aluminate cement, and blended cement mortars. The investigation proved the efficiency and suitability of pyrophyllite employed as a substitution for clay in ceramics and a cement replacement in mortars.
Phyllosilicate mineral pyrophyllite is predominantly used in the ceramic industry because it exhibits high refractoriness. Due to its thermal transformation into mullite, pyrophyllite is stable at elevated temperatures, making it a suitable mineral additive for refractory non-shaped materials and various ceramic shaped products. In this study, pyrophyllite is employed as 50 % clay replacement in the ceramics and up to 30 % cement replacement in mortars. Physico-mechanical properties were investigated. The firing shrinkage in the ceramics treated at 1200 °C was reduced by pyrophyllite addition. Pyrophyllite acted as additional pozzolana during cement hydration. Within the microstructure, it formed micro-reinforcement in the shape of crystalline folia, which improves the mechanical properties of ordinary Portland cement, high aluminate cement, and blended cement mortars. The investigation proved the efficiency and suitability of pyrophyllite employed as a substitution for clay in ceramics and a cement replacement in mortars.Филосиликатни минерал пирофилит се претежно користи у керамичкој индустрији јер показује високу ватросталност. Због своје термичке трансформације у мулит, пирофилит је стабилан на повишеним температурама, што га чини погодним минералним додатком за ватросталне необликоване материјале и различите керамичке обликоване производе. У овом раду пирофилит је коришћен као замена за 50 % глине у керамици и до 30 % замене за цемент у малтерима. Испитивана су физичко-механичка својства. Скупљање при печењу у керамици третираној на 1200 °C смањено је додавањем пирофилита. Пирофилит се понашао као додатни извор поцоланског материјала током хидратације цемента. Унутар микроструктуре формирао је микроарматуру у облику кристалне фолије, што је побољшало механичка својства малтера на бази обичног Портланд цемента, високоалуминатног цемента и мешаних цемента. Истраживањем је доказана ефикасност и погодност пирофилита који се користи као замена за глину у керамици и замена за цемент у малтерима