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Hemp - A Traditional Fiber With Modern Applications
No full textThe use and production of hemp fibers ranged from being extensively used to almost cessation of their production in the mid-twentieth century. However, after overcoming confusion about hemp, the conditions for its renaissance have been created. The transition towards a bio-based economy, sustainable development, and CO2-neutral production triggered the use of eco-friendly, biodegradable, and renewable hemp fiber for textiles and other applications. The sustainable advantages of hemp fibers include easy adoption to different climatic conditions, short cropping period, low soil quality and nutrient demands, moderate water usage, and high biomass yield. High specific strength and stiffness and excellent hygienic and protective properties of hemp fiber raised interest in developing various hemp-based products for versatile applications. This chapter discusses the properties of hemp fibers and their processing at the current level of technological development. The sustainability aspects of hemp fibers are summarized. The chapter highlights the versatile applications of hemp fibers in the clothing and technical textile sector, paper industry, construction, and energy sectors, including innovative uses. Hemp-based composite materials are also presented. In addition to the benefits offered by hemp fiber application, the challenges of its future development are discussed for each application sector
Self-healing efficiency of ceria-doped Zn-Co coatings: Insights into particle-free versus biphasic plating baths
No full textAchieving the superior properties of nanocomposite materials involves addressing several challenges, particularly the agglomeration of nanoparticles in the plating bath. This study focuses on the electrodeposition and characterization of Zn-Co-CeO2 composite coatings using a particle-free plating bath, an effective strategy for mitigating agglomeration. For comparison, the composite coatings were also deposited from a traditional biphasic plating solution. The coatings were deposited galvanostatically at various current densities. Scanning electron microscopy revealed that using a particle-free plating solution in conjunction with lower current densities enhanced the compactness and the overall quality of the coatings. Lower current densities favoured the codeposition of particles, as indicated by energy-dispersive X-ray spectroscopy results. Notably, the coatings produced from the particle-free bath exhibited significantly improved corrosion resistance and durability in chloride-rich environments, attributed to their self-healing properties, as shown by electrochemical impedance spectroscopy
Multifunctional reusable Ag-decorated ZnO nanostructured photocatalyst obtained by green synthesis
No full textThis work examined an environmentally friendly precipitation method for preparing zinc oxide decorated with
silver using chitosan as a non-toxic reducing agent. The obtained powders were characterized in detail by XRPD,
FESEM, HRTEM/SAED, PSD, and UV–VIS techniques. Ag/ZnO samples contained wurtzite spherical nanoparticles with an average crystallite size of about 25 nm and cubic Ag distributed on the surface. Compared to the
unmodified ZnO, modification with Ag increased absorption of the visible light regarding the formation of
additional charge carriers, i.e. hot electrons, due to the surface plasmon resonance effect. The recyclable Ag/ZnO
photocatalyst with an optimal content of 1.5 mol. % of Ag, was successfully applied under simulated solar light
for the degradation of four industrial dyes: Reactive Orange 16, Mordant Blue 9, Acid Green 25, and Ethyl Violet.
High repeatability and reproducibility were confirmed. The kinetics and full mechanism of the photodegradation
process through the simultaneous and synergistic influence of light-harvesting Ag and ZnO were also suggested
Polydisperse Pt Deposits Over TiO2-Nanotube-Array-Supported Ru Nanoparticles: Harnessing the Interfacial Synergy for Efficient Hydrogen Evolution Electrocatalysis
No full textDeveloping cost-effective precious metal electrocatalysts for the hydrogen evolution reaction (HER) is key to realizing the economic viability of acidic water electrolysis. Herein, galvanic displacement is employed for in situ formation of bimetallic Pt/Ru deposits on H-intercalated TiO2 nanotube arrays. It is found that a two-step procedure yields polydisperse deposits with a dominant fraction of Ru nanoparticles coated with atomic and subnanometric Pt islands. These Pt|Ru nanointerfaces induce charge transfer from Pt to Ru, which modulates the electronic structure of Pt sites for accelerated HER kinetics. By varying the platinization time in the second step, a balance between the exposure of catalytically active Pt|Ru nanointerfaces and the total number of Pt surface sites is achieved. The optimized composite, termed Ru-30min@Pt-30min, requires an overpotential of 58 mV to deliver a current density of 100 mA cm−2 in 1.0 m HClO4 and maintains performance stability and structure integrity under prolonged operation. Moreover, it presents a 3.5-fold increase in precious metal mass activity over Pt/C at η = 80 mV. Theoretical calculations reveal that the electronic interactions generated by Pt-modification of Ru and hydrogenated TiO2 surfaces provide multiple active sites with improved Hads energetics compared to pure Pt and Ru
Influence of Pre-Corrosion in NaCl Solution on Cavitation Resistance of Steel Samples (42CrMo4)
No full textMarine applications often involve metallic materials, including steel, that must endure harsh conditions such as cavitation erosion (CE). This study investigates the CE behavior of 42CrMo4 steel, both in its original state and after pre-corrosion in a 3.5% NaCl solution for 120 days, simulating a simplified marine environment. Cavitation testing was conducted using an ultrasonic vibratory setup with a stationary sample, at intervals of 10 and 30 min, with a total testing time of 150 min. Mass loss (ML), mass loss rate (MLR), mean depth of erosion (MDE), and level of degradation (LoD) were calculated, while surface roughness (Rz) was measured using a TR200 tester. Surface changes were analyzed through field emission scanning electron microscopy (FESEM) and image analysis techniques. Morphological parameters such as the number of pits, average diameter, and total pit area were used to quantify surface damage. Results showed that pre-corroded samples exhibited a significantly higher erosion rate than non-corroded ones. Pre-corrosion introduced microcracks and surface defects that served as initiation sites for cavitation damage. These imperfections increased surface roughness and created favorable conditions for pit formation, leading to faster and deeper material loss. Image and FESEM analyses confirmed the presence of larger and deeper pits in pre-corroded samples compared to the smaller and shallower pits in non-corroded specimens. This study highlights the impact of pre-corrosion on the cavitation resistance of 42CrMo4 steel and demonstrates the effectiveness of combining mass loss data with morphological and surface analyses for evaluating cavitation damage under marine-like conditions
Advanced Electrocatalyst Design for Efficient Hydrogen Production via Water Electrolysis
No full textThe development of efficient, durable, and cost-effective electrocatalysts for the hydrogen evolution reaction (HER) is pivotal for sustainable hydrogen production via water electrolysis. In pursuit of this goal, we investigated ruthenium-based catalysts supported on titanium oxynitride-carbon (TiON-C) hybrid materials as an alternative to benchmark Pt/C materials. Initially, low-loaded Ru nanoparticles were synthesized on TiON-graphene oxide (Ru/TiON-C), achieving outstanding HER activity in alkaline media. Despite a modest Ru loading of 6 wt.%, Ru/TiON-C surpassed Pt/C benchmarks, delivering 2.5 times higher turnover frequency and 4.5 times higher mass activity. This exceptional performance was attributed to metal-support interaction (MSI) between TiON and Ru, which enhanced water dissociation kinetics and favourably tuned hydrogen adsorption energies at Ru active sites. Strong nanoparticle anchoring on TiON further ensured excellent structural stability under prolonged electrochemical operation [1]. Expanding on these insights, Ir was introduced into the system to obtain core-shell Ru@Ir nanoparticles supported on a TiON-C composite (Ru@Ir/TiON-C). Ru@Ir/TiON-C catalyst leveraged the synergistic effects of Ru and Ir together with MSI, resulting in superior HER activity across both acidic and alkaline environments. Ru@Ir/TiON-C matched the activity of the commercial Pt/C in acid media and outperformed it in alkaline conditions. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations confirmed optimized adsorption energetics for both hydrogen and hydroxide species, elucidating the observed performance enhancements. Overall, this continual study highlights the crucial role of MSI in fine-tuning electrocatalytic properties and minimizing noble metal usage. The synergy between MSI and the Ru@Ir core–shell nanostructures further enhanced electronic interactions, optimized active site performance, and improved catalyst durability. These findings provide a promising pathway for designing versatile, high-performance HER electrocatalysts capable of efficient hydrogen production across a broad pH range
Quantification of Total Phenolics, Phenolic Compounds and Anthocyanins as Contributors to the Antioxidant Activity of Wine
No full textWine is a product of the alcoholic fermentation of grapes or some other fruits, characterized by a highly complex chemical composition. The chemical profile of wine largely depends on the ripeness and quality of the grapes, as well as the agroecological conditions in which the grapes were cultivated. In addition, technological procedures during the primary processing of grapes, the use of oenological agents, temperature regimes during alcoholic fermentation and maceration, oxygen exposure, and the conditions of wine care, storage, and final processing can significantly influence both the sensory characteristics and the chemical composition of the final product. The aim of this study was to determine the content of total phenolics, phenolic compounds profile, and anthocyanins as potential sources of antioxidant activity in wine. Seven wine samples were analyzed, originating from different geographical regions and produced from various grapevine cultivars. The content of total phenolics and anthocyanins was determined using UV-VIS spectrophotometry. The detected concentrations of total phenolics ranged from 866.7 mg/L to 1833.3 mg/L, while the anthocyanin content varied between 31.26 mg/L and 117.90 mg/L. Individual phenolic compounds were identified using liquid chromatography, with gallic acid and catechin found to be the dominant components. The obtained results, along with basic physicochemical parameters of the wines, were processed using chemometric multivariate analysis methods to identify patterns and correlations among the analyzed samples
Prisustvo acesulfama u vodi beogradskih reni bunara kao indikatora komunalnog zagađenja
No full textGrad Beograd je jedna od retkih evropskih prestonica koja ne poseduje postrojenje za prečišćavanje komunalnih otpadnih voda, usled čega se velika količina neprečišćenih otpadnih voda ispušta u reke Savu i Dunav. Ove otpadne vode sadrže različite vrste organskih i neorganskih zagađujućih materija, kao i patogenih organizama koji transportom kroz zemljište mogu da dospeju do podzemnih voda i izvora vode za piće. Iz ovog razloga, u okruženju sa velikim komunalnim opterećenjem, za efikasnu kontrolu kvaliteta voda, veoma su važni pouzdani markeri fekalnog zagađenja. Korišćenje bakterijskih indikatora najčešća je metoda u proceni kontaminacije komunalnim otpadnim vodama, međutim ovaj pristup ima svoje nedostatke poput nespecifičnosti za izvor, kratak životni vek u prirodnim vodama i duže vreme potrebno za analizu. Poslednjih godina sve više su u upotrebi hemijski markeri za identifikaciju kanalizacionog zagađenja, koji omogućavaju bržu i pouzdaniju detekciju, imaju veću specifičnost za izvor i otpornost na degradaciju. Među njima, veštački zaslađivači, kao široko korišćeni prehrambeni aditivi, predstavljaju veoma pouzdane i usko specifične markere zagađenja komunalnim otpadnim vodama, zbog njhove metaboličke inertnosti u ljudskom telu i prisutnosti u visokim koncentracijama u otpadnim vodama, kao i velike stabilnosti u životnoj sredini
Influence of Aging and UV Radiation on Antibacterial Properties of Knitted Fabrics Dyed with Achillea millefolium L. Extract
No full textIn recent years, there has been increasing public concern about ultraviolet radiation (UVR), and clothing is considered to provide the most effective protection against it. In this study, the influence of aging and UVR on the antibacterial properties and degree of coloration of knitted fabrics was investigated. Knitted fabrics of different raw materials compositions in single weaves made of three types of yarn: cotton (CO), bamboo (BAM), and polyester (PES), were used. Samples were treated with methanol extract of Achillea millefolium L. conc. 100 mg/mL, to which citric acid and tannic acid were added, using ultrasonic atomization. Using an ultrasonic atomizer increased the speed of dyeing, shortened the processing time and allowed the use of a smaller amount of extract compared to conventional dyeing. The antibacterial properties of knitted fabrics obtained against Staphylococcus aureus and Escherichia coli were evaluated. The tests of antibacterial properties and color strenght (K/S) of knitted fabrics were done after dyeing, after aging (30 months), and after exposure to UV light with a wavelength of 254 nm and 365 nm. The antibacterial effect of knitted fabrics dyed with A. millefolium L. extract on S. aureus after natural aging and treatment with UV wavelength of 254 nm results in a reduction of the zone of inhibition (Zi) from 23% (BAM) to 57% (CO), compared to Zi after dyeing. Treatment of the samples with UV light with a wavelength of 365 nm increased the Zi against S. aureus, in PES knitted fabric was even higher than after dyeing, while there were no significant changes in E. coli. In CO and BAM knitted fabrics, after aging and exposure to UV radiation, high protection factors (UPF) were found, the values of which ranged from 31.38 to 51.68. Aging and exposure to UV light affect the degree of dyeing and color fastness, which are more pronounced in knitted fabrics made of cotton and bamboo fibers compared to polyester. In addition to the research of the impact of UVA radiation (365 nm), it was important to emphasize that research on UVC radiation (254 nm) was conducted to determine how the disinfection process affects the antibacterial properties of knitted fabric treated with A. millefolium extract.The results obtained from research into the stability of antibacterial treatment to aging and UV radiation represent a significant contribution to the research in the field of medical textiles and textiles intended for the production of clothing for allergic dermatitis. These findings highlight the importance of studying the effects of UV radiation and aging processes on the color fastness and antimicrobial properties of textile materials treated with herbal extracts. The developed materials can be used to protect people from UV radiation. In addition, to create sustainable textiles, future research should include different ways of preparing extracts from plant waste, especially from juice or wine production. The obtained extracts from plant waste would be used to develop innovative processes for antimicrobial dyeing and printing of textiles. In this way, products with improved color fastness and antimicrobial properties against UV radiation and aging could be obtained. The antimicrobial effect of textiles would be tested on a larger number of microorganisms. Depending on the obtained antimicrobial effect, textiles treated with herbal extracts could be used for various purposes, for the production of children’s toys, decorative pillows, sportswear and work clothes in hospitals
Interaction Between Radon, Air Ions, and Ultrafine Particles Under Contrasting Atmospheric Conditions in Belgrade, Serbia
No full textRadon’s radioactive decay is the main natural source of small air ions near the ground. Its exhalation from soil is affected by meteorological factors, while aerosol pollution reduces air ion concentrations through ion-particle attachment. This study aimed to analyze correlations between radon, ions, and air pollution under varying conditions and to assess potential health impacts. Measurements were taken at two sites: in early autumn at a suburban part of Belgrade with relatively clean air, and in late autumn in central Belgrade under polluted conditions, with low temperatures and high humidity. Parameters measured included radon, small air ions, particle size distribution, PM mass concentration, temperature, humidity, and pressure. Results showed lower radon concentrations in late autumn due to high soil moisture and absence of nocturnal inversions. Radon and air ion concentrations exhibited a strong positive correlation for both polarities under suburban conditions, whereas measurements in the urban setting revealed a weak negative correlation, despite radon concentrations in soil gas being approximately equal at both sites. Small ion levels were also reduced, mainly due to suppressed radon exhalation and increased aerosol concentrations, especially ultrafine particles. A strong negative correlation (r 1 µm) showed weak or no correlation due to their lower and more stable concentrations. In contrast, early autumn measurements showed a diurnal cycle of radon, characterized by nighttime maxima and daytime minima, unlike the consistently low values observed in late autumn