Band 116, Heft 3

Bisphenol A (BPA), a widely used industrial chemical, is notorious for its bio-accumulative persistence and toxicity, posing significant threats to environmental and public health. The presence of BPA in industrial and wastewater effluents has become a growing concern, necessitating effective removal techniques. Current wastewater treatment methods often fall short in addressing the complexity of BPA contamination under different conditions, which highlights the urgent need for innovative solutions. One promising approach involves the use of clay and clay-derived materials, which have gained global recognition for wastewater remediation due to their abundance, eco-friendliness, low cost, tunability, and potential for regeneration. Recent research trends focus on the functionalisation of clay materials (FCMs), enhancing their efficiency in adsorbing, degrading, and removing emerging organic pollutants such as BPA, as well as heavy metals, pesticides, and polyaromatic hydrocarbons. The functionalisation of clays with various modifiers has been shown to improve their sorption capacity, degradation efficiency, and hydrophobicity. This review aims to systematically highlight the use of FCMs for the removal of BPA from industrial and wastewater effluents. A detailed description of enhanced clay materials and processes of BPA removal from these effluents has been presented in this study. However, to establish its position as an ideal candidate for BPA removal, more investigations are critical to adopt the best modification agent(s) and conditions for functionalisation.

This study presents an innovative and sustainable method for synthesizing hydroxyapatite (HA) from Catla catla fish bones, addressing the need for environmentally friendly materials in biomedical applications. Fish bone waste is transformed into high-performance HA through acid pre-treatment, oven drying, and calcination at 900 °C. Characterization via Fourier-transform infrared spectroscopy and X-ray diffraction confirms the formation of HA with particle sizes ranging from 0.3–0.8 µm, which is ideal for enhancing surface area in biomedical contexts. Scanning electron microscopy and energy-dispersive X-ray spectroscopy reveal a highly porous structure and a Ca/P ratio of 1.68, closely resembling natural bone composition. The bioactivity of HA was evaluated using simulated body fluid over 7 and 28 days, with scanning electron microscopy and energy-dispersive X-ray analyses confirming hydroxycarbonate apatite layer formation, indicated by increased Ca and P content. X-ray diffraction further validates the bioactive nature of HA. In-vitro degradability testing demonstrated controlled degradation over 28 days, alongside pH changes in the SBF solution. Cytotoxicity analysis using human Wharton’s jelly mesenchymal stem cells confirmed the non-toxic nature of HA, showing a cell viability rate of 89.7 ± 3.1 % after 48 h. These findings emphasize the potential of fish bone-derived HA to be used in coating orthopedic and dental implants, creating porous bone scaffolds, and formulating bone cement, establishing it as a highly promising material for diverse biomedical applications.

Bamboo is rich in nutrients, bioactive compounds, and antioxidants. Phenols, flavonoids, and vitamins C and E are the primary antioxidants present. In this report, pristine ZnO NPs were prepared by a green co-precipitation route using a bamboo stem extract. The Rietveld refined X-ray diffraction pattern confirmed pure phase formation of ZnO NPs and having a wurtzite hexagonal structure with space group = P 63 mc . The William˗Hall method was used to calculate the crystallite size which was found to be 35.38 nm with a compressive strain of −1.43 × 10 −3 . Scanning electron microscopy confirmed the mushroom-like surface morphology. Fourier transform infrared spectroscopy study, antisymmetric stretching confirms Zn–O bonding. A strong absorption peak around 380 nm was observed in ultra-violet spectra and a broad emission band at ∼389.5 nm (3.18 eV) was confirmed by photo-luminescence spectroscopy.

The solid-state reaction method was used to prepare the lead-free Bi 0·5 Na 0·5 Nb 0·5 Fe 0·5 O 3 ceramic. The X-ray diffraction pattern of the prepared ceramic confirmed the formation of tetragonal crystal structure with P4mm space group. The field emission scanning electron microscopy analysis reveals densely packed grains of different shape and sizes. The average grain size was calculated to be 16.22 µm. Complex impedance spectroscopy was used to analyze the electrical response of the ceramic. The Nyquist plot shows the influence of both grain and grain boundary effects on the electrical properties of the material. The impedance analysis confirmed the non-Debye type of relaxation mechanism and negative temperature coefficient of resistance behaviour of the compound. The frequency dependent ac conductivity was found to obey Jonscher’s power law.

Self-lubricating composites are new-generation composites for automotive and aerospace applications due to their attractive structural and lubricating properties. Aluminum-based composites with 2D-WS 2 reinforcement could improve the tribological properties to reduce the wear rate of the components. This study reports the fabrication and augmentation of structural and mechanical behavior of a novel Al-based self-lubricating hybrid composite. The density and hardness of the composite increase up to 2.94 g cm −3 and 112 ± 6.3 HV respectively with hybrid reinforcements of SiC, Al 2 O 3 , and 2D-WS 2 . The microstructure shows SiC, Al 2 O 3 are distributed uniformly and WS 2 phase is localized at the grain boundary. For Al 2 O 3 and 2D-WS 2 combination, the friction coefficient is 0.16 and for the Al–Al 2 O 3 –SiC–WS 2 , it is 0.14. Correspondingly the corrosion rate is 0.00213 mm a −1 for Al–Al 2 O 3 –SiC–WS 2 as compared to Al–Al 2 O 3 –WS 2 (0.01565 mm a −1 ) and Al–SiC–WS 2 (0.01477 mm a −1 ) composites. Based on the experimental findings Al-based composites with hybrid reinforcements lead to reduced wear and corrosion rate suitable for tribological applications.

A series of experimental tests were carried out in this study to investigate the effect of tempering temperature on the metallurgical and mechanical properties of nitrided low-alloy steels. The low-alloy steel samples were previously subjected to tempering treatment. Phase constituents, hardness distribution, residual stresses, and growth rate of the nitrided layers are investigated using scanning electron microscopy, X-ray diffraction, Vickers microhardness, and mass spectrometry. It was found that the application of a tempering treatment at 600 °C before the nitriding process was accompanied by a high hardness and a distinct residual stress–depth profile inducing an improvement of the mechanical properties such as fatigue and wear resistances. Furthermore, to estimate the diffusion parameters and analyze their variation with the nitriding temperature, we proceeded in two steps. First, numerical simulations using the Abaqus finite element calculation code were carried out to calculate the nitrogen concentration and its diffusivity in the steel sample. Then, from these results, a mathematical approach was proposed to evaluate the diffusivity and the maximum nitrogen content.

Near fully-dense B 4 C/Al functionally graded materials were prepared by a one-step spark plasma sintering infiltration technique. Microstructural examination and X-ray diffraction analysis indicated that no observable reaction occurred between B 4 C and Al during the spark plasma sintering infiltration process. The Vicker’s hardness of the as-prepared B 4 C/Al material exhibited a gradient decrease from the highest value of 30.5 GPa to the lowest of 1.1 GPa, demonstrating an excellent hardness gradient. This typical processing method could serve as an alternative strategy for fabricating similar ceramic/metal functionally graded materials systems, which consist of major compositions with significant melting point differences.