The green synthesis of silver nanoparticle formation using medicinal plants, rich in bioactive compounds, aids in overcoming challenges associated with physical and chemical approaches of nanoparticle synthesis. The current work investigated the biogenic synthesis of Tn-AgNPs using aqueous extracts of Trapa natans stems, a non-conventional medicinal plant, rich in bioactive compounds. The formation of T. natans (Tn)-AgNPs was confirmed by the colour shift and by recording the surface plasmon resonance (SPR) absorption peaks in the range of 420–440 nm in the UV–visible spectrum. Identification of functional groups involved in reduction and stabilisation was conducted using the FTIR spectrum. Transmission electron microscopy (TEM) revealed the formation of short silver nanorods with a length ranging from 160 to 180 nm and a width of approximately 15–30 nm. X-ray diffraction examinations revealed a highly crystalline structure of the resultant Tn-AgNPs. The well diffusion assay demonstrated antibacterial efficacy of Tn-AgNPs with increasing concentration against laboratory reference strain Pseudomonas aeruginosa (ATCC 27853). Additionally, the growth kinetics assay demonstrated significant reductions in the growth absorbance after 24 h. Subsequently, these nanoparticles are also biocompatible up to 20 ppm, as revealed by anti-haemolysis activity. This work aligns with SDG3 and highlights the potential of Tn-AgNPs as an alternative antibacterial agent.
Membrane scaling, particularly CaSO4 (gypsum) crystallisation, severely limits the practical application of pervaporation (PV) desalination for high-salinity wastewater treatment. Herein, an online interception strategy using nitric acid-activated alumina granules (AAG) is proposed to redirect gypsum scaling from the membrane surface to a sacrificial medium. By tuning nitric acid activation, the physicochemical properties of AAG were optimised. AAG activated with 7.5% nitric acid exhibits an optimal pore structure (specific surface area of 295.4 m2/g, pore volume of 0.361 cm3/g) and surface positive charge, significantly reducing the heterogeneous nucleation energy barrier for gypsum crystallisation. This enables the transfer of scaling from the membrane surface to AAG, reducing the membrane surface scaling amount by approximately 45%. Combined with the extended XDLVO theory analysis, the dominant mechanism of surface-induced heterogeneous nucleation by AAG was elucidated. Moreover, ultrasonic–EDTA cleaning enables efficient regeneration of AAG, and the strategy is validated using real reverse osmosis concentrate. This work establishes a scaling control paradigm based on crystallisation relocation rather than inhibition, providing mechanistic insight and a scalable approach for fouling mitigation in PV desalination.
This study develops a dual strategy of synthesis optimisation and B-site substitution to improve low-temperature CO oxidation of LaFeO3 perovskites. A modified co-precipitation method uses organic additives (F127, sucrose, citric acid) as surface area promoters and an ammonia precipitant. Four-factor three-level orthogonal experiments optimise pH, calcination temperature/time and additive type. Calcination temperature dominates performance, followed by additive species, calcination time and pH. The optimal catalyst (pH = 10, 800 °C, 3 hours, citric acid) attains 99.1% CO conversion at 300 °C via enlarged surface area and evenly distributed active phases. 20% Co substitution for Fe creates abundant lattice defects and oxygen vacancies in LaFe0.8Co0.2O3, boosting oxygen mobility and redox ability. It realises full CO conversion at 225 °C, 75 °C lower than pure LaFeO3 with stable structure. Ni/Cu/Mn doping comparisons confirm Co's optimal promotion. This work proves synergistic nanostructure modulation and defect engineering to fabricate efficient perovskites and guides low-temperature CO removal.
Methylene blue is a toxic and persistent dye that requires effective removal from aquatic environments. This study reports sunlight-assisted degradation of methylene blue using surface-decorated AuNP@ZIF-8 and AuNS@ZIF-8 nanocomposites prepared by a time-gated growth strategy, in which preformed gold colloids were added 1 h after the onset of ZIF-8 crystallisation to favour surface localisation. Under indirect indoor sunlight, 1 mg/L methylene blue showed 7% and 14% degradation after 150 minutes with AuNP@ZIF-8 and AuNS@ZIF-8, respectively, while methylene blue alone showed negligible photolysis. UV-Vis spectral changes indicated oxidative degradation rather than simple chromophore bleaching. Under direct outdoor sunlight at 10 mg/L methylene blue and 10 mg/L catalyst, all catalyst systems showed similar degradation of about 57-58% over 240 minutes, whereas methylene blue alone reached 47%, indicating that high photon flux can mask plasmon-specific effects. SEM, PXRD, Raman and UV-Vis confirmed successful composite formation, preserved ZIF-8 crystallinity, and stronger light-matter interaction in AuNS@ZIF-8. These stable, visible-light-responsive nanocomposites show promise for low-resource environmental remediation.
