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.
This study reports the eco-friendly synthesis of carbon dots (C-dots) from Morus nigra fruits and evaluates their structural, optical, and photocatalytic properties. Transmission electron microscopy (TEM) analysis revealed predominantly spherical C-dots with an average diameter of 4.67 +/- 1.6 nm and an interplanar spacing of 0.286 nm, confirming their crystalline nature. X-ray diffraction (XRD) revealed an amorphous structure with a broad peak at similar to 21.4 degrees, characteristic of small sp(2) domains. X-ray photoelectron spectroscopy (XPS) confirmed the presence of carbon, oxygen, and nitrogen, with surface functional groups including C=O, C=N and O-C=O. The C-dots demonstrated effective photocatalytic activity, degrading methylene blue (MB) dye under solar irradiation with an efficiency of 95.8% at a 2.5 mg/L concentration, following first-order kinetics (rate constant of 0.0345 min(-1)). Photoluminescence (PL) studies showed excitation-dependent emission, with optimal performance at 350 nm, yielding the highest intensity and the longest average fluorescence lifetime of 21.88 ns. The CIE chromaticity coordinates further confirmed the excitation-dependent green luminescence. These results highlight the potential of Morus nigra-derived C-dots for environmental remediation, optical sensing and security-related applications.
