Removal efficiency of methylene blue using geopolymeric materials based on pumice: influence of sodium hydroxide concentration in alkaline activator

Wastewater streams from industrial sources contain various dissolved organic pollutants that pose environmental contamination challenges even at extremely low concentrations if discharged. Porous materials, such as graphene-based functional frameworks, have been demonstrated to efficiently adsorb such contaminants, but significant scope remains to improve their adsorption efficiency, versatility and reusability. We have recently developed the graphene oxide vortex-ring (GO-VR) particles, whose unique ‘donut’ shape has been shown to deliver exceptional adsorptive removal efficiency. In this study, we further develop a carboxymethylcellulose (CMC)- functionalised GO-VR particle system that achieves ambi-functional adsorptive removal of cationic and anionic model dyes, methylene blue (MB) and methyl orange (MO). Various key factors affecting the adsorption process, including pH, adsorbent dose, particle shape, contact time, and initial dye concentration, are optimised and investigated. The optimum values of pH for MB and MO adsorption are 10 and 6, respectively, at which the adsorption capacity of GO/CMC-VR particles for MB and MO are 988 ± 5.84 mg/g and 783 ± 13 mg/g, respectively, resulting in 100% contaminant removal even at very low contaminant concenration of 5 ppm and using a very low adsorbant dose of 0.005 mg/ml. The pseudo-second-order kinetic adsorption model fits well to the fast remediation rates, confirming that the driving force is predominantly electrostatic. Furthermore, we demonstrate that the particles can be regenerated in an elution cycle and reused in adsorption-desorption cycles, retaining their high adsorption efficiency and improving the sustainability of this approach. GO/CMC-VR particles are rapidly emerging as a promising universal adsorbent for the remediation of dissolved pollutants from wastewater. • GO/CMC-VR with a donut-shape particle is synthesised. • CMC functionalization enables dual removal of cationic and anionic azo dyes. • High adsorption capacities achieved for MB and MO at optimised pH. • Fully dye removal at ultra-low adsorbent dosage and low contaminant concentration. • Rapid kinetics and excellent regeneration ensure sustainable use.

In this study, powders of BaBi (1- x ) Co x O 3 (with x = 0, 1, 2, 4, and 8 mol%) were synthesized using a sol-gel method. These samples were characterized by several techniques, including X-ray diffraction (XRD), Raman scattering, UV–Visible spectroscopy, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS, Mott-Schottky), and field-emission scanning electron microscopy (FESEM) with associated EDX chemical analysis. The photocatalytic properties were then assessed against methylene blue (MB) dye. The results indicate that Co doping preferentially occurs at the Bi 3+ sites, leading to the formation of defects in the BaBiO 3 lattice. These defects significantly enhance the photocatalytic activity, leading to approximately 80% MB degradation within 120 min. The photocatalytic activity of BBO against MB dye showed a 14% increase in efficiency under acidic pH conditions, whereas the BBO8C sample proved to be 22% more efficient in a neutral medium compared to the acidic environment. The photocatalytic process was primarily driven by electron-mediated phenomena, as indicated by the 8% and 71% reductions in activity for BBO and BBO8C, respectively, upon the addition of electron scavengers. The findings suggest that Co-doped BaBiO 3 is a promising material for liquid waste treatment, demonstrating effectiveness in degrading methylene blue dye under various environmental conditions. • Facile sol-gel synthesis of Co-doped BaBiO 3 without secondary phases. • Co doping shifts the CB from −0.26 to −0.77 V for enhanced photoactivity. • BaBiO 3 :8%Co achieved 80% degradation of MB dye within 120 min. • The photocatalytic process is primarily driven by electrons. • High chemical stability and reusability over four consecutive catalytic cycles.

The paper explores the synthesis, characterization, and photocatalytic activity of La 2 O 3 nanoparticles synthesized through the hydrothermal method at reaction temperatures of 150 °C and 200 °C, selected based on preliminary optimization and literature reports to balance nucleation, crystallinity enhancement, and defect suppression. XRD study validated the development of cubic phase La 2 O 3 with mean crystallite sizes of 17.36 nm and 20.21 nm, showing improved crystallinity with increasing temperature. Vibrational modes were observed by Raman spectroscopy, and a temperature dependent optical band gap shift was observed by the UV-Vis analysis, which is characteristic of the optical properties. It was revealed in morphological studies that the nanoparticles were rounded in shape and had sizes ranging between 52 and 60 nm. PL spectra demonstrated that higher synthesis temperatures reduced charge carrier recombination by minimizing structural defects, thereby improving optical performance. It was also found that La 2 O 3 nanoparticles obeyed the first-order kinetics in the degradation of methylene blue (MB) and rhodamine B (RhB) dyes since photocatalytic experiments were conducted. The efficiencies of the degradation in mercury light were 90.9% with MB and 85.2% with RhB, with rate constants of 1.39 x 10 - 2 min -1 and 1.08 x 10 -2 min -1 , respectively. The use of scavenger tests revealed that the primary reactive species are the hydroxyl radicals (OH) because the isopropyl alcohol had a significant impact on the photocatalytic activity, whereas EDTA and benzoquinone revealed the presence of minor roles of holes and superoxide radicals. These findings establish clear temperature, structure, and property performance relationships in La2O3 nanoparticles, demonstrating temperature-tunable bandgap engineering for optimized photocatalysis, making La 2 O 3 a promising photocatalyst for environmental remediation and advanced nanotechnology applications. • Hydrothermal temperature tunes La 2 O 3 crystallinity and defects • Bandgap narrowed from 5.01 eV to 4.79 eV at 200 °C • Reduced charge recombination confirmed by PL analysis • 90.9% MB and 85.2% RhB degradation achieved • Stable photocatalytic performance over five cycles

Recently, environmentally friendly green synthesis technologies utilizing nanoparticles have been developed for removing harmful textile dyes, which currently cause significant harm to human health and the ecosystem. In this regard, our study investigates the green synthesis of silver nanoparticles (PSC-AgNPs) using Paliurus spina-christi fruit (PSC) as a stabilizing agent and evaluates their photocatalytic properties and in vitro cytotoxicity studies. The synthesized PSC-AgNPs exhibited surface plasmon resonance (SPR), the phytochemicals responsible for the bioreduction of AgNPs, nanoscale size, uniform spherical morphology and well-defined crystalline structure, as confirmed by spectroscopic and microscopic analyses. The effectiveness of the synthesized PSC-AgNPs in removing dyes from aqueous solutions was evaluated using methylene blue (MB) as a synthetic basic dye and Reactive Red 194 (RR 194) as a textile dye. Notably, the photocatalytic activity of the synthesized PSC-AgNPs in degrading the RR 194 dye has been demonstrated for the first time. The removal efficiency of MB and RR 194 dyes treated with the PSC-AgNPs reached 96.84% at 120 min and 69.73% at 160 min, respectively. Furthermore, the in vitro cytotoxicity of PSC extract and PSC-AgNPs against human pancreatic cancer cells (MIA PaCa) was assessed using the MTT assay, resulting in a dose-dependent response. In light of these results, the eco-friendly synthesized AgNPs exhibited effective photocatalytic capabilities in degrading MB dye and RR194 dye without the addition of any catalysts, making them a promising candidate for environmental remediation.

Biocompatible goethite crystal phase iron oxide nanoparticles from Pithecellobium dulce exhibit dye degradation potential and protective effect against aquatic pathogen Aeromonas hydrophila infection in a zebrafish model

Anthocephalus cadamba leaf extract mediated synthesis of copper oxide nanoparticles and evaluation of their methylene blue dye degradation, antioxidant and anti-inflammatory properties

Nuclear factor erythroid 2-related factor 2 induction abrogates mitochondrial stress through parkin regulation.

Flexible glucose biosensor via co-electrodeposition of methylene blue and glucose oxidase on carbon nanotube yarns.

Boosting the adsorption capacity/selectivity of graphene oxide membranes via photocatalytic perforation for water treatment

Flexible SERS tape: A plasmonic hybrid of AuNPs and layered K2Ti8O17 nanowire network for on-site detection of pesticide residues.

Repeated sublethal photodynamic inactivation does not increase biofilm formation or induce resistance in Acinetobacter baumannii.

Multiple interactions tailoring nanocellulosic-carbon dots membrane for synergistic, self-cleaning and recyclable interception of heavy metals/dyes pollutants in wastewater.

Acid-treated sodium alginate-based composite gel microspheres toward methylene blue removal: Fabrication and mechanistic insights.

Novel nanocomposites including oxide, carbonate, and hydroxide phases for efficient methylene blue dye adsorption

Calcium ferrate-ozone for enhanced removal of methylene blue: An innovative hybrid system

Visible-light photocatalytic removal of methylene blue using g-C3N4/CuWO4 nanocomposites

Synergistic effects of combining ZIF-8 and graphene oxide inside cellulose acetate-based mixed matrix membranes on the removal of methylene blue

Flexible and application-oriented surface-enhanced Raman spectroscopy (SERS) substrates are in high demand for trace-level molecular detection in complex environmental matrices. Herein, we report the development of a flexible hybrid SERS substrate supported on polydimethylsiloxane (PDMS), integrating phase-engineered 1T/2H-MoS2 nanoclusters decorated with Au nanoparticles (denoted as PDMS@1T/2H-MoS2@Au). Benefiting from the synergistic coupling between localized surface plasmon resonance (LSPR) of Au nanoparticles and charge-transfer-induced chemical enhancement from 1T/2H mixed-phase MoS2, the as-fabricated substrate exhibits strong and tunable SERS responses under multiwavelength excitation. Systematic SERS performance evaluations demonstrate that the substrate achieves high sensitivity with a detection limit down to 10-10 M for methylene blue (MB), excellent signal uniformity with a relative standard deviation (RSD) of 6.57%, and long-term stability with negligible signal degradation over 2 months, outperforming most flexible SERS substrates. Notably, multivariate analysis based on principal component analysis (PCA) reveals selective signal amplification toward MB in multicomponent dye systems, where the first principal component shows a strong correlation with the Raman fingerprint of MB. After spectral normalization, the PCA score plots further confirm the reliable molecular discrimination capability among multiple dye molecules. Importantly, the practical applicability of the flexible PDMS@1T/2H-MoS2@Au substrate is validated by the trace-level detection of the pesticide thiram on real apple surfaces through conformal contact, achieving a detection limit as low as 10-9 M. This work presents an application-focused sensing workflow, from the elucidation of the enhancement mechanism to real-sample analysis, highlighting the great potential of flexible MoS2-Au hybrid SERS substrates for advanced environmental and food safety molecular sensing.

Neonatal cyanosis is commonplace, usually from respiratory or cardiac causes. Consideration of alternative or combined aetiologies was required when a 3-hour-old term male neonate with central cyanosis, low oxygen saturation (SpO2), and persistent pulmonary hypertension of the newborn (PPHN) confirmed on echocardiography, failed to respond to PPHN interventions. The high oxygen saturation gap and methemoglobin (MetHb) level of 16.2% shifted the working diagnosis to methemoglobinaemia. Possible triggering drugs were stopped and methylene blue was given without effect, prompting testing for haemoglobin variants. Though the SpO2 remained in the mid-80s, MetHb levels decreased, pulmonary pressures normalised by day of life (DOL) 4, and he was discharged home on DOL 22. Diagnostic testing confirmed the haemoglobin F-M-Fort Ripley mutation (HBG2: c.277C>T), a variant that affects fetal haemoglobin only and is therefore self-limited. In this case, the concurrent presentation of PPHN and congenital methaemoglobinaemia created significant diagnostic and therapeutic challenges.