Search Results (133)

In the present study, Fe₃O₄@hydrothermal carbon was prepared successfully using rice straw waste. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis confirmed that the material had rich and strong redox-active centers on its surface, indicating that it has potential to be used as a redox mediator for electron transfer. Fe₃O₄@hydrothermal carbon was added into the anaerobic sludge treatment system for the collaboration of dye decolorization. The results showed that azo dye decolorization efficiency reached the maximum value (98.3%) with the presence of Fe₃O₄@hydrothermal carbon, which was 16.6% higher than control reactor (without Fe₃O₄@hydrothermal carbon added). In addition, Fe₃O₄@hydrothermal carbon exhibits good reusability and the dye decolorization rates in the “anaerobic sludge–material” combining system were significantly higher than that in the “sludge-alone” system during the semi-continuous wastewater treatment process. Mechanistic investigations revealed that the enhanced decolorization is driven by a synergistically constructed interspecies electron transfer pathway. Specifically, the addition of Fe₃O₄@hydrothermal carbon improved the formation of the extracellular polymeric substance (EPS), which had positive effects on sludge stability and its interaction with the material. CV and electron transport system (ETS) activity analysis showed that the sludge exhibited high electrochemical activities with the support of the material, which led to a high electron transfer efficiency between the electron-donating and accepting microbial pairs in the treatment system. The high-throughput sequencing analysis showed that the structure of the microbial community changed during the semi-continuous treatment process; Megasphaera and Clostridium accounted for more than 87.5% of the total abundance of the bacterial community in the anaerobic sludge with material addition. Driven by the material-mediated process, these enriched functional taxa exhibited a high electron transfer efficiency between electron-donating and accepting pairs, accelerating the catalytic cleavage of azo bonds and ultimately improving the overall anaerobic treatment performance. Full article

The adsorption and desorption behavior of the azo dye Orange II (OII) was investigated using composite beads prepared from shrimp shell–derived chitosan (50 wt%) and montmorillonite-rich clay. The structural and morphological properties of the synthesized beads were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR (Fourier Transform Infrared Spectroscopy). Batch adsorption experiments were performed to evaluate the removal efficiency of OII from aqueous solutions under various conditions, revealing that a low adsorbent dosage (0.5 g L⁻¹) and an acidic medium (pH 4) provided optimal adsorption performance. Adsorption kinetics and equilibrium isotherms were analyzed to elucidate the adsorption mechanism. Thermodynamic parameters indicated that the adsorption process was spontaneous (ΔG° < 0) and endothermic (ΔH° > 0). Equilibrium data were fitted to both Langmuir and Freundlich isotherm models, with the Freundlich model providing the best correlation (R² = 0.99), suggesting multilayer adsorption on a heterogeneous surface. The adsorption capacity increased significantly with temperature, rising from 98.35 mg g⁻¹ at 298 K to 182.57 mg g⁻¹ at 318 K, further confirming the endothermic nature of the process. Kinetic analysis revealed relatively rapid adsorption, with maximum adsorption capacities increasing from approximately 100 mg g⁻¹ at 25 °C to 123 mg g⁻¹ at 45 °C. Regeneration and reusability tests demonstrated that the composite beads could be reused through adsorption–desorption cycles; however, a gradual decline in removal efficiency was observed, decreasing from 97% in the first cycle to 25% after the fifth cycle. This decrease is likely associated with partial structural degradation or the detachment of bead components during repeated regeneration. Overall, the results highlight the potential of chitosan–clay composite beads as promising and sustainable adsorbents for the removal of azo dyes from aqueous media. Full article

Background/Objectives: Investigating the modified derivatives of known cell-penetrating peptides can highlight the important residues in the peptide sequence and help understand the cellular uptake mechanism better. Moreover, comparing peptides with different fluorescent-dye positions can highlight the importance of the conjugation site. Earlier, it was demonstrated that the fluorescence quencher 4-((4-(dimethylamino)phenyl)azo)benzoyl (Dabcyl) group can enhance the internalization efficiency of highly cationic oligoarginine peptides. However, its effect in the case of arginine-rich penetratin, a secondary amphipathic cationic CPP, remains undiscovered. Methods: Here, several penetratin derivatives were studied in which the aromatic residues were substituted and the effect of Dabcyl modification was also studied on the cellular uptake of peptides by flow cytometry. Results: The triple Nal-substituted penetratin and dodeca-penetratin with N-terminally positioned carboxyfluoresein (Cf) dye demonstrated remarkable internalization efficiency compared to penetratin. Moreover, almost all the Dabcyl-modified peptides were superior to penetratin except two peptides with C-terminal Cf-labelling. This result highlights the importance of the structure of the conjugate. The position of the cargo molecule may have a high impact on internalization ability. The relatively low cellular uptake of the Trp48 residue-substituted Dabcyl-Pen12 points to the importance of this residue in the cellular uptake of dodeca-penetratin. The confocal microscopic studies revealed that, besides the greater penetration efficiency of Dabcyl penetratin derivatives, these peptides enter the cytoplasm of cells in an increased manner. Conclusions: We identified several intriguing derivatives and expanded the applicability of Dabcyl, while also highlighting its limitations. Additionally, the critical role of Trp48 in the penetratin sequence was reaffirmed, along with the importance of the fluorescent molecule’s position. Full article

The secondary effluent from printing and dyeing wastewater contains recalcitrant organic pollutants, such as azo dye derivatives. Their persistence in aquatic environments not only creates ecological risks but also hampers the high-value reuse of reclaimed water. This study investigated the influence of typical binary anions on the degradation performance of low-concentration azo dye wastewater using a Ti/RuO₂-IrO₂ anode electrochemical oxidation system. The results demonstrated that maximum COD removal efficiency could reach 50.22%, and the controlling factors synergistically regulated the contribution and competition between Reactive Chlorine Species and free radicals. This led to a characteristic “rapid rise–decline–slow rebound” phenomenon in the COD removal rate, with the inflection points co-influenced by the current density, conductivity, and binary anion ratio of the electrochemical process. Furthermore, it alters the degradation pathway of the azo dye to “azo bond cleavage → demethylation/desulfonation → dehydroxylation/deamination oxidation → benzene ring opening”. Within a fixed duration of 60 min, the Response Surface Methodology model identified the optimal COD degradation conditions as follows: current density of 19.72 mA/cm², Cl⁻/SO₄²⁻ ratio of 5.40, and conductivity of 8.30 mS/cm. This research elucidates the differences between the electrochemical oxidation degradation pathway of low-concentration azo dye wastewater under the regulation of typical binary anions and the conventional pathway. It also reveals the regulatory effects of current density, conductivity, and binary anion ratio on the degradation patterns. Full article

This study evaluated the electrochemical and oxidative performance of titanium-supported RuO₂–SnO₂–Sb₂O₅ mixed metal oxide electrodes (hereafter denoted as RuO₂–SnO₂–Sb₂O₅/Ti) for degrading three aniline-based dyes and their mixture using electro-oxidation (EOx), electro-Fenton (EF), and photoelectron-Fenton (PEF) processes. Electrochemical characterization showed quasi-reversible redox behavior and fast electron-transfer kinetics, while SEM, AFM, and EDS analyses revealed a rough surface with fissures and agglomerates that increased the real electroactive area to 4.85 cm², supporting the high catalytic activity. Spectroscopic analyses confirmed the functional groups typical of azo dyes, and RNO assays verified sustained hydroxyl-radical production during electrolysis. Current density was the main operational factor: at 50 mA cm⁻², decolorization exceeded 90% due to enhanced ^•OH generation, whereas higher initial dye concentrations decreased reaction rates because of surface saturation and diffusion limitations. Among the oxidation processes, EF was most effective for Brown KK and Brown 5VR, EOx performed best for Brown NT, and PEF showed a slight advantage for the dye mixture owing to UV-assisted regeneration of reactive species. COD removal followed similar trends, with Brown KK mineralizing fastest and Brown 5VR showing the highest recalcitrance. Analysis of H₂O₂ and active chlorine indicated that EOx favors the accumulation of chlorine-derived oxidants, whereas PEF maximizes H₂O₂ conversion to ^•OH and reduces chlorinated by-products, positioning PEF as the most efficient and environmentally favorable option for treating chloride-containing wastewater. Full article

Textile wastewater contains recalcitrant azo dyes and auxiliary chemicals that are resistant to conventional biological treatment, resulting in persistent organic pollution in aquatic ecosystems. While supercritical water oxidation (SCWO) achieves superior chromophore mineralization, its high energy requirements limit industrial scalability. Conversely, biomass-derived activated carbon (BAC) offers a low-cost adsorption solution, but it rapidly becomes saturated with toxic oxidation intermediates. Notably, the literature lacks systematic analyses of hybrid SCWO-BAC systems with integrated thermal energy, which represents a crucial gap in assessing their economic feasibility. This review employed a systematic methodology, selecting studies relevant to the topic from peer-reviewed publications and databases, including Scopus, SciELO, ScienceDirect, and Google Scholar, for critical synthesis. Using SCWO as a pretreatment (which significantly reduces COD load), followed by BAC polishing, results in superior detoxification compared to individual processes. However, three barriers hinder scale-up: (i) chloride ion corrosion in real effluents; (ii) irreversible collapse of BAC pores after multiple regeneration cycles; and (iii) absence of standardized ecotoxicity data for hybrid-treated streams. This work outlines a technological roadmap for integrated supercritical water oxidation and biological activated carbon (SCWO-BAC) systems, targeting economically viable operational parameters for industrial-scale implementation. Full article

The main objective of the work was to prepare a series of new activated biocarbons by chemical activation of black chokeberry seed and to assess their suitability for removing cationic and anionic dyes from an aqueous medium. Activation of the precursor was performed at 550 °C with orthophosphoric acid, using conventional or microwave-assisted heating. The activated biocarbons were characterized in terms of elemental composition, textural parameters, surface morphology, acid-base character of the surface, as well as electrokinetic properties. Adsorption tests were carried out against two organic compounds: methylene blue (thiazine dye of cationic character) and Congo red (azo dye of anionic character). The influence of the initial dye concentration (5–120 mg/L), temperature (20–40 °C), and solution pH (2–10) on dye removal efficiency from the liquid phase was investigated. Additionally, kinetic adsorption tests were carried out to determine the rate and mechanism of the dyes removal process. Microwave-assisted chemical activation with H₃PO₄ proved to be a very effective approach for generating a high specific surface area (884 m²/g) and a micro/mesoporous structure, which directly increases the adsorption capacity of activated biocarbons towards cationic and anionic synthetic dyes. The maximum adsorption capacities for methylene blue and Congo red were 194.5 and 68.6 mg/g, respectively. It was also confirmed that the choice of heating method at the activation stage plays a key role in determining the physicochemical properties and adsorption performance of the activated biocarbons prepared from waste biomass. In general, carbonaceous adsorbents derived from black chokeberry seeds exhibit high potential for the treatment of dye-contaminated wastewater. Full article

Organic phase change materials (OPCMs) show immense application potential in solar energy storages owing to high energy storage capacity and latent heat efficiency. However, it is difficult to achieve prolonged energy storage due to the sensitivity of phase change to environmental temperature, and adding other substances will lead to a decrease in total energy density. Herein, azobenzene organic phase change composite (C₁₄Azo-MA) was designed and prepared by doping myristic acid (MA) with an azobenzene derivative (C₁₄Azo) featuring a carbon chain identical to that of the MA matrix. C₁₄Azo-MA was systematically characterized by UV–Visible absorption spectroscopy and differential scanning calorimetry. The results showed that the C₁₄Azo-MA retains the same isomerization properties as the C₁₄Azo dopant. C₁₄Azo-MA, due to its molecular photoisomerization and enhanced intermolecular interactions, establishes a new energy barrier and forms supercooling within C₁₄Azo-MA, thereby allowing the storage of thermal energy below the crystallization temperature of MA. Notably, the C₁₄Azo-MA exhibits a high energy density of 225.08 J g⁻¹, surpassing that of pure MA by 14.42%. This work holds significant potential for solar energy storage applications. Full article

A review of studies has shown that aromatic azo and hydrazo derivatives are used in a wide spectrum of fields, including food, pharmaceutical, and cosmetic products, as well as in technical and electronic technologies, which has contributed to the development of new such compounds. In this work, the structures of newly obtained 4-methyl-3,5-dinitro-2-(2-phenylhydrazinyl)pyridine (4MDNPHP) and its azo derivative, 4-methyl-3,5-dinitro-2-[(E)-phenyldiazenyl]pyridine (4MDNPAP), were established by spectroscopic (NMR, IR, Raman, and UV-Vis) and emission studies. Single-crystal X-ray diffraction analysis was used to determine the molecular structure of the studied compounds, and the results were compared with DFT calculations (B3LYP/6-311G(2d,2p)). The collected X-ray data revealed that the crystal of the hydrazo compound (4MDNPHP) belongs to the triclinic space group P$\overline{1}$ (Z = 2), whereas the crystal of the azo compound (4MDNPAP) follows the symmetry of the monoclinic space group P2₁/n (Z = 4). Both presented derivatives crystallized with one molecule in the asymmetric unit. Specific properties of the hydrazo bridge C_ϕ-NH-NH-C_θ moiety and its azo counterpart C_ϕ-N=N-C_θ were considered in detail. Full article

Eugenol, a natural product abundant in clove oil, represents a promising precursor for the synthesis of azo dyes, proving potential for textile coloration. The eugenol azo dyes were synthesized and characterized, showing stable absorption profiles across a wide pH range. Their application to cotton and wool knitted fabrics by exhaustion dyeing demonstrated good affinity, particularly for wool, while chitosan pretreatment improved washing fastness in cotton. These eugenol-derived azo dyes emerge as promising candidates for sustainable textile coloration. Full article

The ability of ultrasound/peracetic acid (US/PAA) to degrade the azo dye Sunset Yellow FCF (SSY) was evaluated considering the impacts of power, pH, inorganic carbon, common salts, radical scavengers, and real water matrices. Pseudo-first-order rate constants revealed synergy indices of 2.90, 3.28, 2.22, and 2.03 at electrical powers of 40, 60, 80, and 100 W, respectively. Selective scavenger assays revealed a mixed radical regime. ^•OH radical involvement was confirmed by inhibition with alcohols (tert-butanol, 2-propanol), benzoic acid, nitrobenzene, sodium azide, and phenol, while suppression by TEMPO highlighted the key role of PAA-derived acyl and peroxyl radicals. Nitrobenzene caused pronounced inhibition at elevated doses, while nitrite acted as a decisive quencher by converting ^•OH and other oxidants into less reactive species. Carbonate alkalinity exerted dual effects: at acidic pH (3.7–4.4) it diverted ^•OH radicals to carbonate radicals and reduced cavitation through dissolved CO₂, whereas at near-neutral pH it buffered conditions toward the optimum (pH 9) and enhanced degradation. Common anions (chloride, sulfate, nitrate) at ≤10 mM produced minor effects. Tests in environmental waters revealed the following reactivity order: seawater > ultrapure water > tap water ≈ Zamzam water > tertiary effluent. Enhanced performance in seawater was attributed to halide-mediated formation of reactive chlorine and bromine species, while inhibition in effluent was linked to organic matter scavenging. Overall, US/PAA emerges as a robust and adaptable advanced oxidation process for azo dye abatement across diverse water matrices. Full article

The search for bioactive compounds with antioxidant properties is critical in combating oxidative stress-related diseases and advancing novel therapeutic agents. Azo dyes, traditionally used in textiles, food, and cosmetics, have recently attracted attention due to their emerging biological activities, including antioxidant potential. In this study, we synthesized and characterized 267 azo dyes derived from natural phenolic cores such as salicylic acid, syringol, and 5,6,7,8-tetrahydro-2-naphthol. Eighteen of these compounds are novel. Structural characterization was performed using NMR, UV-Vis, IR spectroscopy, and mass spectrometry. Antioxidant activity was assessed using in vitro assays with ABTS radical scavenging method. SAR analysis revealed that dyes derived from syringol and 5, 6, 7, 8-tetrahydro-2-naphthol showed the most consistent and potent antioxidant activity. Notably, azo dyes bearing fluoro and nitro substituents in the para position exhibited the lowest IC₅₀ values, highlighting the influence of electron-withdrawing groups and substitution patterns on antioxidant behavior. This work establishes a precedent for SAR-driven evaluation of azo dyes using ABTS and supports their further exploration as functional antioxidant agents in medicinal chemistry. Full article

Organic phase change materials (OPCMs) offer high energy density for thermal storage but suffer from crystallization kinetics dependent on ambient temperature, leading to uncontrolled heat release and limited storage lifetime. Although doping OPCMs with azobenzene (Azo) derivatives enables optically controlled energy storage and release, existing systems require UV irradiation for E-to-Z isomerization. This UV dependency seriously hinders their development in practical solar applications. Herein, we develop a visible-light-responsive Azo@OPCM composite by doping tetra-ortho-fluorinated azobenzene into eicosane. Systematic characterization of composites with different dopant ratios via UV–visible spectroscopy and differential scanning calorimetry reveals that green-light irradiation drives E-to-Z isomerization, achieving 97–99% Z-isomer conversion. This photoisomerization could introduce supercooling through photo-responsive energy barriers generated by Z-isomer, allowing thermal energy storage at lower temperatures. Subsequent blue-light irradiation triggers Z-to-E reversion to eliminate supercooling and enable optically controlled heat release. Additionally, by regulating the molar ratios of dopant, the optimized composites achieved 280.76 J/g energy density at 20% molar doping ratio, which surpassed that of pure eicosane and the reported Azo-based photothermal energy storage system. This work establishes a complete visible-light-controlled energy harvesting–storage–release cycle with significant potential for near-room-temperature solar thermal storage applications. Full article

This study systematically investigated the decolorization efficacy and detoxification effect of crude laccase derived from Pleurotus ostreatus yang1 on azo and triphenylmethane dyes. This research encompassed decolorization efficiencies for 15 dyes (7 azo dyes and 8 triphenylmethane dyes), time course decolorization kinetics, and detoxification assessment using rice (Oryza sativa) and wheat (Triticum aestivum) seed germination as phytotoxicity indicators for both single-dye and mixed-dye systems. Molecular docking was employed to elucidate the laccase–dye interaction mechanisms. The results demonstrated that crude laccase from Pleurotus ostreatus yang1 exhibited significant decolorization efficiency and effective detoxification capacity toward both azo dyes and triphenylmethane dyes. It also displayed considerable decolorization efficiency for mixtures of azo and triphenylmethane dyes (mixture of two types of dyes), along with strong detoxification capability against the phytotoxicity of mixed dyes. Crude laccase showed robust continuous batch decolorization capability for azo dyes Alpha-naphthol Orange (α-NO) and Mordant Blue 13 (MB13). Similarly, it achieved high continuous batch decolorization efficiency for triphenylmethane dyes (e.g., Cresol Red, Acid Green 50) while maintaining stable laccase activity throughout the decolorization process. Crude laccase demonstrated excellent reusability and sustainable degradation performance during the continuous batch decolorization. The decolorization of crude laccase could significantly reduce or completely eliminate the phytotoxicity of both single dyes and mixtures of two dyes (pairwise mixtures of different types of dyes, totaling 18 different combinations). The results of molecular docking between the laccase protein and structurally diverse dyes further elucidated the underlying causes and potential mechanisms for variations in the catalytic ability of laccase toward different structural dyes. In summary, crude laccase from Pleurotus ostreatus yang1 possessed great application value and potential for efficiently degrading and detoxifying dye pollutants of different structural types. Full article

Eugenol-based azo dyes illustrate how bio-sourced compounds like eugenol can be transformed through synthetic processes into functional and colorful compounds. The main purpose of the present work was to develop new responsive colorimetric sensors for metal cations based on eugenol-derived azo compounds. The incorporation of the azo group into the eugenol framework allows for strong electronic interactions with metal cations, leading to distinct color changes observable to the naked eye. These azo-eugenol dyes exhibit shifts in their UV-Vis absorption spectra upon complexation with metal cations such as copper (Cu²⁺) and lead (Pb²⁺), making them effective sensors for environmental and analytical applications. The eugenol-based azo dyes were subjected to photophysical studies to understand selectivity, response time, and stability in relation to metal cations, which will be a starting point for the monitoring of toxic metal contaminants in aqueous environments. Full article