Azo Dye Research Articles

Green Synthesized Composite AB-Polybenzimidazole/TiO2 Membranes with Photocatalytic and Antibacterial Activity

Novel AB-Polybenzimidazole (AB-PBI)/TiO2 nanocomposite membranes have been prepared using a synthetic green chemistry approach. Modified Eaton’s reagent (methansulfonic acid/P2O5) was used as both reaction media for microwave-assisted synthesis of AB-PBI and as an efficient dispersant of partially agglomerated titanium dioxide powders. Composite membranes of 80 µm thickness have been prepared by a film casting approach involving subsequent anti-solvent inversion in order to obtain porous composite membranes possessing high sorption capacity. The maximal TiO2 filler content achieved was 20 wt.% TiO2 nanoparticles (NPs). Titania particles were green synthesized (using a different content of Mentha Spicata (MS) aqueous extract) by hydrothermal activation (150 °C), followed by thermal treatment at 400 °C. The various methods such as powder X-ray diffraction and Thermogravimetric analyses, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Energy-dispersive X-ray spectroscopy, Electronic paramagnetic resonance, Scanning Electron Microscopy and Transmission Electron Microscopy have been used to study the phase and surface composition, structure, morphology, and thermal behavior of the synthesized nanocomposite membranes. The photocatalytic ability of the so-prepared AB-Polybenzimidazole/bio-TiO2 membranes was studied for decolorization of Reactive Black 5 (RB5) as a model azo dye pollutant under UV light illumination. The polymer membrane in basic form, containing TiO2 particles, was obtained with a 40 mL quantity of the MS extract, exhibiting the highest decolorization rate (96%) after 180 min of UV irradiation. The so-prepared AB-Polybenzimidazole/TiO2 samples have a powerful antibacterial effect on E. coli when irradiated by UV light.

A Review on Biomass-Derived Carbon Quantum Dots: Emerging Catalysts for Hydrogenation Catalysis.

The circular economy and the depletion of Earth's resources highlight the need to transform waste into value-added emerging materials like carbon quantum dots (CQDs), which show great promise in energy storage, catalysis, and other applications. The production of catalytically active CQDs from biomass garners significant attention due to their unique advantages, such as ease of availability, natural abundance, renewability, low cost, and environmental friendliness. This review addresses the synthesis of CQDs from biomass, the factors influencing their properties and performance, and their diverse applications in catalytic hydrogenation reactions, selective reduction of nitroaromatic compounds, and azo dyes. Recent studies demonstrate that biomass-derived CQDs exhibit significantly improved catalytic activity, selectivity, and stability, effectively addressing the long-standing challenges of low activity and poor stability in catalysts derived from conventional sources.

Transfer Hydrogenative Cleavage of N═N Bond of Azoarenes to Aminoarenes Using Ruthenium Catalyst

AbstractTextile industry contaminants cause significant pollution of water resources, making them a major worry in the modern age. Azo dyes, one of the most harmful synthetic colors generated in textile industry pollutants, are particularly persistent in water bodies due to their chemical composition. In this study, an efficient transfer hydrogenative cleavage of the ─N═N─ moiety containing azoarene to their corresponding aminoarenes is accomplished using a terpyridine‐based ruthenium complex. This report depicts the suitable transformations from the azoarene by adopting a minimal base and catalyst loading. The preliminary mechanistic studies disclosed the selective conversion of azoarenes to its complete ─N═N─ cleavage products, aminoarenes, through the hydrazoarenes intermediate.

In Situ Growth of Ag-ZnO Nanorods on Graphitic Carbon Nitride for SERS Detection of Rhodamine 6G

Abstract Sensing azo dyes has received significant attention due to their environmental impact and harm to human health. A cellulose-paper-based surface-enhanced Raman scattering (SERS) substrate with a hierarchical Ag-ZnO@GCN nanorod composite was successfully prepared by hydrothermal method. The intended hierarchical nanocomposite was prepared using a facile and economically feasible method. The optical, functional group, structural profile, phase formation, and surface morphology of the prepared AZCN-80, AZCN-120, and AZCN-160 were characterized using UV-Vis, Fourier transform infrared spectroscopy, Raman, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analysis. The physicochemical characterization results demonstrated that this ubiquitous nanorod composite considerably enhanced the SERS sensing performance for detecting harmful organic molecules, specifically rhodamine 6G (R6G). In addition, the fabricated paper-based AZCN-160 substrate exhibited good linearity with a range of 10-5 to 10-15 M, with an R2 value of 0.96 compared to that of AZCN-80 and AZCN-120. Therefore, the paper-based SERS substrate developed in this study is a “proof-of-concept” strategy for designing and constructing efficient and effective molecular sensors for real-time sensing and monitoring.

Dichromate Contaminated Water Treatment using Novel Crystal Violet Azo Dye- Sulphonated Poly(Glycidyl methacrylate) Nano-Composite Adsorbent

In this study, the Cr(VI) metal ions have been removed from dichromate-contaminated water using a novel Azo Dye-Sulphonated Poly (glycidyl methacrylate) nano-composite adsorbent for the first time. Crystal violet Azo dye model (CV) has been immobilized onto nano-sulfonated Poly (glycidyl methacrylate) particles (SPGMA) through the adsorption process to obtain the novel crystal violet Azo Dye-Sulphonated Poly (glycidyl methacrylate) nano-composite adsorbent (CV-SPGMA). The effect of the adsorption conditions on the removal process of Cr (VI) metal ions such as dichromate concentration, adsorption time, temperature, pH, adsorbent dose, and finally agitation speed on the Cr(VI) metal ions removal was studied. The Cr(VI) metal ions removal process has been characterized using isotherms, kinetics, and thermodynamics models. The developed novel CV-SPGMA nano-composite adsorbent chemical structure and morphology were characterized using characterization tools such as FTIR, TGA, and SEM-EDAX analyses before and after the adsorption process. The developmentof the novel CV-SPGMA nano-composite adsorbent for the removal of Cr(VI) ions from dichromate-contaminated waters under mild adsorption conditions opens a new field of multiuse of the same adsorbent in the removal of more than one contaminant.

4D Printing of Liquid Crystal Emulsions for Smart Structures with Multiple Functionalities

Abstract3D printing, and more recently 4D printing, has emerged as a transformative technology for fabricating structures with complex geometries and responsive properties. However, employing functional colloidal solutions as inks for printing remains unexplored. In this work, we present a novel and versatile 4D printing approach for fabricating functional and complex‐shaped objects using polymerizable liquid crystal (LC) emulsion droplets. Leveraging a digital light processing (DLP) 3D printing technique, we achieve rapid production of intricate 3D geometries with high resolution. The printed structures retain the LC ordering from the precursor droplets, imparting the final objects with shape memory properties, including shape fixation and recovery upon heating or light exposure. Light‐responsive behavior is introduced post‐printing by embedding an azo dye into the 3D structures. Additionally, we explore the potential to create intrinsically porous 3D structures by selectively removing non‐reactive components from the printed geometries, adding an extra level of functionality to the printed objects. Furthermore, we incorporate chiral nematic LCs into the emulsion droplets, producing 3D objects with tunable reflective properties. To our knowledge, this is the first example of DLP 3D printing with emulsions, offering an effective and versatile pathway for developing 4D‐printed materials with potential applications in optics, robotics, microfluidics, and biomedicine.

Real-time in situ monitoring as a tool for comparison of electrochemical advanced oxidation processes for the decolourisation of azo and indigoid dyes.

The widespread use of synthetic dyes has led to the release of substantial amounts of dye-contaminated wastewater, posing significant environmental and health concerns. This study focuses on the use of anodic and electrochemically activated persulfate oxidation for the degradation of organic contaminants. Specifically, the structural variations of nine dyes in the indigoid and azo families, and their impact on the efficiency of electrochemical oxidation were analysed. An in situ continuous monitoring apparatus with a UV-visible detector was employed to collect data in real-time. The electrochemically activated persulfate system demonstrated higher efficiency compared to the anodic oxidation approach. In both systems the efficiency of decolourisation was highly dependent on the structure of the pollutant. Electron-withdrawing substituents in direct conjugation with the chromophore, bulky auxochromes, and extended aromatic systems significantly decreased the decolourisation efficiency. Conversely, changing the location of electron-withdrawing groups and adding electron-donating substituents increased the decolourisation efficiency, even overcoming the detrimental effects of bulky groups and extended conjugation. This type of systematic structural comparison study is essential for highlighting the interconnected nature of pollutant structure and degradation speed so that efficient electrochemical oxidation systems can be designed for the treatment of genuine wastewater effluent containing more than one pollutant.

DIRECT HF ETCHING-DERIVED Ti3C2TX: A POTENT ADSORBENT FOR BASIC RED 46 DYE

Dye contamination poses a significant threat to water sources and ecosystems, necessitating the development of efficient treatment methods. Basic Red 46 (BR 46), a highly toxic and persistent azo dye, presents specific challenges in removal from water resources. This study investigates the adsorption efficiency of Ti3C2Tx (Titanium Carbide) MXene, synthesized via direct HF (Hydrofluoric acid) etching, for BR 46 removal. The physicochemical properties of Ti3C2Tx were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Additionally, the effects of pH, MXene amount, and initial BR 46 concentration on BR 46 adsorption were also investigated. The results show a maximum BR 46 removal efficiency of 99.98% at pH 2, 4 g/L Ti3C2Tx dose, 50 mg/L BR 46 concentration, and 90 min contact time. This research underscores the potential of Ti3C2Tx MXene as a potent adsorbent for BR 46 dye removal, offering insights for future water treatment applications.

Hazelnut Shells as a Tenable Biosorbent for Basic Red 18 Azo Dye Removal

The increasing pollution from the textile industry, particularly organic azo dyes, presents a significant environmental challenge, necessitating the development of effective and sustainable treatment methods. This study investigates the adsorption potential of hazelnut shells (raw—RHSs; modified—MHSs) for the removal of organic azo dyes from aqueous solutions. As biomass, hazelnut shells are biodegradable and represent a sustainable alternative to synthetic adsorbents, thereby reducing the ecological footprint. Through a series of batch adsorption experiments, the influence of various parameters, including pH, contact time, concentration, and temperature, on adsorption capacity was examined. Characterization of the hazelnut shells was conducted using optical microscopy and ATR-FTIR, XRF, and XRD spectroscopy, confirming its suitability as a biosorbent. The analyzed isotherms showed that adsorption onto RHSs was best fitted by the Freundlich model, while adsorption onto MHSs was best fitted by the Temkin model. Kinetic studies demonstrated that the adsorption process is well described by the pseudo-second-order model, suggesting that chemical adsorption plays a significant role. The maximal adsorption capacity was 62.11 mg/g for RHSs and 80.65 mg/g for MHSs, highlighting the potential of hazelnut shells as an abundant, low-cost, and eco-friendly adsorbent. Furthermore, recycling studies indicated the feasibility of the adsorbent, underscoring its practical applicability in real scenarios.

Ecological risk assessment of p-toluidine in freshwater, sediment, and soil media.

Para-toluidine (p-toluidine) is a high production volume chemical, of which about 5,000 tons/year are imported into Korea as of the 2018 registration. This substance is mainly used as an intermediate in the manufacture of paints, azo dyes, and pigments. In this study, an ecological risk assessment of p-toluidine was performed to investigate the risk to the environment assuming the worst-case exposure scenario. Ecotoxicity data was collected from the literature and the predicted no effect concentration (PNEC) was derived. The predicted environmental concentration (PEC) was calculated using the SimpleBox Korea v2.0 model. Hazard quotient (HQ) was calculated based on PEC and PNEC. The concentration of p-toluidine was measured in soil samples from workplaces with a HQ exceeding 1 to verify the results of modeling. PNECs for surface water, sediment, and soil were 0.00022 mg/L, 0.0025 mg/kg (dw), and 0.00037 mg/kg (dw), respectively. Based on regional-scale PEC, the HQ of freshwater, sediment, and soil media were all less than 1, but the HQ exceeded 1 at some local sites. Based on the fact that the measured environmental concentration in soil samples around the workplace is below the limit of detection and that all waste is incinerated at the actual workplace, p-toluidine is not likely to pose a high risk to the environment in Korea.

Synthesis and application of natural clam shell derived adsorbents for removal of azo dyes from wastewater

The research aims to evaluate their effectiveness as adsorbents for azo dyes. The nanomaterials were synthesized via hydrothermal methods, and their adsorption capacities were scrutinized against a spectrum of dyes, including methylene blue (MB), crystal violet (CV), rhodamine B (RB), malachite green (MG), safranin (SR), as well as commercial red and blue dyes. Remarkably, the clam shell nanoparticles (CSNPs) exhibited notable dye removal efficiencies, achieving removal rates of approximately 87%, 89%, 97.75%, 97.60%, and 97.11% for MB, RB, CV, MG, and SR, respectively. These removal rates were accomplished within varied interaction times ranging from 45 to 10 minutes, utilizing a dose of 100 mg/L of nanoadsorbent. Furthermore, the nanomaterials displayed removal efficiencies exceeding 80% against commercial blue and red dyes. Considering their exceptional adsorption capacities, clam shell nanomaterials stand out as cost-effective, efficient, and environmentally friendly biosorbents for effectively removing dyes from aqueous solutions. This study highlights the promising potential of clam shell-based nanomaterials in addressing the challenges presented by water pollution.

An effective photocatalytic decomposition of azo dyes by NiO/ZnO/g-C3N4 ternary nanocomposite under solar light excitation

An effective photocatalytic decomposition of azo dyes by NiO/ZnO/g-C3N4 ternary nanocomposite under solar light excitation

Preparation, characterization, applications and analytical studies of some new azo dyes derived from sulfanilamide

Preparation, characterization, applications and analytical studies of some new azo dyes derived from sulfanilamide

Expression of Concern: “Laccase producing bacteria influenced the high decolorization of textile azo dyes with advanced study” [Environmental Research, 207 (2022) 112211]

Expression of Concern: “Laccase producing bacteria influenced the high decolorization of textile azo dyes with advanced study” [Environmental Research, 207 (2022) 112211]

Preparation, characterization and biological studies of azo dye Schiff base metal complexes derived from 2-aminothiophenol

Preparation, characterization and biological studies of azo dye Schiff base metal complexes derived from 2-aminothiophenol

Efficient removal of anionic Amaranth azo dye from the aqueous environment using papaya leaf stalks: Studies on batch adsorption, mechanism, and desorption

Papaya leaf stalks (PLS) were utilized in the current research to eliminate Amaranth (AM) dye from an aqueous medium. PLS was characterized through various techniques, including BET/BJH, pHPZC, XRD, FTIR, FESEM, and EDX. The FTIR analysis unveiled that -OH (hydroxyl), -C=O (carbonyl), and -COOH (carboxylic) groups were involved in binding AM to the surface of PLS. Batch mode adsorption tests were conducted, and various operational variables like pH, the mass of PLS, AM dye concentration, contact duration, stirring speed, temperature, and regeneration of the PLS were investigated. The maximal AM removal efficiency of 91.1 ± 2.601% was observed at pH 2.0. The pHPZC of the PLS was determined to be 5.5. The experiment results were analyzed using isotherm models (Freundlich, Temkin and Langmuir) and kinetic models (pseudo-second-order and pseudo-first-order). The pseudo-second-order kinetic and Langmuir isotherm models provided the best fit. The maximal sorption uptake of AM dye on PLS was achieved at 121.3 ± 1.493 mg/g at 298 K. The thermodynamic variables indicated that the sorption process was spontaneous (ΔGo < 0), exothermic (ΔHo > 0), and feasible (ΔSo > 0) at different temperatures. The AM adsorption on PLS was mainly due to electrostatic interactions. Desorption tests were also carried out to investigate the feasibility of regenerating PLS, and 89.2 ± 1.184% of the adsorbed AM was recovered using 0.2 M-NaOH. The reusability results indicated that 76.9 ± 2.204% of the adsorption efficiency could still be maintained even after six cycles. These results demonstrate that PLS is an environmentally friendly and suitable material for removing AM from wastewater.

A Novel Synthesis of a Calix [4] Arene, MIL‐101(Fe), and Copper(II) Oxide Nanocomposite (Calix/MIL‐101(Fe)/CuO): Synthesis, Characterization, Degradation, and Pollutant Removal Ability

AbstractDyes are organic compounds. Azo dyes, as the most important dyes, are usually synthesized and reduced after entering the human body, turning into mutagenic and carcinogenic amines. A new efficient composite containing calix [4] arene (Calix), metal‐organic framework (MIL‐101(Fe)), and copper(II) oxide (Calix/MIL‐101(Fe)/CuO) was synthesized and utilized for the degradation of Malachite Green (MG). The dye removal efficiency was 17% for Calix, 56% for CuO, 64% for MIL‐101(Fe), and 98.8% for the Calix/MIL‐101(Fe)/CuO composite using LED visible light. The degradation of MG by Calix/MIL‐101(Fe)/CuO using different doses, including 0, 1, 2, 3, and 4 mg, was 8%, 64%, 75%, 85%, and 98.8%, respectively. The degradation kinetic rate constants for 0, 1, 2, 3, and 4 mg of Calix/MIL‐101(Fe)/CuO were 0.0134, 0.1086, 0.1182, 0.1308, and 0.1727 (zero‐order rate), 5E‐04, 0.007, 0.008, 0.011, and 0.023 (first‐order rate), and 4E‐05, 0.0007, 0.001, 0.0017, and 0.0211 (second‐order rate), respectively. The MG degradation kinetics obeyed the zero‐order model. The Calix/MIL‐101(Fe)/CuO exhibited high reusability for MG degradation. The results suggest that Calix/MIL‐101(Fe)/CuO could serve as an alternative photocatalyst for the degradation of contaminants in aqueous media.

Biological treatment of methyl orange dye and textile wastewater using halo-alkaliphilic bacteria under highly alkaline conditions.

As the textile wastewater is highly saline and has high pH it is important to employ extremophilic microbes to survive in harsh conditions and provide effective bioremediation of textile dyes. This study aims to find a sustainable solution for dye removal by investigating the potential of an indigenously isolated bacterium, Nesterenkonia lacusekhoensis EMLA3 (halo-alkaliphilic) for treatment of an azo dye, methyl orange (MO) and textile effluent. MO dye decolorization studies were conducted using mineral salt media (MSM) by varying incubation time (0-120h), initial dye concentration (50-350mg/L), pH (7.0-12.0), inoculum dose (3-10%), agitation (stationary, 100rpm and 200rpm), and temperature (20-55°C). Dye removal by the bacterium for 50mg/L of dye was > 97.0% within 72h of incubation at pH 11.0 in stationary condition. Bacterium had excellent reusability i.e. > 97% dye removal for up to 5 cycles. Moreover, bacterium has the potential for co-removal of chromium (VI) (3.5-28mg/L), and also almost complete dye removal in presence of high amount of NaCl. Liquid chromatography-mass spectrometry showed degradation as the mechanism of dye removal. Application of the bacterium to MO dye spiked real textile wastewater showed excellent dye removal. Phyto-toxicity assessment conducted on Vigna radiata and Triticum aestivum seeds, showed 100% germination of biotreated textile wastewater indicating its reuse potential.

Synthesis of morphology-controlled ternary nanocomposite with the aid of surfactant (CATAB) as structure-directing agent for catalytic oxidation of organic azo dye

ABSTRACT A novel synthesis approach was applied to deposit tri-metal oxide nanocomposite, AL₂O₃/TiO₂/ZnO, onto surfactant template in an attempt to control the morphology and reduce the aggregation . Consequently, increases the surface area available for catalytic activity. Different samples were prepared by varying the amount of CTAB as a structure-directing agent. Samples were characterized by SEM, XRD, UV-Vis, DLS, TGA, FTIR, and nitrogen adsorption. The nanocomposites were tested for the catalytic oxidation of Congo red (CR). Calcination resulted in higher activity as a result of removing the template and thus leaving empty pores with higher surface area. Before calcination, the amount of CATAB added inversely affected both available surface area and activity. The maximum oxidation efficiency was 92%. TOC analysis confirmed mineralization of CR by 82% drop. After four successive cycles, only 3% reduction in catalysis activity was observed. Overall, this proposed method is very promising in controlling morphology, structural properties, and catalytic activity of catalyst.

A brief review on recent high-performance platforms for electrochemical sensing of azo dye Allura Red (E129): food safety and pharmaceutical applications

Artificial dyes are increasingly widespread, especially in foodstuffs and pharmaceutical products as an industry marketing strategy to attract consumers. Consumption of the synthetic azo dye Allura Red (AR) has potential risks to human health and can cause several adverse health effects such as genotoxicity, carcinogenicity, attention deficit hyperactivity disorder, allergic and asthmatic diseases in children. The limited number of electrochemical sensing platforms for AR successfully applied for safety assessment of foods, beverages, and drug formulations testifies that the food and pharmaceutical matrices present significant analytical challenges and there is still a need to amplify the analytical performances of these systems. The authors intensively reviewed recent papers (mainly since 2019) emphasizing electrode engineering, strategies for electrochemical signal amplification, and analytical applications in food and drug control. A critical discussion on the latest interesting innovations and perspectives of the most promising electrochemical tools for AR electro­analysis is presented. The challenges and limitations in the design of electrochemical sensors for AR analysis are also discussed with a view to providing new directions for future research and development of sustainable sensing devices, paving the way for advancements in this field.