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Indigo is widely used in textile industries for denim garments dyeing and is mainly produced by chemical synthesis which, however, raises environmental sustainability issues. Bio-indigo may be produced by fermentation of metabolically engineering bacteria, but current methods are economically incompetent due to low titer and the need for an inducer. To address these problems, we first characterized several synthetic promoters in E. coli and demonstrated the feasibility of inducer-free indigo production from tryptophan using the inducer-free promoter. We next coupled the tryptophan-to-indigo and glucose-to-tryptophan pathways to generate a de novo glucose-to-indigo pathway. By rational design and combinatorial screening, we identified the optimal promoter-gene combinations, which underscored the importance of promoter choice and expression levels of pathway genes. We thus created a new E. coli strain that exploited an indole pathway to enhance the indigo titer to 123 mg/L. We further assessed a panel of heterologous tryptophan synthase homologs and identified a plant indole lyase (TaIGL), which along with modified pathway design, improved the indigo titer to 235 mg/L while reducing the tryptophan byproduct accumulation. The optimal E. coli strain expressed 8 genes essential for rewiring carbon flux from glucose to indole and then to indigo: mFMO, ppsA, tktA, trpD, trpC, TaIGL and feedback-resistant aroG and trpE. Fed-batch fermentation in a 3-L bioreactor with glucose feeding further increased the indigo titer (≈965 mg/L) and total quantity (≈2183 mg) at 72 h. This new synthetic glucose-to-indigo pathway enables high-titer indigo production without the need of inducer and holds promise for bio-indigo production.

The sequestration of orange G (OG) and indigo carmine (IC) dye by utilizing novel incense stick (IS) ash adsorbent was examined in the current study. The dye uptake capacity of the adsorbent was explored through several batch experiments. The efficiency of the adsorbent was studied by different factors viz. adsorbent dose, agitation time, pH, temperature, and dye concentration. The study of the kinetic model described that the pseudo-second-order model was more effective for orange G and indigo carmine dye removal. Adsorption equilibrium was examined by the Langmuir and Freundlich model. The data obtained from the isotherm study for both dyes were well described and fitted to the Langmuir model. The incense stick ash adsorbent material was characterized by SEM, EDAX, BET, and FTIR techniques. The porosity of the adsorbent surface is described by the BET surface area of 6.934 m2/g and the micropore surface area of 4.550 m2/g. At a dye concentration of 50 mg/L and adsorbent dosage of 200 mg, the maximum dye uptake for orange G and indigo carmine was found 26.10 mg/g and 20.53 mg/g, respectively. For OG dye, the values of the thermodynamic parameters ∆H0 and ∆S0 were 40.99 kJ/mol and 0.015 kJ/mol, and for IC dye, 58.81 kJ/mol and 0.191 kJ/mol respectively. Regeneration performance of the used adsorbent was investigated by alkaline treatment. In comparison to the IC dye, the OG dye desorbs at a greater rate of 42.56%. According to this study, using incense stick ash to remove textile dyes would be a cost-effective and environmentally friendly green alternative. [ABSTRACT FROM AUTHOR]

Abstract Background At present, conventional endoscopy and chromoendoscopy using indigo carmine (IC) is a very useful method to determine the demarcation line (DL) of early gastric cancer lesions, but it is not suitable for all lesions. Aims This study aimed to determine the applicable conditions for IC chromoendoscopy. Methods We retrospectively evaluated 187 lesions in 181 patients who had an endoscopic diagnosis of EGC and were treated with endoscopic submucosal dissection (ESD). According to the existence of the DL between the lesion mucosa and normal mucosa with IC chromoendoscopy, the lesions were divided into two groups: clear group and unclear group. Clinicopathological characteristics were evaluated in each group. From January 2022 to March 2023, the postoperative pathological sections of 19 lesions (81 slices) in the clear group and 19 lesions (80 slices) in unclear group were scanned with high definition, and the crypt structure between the two groups was evaluated. Results There was no significant difference in clinical factors between the clear group and unclear group. There were significant differences in crypt area, crypt length, and crypt opening diameter between the two groups. In the clear group, there were significant differences in crypt area, crypt length, and crypt opening diameter between the normal area and cancer area, but there was no significant difference in the unclear group. Conclusions The margins of lesions with fused or absent crypt structures, a small crypt area, a short crypt length, and a short crypt opening diameter can be easily determined with IC chromoendoscopy.

This study explores a novel sulfonation method for analyzing blue-dyed fabrics containing reactive, direct and indigo dyes. The proposed method accurately distinguishes indigo fabrics by converting indigo blue into indigo carmine using concentrated H2SO4, resulting in distinct spectral analysis through UVVisible spectrophotometry. Generally, UV-Visible spectroscopy shows absorption peak characteristics influenced by analyte and environmental properties, leading to broadening and wavelength shifts. Therefore, statistical analysis of peak characteristics, including center, centroid, Full Width at Half Maximum (FWHM), height and L/R ratio, was performed on the obtained spectra to facilitate comprehensive quality evaluation of indigo-dyed fabrics. The proposed method demonstrated good precision and accuracy, with %RSD values indicating excellent repeatability and reproducibility, contingent on consistent sample preparation, narrow analyte peaks and minimized background signals. Furthermore, this method was applied to analyze the collected indigo-dyed fabrics from Sakon Nakhon Province, revealing the center value (611.79 nm) as a precise marker for indigo dye, with a narrow control range (607.02 - 616.56 nm) and a low coefficient of variation (CV) of 0.26 %. Moreover, centroid, L/R ratio and FWHM significantly contributed to fabric classification and quality assessment. This research offers valuable insights to improve indigo fabric production in Sakon Nakhon Province, leading to more reliable authentication and quality control of the natural indigo-dyed industry. [ABSTRACT FROM AUTHOR]

This study aims to synthesize and characterize silver nanoparticles (AgNPs) from Leucaena leucocephala leaf extract and evaluate their effectiveness in photo-catalytically degrading indigo carmine (IC) dye in an aqueous solution. The synthesized AgNPs were characterized using UV-visible spectrophotometry (UV-Vis), diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. Response surface methodology (RSM) based on central composite design (CCD) was employed to optimize the conditions for the photocatalytic degradation of IC dye under solar light. The results show that 97.52% of the maximum photodegradation of IC dye was achieved using a dye concentration, catalyst volume, and reaction time of 19.7 mgL-1, 4.47 mL, and 97 min, respectively. RSM results revealed optimal conditions for IC dye degradation under solar irradiation. Moreover, the kinetics study of IC dye showed a good correlation with the pseudo-first order kinetic model. [ABSTRACT FROM AUTHOR]

Background: At present, conventional endoscopy and chromoendoscopy using indigo carmine (IC) is a very useful method to determine the demarcation line (DL) of early gastric cancer lesions, but it is not suitable for all lesions. Aims: This study aimed to determine the applicable conditions for IC chromoendoscopy. Methods: We retrospectively evaluated 187 lesions in 181 patients who had an endoscopic diagnosis of EGC and were treated with endoscopic submucosal dissection (ESD). According to the existence of the DL between the lesion mucosa and normal mucosa with IC chromoendoscopy, the lesions were divided into two groups: clear group and unclear group. Clinicopathological characteristics were evaluated in each group. From January 2022 to March 2023, the postoperative pathological sections of 19 lesions (81 slices) in the clear group and 19 lesions (80 slices) in unclear group were scanned with high definition, and the crypt structure between the two groups was evaluated. Results: There was no significant difference in clinical factors between the clear group and unclear group. There were significant differences in crypt area, crypt length, and crypt opening diameter between the two groups. In the clear group, there were significant differences in crypt area, crypt length, and crypt opening diameter between the normal area and cancer area, but there was no significant difference in the unclear group. Conclusions: The margins of lesions with fused or absent crypt structures, a small crypt area, a short crypt length, and a short crypt opening diameter can be easily determined with IC chromoendoscopy. [ABSTRACT FROM AUTHOR]

In this study, indigo carmine (IC)-calcium carbonate lakes with different crystalline forms of calcium carbonate were prepared through co-precipitation methods, and the properties of these lakes and their formation mechanisms were investigated. The results showed that amorphous calcium carbonate (ACC) exhibited the smallest particle size and the largest specific surface area, resulting in the highest adsorption efficiency. Vaterite, calcite, and aragonite followed after ACC in decreasing order of adsorption efficiency. Kinetic analysis and isothermal analysis revealed the occurrence of chemisorption and multilayer adsorption during formation of the lakes. The FTIR and Raman spectra suggested participation of sulfonic acid groups in chemisorption. Appearance of IC significantly altered TGA curves by changing weight loss rate before decomposition of calcium carbonate. EDS analysis revealed the adsorption of IC predominantly happened on the surface of calcium carbonate particles rather than the interior. [ABSTRACT FROM AUTHOR]

This paper proposes recycling spent cathodes (SC) from Li-ion batteries to decolorize indigo carmine (IC) solutions, thus eliminating the need for hydrogen peroxide (H2O2) or ultraviolet (UV) light exposure. The discoloration of indigo carmine is significantly influenced by the pH level, especially from 5 to 2. At lower pH values (pH ≤ 2), the decolorization kinetics are not affected by H+ ions and follow first-order kinetics. A 10-ppm solution at pH = 3 was decolorized in approximately 20 min, suggesting that SC from Li-ion batteries are promising for advanced oxidative processes. The study also emphasizes the risks associated with improper disposal of Li-ion batteries, as SC can chemically react with organic molecules similar to indigo carmine in landfills, without the presence of peroxide or sunlight. Mass spectrometry has helped identify the discoloration mechanism, which involves the oxidative reaction of indigo carmine leading to the formation of isatin acid. [ABSTRACT FROM AUTHOR]

Effluents from textile industries pose significant environmental and human health problems especially since some textile factories discharge highly colored wastewater into the River, affecting water quality and local activities. This study aims to develop an ecofriendly method to remove Indigo Carmine (IC) dye from the water using Walnut shells-based activated carbon (WSAC). Adsorption was conducted by mixing powdered WSAC with IC dye at 120 rpm. Parameters such as contact time, absorbent quantity, and dye concentration were examined. Samples were analyzed using UV-Vis spectrophotometry at 610 nm. Kinetic and isotherm models were used to describe adsorption properties. The study found that 98 % of IC dye could be removed using 750 mg of powdered activated carbon in 100 ml solution, with an equilibrium time of 40 minutes. The pseudo-second-order model best described the adsorption with a correlation coefficient of R² = 0.9905. [ABSTRACT FROM AUTHOR]

The food industry uses indigo carmine (IC) extensively as a blue colorant to make processed food for young children and the general population more attractive. Given that IC can act as a ligand, this raises concerns about its interactions with essential metal ions in the human body. In view of this interest, in the present investigation, the copper(II)/indigo carmine system was thoroughly investigated in aqueous solution and in the solid state, and the detailed structural characterization of the complexes formed between copper(II) and the ligand was performed using spectroscopic methods, complemented with DFT and TD-DFT calculations. NMR and UV/Vis absorption spectroscopy studies of the ligand in the presence of copper(II) show changes that clearly reveal strong complexation. The results point to the formation of complexes of 1:1, 1:2 and 2:1 Cu(II)/IC stoichiometry in aqueous solution, favored in the pH range 6–10 and stable over time. DFT calculations indicate that the coordination of the ligand to the metal occurs through the adjacent carbonyl and amine groups and that the 1:1 and the 2:1 complexes have distorted tetrahedral metal centers, while the 1:2 structure is five-coordinate with a square pyramidal geometry. FTIR results, together with EDS data and DFT calculations, established that the complex obtained in the solid state likely consists of a polymeric arrangement involving repetition of the 1:2 complex unit. These results are relevant in the context of the study of the toxicity of IC and provide crucial data for future studies of its physiological effects. Although the general population does not normally exceed the maximum recommended daily intake, young children are highly exposed to products containing IC and can easily exceed the recommended dose. It is, therefore, extremely important to understand the interactions between the dye and the various metal ions present in the human body, copper(II) being one of the most relevant due to its essential nature and, as shown in this article, the high stability of the complexes it forms with IC at physiological pH. [ABSTRACT FROM AUTHOR]

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety of indigo carmine as a colourant feed additive for cats, dogs and ornamental fish. In its previous opinion, the FEEDAP Panel concluded that indigo carmine is safe for cats and dogs at levels up to 250 mg/kg complete feed and for ornamental fish up to 1000 mg/kg complete feed. These conclusions were limited to indigo carmine with a purity of at least 93% colouring matter. For the current assessment, the applicant submitted additional data on the characterisation and on the toxicological profile to support the safety of the additive with the purity of at least 85% colouring matter. Based on the new data submitted, the FEEDAP Panel concludes that indigo carmine (purity of at least 85% colouring matter) is safe for cats and dogs at levels up to 250 mg/kg complete feed and for ornamental fish up to 1000 mg/kg complete feed. [ABSTRACT FROM AUTHOR]

Water contamination from industrial dyes poses a significant threat to the environment and human health. This study focuses on the development of advanced porous cross‐linked chitosan‐based hydrogels and superparamagnetic hydrogel nanocomposites for efficient removal of indigo carmine (IC) dye from water. The hydrogels were cross‐linked using benzophenonetetracarboxylic dianhydride (BTDA) and incorporated functionalized magnetic iron nanoparticles (CP‐MNPs). A comparative study revealed that the superparamagnetic hydrogel nanocomposite exhibited superior performance in IC dye adsorption. Higher IC removal efficiencies were observed at lower amounts of cross‐linker, pH, and adsorbent dosage. The superparamagnetic hydrogel nanocomposite demonstrated superior IC dye adsorption compared with the chitosan hydrogel. The adsorption process followed a pseudo‐second‐order kinetic model and Langmuir isotherm model. Thermodynamic data indicated that the adsorption onto the superparamagnetic hydrogel nanocomposite was endothermic and spontaneous, making it a promising material for environmental applications. [ABSTRACT FROM AUTHOR]

AbstractActivated carbon from green walnut shells was synthesized; characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX); and used as an adsorbent for the separation and preconcentration of indigo carmine. The pH, adsorbent mass, sample volume, foreign ion effect, eluent type, and eluent volume were optimized. The preconcentration factor was 20.0 and the enrichment factor was 19.68. The developed SPE method provided a limit of detection of 40.8 µg L−1 and limit of quantification of 136.1 µg L−1. The analyte recoveries were from 92 to 102%. The intra-day and inter-day relative standard deviations were 3.2% and 3.8%. The protocol was employed for the separation, preconcentration, and spectrophotometric determination of indigo carmine in water, candies, hair dyes, edible cake decorations, fruit juices, and textiles. [ABSTRACT FROM AUTHOR]

We present the synthesis of a cross-linking enzyme aggregate (CLEAS) of a peroxidase from Megathyrsus maximus (Guinea Grass) (GGP). The biocatalyst was produced using 50%v/v ethanol and 0.88%w/v glutaraldehyde for 1 h under stirring. The immobilization yield was 93.74% and the specific activity was 36.75 U mg−1. The biocatalyst surpassed by 61% the free enzyme activity at the optimal pH value (pH 6 for both preparations), becoming this increase in activity almost 10-fold at pH 9. GGP-CLEAS exhibited a higher thermal stability (2–4 folds) and was more stable towards hydrogen peroxide than the free enzyme (2–3 folds). GGP-CLEAS removes over 80% of 0.05 mM indigo carmine at pH 5, in the presence of 0.55 mM H2O2 after 60 min of reaction, a much higher value than when using the free enzyme. The operational stability showed a decrease of enzyme activity (over 60% in 4 cycles), very likely related to suicide inhibition. [ABSTRACT FROM AUTHOR]

The quest for cleaner environments is a global concern. Hence, the investigation of degradation of the indigo carmine dye (IC) with peroxydisulphate ion in an aqueous sulphuric acid system with a view to understanding its kinetic degradation and mechanism. The degradation depicts first‐order kinetics in [S2O82−] and [IC], and the degradation mole ratio of IC: S2O82− is 1:1. The degradation rate is dependent on the change in ionic strength and medium permittivity of the system. Also, added ions (NH4+ and NO3−) influence the degradation rate of the dye which further supported the outcome of the change in ionic strength. Free radical participation is ruled out. The experimental rate law is given as (Kk3[H+])[IC][S2O82−]. Owing to the absence of detectable intermediates in the degradation process, an outer‐sphere mechanism is proposed. The study is significant in textile industries and medical settings for making environments less toxic with a well‐understood degradation rate pathway. [ABSTRACT FROM AUTHOR]

Synthetic dyes are extensively used in industrial areas, including plastic, textile, and food. However, they are a major environmental problem due to their negative effects on water quality and living organisms. To address one of these problems, MIL-53 (Al) is served as an adsorbent for removing indigo carmine dye, being widely used in textile industries. The synthesis of MIL-53 (Al) was carried through the hydrothermal method and different synthesis conditions were studied to find the best adsorbent to remove indigo carmine. FTIR, XRD, SEM, and EDS were used to assess materials. Isotherm models and kinetic models were investigated for indigo carmine adsorption, revealing that the Langmuir isotherm model and pseudo-second-order kinetic model provided best fit to data. The highest adsorption capacity was calculated as 145 mg/g. The study contributes valuable insights into the adsorption of indigo carmine by MIL-53 (Al). [ABSTRACT FROM AUTHOR]

A simple and reliable method based on a composite of Nafion (Naf), multiwalled carbon nanotubes (MWCNTs), and mesoporous silica (SBA-15) modified glassy carbon electrode (GCE) is reported for individual and simultaneous determination of indigo carmine (IC, dye) and carbendazim (CBZ, pesticide). SBA-15 was synthesized and characterized and used to design a GCE/Naf/MWCNTs/SBA-15 sensor, which was characterized by electrochemical techniques and used for the determination of IC and CBZ. Using the optimum conditions for differential pulse voltammetry (DPV), the peak currents were linear from 1.0 µM to 11.0 µM. The limits of detection for individual measurements were 0.50 µM and 0.57 µM for IC and CBZ, respectively, while those for simultaneous detection were 0.28 µM and 0.30 µM. The interferences studies show that GCE/Naf/MWCNTs/SBA-15 exhibited excellent selectivity. The developed procedure was successfully applied to determine IC and CBZ in spring, tap, and lake water. [ABSTRACT FROM AUTHOR]

The feasibility of an adsorbent material like biochar (BC) depends on its regeneration capacity and its ability to achieve high removal efficiencies on real wastewater (WW) effluents. In this study, the regeneration capacity of the Pinus patula BC previously used in the removal of Indigo Carmine from water was evaluated. The regeneration technique that resulted in the highest desorption efficiency was a thermo-chemical method that consisted of heating the spent BC in a stove at 160 °C for 45 min followed by regeneration with ethanol (C2H6O) at a concentration of 75% for 6 h. Through this regeneration method, it was found that Pinus patula BC could be used in seven consecutive adsorption–desorption cycles. The feasibility of this BC was also assessed by evaluating the adsorbent's efficiency in real textile WW. Under optimal operational conditions (solution pH = 3, BC dose = 13.5 g/L, and BC particle size = 300–450 µm), the highest removal efficiencies in terms of colour and dissolved organic carbon (DOC) were 81.3 and 76.8%, respectively, for 120 min of treatment. The results obtained in the regeneration studies and the treatment of real textile WW suggested that the use of Pinus patula BC could be suitable to be scaled to an industrial level, contributing to sustainable development and the circular bioeconomy by using a waste to solve the dye pollution problem of another waste. [ABSTRACT FROM AUTHOR]

Indigo carmine (IC) was used as an analyte and a layer of film with serine as the functional monomer was electropolymerized to create a poly(serine)-modified carbon paste electrode (PSMCPE). Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and electrochemical technology, in that order, were used to characterize the morphology, structure, and electrochemical characteristics of the PSMCPE. Experimental parameters including the reagent molar ratio, the number of electropolymerization cycles, scan rate, and electrolyte pH level, were methodically optimized during the sensor's fabrication. Under optimal conditions, cyclic voltammetry (CV) and differential pulsed voltammetry (DPV) were used for IC detection. The PSMCPE response current for IC exhibited a significant enhancement compared to that of the bare carbon paste electrode (BCPE). The linear range of IC measured by DPV was determined to be 0.2–3.5 μM, with the corresponding lower detection limit (LOD) 1.3211 × 10−7 M and lower limits of quantification (LOQ) 4.403 × 10−7 M. The modified electrode confirmed outstanding repeatability, reproducibility, and stability. Finally, the real-time application of the sensor was confirmed by investigating IC in a water sample, when good IC recovery was observed. [ABSTRACT FROM AUTHOR]

High cost and low operational stability are the most important challenges limiting the possible use of laccase in the removal of textile dyes. To overcome these challenges, in this study, polyvinylpyrrolidone (PVP)-coated magnetic nanoparticles (MNPs) were produced and characterized. To our knowledge, this is the first study to explore the feasibility of immobilizing a Trametes trogii laccase enzyme on Fe3O4/PVP MNPs. The characterization of samples and the successful immobilization of laccase were verified by characterization methods. Besides, the biochemical properties and stability of the Fe3O4/PVP/Lac were evaluated in terms of optimum pH, optimum temperature, thermostability, thermodynamic and kinetic parameters, storage stability, operational stability, and decolorization efficiency of two different textile dyes. The optimum activities were recorded at pH 2.5 °C and 30 °C. The Fe3O4/PVP/Lac displayed remarkable thermal stability and activation energy for denaturation, enthalpy, Gibbs free energy, and entropy results confirmed the enhanced stability of Fe3O4/PVP/Lac against high temperatures. Meanwhile, the Fe3O4/PVP/Lac retained about 58% of its original activity after seven consecutive reuses, while it retained up to 25% of its original activity after 28 d of storage at room temperature. Km and Vmax for the Fe3O4/PVP/Lac were calculated to be 126 µM and 211 µmol/min, respectively. Finally, after 8 and 6 cycles of repeated use, the Fe3O4/PVP/Lac still decolorized 32.34% and 32.23% of Remazol Brilliant Blue R (RBBR) and Indigo Carmine (IC), respectively. As envisioned, this study suggests a promising way to solve the problems of high price and poor operational stability of the enzyme during biocatalytic decolorization of textile dyes in wastewaters. [ABSTRACT FROM AUTHOR]

This paper introduces a novel approach for the synthesis of photocatalytic nanocomposites via a fast reaction occurring at ambient conditions between the strong base NaOH and FeCl3 solution to obtain a fresh precipitate of Fe(OH)3 in the presence of TiO2 nanoparticles. FE-SEM analysis revealed a restructured state of TiO2 particles on the surface of colloidal Fe(OH)3. Solid-phase studies, including XRD and FT-IR, indicated a phase transformation from Fe(OH)3 to γ-Fe2O3 during the formation of the nanocomposite. UV–Vis diffuse reflectance measurements confirmed a significant reduction in the band gap of the synthesized composite, indicating its potentials as a photocatalyst under visible light irradiation. Another advantage of this composite type is its rapid sedimentation ability within minutes, facilitating post-processes such as phase separation and catalyst reuse on a large scale, which are challenging in the case of TiO2 nanoparticles. Inducing photocatalysis under visible light, the efficiency in degrading persistent colorants was demonstrated through a case study of indigo carmine (IC), which exhibited a threefold improvement in degradation efficiency for the case of the nanocomposite compared to the original TiO2. Indeed, the IC degradation process was studied in consideration of various factors such as Fe/Ti ratio in the catalyst, illumination time, colorant concentration, catalyst dosage, and pH of the environment. Additionally, mineralization studies confirmed the oxidation of IC to CO2 rather than the formation of potentially toxic intermediates. Furthermore, the stability of the catalyst was examined through six cycles of reuse.

This study explores the adsorption of indigo carmine dye using bio-combusted cerium oxide nanoparticles (CeO2 NPs). CeO2 NPs were synthesized using a bio-combustion method, and then subjected to structural, morphological, and optical characterization for thorough investigation. Structural investigation was carried out using X-ray diffraction (XRD), which revealed a cubic structure with evaluated average crystallite size of 11.55 nm. Later, the same was verified by employing W–H plot (13.57 nm). UV–Vis spectroscopy revealed an effective band gap of 3 eV suited for photocatalytic applications. The metal-oxygen phonon band at 986.32 cm−1 and 871.96 cm−1 is confirmed using Infrared Spectroscopy (FTIR). The morphological analysis was done using Transmission and Scanning Electron Microscopy (TEM and SEM), which revealed well-dispersed, aggregated structure enclosing spherical nanoparticles with an average size of ∼14 nm. The early precursors were validated using EDAX analysis and SEM. Optical characteristics were investigated using photoluminescence (PL), which revealed a large charge transfer band between 360 nm and 435 nm. The dye removal efficiency of CeO2 NPs was evaluated against Indigo Carmine dye using UV light. The results showed that the significantly adsorption, with more than 70 % removed after 150 min. Kinetic experiments revealed that the depreciation occurred via a pseudo-first-order reaction process. Furthermore, the impacts of certain factors such as dye dosage, pH, reusability, and scavenger on adsorption rate were explored and shown to be effective values for the adsorption process. This study emphasizes the potential of CeO2 NPs as excellent photocatalysts for environmental remediation, especially in dye removal applications.

Abstract Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety of indigo carmine as a colourant feed additive for cats, dogs and ornamental fish. In its previous opinion, the FEEDAP Panel concluded that indigo carmine is safe for cats and dogs at levels up to 250 mg/kg complete feed and for ornamental fish up to 1000 mg/kg complete feed. These conclusions were limited to indigo carmine with a purity of at least 93% colouring matter. For the current assessment, the applicant submitted additional data on the characterisation and on the toxicological profile to support the safety of the additive with the purity of at least 85% colouring matter. Based on the new data submitted, the FEEDAP Panel concludes that indigo carmine (purity of at least 85% colouring matter) is safe for cats and dogs at levels up to 250 mg/kg complete feed and for ornamental fish up to 1000 mg/kg complete feed.

This method was developed using ultrasonic-assisted hydrophobic deep eutectic solvent based dispersive liquid liquid microextraction (UA HDES DLLME) to determine trace levels of indigo carmine in food samples prior to analysis by UV Vis spectrophotometer at 610 nm. Some important analytical parameters such as pH, and sample volume and influence of foreign components were considered for optimization studies. A suitable extraction medium for indigo carmine was obtained at pH 3.0 and the mentioned above optimum conditions were determined. For instance, 15 mL sample volume, 1 mL final volume and a short centrifucation and ultrasonication time have been found. The limit of detection and limit of quantification were determined to be 2.79 ng mL−1, 9.31 ng mL−1 respectively. Moreover, the performed UA HDES DLLME process implemented to beverage, colored chocolate, chewing gum and nail polish samples. Analyte addition studies were carried out on an energy drink sample to demonstrate the accuracy of the method. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4) is robust and stable metal free polymeric materials that have recently gained interest towards photocatalytic applications. It shows visible-light driven photocatalytic activity with a major drawback of higher recombination rate of charge carriers and moderate oxidation ability. These issues are overcome by structural modifications using facile polymerization of acidized melamine thus controlling the structure of graphitic carbon nitride. The major factors affecting the photocatalytic activity were experimentally optimized and effect of these parameters was evaluated using the Box–Behnken Design of response surface methodology. The fabricated fibrous graphitic carbon nitride (NFgCN) shows a superior activity of 81.0 μmol g−1 h−1 hydrogen generation and 99.9 % degradation of indigo carmine (IC) dye in 90 min. The NFgCN shows 5 times higher activity for hydrogen generation compared to the pristine g-C 3 N 4. Fig. Phonon Confinement Effect in g-C 3 N 4 for Enhanced Photocatalysis: Dye Degradation and Water Splitting. [Display omitted] • Sonochemically synthesized Fibrous g-C 3 N 4 via acidization method. • Exceptional Fibrous g-C 3 N 4 shows 81.0 μmol g−1 H 2 evolution. • Fibrous g-C 3 N 4 shows 99.9 % photocatalytic degradation Indigo carmine. • Outstanding photocatalysis: Quantum and Phonon confinement elevate optical properties. [ABSTRACT FROM AUTHOR]

Herein we demonstrate the influence of aliovalent (Ca2+) substitution in the single-phase orthorhombic La 1-x Ca x FeO 3 (with x = 0.01, 0.03, 0.05, 0.07, 0.09) nanoparticles prepared by simple combustion method. The samples were systematically studied using XRD, SEM-EDS, and UV–Vis-DRS characterization techniques for their structural, microstructural-elemental, and optical (band structure) characteristics. Also, the catalytic attributes were evaluated through photocatalytic studies against indigo carmine in the presence of visible light. It was observed that La 1-x Ca x FeO 3 nanoparticles crystallized in orthorhombic structure at its as-synthesized form. The SEM analysis showed that the spherical nanoparticles with high porosity and agglomerations were further reduced with increasing Ca2+ concentration. The inclusion of Ca2+ also demonstrated the change in the band structure, as the band gap of the material reduced from 2.24 eV to 1.75 eV while the Ca2+ content increased from 1 mol% to 9 mol%. Furthermore, elevating the Ca2+ levels in the La 1-x Ca x FeO 3 resulted in enhanced photocatalytic decomposition of the indigo carmine dye, exhibiting a maximum efficacy of 96.5 % at neutral pH and a stabilization period of 120 min under visible light. The increase in photocatalysis is attributed to the formation of Fe4+ ions and oxygen vacancies induced by the aliovalent cation (Ca2+) replacement at the La3+ site in the LaFeO 3 host matrix. The results suggest that the prepared LaFeO 3 nanoparticles are potential nano-catalysts for photocatalytic activities against indigo carmine under visible light. [ABSTRACT FROM AUTHOR]

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Development of nanofiber membranes with the ability to remove organic dye such as Indigo Carmine (IC) from effluent wastewater is of immense help to the textile industry. In the present study, we investigate the preparation of cellulose acetate (CA) nanofiber membranes with optimized performances using electrospinning technique for effective removal of Indigo Carmine (IC) dye. Electrospinning parameters and solvent system containing acetic acid were adjusted to obtain CA nanofibers membranes which better suits dye removal application. The obtained nanofiber membranes were characterized using Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FT-IR) and contact angle analysis. Results show that nanofiber webs with optimized electrospinning parameters were continuously formed and are substantially free of defects such as beading, with an average diameter of 950 ± 50 nm. Hydrophobicity of membranes were successfully modified and showed important increase of contact angle values from 37° to 107°. The stirring time was varied to improve the solution homogeneity and consequently the response of membranes in filtration treatment. The CA membranes performance was evaluated through water flux and permeability measurement and tested on IC dye removal. The results showed a rate of dye removal around 83 % and a maximum adsorption capacity (Qm) of 13.09 mg/g for the optimized CA membranes.

In this study, indigo carmine (IC)-calcium carbonate lakes with different crystalline forms of calcium carbonate were prepared through co-precipitation methods, and the properties of these lakes and their formation mechanisms were investigated. The results showed that amorphous calcium carbonate (ACC) exhibited the smallest particle size and the largest specific surface area, resulting in the highest adsorption efficiency. Vaterite, calcite, and aragonite followed after ACC in decreasing order of adsorption efficiency. Kinetic analysis and isothermal analysis revealed the occurrence of chemisorption and multilayer adsorption during formation of the lakes. The FTIR and Raman spectra suggested participation of sulfonic acid groups in chemisorption. Appearance of IC significantly altered TGA curves by changing weight loss rate before decomposition of calcium carbonate. EDS analysis revealed the adsorption of IC predominantly happened on the surface of calcium carbonate particles rather than the interior.

The food industry uses indigo carmine (IC) extensively as a blue colorant to make processed food for young children and the general population more attractive. Given that IC can act as a ligand, this raises concerns about its interactions with essential metal ions in the human body. In view of this interest, in the present investigation, the copper(II)/indigo carmine system was thoroughly investigated in aqueous solution and in the solid state, and the detailed structural characterization of the complexes formed between copper(II) and the ligand was performed using spectroscopic methods, complemented with DFT and TD-DFT calculations. NMR and UV/Vis absorption spectroscopy studies of the ligand in the presence of copper(II) show changes that clearly reveal strong complexation. The results point to the formation of complexes of 1:1, 1:2 and 2:1 Cu(II)/IC stoichiometry in aqueous solution, favored in the pH range 6–10 and stable over time. DFT calculations indicate that the coordination of the ligand to the metal occurs through the adjacent carbonyl and amine groups and that the 1:1 and the 2:1 complexes have distorted tetrahedral metal centers, while the 1:2 structure is five-coordinate with a square pyramidal geometry. FTIR results, together with EDS data and DFT calculations, established that the complex obtained in the solid state likely consists of a polymeric arrangement involving repetition of the 1:2 complex unit. These results are relevant in the context of the study of the toxicity of IC and provide crucial data for future studies of its physiological effects. Although the general population does not normally exceed the maximum recommended daily intake, young children are highly exposed to products containing IC and can easily exceed the recommended dose. It is, therefore, extremely important to understand the interactions between the dye and the various metal ions present in the human body, copper(II) being one of the most relevant due to its essential nature and, as shown in this article, the high stability of the complexes it forms with IC at physiological pH.

BackgroundIndigo naturalis (IN) is an herbal medicine that has been used for ulcerative colitis with an unclear mechanism of action. Indigo and indirubin, its main constituents, are ligands of the aryl hydrocarbon receptor (AhR). We assessed the safety, efficacy, and colon AhR activity of IN given orally to patients with treatment-refractory ulcerative colitis. The role of AhR in IN benefit was further evaluated with an AhR antagonist in a murine colitis model.MethodsThis open-label, dose-escalation study sequentially treated 11 patients with ulcerative colitis with either IN 500 mg/day or 1.5 g/day for 8 weeks, followed by a 4-week non-treatment period. The primary efficacy endpoint was clinical response at week 8, assessed by total Mayo score. Secondary endpoints included clinical remission, Ulcerative Colitis Endoscopic Index of Severity, quality of life, and colon AhR activity measured by cytochrome P450 1A1 (CYP1A1) RNA expression.ResultsTen of 11 (91%) patients, including 8/9 (89%) with moderate-to-severe disease, achieved a clinical response. Among these 10 patients, all had failed treatment with 5-aminosalicylic acid, 8 patients with a tumour necrosis factor (TNF)-alpha inhibitor, and 6 patients with TNF-alpha inhibitor and vedolizumab. Five patients were corticosteroid dependent. Clinical response was observed in all five patients who had been recommended for colectomy. Three patients achieved clinical remission. All patients experienced improved endoscopic severity and quality of life. Four weeks after treatment completion, six patients had worsened partial Mayo scores. Four patients progressed to colectomy after study completion. Colon CYP1A1 RNA expression increased 12 557-fold at week 8 among six patients evaluated. No patient discontinued IN due to an adverse event. Concomitant administration of 3-methoxy-4-nitroflavone, an AhR antagonist, in a murine colitis model abrogated the benefit of IN.ConclusionIN is a potentially effective therapy for patients with treatment-refractory ulcerative colitis. This benefit is likely through AhR activation.Trial registration numberNCT02442960.

Dyes, such as indigo carmine, have become indispensable to modern life, being widely used in the food, textile, pharmaceutical, medicine, and cosmetic industry. Although indigo carmine is considered toxic and has many adverse effects, it is found in many foods, and the maximum permitted level is 500 mg/kg. Indigo carmine is one of the most used dyes in the textile industry, especially for dyeing denim, and it is also used in medicine due to its impressive applicability in diagnostic methods and surgical procedures, such as in gynecological and urological surgeries and microsurgery. It is reported that indigo carmine is toxic for humans and can cause various pathologies, such as hypertension, hypotension, skin irritations, or gastrointestinal disorders. In this review, we discuss the structure and properties of indigo carmine; its use in various industries and medicine; the adverse effects of its ingestion, injection, or skin contact; the effects on environmental pollution; and its toxicity testing. For this review, 147 studies were considered relevant. Most of the cited articles were those about environmental pollution with indigo carmine (51), uses of indigo carmine in medicine (45), and indigo carmine as a food additive (17).

The aim of the study was to assess the feasibility of utilizing sodium alginate biopolymer as animmobilization carrier for laccase in the removal of indigo carmine (IC), an anionic dye. The main goal of this work was to optimize the decolourization process by selecting the appropriate immobilized enzyme dose per 1 mg of dye, as well as the process temperature. The effective immobilization of laccase using sodium alginate as a carrier was confirmed by Raman spectroscopy. An analysis of the size and geometric parameters of the alginate beads was also carried out. Tests of IC decolourization using alginate-laccase beads were conducted. Applying the most effective dose of the enzyme (320 mg of enzyme/1 mg of IC) made it possible to remove 92.5% of the dye over 40 days. The optimal temperature for the IC decolourization process, using laccase immobilized on sodium alginate, was established at 30-40ºC. The obtained results indicate that laccase from Trametes versicolor immobilized on sodium alginate was capable of decolourizing the tested dye primarily based on mechanism of biocatalysis.

SBA‐15/polypyrrole composite was synthesized by polymerizing pyrrole in the presence of SBA‐15. The samples were characterized using the following techniques: low‐angle XRD, wide‐angle XRD, FTIR, FESEM, TGA, HRTEM, and BET. From the low‐angle XRD analysis, it confirms the formation of a mesoporous hexagonal structure (p6 mm). From the HRTEM image, an orderly arrangement of mesopores is evident. Using adsorption techniques, our objective is to remove sunset yellow, indigo carmine, titan yellow, and orange G dye from aqueous solutions with SBA‐15/polypyrrole composite. The removal efficiency for all the dyes was greater than 90 %. The isotherm was verified to follow the Langmuir isotherm model. The maximum adsorption capacities for sunset yellow, indigo carmine, titan yellow, and Orange G were found to be 78.74 mg/g, 83.33 mg/g, 78.74 mg/g, and 106.38 mg/g, respectively. The adsorption kinetics followed a pseudo‐second‐order model, and the R2 value was greater than 0.99 for all the dyes. The thermodynamic parameters of ΔG°, ΔS°, and ΔH° showed negative values, indicating that the adsorption was spontaneous, decreased entropy, and was exothermic. The recycling of the SBA‐15/polypyrrole composite resulted in a 90 % removal efficiency for three cycles. Therefore, the present adsorbent could be applied to treat industrial effluents that contain these dyes. [ABSTRACT FROM AUTHOR]

A class of polymeric materials known as "hydrogel products" have a hydrophobic structure that enables them to hold significant volumes of water in their three-dimensional networks. It is thought that it is of utmost importance that they can be used extensively in a variety of industrial, biomedical and environmental applications. In this view, I have synthesized a uniuqe hydrogel made from cellulose extracted from banana pseudostem (BPC). This hydrogel exhibits superabsorbent properties. The synthesis was achieved by free-radical graft copolymerization of poly 2-(acryloyloxy) ethyl trimethylammonium chloride copolymer N,N-dimethylacrylamide (AETAC- co -DMA) onto a BPC backbone using ammonium persulfate as the initiator and methylene bisacrylamide as the cross-linking agent. The graft copolymer was studied using FT-IR spectroscopy to confirm its structure. It was further characterized by field-emission scanning electron microscopy (FESEM) and thermogravimetric analysis (TGA) to determine its morphological and thermal properties, respectively. The Effect of various parameters of free-radical graft copolymerization on the swelling behavior of the hydrogel was studied and the optimized copolymer was used to conduct pH and salt sensitivity tests on the hydrogel. The maximum water uptake of the hydrogel was found to be 427 g /g under optimum conditions of initiator, monomer and cross-linker concentrations of 0.0657 mol/L, 1.6 mol and 0.0972 mol/L correspondingly. The hydrogel was found to be pH and salt-sensitive and the salt uptake followed the order KCl>NaCl>CaCl>FeCl3. The excellent water absorbency, pH and salt responsiveness of the prepared hydrogel suggest its applicability not only in agriculture and wastewater treatment, but also in biomedicine for the controlled release of drugs. [ABSTRACT FROM AUTHOR]

A promising electrochemical sensor was developed using an electro-polymerization technique for the simultaneous detection of indigo carmine and tartrazine. The modified sensor exhibited enhanced electrochemical performance compared to the bare carbon paste electrode. Here we used cyclic voltammetry and differential pulse voltammetry methods, the IC showed a good linear response with a correlation value of 0.9956 in the concentration range from 2–27.5 µM. The limit of detection and limit of quantification were determined to be 16.9 nM and 56.33 nM, respectively. Real sample analysis of IC was tested using a tap water by spike method containing indigo carmine demonstrated good recovery results. The poly(dopamine) modified carbon paste electrode holds great potential as an ideal sensor for indigo carmine determination and opens new possibilities for biosensor development. [ABSTRACT FROM AUTHOR]

In this study, efficiency and cost of the Fenton, electro-Fenton, and biosorption processes for treatment of ariazol brown GR and indigo carmine dye mixture were compared. The Box-Behnken experimental design and response surface methodology (RSM) were used to optimize the process variables such as pH, [Fe2+], [H2O2], voltage, biosorbent dose, and time. Finally, the costs of 1 m3 wastewater treatment were calculated in optimal conditions. The operating costs for classical Fenton, electro-Fenton, and biosorption processes were 0.92, 0.48, and 0.13 US$ per 1 m3 wastewater, respectively. The efficiency of the Fenton and electro-Fenton processes for dye removal was similar, but the cost of the electro-Fenton method was half of the Fenton. Furthermore, the electro-Fenton was nine times faster than the Fenton. Efficiency of electro-Fenton was better than the biosorption process even if it is repeated four times with fresh biosorbent (total cost is the same as electro-Fenton). As a general conclusion, the electro-Fenton process is an appropriate choice based on speed and cost in wastewater treatment with respect to Fenton and biosorption processes. [ABSTRACT FROM AUTHOR]

Indigo carmine (IC) is a highly toxic dye that is present in industrial wastewater and leads to serious environmental issues. This synthetic dye can harm ecosystems even at low concentrations. In the present research, Terminalia catappa (TC) shell was modified using the egg white (EW) of broiler chicken (TC-EW) to increase its adsorption capacity for IC removal. The optimum conditions were reached at the pH 2, initial concentration of IC 800 mg/L, contact time 30 min, particle size (≤ 36 μm), and agitation speed of 100 rpm in 25 mL IC dye containing a biosorbent dose of 0.1 g at the temperature of 27 °C. The maximum adsorption capacity of TC-EW to adsorb IC was 106.98 mg g−1. The equilibrium behavior was fit to Langmuir isotherm showing monolayer adsorption. The kinetics of adsorption was fit to pseudo-second-order showing chemical interactions through the sharing or electron exchange of the dye compound and the biosorbent. Mechanism of IC into the TC-EW is by electrostatic attraction, pore diffusion, hydrogen bonding, ion exchange, and π-π interaction. The analysis of the process thermodynamic revealed that it was endothermic and spontaneous at temperature 300–318 K. The effective desorption of IC onto TC-EW shell was achieved using 30% glycerol in alkaline condition and can be re-used for up to 3 cycles. [ABSTRACT FROM AUTHOR]

Acid-activated corn husk waste (CHW) was used to investigate the adsorption mechanism of Indigo Carmine (IC) dye from an aqueous solution. The effect of different operating parameters such as pH (1-7), initial IC dye concentration (40-400 mg/L), contact time (5-75 min), and heating temperature (25–200 °C) was measured on the removal of IC dye by the CHW. The maximum uptake of IC dye was observed at an initial pH of 2. The maximum capacity of 13.57 mg/g and the maximum dye removal of 89.01 % in wastewater. The adsorbents were characterized using Fourier Transforms Infrared Spectrophotometry (FTIR), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray Fluorescence (XRF), and Thermogravimetry Analysis. The characterization process reveals the differences in adsorbent characteristics before and after the adsorption processes. The Langmuir showed the best fitting (R2 = 0.977) and described multilayer adsorption on diverse surfaces. The pseudo-second-order kinetic model best correlated with the experimental data (R2 = 0.981). Thermodynamics revealed that adsorption was favorable spontaneous and exotherm. The study's results indicated that using CHW as a low-cost adsorbent to treat IC dye was efficient and beneficial to the environment. [ABSTRACT FROM AUTHOR]

A novel ternary composite photocatalyst, Bi2O3-CdO-CdCO3, was synthesized via a solvothermal method, followed by heat treatment at various temperatures with and without glass wool (GW). Characterization using X-ray diffraction (XRD), UV-Visible diffuse reflectance spectra, Brunauer-Emmett-Teller, scanning electron microscopy, and X-ray photoelectron spectroscopy confirmed the formation of nanomaterials. Photocatalytic activity was assessed by measuring the photodiscoloration of Indigo carmine dye under visible light and compared to CdO, Bi2O3, and TiO2-P25. Remarkably, the highest efficiency was achieved with the GW-coated material treated at 400°C. XRD analysis revealed the presence of four phases in the non-calcined material, irrespective of GW presence. However, the 400°C treatment induced phase transformation, resulting in six phases in the material without GW and three phases in that with GW. Notably, GW presence influenced this transformation, yielding three dominant phases: Bi2O3, CdO, and CdCO3, accounting for approximately 52%, 24%, and 24%, respectively, in contrast to the case without GW. The coexistence of these three phases on GW fibers significantly enhanced photocatalytic efficiency and longevity under visible light compared to the non-calcined material and material without GW. [ABSTRACT FROM AUTHOR]

We present the synthesis of a cross-linking enzyme aggregate (CLEAS) of a peroxidase from Megathyrsus maximus (Guinea Grass) (GGP). The biocatalyst was produced using 50%v/v ethanol and 0.88%w/v glutaraldehyde for 1 h under stirring. The immobilization yield was 93.74% and the specific activity was 36.75 U mg−1. The biocatalyst surpassed by 61% the free enzyme activity at the optimal pH value (pH 6 for both preparations), becoming this increase in activity almost 10-fold at pH 9. GGP-CLEAS exhibited a higher thermal stability (2–4 folds) and was more stable towards hydrogen peroxide than the free enzyme (2–3 folds). GGP-CLEAS removes over 80% of 0.05 mM indigo carmine at pH 5, in the presence of 0.55 mM H2O2 after 60 min of reaction, a much higher value than when using the free enzyme. The operational stability showed a decrease of enzyme activity (over 60% in 4 cycles), very likely related to suicide inhibition.

Water pollution caused by organic compounds, generated from different industries, has gained attention worldwide today. In this regard, significant efforts have been made for a suitable dye degradation technology. Zinc oxide (ZnO)–based photocatalysts are considered novel materials to degrade organic effluents in contaminated water. The facile synthesis of Ag/ZnO nanocomposites and its application for the enhanced degradation of indigo carmine (IC) dye under visible light irradiation is reported in this paper. The prepared photocatalysts were characterized using various analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron (XPS) spectroscopy, FTIR, Raman, impedance study, UV–Vis, and photoluminescence (PL). Prepared Ag/ZnO nanocomposites were tested for degradation of IC dye in visible light. The degradation efficiency of IC dye was found to be 95.71% in 120 min, with a rate constant of 0.02021 min−1. This improved photocatalytic activity of Ag/ZnO nanocomposites was mainly due to the absorption of visible light caused by surface plasmon resonance (SPR) derived from Ag nanoparticles (NPs) and electron–hole separation. Radical trapping experiments suggest that holes (h+) and superoxide radical (O2•–) are the key factors in photocatalytic IC dye degradation. [ABSTRACT FROM AUTHOR]

Dyes, such as indigo carmine, have become indispensable to modern life, being widely used in the food, textile, pharmaceutical, medicine, and cosmetic industry. Although indigo carmine is considered toxic and has many adverse effects, it is found in many foods, and the maximum permitted level is 500 mg/kg. Indigo carmine is one of the most used dyes in the textile industry, especially for dyeing denim, and it is also used in medicine due to its impressive applicability in diagnostic methods and surgical procedures, such as in gynecological and urological surgeries and microsurgery. It is reported that indigo carmine is toxic for humans and can cause various pathologies, such as hypertension, hypotension, skin irritations, or gastrointestinal disorders. In this review, we discuss the structure and properties of indigo carmine; its use in various industries and medicine; the adverse effects of its ingestion, injection, or skin contact; the effects on environmental pollution; and its toxicity testing. For this review, 147 studies were considered relevant. Most of the cited articles were those about environmental pollution with indigo carmine (51), uses of indigo carmine in medicine (45), and indigo carmine as a food additive (17). [ABSTRACT FROM AUTHOR]

The aim of this work was to compare the adsorption efficiency of two clay materials, namely activated smectite (SMT) and laterite clay (ALT). The comparison was focused on the removal of indigo carmine (IC) dye from aqueous solution. The characterizations showed that the initial materials were mainly mesoporous for effective adsorption. Batch adsorption studies were investigated to optimize the operating parameters such as adsorbent dose, contact time, solution pH, and initial concentration. The pH of point of zero charge (pHpzc) was found to be 2.5, and the optimal adsorption pH obtained was 2 for laterite clay (ALT) and activated smectite (SMT) adsorbents with adsorption capacities of 1.64 mg/g and 1.37 mg/g, respectively, and 10 min as contact time. Surface heterogeneity of both adsorbents was proportional to the amount of IC adsorbed. Freundlich, Langmuir, Dubinin–Kaganer–Radushkevich (D–K–R), and Temkin isotherm models clearly described the retention of the IC on these mesoporous materials. The values of adsorption energies located between 2.23 and 2.54 kJ/mol demonstrated the physisorption of the process. The adsorption capacities obtained by Langmuir model were 4.08 and 4.38 mg/g for ALT and SMT, respectively. The pseudo-second-order kinetic model has been approvingly fitted with complete curves derived from experimental data of both adsorbents. ALT was found to be more effective in the removal of IC compared to SMT. Activated smectite and laterite clay appear to be tenable and profit-making materials for the clean-up of indigo carmine from wastewater. [ABSTRACT FROM AUTHOR]

Aluminium doped zinc oxide (AZO) nanomaterials (AlxZn1-xO) with x fraction varying as 0.02 and 0.04 were synthesized using the auto-combustion method using glycine as a fuel. The synthesized catalysts were characterized with X-ray diffraction (XRD), UV–Visible Spectroscopy (UV–Vis), Raman spectroscopy, Photoluminescence (PL) spectroscopy, and High Resolution Transmission Electron Microscopy (HR-TEM). XRD results showed that synthesized materials possessed good crystallinity, while UV–VIS was employed to find the band gaps of synthesized materials. Raman was used to determine the vibrational modes in the synthesized nanoparticles, while TEM analysis was performed to study the morphology of the samples. Industrial effluents such as indigo carmine and azo carmine G were used to test the photodegradation ability of synthesised catalysts. Parameters such as the effect of catalyst loading, dye concentration and pH were studied. The reduction in crystallite size, band gap and increased lattice strain for the 4% AZO was the primary reason for the degradation in visible irradiation, degrading 97 and 99% equimolar concentrations of indigo carmine and azo carmine G in 140 min. The Al doped ZnO was found to be effective in faster degradation of dyes as compared to pure ZnO in presence of natural sunlight. [ABSTRACT FROM AUTHOR]

Indigo carmine (IC) is an organic salt used as a colorant in food industries and in various pharmacological industries. The consumption of IC has numerous adverse effects on human health and its detection is of great importance. In this work, cyclic voltammetric (CV) analysis of IC was performed by developing an electropolymerized niacin modified carbon paste electrode (PNNMCPE). The morphological features of the bare carbon paste electrode (BCPE) and the PNNMCPE were studied through field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS) and energy-dispersive X-ray spectroscopy (EDXS). The electro-active surface area was calculated to be 0.032 cm2 for PNNMCPE and 0.014 cm2 for BCPE. An increase in the active surface area of the modified electrode resulted in the enhanced current sensitivity. The influence of electrolyte pH was analyzed and the obtained results indicated that the oxidation of IC on the PNNMCPE is associated with equal number of electrons and protons. The study of the impact of scan rate on the peak current and peak potential shows that the electrode surface shows adsorption controlled kinetics. The electro catalytic activities of BCPE and PNNMCPE towards IC were examined using CV in phosphate buffer solution (PBS). Under optimal experimental conditions, the designed electrode demonstrated a considerably low limit of detection (LOD) of 3.39 × 10–7 M and low limit of quantification (LOQ) of 11.30 × 10–7 M. The fabricated sensor showed high level of selectivity towards IC detection in the presence of common interfering metal ions and certain vitamins. Simultaneous analysis of IC was carried out in the presence of methyl orange (MO) with convincing results. The prime attributes such as reproducibility, stability and repeatability of the modified sensor were observed to a significant extent. The practicality of the modified sensor was substantiated by analyzing the presence of IC in candy coated chocolates and tap water samples. It is quite apparent from the outcome of the current work that the developed PNNMCPE is a novel, reliable, affordable and efficient sensor in the quantification of IC in food and water samples. [ABSTRACT FROM AUTHOR]