Monoazo Dyes Research Articles

Green synthesis of ZnO, Fe3O4, and TiO2 nanoparticles: exploring enhanced bacterial inhibition, catalysis, and photocatalysis for sustainable environmental applications

ABSTRACT This study investigates the physicochemical and biological properties of metal oxide nanoparticles (TiO2, ZnO, and Fe3O4) synthesised via the phytosynthesis method using an extract from Boerhaavia diffusa leaves (BDL). The proteins and phenols present in the BDL extract played essential roles in reducing and stabilising TiO2, ZnO, and Fe3O4 nanoparticles. The study reveals size-dependent morphological, structural, and biological characteristics of the produced nanoparticles. FTIR spectra confirm the involvement of BDL extract in the synthesis process of TiO2, ZnO, and Fe3O4 nanoparticles. Transmission electron microscopy (TEM) analysis of TiO2 nanoparticles identified small, spherical particles (9 nm in diameter). BDL-derived TiO2, ZnO, and Fe3O4 demonstrated significant photocatalytic activity, achieving degradation rates of 98.96%, 96.26%, and 94.42%, respectively, in the decomposition of mono-azo dye after 40 minutes of UV irradiation. The reaction rates for BDL-derived TiO2, ZnO, and Fe3O4 were 0.367/min, 0.186/min, and 0.061/min, respectively, when catalysing the reduction of 4-Nitrophenol (4-NP) to 4-Aminophenol using NaBH4. BDL-derived TiO2 nanoparticles exhibited significant antibacterial effectiveness, showing a 23.6 mm zone of inhibition against Salmonella typhi. The BDL-derived TiO2, ZnO, and Fe3O4 nanoparticles exhibited remarkable cytotoxicity against lung cancer cell lines with IC50 values of 76.36 µg/mL, 90.21 µg/mL, and 94.61 µg/mL, respectively. This study reveals the potential of BDL-derived TiO2, ZnO, and Fe3O4 nanoparticles for applications in antibacterial, anticancer, catalytic, and photocatalytic fields, contributing to sustainable development of multifunctional nanomaterials for various technical and environmental advancements.

Synthesis and characterization of aniline-based azo molecules: In vitro pharmacological and emission studies.

The present work involves the synthesis of novel dispersed mono-azo dyes using different coupling components and 2-methoxy-5-nitro aniline as amine through a simple and convenient diazo-coupling method. The structures of the newly synthesized mono azo dyes were confirmed by using various spectral techniques such as 1H NMR, Fourier transform infrared, and high-resolution mass spectrometry. At room temperature, the electronic absorption spectra and fluorescence spectra of the synthesized mono azo dyes were recorded with different solvents. The global reactive parameters for the synthesized azo molecules were evaluated by performing density functional theory through the 6-311++G (d, p) basis set. The anti-microbial activities for the synthesized azo compounds were carried out, and the compounds G1 and G2 exhibited good antibacterial and anti-fungal activities. The in silico molecular docking studies of the azo molecules revealed that all the compounds exhibited extraordinary binding affinity as that of the standard drug. Further, the anti-tuberculosis study against the Mycobacterium tuberculosis for the synthesized azo dyes was evaluated, and from the results, it was revealed that the compound G4 showed good sensitivity among the other synthesized azo compounds.

Compost as Green Adsorbent for the Azo Dyes: Structural Characterization and Dye Removal Mechanism

The study aimed to determine the feasibility of using compost as a ‘green adsorbent’ for the removal of five anionic azo dyes belonging to the monoazo, disazo and trisazo classes: Direct Red 81 (DR-81), Direct Blue 74 (DB-74), Reactive Blue 81 (RB-81), Reactive Red 198 (RR-198) and Acid Black 194 (ABk-194) from aqueous solutions. The adsorption capacity of the compost was determined using a batch method with initial dye concentrations ranging from 1 to 1000 mg/L. The kinetics of dye removal followed a pseudo-second-order model, indicating chemisorption as the rate-limiting step. The monoazo dyes RB-81, RR-198 and ABk-194 with the smaller molecule size were adsorbed the fastest. The Langmuir and Sips models best fit the adsorption system with maximum adsorption capacities in the range of 12.64 mg/g (RR-198)—20.92 mg/g (ABk-194) and 12.57 mg/g (RR-198)—25.43 mg/g (ABk-194), respectively. The adsorption depended on the dye structure, especially on the ratio of the numbers of proton donors to proton acceptor locations in functional groups. The differences in the adsorption mechanism could be explained by thermodynamic properties such as dipole moments, HOMO–LUMO energy gap, polarizability, electron affinity, ionization potential, electronegativity and chemical hardness obtained by Density Functional Theory.Graphical

Rational synthesis of Azo ligands and copper complexes: Insights into potential therapeutic agents

In the pursuit of innovation, four distinct mono Azo dyes D1-D4 were synthesized. These dyes were crafted through a coupling reaction involving 1-naphthol, resorcinol and salicylic acid with diazonium salts derived from a diverse array of aromatic amines, including aniline and sulphanilic acid. Subsequently, they are transformed into copper Azo complexes, namely (D1CuC-D4CuC). The structural underpinnings of these mono Azo dyes and their corresponding copper complexes were unveiled using an arsenal of analytical techniques: FTIR, 1H NMR, 13C NMR, and UV-visible spectroscopy which unequivocally confirmed their synthesis. A computational protein-ligand docking approach was used to assess the binding affinity of ligands and metal complexes to an anti-oxidant receptor protein (PDB ID:2HCK) which showed excellent binding interactions. The findings from an in vitro antioxidant activity using the DPPH scavenging method exhibited: Complexes > Ligands. As an antioxidant agent, the synthesized compounds may prove to be a great therapeutic option. This research introduces a novel approach by utilizing Azo dyes as ligands, leveraging their exceptional electronic tunability and stability to form innovative copper complexes. Their pharmacological applications will be explored, potentially yielding drugs with improved efficacy and selectivity.

Synthesis of anthraquinone-based azo-metal(II) complexes as potent anti-oxidizing agents

The 3-diethylaminophenol (3-DEAP) incorporated anthraquinone mono-azo dye derivative [(E)-1-((4-(diethylamino)-2-hydroxyphenyl)diazenyl)anthracene-9,10-dione] DAAD was synthesized through an electrophilic substitution reaction. The interaction between the -OH functional group and the nitrogen atom of the azo moiety may result in intramolecular proton transfer in the DAAD. DAAD was treated with metal ions such as Co(II), Ni(II), and Cu(II) acetates in a ratio of 2 : 1 revealing an octahedral structure. Many analytical and spectroscopic methods, including UV-vis, FT-IR, (1H and 13C) NMR, HRMS, TGA, VSM, ESR, and powder XRD methods, were used to verify the structural characteristics of the compounds. Additionally, the potency of the in-vitro antioxidant properties of the ligand and its Cu(II), Ni(II), and Co(II) complexes were evaluated; the results revealed that the Co(II) complex showed a maximum percent inhibition of 85 μM against the standard ascorbic acid.

Electrochemical treatment of azo dye wastewater by dynamic flow diaphragm system: Response surface methodology optimization and energy consumption analysis

In this experiment, the degradation process of azo dye wastewater was studied based on the diaphragm double chamber electrochemical reactor, taking the mono azo dye amaranth as an example. Through the circulation flow of appropriate volume of wastewater in the cathode and anode chamber, the simultaneous action of cathode and anode was realized, and the degradation and decolorization efficiency of azo wastewater was improved while reducing energy waste. The optimal reaction conditions optimized by response surface methodology were as follows: the voltage was 20.74 V, the plate spacing was 4.89 cm, and the cycle speed was 60.66 rad / min. The optimal decolorization rate was 99.66 %. The energy consumption analysis of the dynamic flow diaphragm system electrochemical method and the static flow diaphragm system electrochemical method for the treatment of azo dye wastewater was compared and analyzed. In addition, the possible degradation process of azo dye wastewater by dynamic flow electrochemistry was inferred by ultraviolet spectroscopy and mechanism prediction analysis. The experimental results show the great potential of the dynamic flow membrane system process in the treatment of azo dyes.

Synthesis, Spectroscopic, Computational, and Biological Evaluation of Pyrazole mono azo dyes

In the present work, a series of new dispersed mono azo dyes (3) were synthesized through conventional diazo-coupling reaction between 4-hydroxy-phenylacetamide with pyrazole derivatives at low temperature. All the synthesized mono azo compounds were characterized by various spectroscopic methods like IR, NMR, electronic spectral, LC-MS, and fluorescence spectral studies. The experimental IR data was compared with that of the theoretical data and it has been observed that, the experimental IR spectral values are found to be lower than that of the theoretical values. The quantum chemical calculations were also carried out to understand the chemical reactivity of the compounds by using B3LYP method in conjugation with 6-311++G (d, p) basis set. The compounds were screened for anti-tuberculosis properties against M. tuberculosis and the compound 7 was found to exhibit a significant inhibitory effect with MIC value of 12.5μg/mL. The anti-microbial studies were carried for synthesized mono azo compounds. Further, the in silico molecular docking study was carried out to know the significant interaction of the synthesized compounds against VEGFR2 target protein.

Synthesis and characterization of resorcinol based trisazo reactive dye ligand and its metal chelates for application on cellulosic fabric

The purpose of this research was to innovate novel trisazo reactive dyestuffs from 1, 2, 4-acid (the 1-amino-2-naphthol-4-sulphonic acid), the resorcinol derivativatized chemical substance, the vinyl sulphone para ester, and their transition metal chelates iron (II), nickle (II), copper (II), and zinc (II). For the synthesis, resorcinol in an alkaline medium was coupled to diazotized 1, 2, 4-acid (1-amino-2-naphthol-4- sulphonic acid) to create the 1, 2, 4-acid (the 1-amino-2-naphthol-4- sulphonic acid)- resorcinol mono-azo dye ligand. The 1, 2, 4-acid (1-amino-2-naphthol-4- sulphonic acid)- resorcinol mono-azo dye ligand was passed through coupling with the diazotized vinyl sulphone para este in an alkaline medium to generate tris-azo reactive dyestuff. Metal chelates of reactive dyestuffs have also been generated using 3d transition metals, namely iron, zinc, iron, copper, as well as nickel. The metallization of the synthesized monoazo dye ligands with sulphate salts of iron, nickel, copper, and zinc, as well as the coupling reaction with diazotized vinyl sulphone para ester resulted hot brand novel vinyl sulfone-type trisazo fiber reactive dyes. To evaluate how successfully the novel synthesized dyestuffs dyed cotton fabric, these were applied to cotton fabric in one percent, three percent, and six percent (stock) solutions relative to the weight of cotton fabric, and were examined for their characteristics. These showed excellent light fastness, rub fastness, and wash fastness when applied to cotton fabric. Analytical data and spectroscopic techniques allying optical studies thereby UV-Visible spectroscopy and FTIR spectral interpretation were utilized to confirm the constituents of whole innovative, novel synthesized tris-azo reactive dye substances. Maximum synthesized tris-azo reactive dyestuffs found to have large values of their wash fastness 4 and above on the grey scale, and light fastness 4 and above on the blue scale, respectively, when dyed on cotton cloth. A comparative study of these dyes was also done with existing standards, the pantone color system. The dye adhesion, reactivity, dissolution, as well as stabilizing qualities were all outstanding, indicating that the fabric was well dissolved. Such artificial trisazo reactive dyestuffs were transferred attractively onto the colored cotton cloth, evenly distributed, well permeated into the fiber, and fastened. Consequently, tris-azo reactive dyestuff ligand, and its metal chelates were appraised accomplished wonderfully, while colored cotton cloth. These dyestuffs will further benefit the creation of innovative industrial items. Consequently, this in-house production of creative resorcinol-based dyestuffs will also usher in a futuristic era of investigation for the country’s economic advancement, and in industrialization.

Biotransformation of the azo dye reactive orange 16 by Aspergillus flavus A5P1: Performance, genetic background, pathway, and mechanism

This study reports the strain Aspergillus flavus A5P1 (A5P1), which is with the capable of degrading the azo dye reactive orange 16 (RO16). The mechanism of RO16 degradation by A5P1 was elucidated through genomic analysis, enzymatic analysis, degradation pathway analysis and oxidative stress analysis. Strain A5P1 exhibited aerobic degradation of RO16, with optimal degradation at an initial pH of 3.0. Genomic analysis indicates that strain A5P1 possesses the potential for acid tolerance and degradation of azo dye. Enzymatic analysis, combined with degradation product analysis, demonstrated that extracellular laccase, intracellular lignin peroxidase, and intracellular quinone reductase were likely key enzymes in the RO16 degradation process. Oxidative stress analysis revealed that cell stress responses may participate in the RO16 biotransformation process. The results indicated that the biotransformation of RO16 may involves biological processes such as transmembrane transport of RO16, cometabolism of the strain with RO16, and cell stress responses. These findings shed light on the biodegradation of RO16 by A5P1, indicating A5P1′s potential for environmental remediation.

Toxic effects and mechanisms of cationic blue SD-GSL on Chlorella vulgaris before and after the biological decolorization process

Biodegradation is regarded as an efficient way to decolorize azo dyes. However, the changes in the algal toxicity of azo dyes during biodecolorization are still unclear. In this study, the physiological responses of Chlorella vulgaris to the hydrophobic and hydrophilic components of cationic blue SD-GSL (a typical monoazo dye) and its biodecolorization products were investigated. The toxicity of each component to Chlorella vulgaris and the sources of the toxicity were analyzed. The cationic blue SD-GSL components inhibited the algal cell division and superoxide dismutase (SOD) activity at all concentrations, and inhibited the synthesis of chlorophyll-a (Chl-a) at concentrations >100 mg/L, whereas increased the malondialdehyde (MDA) content. The hydrophobic and hydrophilic components of its biodecolorization products had enhanced inhibition rates on cell density (10.7% and 15.6%, respectively), Chl-a content (31.2% and 8.4%, respectively), and SOD activity (13.5% and 1.9%, respectively) of Chlorella vulgaris, and further stimulated an increase in MDA content (4.4% and 7.0%, respectively), indicating that the biodecolorization products were more toxic than the pristine dye. Moreover, the toxic effect of hydrophobic components on Chlorella vulgaris was stronger than that of hydrophilic components. The sensitivity sequence of Chlorella vulgaris to the toxicity of cationic blue SD-GSL and its biodecolorization product components was: Chl-a synthesis > SOD activity > cell division. SUVA analysis and 3D-EEM analysis revealed that the enhanced algal toxicity of the biodecolorization products of cationic blue SD-GSL was attributed to the aromatic compounds, which were mainly concentrated in the hydrophobic components. UPLC-Q-TOF-MS was used to verify dye biodecolorization byproducts. The information obtained from this study helps to understand the decolorization products toxicities of the biologically treated azo dyes, thereby providing new insights into the environmental safety of textile wastewater after traditional biological treatment.

Evaluation of mutagenic activity of the food dye Ponceau 4R in a micronuclear test in mice

Introduction. Food monoazo dye E124 Ponceau 4R is used in the food, pharmaceutical, and cosmetic industries. An analysis of the available data on the evaluation of the genetic safety of E124 based on the main marker events of genotoxicity revealed their inconsistency, possibly associated with quantitative and/or qualitative differences in the studied samples for impurities. 
 The aim of the work is to evaluate the mutagenic activity in the micronucleus test in mice of several commercial samples of E124 present on the domestic market.
 Materials and methods. Three samples of E124 from different manufacturers (India) were studied. To assess the identity of Ponceau 4R substances, there was used method of MIR-spectroscopy – universal ART technique. Aqueous dye solutions were administered to the stomach of male CBA × C57Bl6/j) mice at doses 
 of 125 to 2000 mg/kg twice with an interval of 24 hours and preparations were prepared 24 hours after the last injection. To assess the frequency of polychromatophilic erythrocytes (PCE) with micronuclei (MN), 4000 PCE were analyzed, the proportion of PCE among all erythrocytes – 500 cells per animal.
 Results. Ponceau 4 R was determined in all samples. All E124 samples caused an increase in the frequency of PCE with MN (p < 0.05–0.001, T test) after exposure at all levels studied in a linear dose-dependent manner. The proportion of PCE from all erythrocytes did not change. 
 Limitations. The data obtained do not allow determining the mechanism of the genotoxic action of the test substance.
 Conclusion. An analysis of the frequency of MN PCEs in the bone marrow in mice after a double injection at doses of 125–2000 mg/kg revealed the genotoxicity of three samples Ponceau 4R.

Free Salt Dyeing by Treatment of Cotton Fabric Using Carboxyethyl Chitosan and Synthesized Direct Dyes to Enhance Dyeing Properties and Antibacterial Activity.

The purpose of this paper is to synthesize and characterize two new direct dyes based on chromenes derivatives. The synthesis of carboxyethyl chitosan (CECS) by the reaction of chitosan and acrylic acid via Michael's addition reaction was conducted. Cotton fabrics were treated with CECS to enhance the exhaustion of dye, fastness properties, and antimicrobial activity of dyed fabric. Chitosan (CS) and acrylic acid were combined in Michael's addition process to successfully produce N-carboxyethylchitosan (CECS). Then, the cotton was treated with different concentrations of carboxyethyl chitosan (0.5-5 wt.%) and then dyed by synthesized mono azo and diazo direct dyes based on chromene derivatives. The results regarding dyeing and antibacterial activity indicated highquality dyeing properties, However, direct dyes showed higher exhaustion and fixation values, fastness properties, and the colorimetric CIE L*a*b* C*h° data of the dyed cotton fabric. Cotton fabrics treated with carboxyethyl chitosan and dyed with direct dyes were found to have higher antibacterial activity upon a concentration of 2.5 wt.%. In addition, the antibacterial activity towards Gram-positive bacteria was reported to be more than Gram-negative bacteria.

The effect of in-situ Pr6O11 phase formation on photocatalytic Performance: Mono azo dye degradation

The structural properties of TiO2, which finds wide application due to its excellent properties, can be improved especially by doping with transition metals to treat wastewater containing dyestuffs in a cheap, sustainable and environmentally responsible way. The positive impact of in situ Pr6O11 phase formation on the catalytic characteristics of the praseodymium ion doped (Pr-TiO2) photo catalyst produced by the acid sol gel method is highlighted in this study. Pr ion doping concentration of 1 wt% and calcination temperature of 400° C were selected. The properties of a Pr6O11/TiO2 composite structure (Pr-TiO2) synthesized utilizing XRD, XPS, and FTIR methods are discussed. Furthermore, the surface area of the pristine TiO2 photocatalyst was 19.22 (m2.g−1) and rose to 101.51 (m2.g−1) in the Pr-TiO2 catalyst, according to BET surface area measurements. The adsorption properties and photocatalytic activity of the catalyst were determined by the examination of the mono azo dyestuff Basic Blue 41 (BB41) degradation in a batch reactor using suspended system photocatalysis (ASF). No oxidation agents were used in this system. Azo dyestuff removal efficiency was measured by total organic carbon (TOC) and the color pollution change of wastewater was measured by UV–vis spectrophotometer.

Decolorization, degradation and detoxification of mutagenic dye Methyl orange by novel biofilm producing plant growth-promoting rhizobacteria

Discharge of untreated dyeing wastewater nearby water-bodies is one of major causes of water pollution. Generally, bacterial strains isolated from industrial effluents and/or contaminated soils are used for the bioremediation of Methyl orange (MO), a mutagenic recalcitrant mono-azo dye, used in textiles and biomedical. However, MO degradation by biofilm producing plant growth-promoting rhizobacteria (BPPGPR) was not studied yet. In this study, 19 out of 21 BPPGPR strains decolorized 96.3–99.9% and 89.5–96.3% MO under microaerophilic and aerobic conditions, respectively from Luria-Bertani broth (LBB) followed by yeast-extract peptone and salt-optimized broth plus glycerol media within 120 h of incubation at 28 °C. Only selected BPPGPR including Pseudomonas fluorescens ESR7, P. veronii ESR13, Stenotrophomonas maltophilia ESR20, Staphylococcus saprophyticus ESD8, and P. parafulva ESB18 were examined for process optimization of MO decolorization using a single factor optimization method. This study showed that under optimal conditions (e.g., LBB, 100 mg L−1 MO, pH 7, incubation of 96 h, 28 °C), these strains could remove 99.1–99.8% and 97.6–99.5% MO under microaerophilic and aerobic conditions, respectively. Total azoreductase and laccase activities responsible for biodegradation were also remarkably activated in the biodegraded samples under optimal conditions, while these activities were repressed under unfavorable conditions (e.g., 40 °C and 7.5% NaCl). This study confirmed that MO was degraded and detoxified by these bacterial strains through breakage of azo bond. So far, this is the first report on bioremediation of MO by the BPPGPR strains. These BPPGPR strains are highly promising to be utilized for the bioremediation of dyeing wastewater in future.

Quinoline–Pyrimidine Monoazo Dye Hybrids: Synthesis, Catalyst Optimization, Molecular Docking and ADMET Studies, Biological Activity, and Dye Ability Assessment

Quinoline–Pyrimidine Monoazo Dye Hybrids: Synthesis, Catalyst Optimization, Molecular Docking and ADMET Studies, Biological Activity, and Dye Ability Assessment

Evaluation of the cytogenetic activity of the food dye Azorubine in a micronucleus test in mice

Introduction. Azorubine E122 (Carmoisine, Food Red 3) monoazo dye is used in the manufacture of desserts, caramels, sweets, marmalades, ice cream, alcoholic and non-alcoholic drinks, etc. The safety assessment of food additives includes the study of genotoxic potential. At the same time, for substances with a high or a small but long-term exposure (including food additives), in vivo tests are required.
 Materials and methods. The genotoxic activity of aqueous solutions of synthetic food azo dyes E122 Azorubin was studied by the micronuclear method on bone marrow cells in mice (males, hybrids F1 CBA × C57Bl6/j). The studied substances were injected into the stomach of mice at doses of 250–2000 mg/kg twice with an interval of 24 hours, with the preparation of bone marrow preparations 24 hours after the last administration. The frequency of micronucleated (MN) polychromatophilic erythrocytes (PCEs) was estimated on the base of the results of the analysis of 4000 PСЕ. The proportion of PСE among all red blood cells was determined by analyzing 500 cells per animal. 
 Results. There was no statistically significant increase in the frequency of PCE with MN over the current control with a double administration of Azorubine in all studied doses. After exposure at doses of 1000 and 2000 mg/kg, the incidence of MN PCEs slightly exceeded the upper limit of the 95% CI of the accumulated negative control and the effect was dose-dependent and statistically significant, which does not allow recognizing the answer as clearly negative.
 Limitations of the study are due to the methodology of the test: only cytogenetic disorders in a single tissue were analyzed under conditions of double enteral administration of the studied sample.
 Conclusion. An analysis of the frequency of MN PCEs in the bone marrow of mice after a double injection of Azorubine at doses of 250–2000 mg/kg made it possible to qualify the result of the experiment as uncertain.

Low‐water‐solublereactive dyes for application in ultrafine polyamide/polyurethane synthetic leather

AbstractUltrafine polyamide/polyurethane synthetic leather (UP/PSL), with a highly natural leather‐like appearance and touch, is widely used in many leather commodities. Generally, acid dyes, which are mostly used for dyeing UP/PSL, exhibit poor colour fastness. While, reactive dyes are well‐known for their good colour fastness. However, reactive dyes are not used to dye UP/PSL because they are water‐soluble and cannot stain the polyurethane (PU) in UP/PSL. In this study, five low water‐soluble reactive dyes with good affinity for both polyamide (PA) and PU were synthesised and characterised using ultraviolet‐visible and infrared spectroscopy, and mass spectrometry. All low‐water‐soluble reactive dyes were monoazo dyes with only one sulfonic group and two different functional groups. The reactive dyes were used to dye UP/PSL at 98°C and fixed at 90°C with 7‐azatridecane‐1,13‐diamine as a crosslinking agent. For comparison, Eriofast Red‐2B (ER‐2B) was used to dye UP/PSL using a special dyeing procedure. ER‐2B showed severe issues related to low utilisation and uneven dyeing, whereas the five low water‐soluble reactive dyes exhibited better performance than ER‐2B. Both the exhaustion and fixation of dyes 1 and 4 exceeded 90.0% when the dosage was less than 3.0% owf (on weight of fabric). In addition, they exhibited good levelling. The washing fastness of the five reactive dyes was excellent and higher than grade 4. The dry rubbing fastness was higher than grade 3‐4. Therefore, UP/PSL can be satisfactorily dyed using the reactive dyes with a solubility of less than 1.0 g/L and meet the requirements of daily life applications.

Study of the electronic effect and quantitative spectra predictions of o-methoxyaniline-terminated monoazonaphthols: a combined experimental and DFT study.

A combined experimental and density functional theory (DFT) study on the UV-Vis spectra of o-methoxyaniline-terminated mono azo dyes was conducted. By applying time-dependent-DFT calculations, details of excitation processes were determined and visualization by hole-electron analysis was undertaken. Fragment-divided analysis revealed the contributions of different parts of the structures for the UV-Vis spectra, that richer/poorer electron density on aromatic rings lead to greater/less maximum absorption wavelengths (λmax) and larger/smaller half peak width (W1/2). Combining theoretical prediction with experimental verification, we answered the question of how the electronegativities of substituents affected the electron densities and how it affected the spectra. In addition, a linear model connecting the λmax and W1/2 to the chemical shifts obtained by NMR spectroscopy was constructed, which laid the foundation for construction of a spectral library.

Efficient Adsorption of Methyl Orange on Nanoporous Carbon from Agricultural Wastes: Characterization, Kinetics, Thermodynamics, Regeneration and Adsorption Mechanism

Nanoporous carbon derived from Moringa oleifera seed waste was synthesized by an original process of flash pyrolysis followed by zinc chloride impregnation. The N2-adsorption–desorption results of the optimized sample revealed a BET surface area of 699.6 m2/g and a pore size of 2 nm. It was evaluated for the adsorption of a mono azo dye, methyl orange (MeO), from aqueous solution. Four isothermal models (Langmuir, Freundlich, Dubinin–Radushkevic and Temkin) were applied to fit the experimental data. The results revealed that Langmuir is the most appropriate isothermal adsorption model to describe the adsorption process (X2 = 1.16); with an adsorption capacity 367.83 mg/g at 298 K, the interaction of MeO dye with the nanoporous carbon surface is a localized monolayer adsorption. The adsorption kinetics was consistent with the pseudo-second-order model and found to correlate well with the experimental data (X2 = 9.06). The thermodynamic study revealed a spontaneous and endothermic adsorption process, and the substances are adsorbed in a random manner. The desorption of MeO dye from MOC-ZnCl2 by sodium hydroxide solution was achieved to a level of about 84%, and the nanoporous carbon was recycled and reused at the fifth cycle. This work demonstrates that MOC-ZnCl2 could be employed as an alternative to commercially available activated carbon in the removal of dyes from wastewater.

ПРОЦЕС “СОНОПЕРОКСАТ” ДЛЯ ОКИСНЮВАЛЬНОЇ ДЕГРАДАЦІЇ МЕТИЛОВОГО ОРАНЖЕВОГО

The efficiency of application of advanced oxidation processes for removal of methyl orange mono azo dye from wastewater is considered. For intensive oxidative degradation of methyl orange, it was proposed to use a combination of ultrasonic cavitation and “Peroxate” process – the “Sonoperoxate” process. Rational conditions for oxidative degradation of methyl orange at its initial concentration in an aqueous solution of 25 mg/dm3 (76.5·10-6 mol/dm3) were established: the molar ratio of methyl orange:hydrogen pero- xide:potassium metaperiodate = 1:50:10; pH of the reaction medium – 3; temperature – 293 K; specific power of cavitation ultrasonic treatment – 68 W/dm3. Under such conditions, the degradation degree of methyl orange of 89.4 % was achieved for 1800 s.