Search Results (14)

In this paper, a toxicological investigation was carried out on a series of azoic direct dyes generally with an affinity for cellulosic fibers, presenting symmetrical and asymmetrical structures having as a central component a non-carcinogenic, mutagenic, or teratogenic and accessible precursor potential substitute for benzidine, namely 4,4′-diaminobenzanilide, and, as coupling components, 2-hydroxybenzoic acid, 2-hydroxy-3,6-naphthalenesulfonic acid, 2-amino-8-hydroxynaphthalene-6-sulfonic acid, 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid, 1-(4′-sulfophenyl)-3-methyl-5-pyrazolone, and 2-hydroxy-6-naphthalenesulfonic acid, respectively. For the purpose of their safe use, this study shows the results regarding the toxicity of the above-mentioned dyes, obtained through biological tests on colonies of Hydractinia echinata (H. echinata). The toxicity tests were performed on heterotrophic bacteria cultures obtained from the Bega River. The minimum toxic concentration was monitored using the dilutions 0.6 g/L, 24 g/L, and 48 g/L, obtained by dilution of a stock solution of 60 g/L. The symmetric dye with the coupling component 2-hydroxybenzoic acid presents the highest degree of toxicity, the lowest being shown by dyes with symmetric and asymmetric structures with the following coupling components: 2-amino-8-hydroxynaphthalene-6-sulfonic acid, 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid, 1-(4′-sulfophenyl)-3-methyl-5-pyrazolone, and 2-hydroxy-6-naphthalenesulfonic acid. Full article

The presence of pollutants in water sources, particularly dyes coming by way of the textile industry, represents a major challenge with far-reaching environmental consequences, including increased scarcity. This phenomenon endangers the health of living organisms and the natural system. Numerous biosorbents have been utilized for the removal of dyes from the textile industry. The aim of this study was to optimize discarded Zygophyllum gaetulum stems as constituting an untreated natural biosorbent for the efficient removal of C.I. Direct Black 80, an azo textile dye, from an aqueous solution, thus offering an ecological and low-cost alternative while recovering the waste for reuse. The biosorbent was subjected to a series of characterization analyses: scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), and infrared spectroscopy (IR) were employed to characterize the biosorbent. Additionally, the moisture and ash content of the plant stem were also examined. The absorption phenomenon was studied for several different parameters including the effect of the absorption time (0 to 360 min), the sorbent mass (3 to 40 g/L), the pH of the solution (3 to 11), the dye concentration (5 to 300 mg/L), and the pH of the zero-charge point (2–12). Thermodynamic studies and desorption studies were also carried out. The results showed that an increase in plant mass from 3 to 40 g/L resulted in a notable enhancement in dye adsorption rates, with an observed rise from 63.96% to 97.08%. The pH at the zero-charge point (pHpzc) was determined to be 7.12. The percentage of dye removal was found to be highest for pH values ≤ 7, with a subsequent decline in removal efficiency as the pH increased. Following an initial increase in the amount of adsorbed dye, equilibrium was reached within 2 h of contact. The kinetic parameters of adsorption were investigated using the pseudo-first-order, pseudo-second-order and Elovich models. The results indicated that the pseudo-first-order kinetic model was the most appropriate for the plant adsorbent. The isotherm parameters were determined using the Langmuir, Frendlich, Temkin, and Dubinin–Radushkevich models. The experimental data were more satisfactory and better fitted using the Langmuir model for the adsorption of dye on the plant. This study demonstrated that Zygophyllum gaetulum stems could be employed as an effective adsorbent for the removal of our organic dye from an aqueous solution. Full article

This paper presents the preparation and characterization of bentonite coated with hydroxide double lamellar Mg/Al-bentonite and Zn/Al-bentonite as a potential adsorbent material. The coating process involved co-precipitation of mixed metal nitrate solution (Mg-Al) or (Zn-Al), followed by immersion of bentonite (B-Na⁺) dispersion. The structures and morphologies of the coated bentonites were characterized using XRD, FTIR, BET, and SEM analysis. The results of the BET analysis indicate that Mg/Al-bentonite and Zn/Al-bentonite have larger surface areas and pore volumes compared to bentonite alone. Specifically, the surface area of Mg/Al-bentonite is 209.25 m²/g with a pore volume of 0.423 cm³/g, while Zn/Al-bentonite has a surface area of 175.95 m²/g and a pore volume of 0.313 cm³/g. In contrast, the surface area and pore volume of bentonite alone are 110.43 m²/g and 0.132 cm³/g, respectively. The Mg/Al-bentonite reaches 85% uptake within 3 h (equivalent to 724.20 mg/g at 25 °C and pH 7), achieving rapid equilibrium. In contrast, the Zn/Al-bentonite achieves a maximum adsorption of 74% within 5 h under identical pH and temperature conditions, corresponding to 650.34 mg/g. The error function values, including the correlation coefficient R², chi-square test χ², and residual sum of squares RSS, were calculated to evaluate both kinetic and isotherm models. The kinetic adsorption data agreed well with a pseudo-second-order model. The adsorption process followed the Sips isotherm model, and the monolayer adsorption capacity of Mg/Al-bent and Zn/Al-bent composites was 872.41 (R² = 0.974) and 678.45 mg/g (R² = 0.983), respectively. The thermodynamic analysis of the adsorption process revealed that it occurred spontaneously with an endothermic characteristic. The parameters ΔS, ΔH, and ΔG were used to determine this. Full article

Dyes are organic compounds capable of transmitting their color to materials, which is why they are widely used, for example, in textile fibers, leather, paper, plastic, and the food industry. In the dying process, measuring the dye’s content is extremely important to evaluate the process efficiency and minimize the dye’s discharge in wastewater, but most of the time, dyes are present in multi-component mixtures; hence, quantification by spectrophotometric methods presents a great challenge because the signal obtained in the measurement overlaps the components in the mixture. In order to overcome this issue, the use of the high-performance liquid chromatography (HPLC) method is recommended; however, it has the disadvantage of being an expensive technique, complex, and requiring excessive sample preparation. In recent years, some direct spectrophotometric methods based on multivariate regression algorithms for the quantification of dyes in bicomponent mixtures have been reported. This study presents a new framework that uses a combined ANN and principal component analysis (PCA) model for the determination of the concentration of three dyes in aqueous mixtures: Tartrazine (TZ), Amaranth Red (AR), and Blue 1 CFC (B1) dyes. The PCA–ANN model was trained and validated with ternary mixture samples of TZ, AR, and B1, and with known different compositions, spectra absorbance samples were measured in a UV-Vis spectrophotometer at wavelengths between 350–700 nm with intervals of 1 nm. The PCA–ANN model showed a mean absolute prediction error and correlation coefficient (r²) of less than 1% and greater than 0.99, respectively. The results demonstrate that the PCA–ANN model is a quick and highly accurate alternative in the simultaneous determination of dyes in ternary aqueous mixtures. Full article

Thiophene ring-enhancing electron delocalization imparts unique properties to azoic chromophore tools. The novel TA-OH dye contains a push–pull π-electron system, including a thiophene-azo scaffold with a hydroxyl group at the ortho position to the azo bridge. The hydroxyl group is expected to lock the azo bridge in its trans conformation, concurring with the photostability and fastness of the dye. The single crystal analysis identified the molecule’s primary conjugation plane, and the theoretical analysis provided electronic pattern insights. The absorption behavior and the trans-to-cis conversion were examined from both experimental and theoretical perspectives. The effect of solvent polarity and the role of pH on the photophysical properties were explored. The solvent polarity strongly affects the absorbance spectrum of TA-OH, therefore potentially making NLO active. Additionally, TA-OH exhibited pH responsiveness akin to classic dichromatic pH indicators, with a noticeable color shift from red to blue observed as pH transitioned from neutral to alkaline. Absorbance titration experiments, along with experimental/theoretical determination of pKa, defined the pH sensing ability. Full article

This paper presents the development of cheap and selective Paper-based Analytical Devices (PADs) for selective Pd(II) determination from very acidic aqueous solutions. The PADs were obtained by impregnating two cm-side squares of filter paper with an azoic ligand, (2-(tetrazolylazo)-1,8 dihydroxy naphthalene-3,6,-disulphonic acid), termed TazoC. The so-obtained orange TazoC-PADs interact quickly with Pd(II) in aqueous solutions by forming a complex purple-blue-colored already at pH lower than 2. The dye complexes no other metal ions at such an acidic media, making TazoC-PADs highly selective to Pd(II) detection. Besides, at higher pH values, other cations, for example, Cu(II) and Ni(II), can interact with TazoC through the formation of stable and pink-magenta-colored complexes; however, it is possible to quantify Pd(II) in the presence of other cations using a multivariate approach. To this end, UV-vis spectra of the TazoC-PADs after equilibration with the metal ions solutions were registered in the 300–800 nm wavelength range. By applying Partial Least Square regression (PLS), the whole UV-vis spectra of the TazoC-PADs were related to the Pd(II) concentrations both when present alone in solution and also in the presence of Cu(II) and Ni(II). Tailored PLS models obtained with matrix-matched standard solutions correctly predicted Pd(II) concentrations in unknown samples and tap water spiked with the metal cation, making the method promising for quick and economical sensing of Pd(II). Full article

The valorization of natural polymeric substrates has increased due to their uses and applications in several fields. The existence of many functional groups in their chemical structures allows them to be easily subjected to chemical modifications. This work focuses on the exploration of a new low-cost and abundant cellulosic biomass, Zilla spinosa fruit. The biomaterial was functionnalized with polyethyleneimine (1%, 3%, 5%, and 8%) in order to impart new reactive sites on its surface. The virgin and functionnalized biomaterials were analysed using several analytical methods; X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FT-IR), Scanning Electron Microscopy (SEM), and Thermogravimetric analysis (TGA). XPS spectrum of Zilla spinosa-polyethyleneimine exhibited the appearance of a new peak at 399 eV, which corresponds to N1s (5.07%). The adsorption characteristics of the prepared adsorbents were evaluated toward calmagite, an azoic and anionic dye. The adsorption capacity of Zilla spinosa-polyethyleneimine (5%) reached 114 mg/g at pH = 5, T = 20 °C, and time = 60 min conditions; though, it does not exceed 8.4 mg/g for the virgin Zilla spinosa under the same experimental conditions. The kinetic data followed both pseudo-first-order and pseudo-second-order kinetic equations suggesting a physicochemical process. The adsorption mechanism was found to be exothermic and non-spontaneous. Overall, Zilla spinosa-polyethyleneimine has demonstrated a high adsorption level which could be considered a promising candidate to remove synthetic dye molecules from contaminated water. Full article

Introduction: Silver nanoparticles (AgNPs), widely recognized for their antimicrobial and antioxidant capacity, can be prepared following both conventional and unconventional routes and have a multitude of applications in numerous scientific domains, including the catalytic degradation of dyes that result from the textile industry [...] Full article

Adsorbent columns, containing different amounts of multi-walled carbon nanotubes (MWCNTs), in a semicontinuous process were studied. The optimal conditions for the discoloration of water contaminated by an azoic organic textile dye were investigated. In particular, as representative of contaminated water, a highly concentrated solution of Reactive Black 5 (RB5) equal to 37 mg/L was utilized. A predetermined volume of dye solution, equal to 100 mL, was subjected to repeated cycles of adsorption until the eluted solution became colorless. This adsorption operation was carried out for different types of columns. Adsorbent performances as a function of characteristics of each column were investigated. For each column, the optimum quantity of MWCNTs, maximum volume of treatable solution, carbon usage rate (CUR), empty bed contact time (EBCT), and adsorption capacity were determined. The permeate was characterized by UV-VIS analysis and TOC analysis, while adsorbent material (MWCNTs) was characterized by thermogravimetric TG-DTA analysis. The column containing 2.5 g of carbon nanotubes was revealed to be the best one for the total amount of Reactive Black 5 adsorbed, i.e., 55 mg/g_(MWCNTs) The research has shown the high adsorption efficiency of carbon nanotubes toward RB5 dye, highlighting the degradation of the dye molecule and the stratification, inside the columns, of the adsorbed compound. Full article

Two yellow bis-azo dyes containing anthracene and two azodiphenylether groups (BPA and BTA) were prepared, and an extensive investigation of their physical, thermal and biological properties was carried out. The chemical structure was confirmed by the FTIR spectra, while from the UV–Vis spectra, the quantum efficiency of the laser fluorescence at the 476.5 nm was determined to be 0.33 (BPA) and 0.50 (BTA). The possible transitions between the energy levels of the electrons of the chemical elements were established, identifying the energies and the electronic configurations of the levels of transition. Both crystals are anisotropic, the optical phenomenon of double refraction of polarized light (birefringence) taking place. Images of maximum illumination and extinction were recorded when the crystals of the bis-azo compounds rotated by 90° each, which confirms their birefringence. A morphologic study of the thin films deposited onto glass surfaces was performed, proving the good adhesion of both dyes. By thermal analysis and calorimetry, the melting temperatures were determined (~224–225 °C for both of them), as well as their decomposition pathways and thermal effects (enthalpy variations during undergoing processes); thus, good thermal stability was exhibited. The interaction of the two compounds with collagen in the suede was studied, as well as their antioxidant activity, advocating for good chemical stability and potential to be safely used as coloring agents in the food industry. Full article

A new, double hydroxide based on Co and Fe was elaborated on by forced hydrolysis in a polyol medium. Complementary characterization techniques show that this new phase belongs to the layered double hydroxide family (LDH) with Co²⁺ and Fe³⁺ ions located in the octahedral sites of the bucite-like structure. The acetate anions occupy interlayer space with an interlamellar distance of 12.70 Å. This large distance likely facilitates the exchange reaction. Acetates were exchanged by carbonates. The as-obtained compound Co-Fe-Ac/_Ex shows an interlamellar distance of 7.67 Å. The adsorption of direct red 2 by Co-Fe-Ac-LDH has been examined in order to measure the capability of this new LDH to eliminate highly toxic azoic anionic dyes from waste water and was compared with that of Co-Fe-Ac/_Ex and Co-Fe-CO₃/_A (synthesized in an aqueous medium). The adsorption capacity was found to depend on contact time, pH, initial dye concentration, and heating temperature. Concerning CoFeAc-LDH, the dye uptake reaches a high level (588 mg/g) due to the occurrence of both adsorption processes: physisorption on the external surface and chemical sorption due to the intercalation of dye by exchange with an acetate anion. The study enables us to quantify the uptake amount of each effect in which the intercalation has the most important amount (418 mg/g). Full article

Laccases have attracted a great deal of interest because of their remarkable ability for the degradation of synthetic dyes present in wastewaters. New laccase producing sources with robust operational and functional properties are being continuously explored. In this work, the potential for the decolorization and detoxification of synthetic dyes was evaluated in two Mexican strains of the genus Trametes. The decolorization capacity of Trametes maxima LE130 and Trametes sp. LA1 was tested in solid and liquid media. The phytotoxicity of the degradation products was determined using Raphanus sativus and Pisum sativum seeds. In solid media, both strains showed a higher decolorization capacity (p ≤ 0.05) than Phanerochaete chrysosporium ATCC 24725, which is known to be very efficient in lignin and dye-degradation. They produced laccase as the main ligninolytic enzyme; T. maxima LE130 secreted a single isoform of 43.9 kDa, while Trametes sp. LA1 produced three isoforms of 67.3, 58.6 and 52.7 kDa, respectively. Trametes sp. LA1 culture fluids were capable of decolorizing and detoxifying chemically diverse dyes (anthraquinonic dye Remazol Brilliant Blue R, azoic Reactive Black 5 and triphenylmethane Crystal Violet) without the addition of redox mediators. Therefore, this could be considered as a new laccase source which could be potentially competitive in the bioremediation of dye-containing wastewaters. Full article

This work aims to investigate possible interferences due to the presence of sodium carbonate on the photodegradation of the reactive Black 5 azoic dye, both in systems containing only titanium oxide and those containing titanium oxide and hydrogen peroxide. The role of hydrogen peroxide is explicitly treated. Sodium carbonate, in fact, is often present in the wastewater of textile industries as it is used in the fiber dyeing phases. The use of TiO₂ nanoparticles is emphasized, and the possible danger is underlined. Each system was subjected to ultraviolet irradiation (UV) by varying the exposure time. After the photodegrading tests, the resulting solutions were analyzed by UV-vis spectrophotometry and High-Resolution Nuclear Magnetic Resonance to measure the residual concentrations of dye. The dye degradation curves and reaction rates for different UV exposure times were obtained and discussed as a function of the used additives. All the data are repeated three times, and they differ only by a maximum of 5%. The results indicated a reduction of about 50% of the initial concentration of Reactive Black 5 after 30 min under optimal experimental conditions. The NMR analysis indicated the formation of a series of aromatic structures that were generated by the UV-induced photochemical fragmentation of the original molecule. Full article

Henna (Lawsonia inermis L.) tattooing has been used in Egypt and India since ancient times. Today this temporary body art is becoming increasingly popular among young people. Various chemicals are added to henna to darken and enhance the definition of tattoos, especially para-phenylenediamine (PPD), which is a strong sensitizer known to cause cross sensitive reactions to azoic dyes and other para-amino compounds. We present the case of an 18-year-old girl who became clinically sensitive to textile dyes after having showed a serious reaction both to her first hair dying when she was 16 years old and following the application of a temporary henna tattoo when she was a kid. The evidence from our literature review showed 33 cases of manifest sensitization to hair dye and only one of observable contact allergy to both hair and textile dyes from henna tattoos. The sensitization of children may have long-life lasting consequences, because of cross-reaction to dyes and other chemicals contained in hair colourants, clothes and drugs. Since tattoos are very popular and globalization has increased the circulation of unauthorized products we point out the need for informative campaigns about the risk of sensitization caused by temporary tattoos. Full article