Search Results (26)

To easily recover and reuse nano-magnetite (Fe₃O₄) during the catalytic process, Fe₃O₄ is successfully dispersed by coprecipitation of Fe(II, III) salts on anchoring sites of bagasse-sugarcane fibers generated by gliding-arc plasma. Previously, we explored the effect of ascorbic acid (ASC), hydrochloric acid (HCl) and plasma-activated water (PAW) acting as oxidation inhibitors of Fe(II) solution. Prepared materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). The obtained results show that the oxidation inhibitor agent influences the morphology, texture and activity of the synthesized bulk-magnetite, where Fe₃O₄-nanorods, Fe₃O₄-nanospheres and Fe₃O₄-nanosheets were, respectively, obtained with PAW, HCl and ASC. The Fenton-plasmacatalytic treatment of amaranth red dye used as a model pollutant for 30 min revealed degradation rates of 53, 79 and 80%, respectively, for Fe₃O₄-ASC, Fe₃O₄-HCl, and Fe₃O₄-PAW each coupled to plasma. The deposition of nano-magnetite on the plasma-activated bagasse-sugarcane fibers (BM) using PAW as the best oxidation inhibitor agent exhibited characteristic FTIR-absorption bands of -OH, -CH₂ and Fe-O, attesting the bagasse-sugarcane-Fe₃O₄ linkage. The supported magnetite revealed a pollutant degradation rate of 99%, which deeply highlights an activity improvement after Fe₃O₄ deposition on plasma-activated bagasse sugarcane. The reusability of supported-Fe₃O₄ catalyst revealed a pollutant degradation rate of 95% after the fourth cycle, thus highlighting its easy recovery and catalytic stability (reuse). Full article

Multi-sulfonated anionic azo dyes are difficult to remove from water because their high solubility and ionized sulfonate groups reduce their affinity toward many oxide adsorbents. In this study, magnesium oxide-modified alumina composites were prepared by loading magnesium oxide onto mesoporous alumina to increase the density of surface hydroxyl groups. Sunset Yellow and Amaranth were selected as model dyes containing two and three sulfonate groups, respectively. Compared with pristine alumina, the modified adsorbents exhibited higher isoelectric points, stronger hydroxyl-related infrared signals, and significantly enhanced adsorption capacities. At pH 4.0, the maximum adsorption capacities reached 787 mg/g for Sunset Yellow and 709 mg/g for Amaranth. Notably, MgA-2 exhibited the highest utilization efficiency of MgO active sites. Adsorption kinetics were well described by the pseudo-second-order model, while equilibrium data followed the Langmuir model. Mechanistic analysis indicated that adsorption process mainly proceeded through ion exchange between surface hydroxyl groups and dye sulfonate groups. The higher adsorption capacity of Sunset Yellow was attributed to its lower number of sulfonate groups and lower demand for hydroxyl binding sites. These results demonstrate that magnesium oxide modification is an effective strategy for enhancing alumina-based adsorbents for the removal of multi-sulfonated anionic dyes from water. Full article

Red Amaranth (RA) Azo dye is a persistent pollutant in wastewater and stands as a toxicological risk, which has led to the development of effective methods for its removal and photocatalytic degradation. Therefore, CeO₂ nanoparticles were synthesized by a controlled precipitation method, and Ultraviolet-Visible (UV–Vis) analysis and Tauc plots yielded a band gap of ~3.24 eV. The CeO₂ nanoparticles showed the fluorite cubic phase, and nearly spherical particles with an average size of ~10 nm. Nitrogen physisorption revealed a type IV isotherm with a Brunauer–Emmett–Teller (BET) surface area of 85.27 m²·g⁻¹ and a total pore volume of 0.27 cm³·g⁻¹, indicating a mesoporous structure and high surface accessibility. The chemical behavior showed Ce and O, consistent with phase purity. Photocatalytic performance was evaluated in 20 ppm aqueous solution of RA under 365 nm UV irradiation (LED 100 W), with a temperature of ~20 °C and a 15 min dark adsorption step. Concentration decay was followed at λ_max = 520 nm by Lambert–Beer. The degradation efficiency η and pseudo-first-order kinetic were obtained from ln(C₀/C_t) vs. time. In addition, chemical oxygen demand (COD) tests were performed on RA solution before and after photodegradation, showing a COD reduction of ~85% (from 19.8 to 3 mg O₂·L⁻¹), which corroborates mineralization beyond chromophore bleaching. Under [C₀ = 20 mg·L⁻¹] and [m_cat = 1.0 g·L⁻¹], CeO₂ achieved [RA = 90% at 180 min, k = 0.0125 min⁻¹]. These results demonstrate that CeO₂ is an effective photocatalyst for RA degradation under UV-A irradiation, integrating adsorption, kinetic behavior, and mineralization performance into a coherent structure–property relationship. Full article

Amaranth (R2) is used as a color additive in cosmetics. In Korea, R2 is permitted only as a cosmetic colorant and is prohibited in products intended for infants and children under 13 years of age; in Europe, it is regulated solely as a cosmetic colorant rather than a hair dye ingredient. Despite its regulatory relevance, dermal absorption data for R2 are lacking. In this study, percutaneous absorption of R2 was evaluated using the Franz diffusion method with excised rat dorsal skin. Quantitative analysis of R2 was developed and validated using high-performance liquid chromatography (HPLC) in accordance with Korean Ministry of Food and Drug Safety guidelines, demonstrating acceptable linearity (r² = 0.9996–0.9999), accuracy (95.5–104.4%), and precision (0.3–5.8%). Two formulations (skin lotion and cream), each containing 1% R2, were applied at 113 mg/cm² for 24 h. Dermal absorption was assessed by analyzing receptor fluid, skin wash, stratum corneum, epidermis, and dermis. Total dermal absorption of R2 was 3.4 ± 2.7% for the lotion and 0% for the cream, corresponding to in vitro skin permeabilities of 34.5 ± 27.0 μg/cm² and 0 μg/cm², respectively. Total recovery ranged from 80.3 ± 8.2% to 91.4 ± 19.4%. These results provide essential data for cosmetic risk assessment of R2. Full article

In this work, 6-aminocaproic acid-modified copper ferrite nanoparticles were synthesized and used as an adsorbent for removing Amaranth dye from water. The modified nanoparticles were easily prepared using a simple and cost-effective method, namely the coprecipitation method. The nanocomposite was characterized by techniques like FTIR, XRD, SEM with EDS, and TEM. To evaluate the adsorption capacity of Amaranth dye, concentrations of Amaranth, contact time, nanocomposite dose, and solution pH were optimized. Further, Langmuir and the Freundlich isotherm models have been investigated. Among these, the Freundlich model showed the most accurate correlation with the experimental result, indicating a multilayer and physico-chemical adsorption of Amaranth dye onto the heterogeneous surface of the prepared nanocomposite. The Langmuir maximum adsorption capacity of this study was ~17 mg g⁻¹. Thermodynamic parameters (∆G° and ∆H°) confirmed that the adsorption process was spontaneous and exothermic. Adsorption kinetic studies showed pseudo second-order fitting with the multi-step adsorption process. The current adsorption performance was best for the first two adsorption–desorption cycles. Full article

This study investigated the aerobic biodecolorization of azo dyes by Shewanella oneidensis MR-1. S. oneidensis MR-1 can rapidly degrade azo dyes under aerobic conditions, even at high concentrations of up to 270 mg/L, demonstrating remarkable dye decolorization capabilities. This decolorization efficiency persists even under high concentrations of oxygen. The introduction of different environmental metal ions led to either inhibitory or stimulatory effects on the decolorization of Methyl Orange and Amaranth. Furthermore, the addition of extracellular electron shuttles and electron scavengers confirmed that dyes were being reduced via electron transfer, and the decolorization capability of S. oneidensis MR-1 correlated with electron density. Our study unveils the rapid degradation ability of S. oneidensis MR-1 for dyes under aerobic conditions, which is closely linked to its electron transfer capacity. This research holds significant implications for a deeper understanding of the biodegradation mechanisms of azo dyes under aerobic conditions. Full article

In this study, ZnO nanoparticles (ZnO NPs) were synthesized using a green method employing fresh Citrus aurantium L. aqueous extract (CA) as a reducing agent. After preparation, the ZnO NPs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and infrared spectroscopy (IR). The products displayed irregular particle shapes on a nanoscale. The adsorption ability of ZnO NPs was tested with amaranth red dye, and the result showed that it had a satisfied capacity for amaranth red. The adsorption data followed the pseudo-second-order model and the Langmuir model, which indicated the adsorption process was controlled by a chemical adsorption process and occurred homogeneously on the surface of absorbents. In addition, the prepared ZnO NPs also exhibited antibacterial abilities against Staphylococcus aureus and Escherichia coli bacteria; antioxidant activities were observed in 2-2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-di(3-ethylbenzthiazoline sulphonate) (ABTS) radicals scavenging assays and the ferric ion reducing antioxidant power (FRAP) assay, which were better than those of traditional ZnO NPs except in the FRAP assay. Based on these findings, the ZnO NPs fabricated with CA aqueous extract displayed promising abilities in the environmental remediation of dye wastewater. Full article

The development of an advanced dye adsorbent that possesses a range of beneficial characteristics, such as high adsorption capacity, swift adsorption kinetics, selective adsorption capability, and robust reusability, remains a challenge. This study introduces a facile method for fabricating an amine-rich porous adsorbent (ARPA), which is specifically engineered for the adsorptive removal of anionic dyes from aqueous solutions. Through a comprehensive assessment, we have evaluated the adsorption performance of ARPA using two benchmark dyes: amaranth (ART) and tartrazine (TTZ). Our findings indicate that the adsorption process reaches equilibrium in a remarkably short timeframe of just 20 min, and it exhibits an excellent correlation with both the Langmuir isotherm model and the pseudo-second-order kinetic model. Furthermore, ARPA has demonstrated an exceptional maximum adsorption capacity, with values of 675.68 mg g⁻¹ for ART and 534.76 mg g⁻¹ for TTZ. In addition to its high adsorption capacity, ARPA has also shown remarkable selectivity, as evidenced by its ability to selectively adsorb TTZ from a mixed dye solution, a feature that is highly desirable for practical applications. Beyond its impressive adsorption capabilities, ARPA can be efficiently regenerated and recycled. It maintains a high level of original removal efficiency for both ART (76.8%) and TTZ (78.9%) even after five consecutive cycles of adsorption and desorption. Considering the simplicity of its synthesis and its outstanding adsorption performance, ARPA emerges as a highly promising material for use in dye removal applications. Consequently, this paper presents a straightforward and feasible method for the production of an effective dye adsorbent for environmental remediation. Full article

The use of semiconductor materials, specifically TiO₂, for photocatalysis of organic pollutants has gained global interest as an effective method for contaminant removal from wastewater. Titanium dioxide (TiO₂) is a widely studied photocatalyst and is considered one of the best for wastewater treatments due to its high stability, affordability, and nontoxicity. The discharge of wastewater from the textile industries, which constitutes around 20% of total textile effluent, has become a significant environmental concern, posing a threat to both the aquatic ecosystem and human health. We aimed to investigate the photodegradation of organic dyes like Amaranth (AM), Methyl Orange (MO), and Quinoline Yellow (QY), individually and in combination, in an aqueous suspension with varying concentrations of TiO₂. Results indicate a significant degradation of all three dyes in the multicomponent, with approximately 40% degradation in the presence of the 0.050 g/L TiO₂ after 360 min. These findings suggest that TiO₂ has a significant potential as a nanocatalyst in complex matrices. Full article

The present study introduces a two-step extraction methodology that integrates cloud point extraction (CPE) with magnetic solid-phase extraction (MSPE) for the extraction and quantification of amaranth dye. Initially, the dye is extracted using CPE in the micellar phase of the non-ionic surfactant Triton X-114. Subsequently, hydrophobic tetraethyl orthosilicate (TEOS)-modified Fe${ }_3$O${ }_4$ magnetic nanoparticles (MNPs) are employed to recover the micellar phase. A comprehensive evaluation was conducted to optimize the key parameters influencing the efficacy of both CPE and MSPE techniques, as well as signal enhancement. Under optimized conditions, the proposed methodology exhibited a linear response in the concentration range of 10 to 90 $\mathsf{\mu }$g Kg${ }^{-1}$, with a correlation coefficient ($R^2$) of 0.9945. The detection limit was determined to be 8.443 $\mathsf{\mu }$g g${ }^{-1}$. This robust and environmentally friendly approach offers a promising avenue for the accurate and efficient determination of amaranth dye in various applications. 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

In this study, g-C₃N₄/BiOI/tourmaline composites were synthesized by loading BiOI and tourmaline on g-C₃N₄ nanofilms using g-C₃N₄, BiOI, and tourmaline as raw materials, aiming to optimize the photocatalytic degradation of amaranth red dye wastewater (AR). Single-factor experiments were conducted to optimize the degradation process. The findings indicate that a degradation rate of 95.88% can be achieved for AR within 150 min of light exposure, given a g-C₃N₄/BiOI/tourmaline dosage of 1 g/L, an initial pH level of 3 for the AR, and an initial AR concentration of 10 mg/L. Upon repeating the experiment for five cycles, the composite exhibited 83.10% activity, demonstrating its stability. Various analytical techniques were employed for material characterization: X-ray diffractometry (XRD) to ascertain the crystalline structure, field-emission scanning electron microscopy (FESEM) to evaluate morphology, X-ray photoelectron spectroscopy (XPS) for elemental analysis, ultraviolet–visible diffuse reflectance spectroscopy (UV-vis DRS) for optical properties, and photoluminescence (PL) spectroscopy to analyze the recombination of excited electrons and holes. Free radical masking experiments further elucidated the photocatalytic mechanism, revealing that the primary active species in the degradation process is the superoxide anion (O₂⁻). This research offers a novel approach to address the limitations of n-type metal-free semiconductor photocatalysts. Full article

Two hybrid composite photocatalysts, denoted as SnP/AA@ZnO and SnP@ZnO, were fabricated by a reaction of trans-dihydroxo[5,10,15,20-tetrakis(4-pyridyl)porphyrinato]tin(IV) (SnP) and ZnO with and without pretreatment of adipic acid (AA), respectively. In SnP@ZnO, SnP and ZnO are likely held together by a coordinative interaction between the pyridyl N atoms of SnP and the Zn atoms on the surface of ZnO. In the case of SnP/AA@ZnO, the SnP centers were robustly coupled with ZnO nanoparticles through the AA anchors. SnP/AA@ZnO exhibited largely enhanced photocatalytic activities for the degradation of anionic amaranth (AM) dye under a visible light irradiation, compared to SnP, ZnO, and SnP@ZnO. The degradation efficiency of AM by SnP/AA@ZnO was 95% within 60 min at a rate constant of 0.048 min⁻¹. The remarkable photocatalytic oxidation performance of SnP/AA@ZnO was mainly attributed to the synergistic effect between SnP and ZnO. This study is valuable for the development of highly effective composite photocatalytic systems in advanced oxidation processes and is of importance for the treatment of wastewater containing dyes. Full article

Dyes are highly toxic and persistent in the environment. Their presence in water causes environmental and social problems. Dyes must be effectively removed from the water. A UV/ZVI/H₂O₂ process was applied to decompose two organic dyes, AM E123 and AM ACID. A commercial ZVI product, Ferox Flow, was used, and its properties were determined using SEM and XRF. The zeta potential, surface area, and optical properties of ZVI were also determined. The efficiency of dye removal in optimal conditions was 85.5% and 80.85% for AM E123 and AM ACID, respectively. Complete decolorization was observed in all samples. The decomposition of both dyes occurred according to a modified pseudo-second-order reaction and there was a statistically significant correlation between the TOC decrease, pH, and process time. The catalyst was observed to have high stability, and this was not affected by the performance of the treatment process even after the third cycle, as confirmed by the results of the catalyst surface analysis and iron diffusion test. Slight differences in process efficiency were observed after each cycle. The need for only a small amount of catalyst to decompose AM E123 and AM ACID, coupled with the ability to reuse the catalyst without the need for prior preparation, may reduce catalyst purchase costs. Full article

The contamination of water is increasing day by day due to the increase of urbanization and population. Textile industries contribute to this by discarding their waste directly into water streams without proper treatment. A recent study explores the treatment potential of copper oxide nanorods (CuO NRs) synthesized on a green basis in the presence of a biopolymer matrix of agar (AA) and alginate (Alg), in terms of cost effectiveness and environmental impact. The synthesized bio nanocomposite (BNC) was characterized by using different instrumental techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), ultra-violet spectroscopy (UV-Vis), scanning electron microscopy-energy dispersive X-ray-elemental analysis (SEM-EDX), transmission electron microscopy (TEM), selected area diffraction pattern (SAED) and X-ray photoelectron spectroscopy (XPS). The optical studies revealed that immobilization of CuO NRs with Alg-Agar biopolymer blend resulted in an increase in light absorption capacity by decreasing the energy bandgap from 2.53 eV to 2.37 eV. The bio nanocomposite was utilized as a photocatalyst for the degradation of amaranth (AN) dye from an aquatic environment under visible light irradiation. A statistical tool known as central composite design (CCD) associated with response surface methodology (RSM) was taken into consideration to evaluate the optimized values of process variables and their synergistic effect on photocatalytic efficiency. The optimized values of process variables were found to be irradiation time (45 min), AN concentration (80 ppm), catalyst dose (20 mg), and pH (4), resulting in 95.69% of dye degradation at 95% confidence level with desirability level 1. The rate of AN degradation was best defined by pseudo-first-order reaction based on the correlation coefficient value (R2 = 0.99) suggesting the establishment of adsorption-desorption equilibrium initially at the catalyst surface then photogenerated ^•O₂⁻ radicals interacting with AN molecule to mineralize them into small non-toxic entities like CO₂, H₂O. The material used has high efficiency and stability in photocatalytic degradation experiments up to four cycles of reusability. Full article