Search Results (26)

Smart packaging materials (SPMs) combine the properties of intelligent and active packaging into a single system, enabling for the monitoring of the packaged product while enhancing its desired conditions. In this study, poly(lactic acid) (PLA) was used as the base polymer and functionalized with in situ synthesized gold nanoparticles (AuNPs) and methyl red (MR) as a pH-sensitive dye. Various additives, including poly(amic) acid (PAA), bromothymol blue (BB), 5-aminosalicylic acid (5AS), glutaraldehyde (GA), and silver and gold nanoparticles (AgNPs, Au NPs), were tested to optimize the SPMs. To evaluate their performance, the synthesized SPMs were characterized using UV-Vis spectroscopy, IR spectroscopy, SEM, microbiological assays, and mechanical tests. Our results revealed that PLA films containing AuNPs and MR exhibited excellent mechanical, chemical, and antimicrobial properties, making them highly suitable for smart packaging applications. In contrast, the addition of PAA disrupted film formation, while AgNPs and blueberry extracts increased the brittleness of the films, thereby limiting their practical use. Furthermore, BB was found to inhibit the in situ synthesis of AuNPs. A real-world application study demonstrated that cheddar cheese wrapped in the optimized PLA films remained unspoiled after 12 months of refrigeration. IR spectroscopy confirmed that no film components migrated into the cheese during the storage period. GA was identified as a critical component for maintaining the structural integrity of the films over the 12-month storage period. This is the first study to report on the development of PLA-based SPMs that incorporate AuNPs, MR, and GA, offering a promising solution for sustainable and intelligent food packaging. Full article

A novel, eco-friendly and cost-effective adsorbent, poly(diallyldimethylammonium) chloride (PDADMAC)-modified clay was developed to enhance its efficacy in removing Methyl Red (MR) from water. Different concentrations of PDADMAC solutions were evaluated during the synthesis and the effects of different operating conditions were investigated. The kinetic data closely followed the pseudo-first-order model, while equilibrium data were well described by Freundlich isotherm. MR removal efficiency decreased as solution pH or NaCl concentration increased, suggesting that electrostatic interaction plays a key role in the adsorption process. Regeneration studies using NaCl solutions revealed that a 1% NaCl solution effectively restored the adsorbent’s capacity. The findings indicate that PDADMAC clay is a promising and sustainable adsorbent for MR removal. Additionally, a three-layer backpropagation artificial neural network (ANN) was developed to predict the MR removal efficiency based on the initial MR concentration, pH, NaCl concentration, and adsorption time. Among these variables, pH was identified as the most influential factor. This approach provides valuable insight into the outcome prediction of a given adsorption process. Full article

Currently, several organic dyes found in wastewater cause severe contamination problems for flora, fauna, and people in direct contact with them. This research proposes an alternative for the degradation of polluting dyes using ZnO nanoparticles (NPs) synthesized by an ecological route using leaf and root extracts of Ambrosia ambrosioides as a reducing agent (with a weight/volume ratio = 4%). Scanning Electron Microscopy (SEM) was used to determine the morphology, showing an agglomeration of cluster-shaped NPs. Using Transmission Electron Microscopy (TEM), different sizes of NPs ranging from 5 to 56 nm were observed for both synthesized NPs. The composition and structure of the nanomaterial were analyzed by infrared spectroscopy (FT-IR) and X-ray diffraction (XRD), showing as a result that the NPs have a wurtzite-like crystalline structure with crystallite sizes around 32–37 nm for both samples. Additionally, the bandgap of the NPs was calculated using Ultraviolet Visible Spectroscopy (UV–Vis), determining values of 2.82 and 2.70 eV for the NPs synthesized with leaf and root, respectively. Finally, thermogravimetric analysis demonstrated that the nanoparticles contained an organic part after the green synthesis process, with high thermal stability for both samples. Photocatalytic analysis showed that these nanomaterials can degrade four dyes under UV irradiation, reaching 90% degradation for methylene blue (MB), methyl orange (MO) and Congo red (CR) at 60, 100 and 60 min, respectively, while for methyl red (MR) almost 90% degradation was achieved at 140 min of UV irradiation. These results demonstrate that it is effective to use Ambrosia ambrosioides root and leaf extracts as a reducing agent for the formation of ZnO NPs, also evidencing their favorable application in the photocatalytic degradation of these four organic dyes. Full article

This work focused on the decolorization of methyl red (MR) from an aqueous solution utilizing Rumex abyssinicus-derived biochar (RAB). RAB was prepared to involve unit operations such as size reduction, drying, and carbonization. The pyrolysis of the precursor material was carried out at a temperature of 500 °C for two hours. After that, the prepared RAB was characterized by the pH point of zero charge (pHpzc), the Brunauer–Emmett–Teller (BET) method, Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared (FTIR) spectroscopy. On the other hand, a batch adsorption experiment of MR removal onto RAB was conducted, considering four operating parameters: pH, contact time, adsorbent dose, and initial dye concentration. The characterization of the adsorbent material revealed a porous and heterogeneous surface morphology during SEM, a specific surface area of 45.8 m²/g during the BET method, the presence of various functional groups during FTIR, and a pHpzc of 6.2. The batch adsorption experiment analysis results revealed that a maximum removal efficiency of 99.2% was attained at an optimum working condition of pH 6, contact time of 40 min, initial dye concentration of 70 mg/L and adsorbent dosage of 0.2 g/100 mL. Furthermore, Freundlich isotherm (R² = 0.99) and pseudo-second-order kinetics (R² = 0.99) models confirmed the heterogeneous surface interaction and chemisorption nature. Generally, this study highlighted that RAB could be a potential adsorbent for the detoxification of MR-containing industrial effluents. Full article

Hollow mesoporous hydroxyapatite (HM-HAP) composites coated with titania are prepared to increase the stability and catalytic performance of titania for azo dyes present in the wastewater system. In this work, HM-HAP particles were first synthesized by a hydrothermal method utilizing the CaCO₃ core as a template and then coated with titania to form TiO₂/HM-HAP composites. Utilizing SEM, XRD, XPS, BET, FTIR, EDS, UV–vis DRS spectroscopy, and point of zero charge (PZC) analysis, the coating morphological and physicochemical parameters of the produced samples were analyzed. The photocatalytic efficiency of the synthesized coated composites was assessed by the degradation of methyl red (MR) dye in water. The results indicated that TiO₂/HM-HAP particles could efficiently photodegrade MR dye in water under UV irradiation. The 20% TiO₂/HM-HAP coating exhibited high catalytic performance, and the degradation process was followed by the pseudo-first-order (PFO) kinetic model with a rate constant of 0.033. The effect of pH on the degradation process was also evaluated, and the maximum degradation was observed at pH 6. The analysis of degraded MR dye products was investigated using LC-MS and FTIR analysis. Finally, a good support material, HM-HAP for TiO₂ coatings, which provides a large number of active adsorption sites and has catalytic degradation performance for MR dye, was revealed. Full article

Iron oxide nanoparticles were synthesized by co-precipitation using three different iron salt stoichiometric mole ratios. Powder X-ray diffraction patterns revealed the inverse cubic spinel structure of magnetite iron oxide. Transmission electron microscopic images showed Fe₃O₄ nanoparticles with different shapes and average particle sizes of 5.48 nm for Fe₃O₄-1:2, 6.02 nm for Fe₃O₄-1.5:2, and 6.98 nm for Fe₃O₄-2:3 with an energy bandgap of 3.27 to 3.53 eV. The as-prepared Fe₃O₄ nanoparticles were used as photocatalysts to degrade brilliant green (BG), rhodamine B (RhB), indigo carmine (IC), and methyl red (MR) under visible light irradiation. The photocatalytic degradation efficiency of 80.4% was obtained from Fe₃O₄-1:2 for brilliant green, 61.5% from Fe₃O₄-1.5:2 for rhodamine B, and 77.9% and 73.9% from Fe₃O₄-2:3 for both indigo carmine and methyl red. This indicates that Fe₃O₄-2:3 is more efficient in the degradation of more than one dye. This study shows that brilliant green degrades most effectively at pH 9, rhodamine B degrades best at pH 6.5, and indigo carmine and methyl red degrade most efficiently at pH 3. Recyclability experiments showed that the Fe₃O₄ photocatalysts can be recycled four times and are photostable. Full article

Ionizing radiation covers a broad spectrum of applications. Since radioactive/radiation pollution is directly related to radiation risk, radiation levels should be strictly controlled. Different detection methods can be applied for radiation registration and monitoring. In this paper, radiation-induced variations in the optical properties of silver-enriched PVA-based hydrogel films with and without azo dye (Toluidine blue O, TBO, and Methyl red, MR) additives were investigated, and the feasibility of these free-standing films to serve as radiation detectors/exposure indicators was assessed. AgNO₃ admixed with PVA gel was used as a source for the radiation-induced synthesis of silver nanoparticles (AgNPs) in irradiated gel films. Three types of sensors were prepared: silver-enriched PVA films containing a small amount of glycerol (AgPVAGly); silver-enriched PVA films with toluidine blue adducts (AgPVAGlyTBO); and silver-enriched PVA films with methyl red additives (AgPVAGlyMR). The selection of TBO and MR was based on their sensitivity to irradiation. The irradiation of the samples was performed in TrueBeam2.1 (VARIAN) using 6 MeV photons. Different doses up to 10 Gy were delivered to the films. The sensitivity of the films was assessed by analyzing the characteristic UV-Vis absorbance peaks on the same day as irradiation and 7, 30, 45, 90, and 180 days after irradiation. It was found that the addition of azo dyes led to an enhanced radiation sensitivity of the AgNPs containing films (0.6 Gy⁻¹ for AgPVAGlyTBO and 0.4 Gy⁻¹ for AgPVAGlyMR) irradiated with <2 Gy doses, indicating their applicability as low-dose exposure indicators. The irradiated films were less sensitive to higher doses. Almost no dose fading was detected between the 7th and 45th day after irradiation. Based on the obtained results, competing AgNP formation and color-bleaching effects in the AgPVAGly films with dye additives are discussed. Full article

Recently, the production of new photocatalytic materials has attracted considerable attention as a promising strategy to mitigate anthropogenic environmental degradation. In this study, cement paste composites (water/cement ratio = 0.5) were prepared using a coating based on nanoparticles of SnO₂ (SnO₂/cement paste) and SnO₂ decorated with Ag₂O (Ag₂O-decorated SnO₂/cement paste) for photocatalytic applications. These coatings were prepared in this study by using the hydrothermal method as the strategy. Thus, photocatalyst efficiency was evaluated through the degradation of methylene blue (MB) and methyl red (MR) as cationic and anionic dyes, respectively, and the simultaneous degradation of MB/MR (1:1 v/v) dyes. Moreover, the photocatalytic mechanism was investigated in the presence of scavengers. Notably, an increase in pH in the range of 2–6 resulted in selective degradation of the MB/MR dye mixtures. Overall, the photocatalytic performance of these materials provides a novel platform technology focused on advanced civil engineering applications, which consequently facilitates the mitigation of various environmental problems. Full article

The present work elucidates the fabrication of Barium Lanthanum Oxide nanosheets (BaLa₂O₄ NSs) via a simple one-pot precipitation method. The acquired results show an orthorhombic crystal system with an average crystallite size of 27 nm. The morphological studies revealed irregular-shaped sheets stacked together in a layered structure, with the confirmation of the precursor elements. The diffused reflectance studies revealed a strong absorption between 200 nm and 350 nm, from which the band-gap energy was evaluated to be 4.03 eV. Furthermore, the fluorescence spectrum was recorded for the prepared samples; the excitation spectrum shows a strong peak at 397 nm, attributed to the ⁴F_7/2→⁴G_11/2 transition, while the emission shows two prominent peaks at 420 nm (⁴G_7/2→⁴F_7/2) and 440 nm (⁴G_5/2→⁴F_7/2). The acquired emission results were utilized to confirm the color emission using a chromaticity plot, which found the coordinates to be at (0.1529 0.1040), and the calculated temperature was 3171 K. The as-prepared nanosheets were utilized in detecting latent fingerprints (LFPs) on various non-porous surfaces. The powder-dusting method was used to develop latent fingerprints on various non-porous surfaces, which resulted in detecting all the three ridge patterns. Furthermore, the as-synthesized nanosheets were used to degrade methyl red (MR) dye, the results of which show more than 60% degradation at the 70th minute. It was also found that there was no further degradation after 70 min. All the acquired results suggest the clear potential of the prepared BaLa₂O₄ NSs for use in advanced forensic and photocatalytic applications. Full article

Photocatalytic degradation technology has developed rapidly in the treatment of organic pollutants due to its high efficiency, mild reaction conditions and easy control. In this paper, a series of heterogeneous photocatalysts, BWZ-en-R (BWZ = [BW₁₁Z(H₂O)O₃₉]⁷⁻, Z = Zn, Cd, Mn, en = ethylenediamine, R = Merrifield resin), were prepared by using ethanediamine as a linker to immobilize Keggin-type transition elements substituting tungstoborates on Merrifield resin and characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The photocatalytic properties of BWZ-en-R (Z = Zn, Cd, Mn) for the degradation of methyl red (MR) were investigated. The results show that the BWZ-en-R (Z = Zn, Cd, Mn) photocatalysts exhibited high photodegradation ability for MR under the irradiation of ultraviolet light, and were easily separated from the reaction media. The maximum degradation rate (%) of MR (40 mL, 25 μM, pH = 2) reached 96.4% for the BWMn-en-R photocatalyst (40 mg) after being irradiated for 30 min, making this a promising photocatalyst candidate for dye degradation. Moreover, the influences of some factors, such as the Z-substituted elements in the BWZ, the BWZ-en-R dosage and the MR initial concentration, on the photocatalytic degradation rate of MR were also examined. Full article

This study aimed to evaluate the methyl red (MR) removal efficiency from aqueous matrices using an eco-friendly anionic surfactant (a calcium surfactant, or CaSF), obtained from frying oil residue. Data obtained by infrared spectroscopy revealed several functional groups that favor the capture of the dye by chemisorption by forming hydrogen bonds and covalent interactions. The kinetic testing results fit the pseudo-second order model, reaching equilibrium in 30 min. Adsorption was greatly influenced by temperature. The Langmuir isotherm was the one best fitting the process at 20 °C, while the Dubinin–Radushkevich isotherm fitted it better at higher temperatures. Under optimized conditions, the maximal MR adsorption capacity of CaSF reached 53.59 mg·g⁻¹ (a removal rate of 95.15%), proving that the adsorbent at hand can be an excellent alternative for the removal of undesirable levels of MR present in aqueous matrices. Full article

Means of eliminating water pollutants or transforming them into less hazardous compounds by green catalysis are desired. The current work was developed with the goal of discovering supports suited for laccase (Lc) immobilization. The effect of the chitosan (CS) molecular weight (Mw) or the polyacrylic acid (PAA) addition was evaluated in microsphere formulation and enzyme immobilization by ESEM, rheology, operational stability, and kinetics. As a practical application, the synthesized products were tested in the methyl red (MR) decomposition and the product identification was performed by high-resolution mass spectrometry. Depending on the required properties, the laccase activity profile (pH, temperature, storage, and Michaelis–Menten parameters) and rheological strength can be modulated by varying the molecular mass of CS or by adding PAA in the support formulation. The immobilized products having the best features regarding MR degradation and recycling abilities were the medium Mw CS microspheres and the system with low Mw CS complexed by PAA, respectively. The degradation mechanism of the dye was proposed accordingly with the identified products by mass spectroscopy. The findings emphasize the potential of the proposed immobilization products to be exploited as viable biocatalysts for dye-contaminated water. Full article

Azo dyes are widely spread in our day life, being heavily used in cosmetics, healthcare products, textile industries, and as artificial food colorants. This intense industrial activity, which inherently includes their own production, inexorably leads to uncontrolled release of dyes into the environment. As emerging pollutants, their detection, particularly in water systems, is a priority. Herein, a fluorescence-based method was employed for the sensitive and selective detection of anionic and neutral azo dyes. Carbon dots (CDs) synthesized from wet pomace (WP), an abundant semi-solid waste of olive mills, were used as probes. An outstanding capability for detection of azo dyes methyl orange (MO) and methyl red (MR) in aqueous solutions was disclosed, which reached a limit of detection (LOD) of 151 ppb for MO. The selectivity of WP-CDs for the anionic azo dye (MO) was established through competitive experiments with other dyes, either anionic (indigo carmine) or cationic (fuchsin, methylene blue, and rhodamine 6G); perchlorate salts of transition metal cations (Cu(II), Co(II), Fe(II), Fe(III), Hg(II), and Pb(II)); and sodium salts of common anions (NO₃⁻, CO₃²⁻, Cl⁻, and SO₄²⁻). Evidence has been collected that supports static quenching as the main transduction event underlying the observed quenching of the probe’s fluorescence, combined with a dynamic resonance energy transfer (RET) mechanism at high MO concentrations. Full article

This study aimed for the application of active chitosan coating incorporating yarrow essential oil (YEO) together with the development of an on-package sensor label based on bromocresol purple (BCP) and methyl red (MR) for shelf-life extension and freshness monitoring of chicken breast fillet. Physiochemical and microbiological attributes of chicken meat coated with sole chitosan, YEO, and chitosan + YEO were compared with those of uncoated (control) samples. Chitosan + YEO coated chicken meat stayed fresh with no significant changes (p > 0.05) in pH (5.42–5.56), TVB-N (12.55–15.36 mg N/100 g), TBARs (0.35–0.40 mg MDA/kg) and total aerobic psycrotrophic bacteria (3.97–4.65 log CFU/g) in days 1–15. There was no response of the dual-sensors label toward the variation in chemical and microbiological indicators of chicken meat coated with chitosan + YEO. However, either uncoated, sole chitosan, or sole YEO treatments indicated a three-stage freshness status with the fresh stage belonged to a period earlier than day 7 (with no distinct color change in both sensor labels); the semi-fresh stage corresponded to storage days between 7–9, wherein a gradual color change appeared (MR from pink to orange, BCP from yellow to light purple); and the spoiled stage occurred in day 9 onward with a drastic color change (MR from orange to light yellow, BCP from light purple to deep purple). In general, the dual-sensors successfully responded to the variation of chemical and microbiological indicators and visual color of uncoated samples during storage time. Based on the obtained results, the application of chitosan + YEO coating efficiently prolonged the freshness of chicken breast meat, where on-package dual-sensors systems were able to detect the freshness stages of meat samples during storage time. Full article

In the present study, a ternary magnetic nanocomposite (SiO₂/MnFe₂O₄/ZIF-8) was synthesized via the embedding of the SiO₂/MnFe₂O₄ nanocomposite within the metal–organic framework (ZIF-8). The synthesized nanocomposite was characterized using suitable techniques including FT-IR, XRD, SEM, TEM, VSM, and BET. The nanocomposite showed a high surface area (S_BET = 831 m²·g⁻¹) and superparamagnetic behavior (23.7 emu·g⁻¹). All characterization techniques confirmed the successful combination of three nanocomposite parts (MnFe₂O₄, SiO₂, and ZIF-8). The nanocomposite was examined for the adsorption of organic dyes, malachite green (MG) and methyl red (MR), from aqueous solutions. The adsorption conditions including ionic strength, contact time, pH, and adsorbent dosage were optimized by studying their change effect. The SiO₂/MnFe₂O₄/ZIF-8 nanocomposite showed high adsorption capacities (1000.03 and 1111.12 mg/g) for the removal of MG and MR, respectively, from water. The isotherm and kinetics studies indicated that the adsorption of MG and MR dyes on the surface of the SiO₂/MnFe₂O₄/ZIF-8 nanocomposite followed the Langmuir isotherm model and pseudo-second-order kinetic model, suggesting the monolayer chemisorption mechanism. The reusability study of up to five successive cycles indicated the successful reuse of the SiO₂/MnFe₂O₄/ZIF-8 adsorbent for dye removal from wastewater. The comparison of the present adsorbent to the previously reported adsorbents indicated that it is a promising adsorbent for dye adsorption from wastewater and must be investigated in the future for the removal of additional pollutants. Full article