Terms Of Dye Research Articles

Efficient fabrication of pH-modified graphene nano-adsorbent for effective determination and monitoring of multi-class pesticide residues in market-fresh vegetables by GC-MS

Toxic pesticide residues in edible vegetables cause major health risks for consumers, hence quantifying them is essential. However, simultaneous and trace level determination of xenobiotic residues of various classes in complex food matrices is still a challenging analytical task. In this experiment, reduced graphene oxide (RGO-B), a carbon nano-structure with stunning adsorbent properties and ultrahigh surface area (pore size ∼6 Å) was efficiently (≥96%) synthesized via pH-controlled reduction process and characterized by ultraviolet-visible (UV–VIS) spectrophotometer, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and Fourier Transform Infrared (FTIR). Adsorption efficiency of different pH-regulated RGOs was studied in terms of dye (Malachite Green) removal percentage. Two-dimensional carbon (sp2) RGO was used as a dispersive solid-phase extraction adsorbent in a modified QuEChERS method in combination (4:1) with primary secondary amine (PSA) to extract 28 multi-class pesticides (OC, OP, SP) from chilli, cabbage, tomato, and cucumber. The experimental results established the best extraction ability and adsorption capacity of RGO over traditional and high-cost adsorbents. Moreover, the introduction of graphene has helped improve the percent recovery (75.36–118.32%) with acceptable (<12.8%) relative standard deviation (RSD) at limits of quantification (LOQs) (S/N = 10:1) levels of 0.01–0.1 mgL−1. Gas chromatography-mass spectrometry (GC-MS)-based multi-pesticide analytical method was successfully validated as per SANTE/12682/2019 guidelines for monitoring 144 market-fresh vegetables in West Bengal, India. The analysis results indicated that eight (8) samples (5.55%) were contaminated with toxicants 5–10 times higher than the European Union Maximum Residue Limits (EU-MRLs). Matrix removal abilities and cost analysis proved that graphene has significant prospects as an expectant non-conventional adsorbent for low-cost (53.3% cheaper) pesticide residue analysis.

Influence of structurally and morphologically different nanofillers on the performance of polysulfone membranes modified by the assembled PDDA/PAMPS-based hybrid multilayer thin film

A highly efficient nanofiltration membrane should exhibit high separation performance in removing divalent salts and organic solutes, as well as high permeation to meet practical separation and purification applications in aqueous media. Here, we designed a series of hybrid multilayer thin film membranes filled with the structurally and morphologically different nanofillers such as hexagonal boron nitride (HBN) nanosheets and metal-organic framework (MOF) nanoparticles, consisting of 3 and 6 layer pairs of polyelectrolyte through the layer-by-layer self-assembly technique (LBL) and characterized them in terms of dye and salt separation, as well as permeation. The rejection performance and permeability of the designed membranes manifested that HBN nanosheets were more effective than MOF nanoparticles in achieving a high-performance membrane. As compared to the bare multilayer thin film membrane, the addition of HBN nanosheets within the negatively-charged layers of the multilayer thin film membrane consisting of 6 bilayers resulted in good retention of up to 93% and 92% for acid blue (ACB) and bromophenol blue (BPB) dye molecules, respectively. Besides, this membrane exhibited 60% and 45% improvement in the water flux for ACB and BPB solutions, respectively, while the rejection of the sulfate ions maintained an acceptable value around 78%. Furthermore, it was found that this HBN-embedded hybrid multilayer membrane had superior potential for the removal of coherent foulant compared to all samples.

Cloud Point Extraction and Spectrophotometric Studies for the Extraction of Nigrosin and Aniline Blue Dyes using Mixed Micelles of TBAB and Triton X-114

The extractions of two anionic dyes viz. nigrosin and aniline blue by cloud point extraction method using mixed micelles of tetrabutylammonium bromide (TBAB) and Triton X-114 were conducted. To get the greatest extraction efficiency, pH of the solution, surfactant concentration, concentration of electrolyte, equilibrium temperature and time were optimized. A linear calibration curve in the range of 0.567-9.07 mg/L (nigrosin) and 0.982-19.645 mg/L (aniline blue) was obtained. Limit of detection were found to be 2.45 ng/L and 2.008 ng/L for nigrosin and aniline blue dyes, respectively. Thermodynamic parameters were also calculated to establish the feasibility of the process. This method was then used to determine the dyes in tap and sea water samples. The extraction efficiency was explained in terms of dye surfactant interaction as shown by observed spectral changes between anionic dye and cationic surfactant followed by solubilization of the complex in non-ionic surfactant.

Decolorization of reactive dye Remazol Brilliant Blue R by zirconium oxychloride as a novel coagulant: optimization through response surface methodology.

The aim of the present study was to investigate the performance of a novel coagulant, i.e. ZrOCl2, for the removal of anthraquinone-based reactive dye from aqueous solution. An ideal experimental setup was designed based on central composite design using response surface methodology to determine the individual and interactive effects of different operational variables (i.e. pH, coagulant dose and dye concentration) on treatment performance in terms of dye and chemical oxygen demand (COD) removal efficiencies. Total 92.58% dye and 85.33% COD removal were experimentally attained at optimized conditions at low coagulant dose, i.e. 156.67 mg/L for the dye concentration of 105.67 mg/L at pH 2. To validate the working pH of the metal coagulant, the static charge of ZrOCl2 was measured using Eh value. The performance of the coagulant was validated with experimental and predicted values in the selected data set, and R2 values for both responses were found to be 0.99 and 0.95 respectively, which shows the reliability of the experimental design. Further, the toxicity of the coagulant was assessed and no such toxicity was found even up to the concentration of 500 mg/L, proclaiming the disposal of sludge may not exhibit any threat to humans. Experimental results suggested that the ZrOCl2 could be used as an eco-friendly coagulant for dye wastewater treatment.

Treatment of artificial wastewater containing two azo textile dyes by vertical-flow constructed wetlands

The release of untreated dye textile wastewater into receiving streams is unacceptable not only for aesthetic reasons and its negative impacts on aquatic life but also because numerous dyes are toxic and carcinogenic to humans. Strategies, as of now, used for treating textile wastewaters have technical and economical restrictions. The greater part of the physico-chemical methods, which are used to treat this kind of wastewater, are costly, produce large amounts of sludge and are wasteful concerning some soluble dyes. In contrast, biological treatments such as constructed wetlands are cheaper than the traditional methods, environmental friendly and do not produce large amounts of sludge. Synthetic wastewater containing Acid Blue 113 (AB113) and Basic Red 46 (BR46) has been added to laboratory-scale vertical-flow construction wetland systems, which have been planted with Phragmites australis (Cav.) Trin. ex Steud. (common reed). The concentrations 7 and 208 mg/l were applied for each dye at the hydraulic contact times of 48 and 96 h. Concerning the low concentrations of BR46 and AB113, the unplanted wetlands are associated with significant (ρ < 0.05) reduction performances, if compared with planted wetlands concerning the removal of dyes. For the high concentrations of AB113, BR46 and a mixture of both of them, wetlands with long contact times were significantly (ρ < 0.05) better than wetlands that had short contact times in terms of dye, colour and chemical oxygen demand reductions. Regarding nitrate nitrogen (NO3-N), the reduction percentage rates of AB113, BR46 and a mixture dye of both of them were between 85 and 100%. For low and high inflow dye concentrations, best removals were generally recorded for spring and summer, respectively.

Experimental study and kinetic modelling of the enzymatic degradation of the azo dye Crystal Ponceau 6R by turnip (Brassica rapa) peroxidase

Textile and food industries wastewaters are characterized by a strong coloration due to use of dyes, among which azo dyes are the most frequently used. These compounds are harmful and their discharge without an adequate treatment causes a negative impact on the environment. Given that conventional biological treatment processes are usually not sufficient to degrade azo dyes, other treatment alternatives must be studied. Enzymes have demonstrated their effectiveness to degrade several types of recalcitrant compounds. In this study, enzymatic degradation of Crystal Ponceau 6R (CP6R) azo dye by turnip (Brassica rapa) peroxidase was assessed in the presence of 100 μM redox mediator (1-hydroxybenzotriazole). The treatment performance was evaluated at different pH values (3, 4, 5, 6 and 7) and the most appropriate pH and contact time were determined. Moreover, a kinetic model of the enzyme-catalyzed reaction was developed by mathematical description of the degradation mechanism, being further validated with experimental data. For the estimation of the kinetic parameters and model validation, a central composite design of type “start points” was made. The results showed that the enzymatic treatment was very effective. CP6R dye degradation higher than 97% was achieved in less than 1 min of reaction at the optimum pH (i.e., 4), at which the maximum reaction rate (43 μM min−1) was obtained. At the other tested pH values, degradation performance was substantially lower (<70%) in the same timeframe, but still satisfactory. Moreover, the proposed kinetic model successfully predicted the CP6R dye degradation under different experimental conditions in terms of dye and enzyme concentrations.

Spectroscopic analysis of naphtholazobenzimidazole in organised solution

Micelle–water partition coefficient (Kx ) of naphtholazobenzimidazole dye (NAB) in aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) has been determined spectrophotometerically. Changes in absorption patterns of dye caused by surfactants and solvents were quantified in terms of dye–surfactant ratio (n D/n S) and solvent water partition coefficients (P), respectively. Multiple residence sites have been suggested for dye molecules within micelles, based on shifts in azo-hydrazone tautomeric equilibrium. Micelle–water partition coefficients were used to evaluate the influence of dye on critical micelle concentration of CTAB and SDS. At same micelle concentration, M, the relative solubility of NAB was greater in cationic surfactant CTAB than in anionic surfactant SDS.

Dye−Polyelectrolyte Layer-by-Layer Self-Assembled Materials: Molecular Aggregation, Structural Stability, and Singlet Oxygen Photogeneration

The interaction of rose Bengal (RB) and fluorescein (FL) with poly[diallyldimethylammonium] chloride (PDDA) was studied in layer-by-layer self-assembled thin films and in solution. The spectroscopic behavior is explained in terms of dye-dye, dye-polyelectrolyte, and in solution, dye-solvent interactions. A correlation among dye hydrophobicity, aggregation tendency, polymer folding in solution, and the stability of self-assembled films is obtained. In spite of the very high dye concentration (approximately 1 M), RB-PDDA multilayer thin films are able to photogenerate singlet molecular oxygen, as demonstrated by chemical monitoring and IR phosphorescence detection.

Photometric studies of the complex formation of Cu 2+ and Cr 3+ ions with Sudan Red B

Photometric method was used to study the complex formation of Sudan Red B with Cu 2+ and Cr 3+ ions. The absorption spectra were monitored and the conditions were optimized in terms of dye and metal concentration, pH and cationic and anionic effects. The log β (stability constants) of the metal–dye complex were calculated using Job's method and these were of the order of 11 and 11.6 for Cr 3+ and Cu 2+ complex, respectively.

Photometric studies of the complexation of Sudan Red B with Mn +2 and Fe +3 ions

A representative azo dye by the name of Sudan Red B, was used as a complexing reagent for Ni and Co ions. Photometric method was used to monitor the metal to ligand formation. The absorption spectra were monitored and the conditions were optimized in terms of dye and metal concentration, pH, and cationic and anionic effects. The log β (stability constant) of the metal–dye complex was calculated using Job's method and this was of the order of 7.52 and 8.28 for Mn and Fe complex, respectively.

Spectrophotometric Studies of the Complexation of Sudan Red B with Co2+and Ni2+Ions

Abstract Sudan Red B, an azo dye, was used as a reagent for the complexation of Ni and Co ions. The studies were carried out spectrophotometrically. The absorption spectra were monitored and the conditions were optimized in terms of dye and metal concentration, pH, and cationic and anionic effects. The log β (stability constants) of the metal–dye complex were calculated using Job's method and these were of the order of 5.5 and 5.6 for Co2+ and Ni2+ complex respectively.

Biological activities of phthalocyanines--V. Photodynamic therapy of EMT-6 mammary tumors in mice with sulfonated phthalocyanines.

Abstract— We tested water‐soluble sulfonated phthalocyanine and three metal chelate derivatives for their tumoricidal effect on the EMT‐6 mammary tumor in mice exposed to red light. The metal‐free sulfophthalocyanine had little effect, whereas the aluminum complex and the lower sulfonated fraction of the gallium complex exhibited tumoricidal activity similar to hematoporphyrin‐based photosensitizer (Photofrin II). The higher sulfonated fractions of the gallium complex were less active as compared to the lower sulfonated fraction. The cerium complex was the most active sensitizer in terms of dye and light doses required to induce tumor necrosis and cure but also showed the highest phototoxicity towards healthy skin. These results suggest that sulfonated phthalocyanines will offer a new alternative in photodynamic therapy of light‐accessible neoplasms.