Dye Precipitation Research Articles

Attraction behavior induces the aggregation and precipitation of organic dyes: Improving efficiency through co-treatment strategy

Organic dyes harm the environment through bioaccumulation, toxicity, water contamination, and persistence. Organic dyes are commonly charged species, while limited works reported the interaction behavior between the charges. In this study, seven typical organic dyes are selected to investigate the general rules of the aggregation-precipitation behaviors between cationic and anionic organic dyes at molecular scale. The maximum precipitation rates of organic dyes reached 96.0 % when the amount of positive charges of cationic dyes was stoichiometric to the negative charges of anionic dyes. The aggregation process is reversible in ethanol solvent and insensitive to temperature, indicating the aggregation behavior is a physical process. The aggregation behavior of cationic and anionic dyes in water and ethanol solvents was simulated at molecular scale. 94.9 % of water molecules dispersed out of the dye clusters within 20 picoseconds in the simulation, while only 0.8 % of ethanol dispersed under the same conditions. The inter-molecule van der Waals force of the ethanol-solvent system was higher than that of the water-solvent system, resulting in the failure of dyes aggregation in ethanol. This study proposed a concise strategy of mixing cationic and anionic dyes in charge balance to cause aggregation and co-precipitation of dyes to improve removal efficiency.

Influence of a cross-linker agent on mechanical and other properties of polysiloxane based scintillators

Polysiloxane scintillators (PSS) are of great interest due to their neutron and gamma-ray (n/γ) discrimination capability and excellent radiation hardness. However, one major drawback is their low mechanical hardness. To address this issue, we present a cross-linking agent, 1,3-diethenyl-1,3-dimethyl-1,3-diphenyldisiloxane (DS), incorporated into PSS to study its effects on various physical properties. It was found that the enhanced inter-chain entanglement of covalently bonded polymer chains by the DS cross-linker significantly improved the mechanical hardness and optical properties. Gravimetric analysis (TGA) indicated a slightl improvement in stability during thermal degradation. This cross-linker at 0-17 wt% concentrations has also slightly positive impact on the PSD performance as demonstrated by measurements of pulse shape discrimination (PSD) using a 238Pu-Be neutron source. The improved cross-linking density helped prevent both the generation of free molecule radicals and diffusion of fluorophore dyes. Consequently, the cross-linked samples remained transparent with no dye precipitation, even after 12 months of storage.

Synthesis and Characterization of New Azo Dye Derived from Sulfamethaxolevia Diazonium Reaction and Study its Abilityas an Acid-base Indicator

Background: Most azo dyes are synthesized by diazotization of a primary amine, followed by conjugation with one or more electron-rich nucleophiles. Objective: This study presents the synthesis of a new azocompound by converting sulfamethoxazole to a diazonium salt. Methods: via reaction with hydrochloric acid and sodium nitrite at temperatures between 0 and 5 °C, the resulting salt is then coupled with a 4-methoxyphenol reagent in alkaline medium at the above temperatures to produce an azodye given the IUPAC name of (4-((2-hydroxy-5-methoxyphenyl)diazenyl)-N-(5-methylisoxazol-3yl)benzenesulfonamide). The azo dye precipitate was purified by crystallization methods using a solvent mixture of ethanol water. Characterization was done using different analytical methods such as IR, UV-Vis and H1-NMR in addition to measurements of physical properties. Results: The reddish-pink azo compound gave a maximum absorbance of 495 nm. Acid-base titrimetric analysis was conducted to examine the chemical indicator properties of the azo dye. Clear color differences were obtained between two spaces in the pH range 2-12, where a reddishpink color was obtained in the basic medium and a yellow color in the acidic medium. Conclusions: A new azo dye successfully presented its properties as an indicator.

Valorization of cardboard waste adsorbents for efficient malachite green removal – equilibrium, kinetics, and thermodynamics

ABSTRACT This work was aimed at evaluating the adsorptive properties of cardboard waste-based adsorbents for malachite green removal. The adsorbents were produced through hydrothermal carbonization and/or phosphoric acid activation and characterized for specific area, surface morphology, and functional groups. Batch adsorption was performed at varying concentrations, contact times, and temperatures. Results show that the activated carbon derived from cardboard waste with surface area of 196 m2/g exhibits a 134 mg/g (31.6%) adsorption capacity of malachite green. On the other hand, the cardboard hydrochar displays a peak capacity at 400 mg/g (94%) due to dye precipitation before the magnitude subsides to 47 mg/g (5.7%) at higher concentration of 820 mg/L. The equilibrium data of activated carbons could be well described by the Langmuir model, while the kinetics fitted well with the pseudo-second order model. The adsorption of malachite green is endothermic and spontaneous at high solution temperature.

Cyclic Voltammetry of C.I. Disperse Orange 62 in an Aqueous Electrolyte.

Disperse dyes are an important group of colorants for dyeing polyester fibers. Approximately 30.000 tons of disperse dyes are released into the waste water annually from spent dyebaths. Therefore, methods for decolorizing such dyes are of general interest. The reductive after-treatment of disperse dyes using reducing agents, such as Na2S2O4, is a widely used process to improve rub fastness through dye reduction. Electrochemical dye reduction could be an alternative process for reductive dye treatment. In this work C.I. Disperse Orange 62 was used as a representative dye to study the direct cathodic reduction of a disperse dye with cyclic voltammetry. As anticipated for dispersed organic matter, relatively low current densities were observed, which strongly depend on the state of dispersion of the dye. The current density was increased by using dispersions prepared through dye precipitation from DMF solution and by the use of N-cetyl-N,N,N,-trimethyl-ammonium bromide as a cationic surfactant. The results demonstrate the successful cathodic reduction of a dispersed organic dye; however, the low solubility of the reaction products in the aqueous electrolyte hinders an efficient cathodic dye reduction.

Titan Yellow dye sensitized and Ethylenediaminetetraacetate photoreduced photogalvanic system

Photogalvanic cells (PG) are capable of generating solar power with storage, which predominantly dependent on the sensitizer/electrolyte/electrode nature. Therefore, the exploitation of suitable combination of photo-sensitizer/electrode/electrolyte is the key for enhancing the electrical output of these cells. Titan Yellow (a novel dye) has good absorbance in the visible region and good water solubility. These characteristics of this dye have prompted authors to exploit it for further enhancing electrical output of PG cells. Therefore, in present study, the Titan yellow dye photo sensitizer-Ethylenediaminetetraacetate (EDTA) reductant-NaOH alkali medium-Pt/Graphite electrodes photogalvanic system has been exploited. The observed power, current, potential, and efficiency is of the order of 126.4 µW, 2200 µA, 770 mV and 4.34%, respectively. PG performance is observed better in the high pH range (for example, ∼22% enhancement in the power with 0.87% rise in the pH; 37.6 µW power at pH 13.65; 46 µW power at pH 13.77). Spectroscopic study shows that the Titan Yellow is the actual light absorbing material in the electrolyte as other chemical components (reductant EDTA, NaOH, water) of the electrolyte do not show any absorbance in the visible spectral range. A comparison of present results with published results shows both sides, i.e., present results are higher than some reported data, and lower than some other reported data. The use of graphite counter electrode in the present study is the reason behind the present results being higher than some reported data. The heat induced precipitation of dye from the electrolyte in the present study is the reason behind the present results being lower than some reported data. Therefore, controlling the Titan Yellow precipitation at elevated temperature is the challenge for future research. In totality, the present research shows that the Titan yellow dye is not a good sensitizer in the photogalvanics.

Solubilization of Nile Red in Micelles and Protomicelles of Sodium Dodecyl Sulfate.

A spectrophotometric study of the solubilization and aggregation of the Nile red dye (NR) in premicellar and micellar aqueous solutions of sodium dodecyl sulfate (SDS) was carried out. The experiments were conducted both with saturated solutions of NR under conditions of thermodynamic equilibrium of the solution with a dye precipitate, and at a constant concentration of NR in a homogeneous solution. In the first case, it was proved theoretically and verified experimentally that with an increase in the SDS concentration, the NR concentration always increases, and at the limit of low concentrations, the dependence is linear. In both cases, the concentration of NR dimers as a function passes through a maximum in the premicellar region. There are no dimers in the micellar region. The extinction coefficients of NR monomers in SDS solutions were determined both below and above the critical micelle concentration (CMC) of SDS. A solubilization curve with branches for the premicellar and micellar regions was constructed, the intersection of which was used to find the CMC value in the system under study. The state of deep supersaturation of the NR solution in the metastable state upon dilution of the micellar system with water was studied. It was found that, in addition to dimers, molecular aggregates of higher orders were also formed.

Production of bioflocculants from spent brewer's yeast and its application in the treatment of effluents with textile dyes

Advances in chemical synthesis have increased the complexity and degradation resistance of dyes used in textile processes. This fact interferes drastically with conventional biological wastewater treatment and demands further methods to avoid environmental damage. In this sense, this work presents a bioflocculant produced by the alkaline hydrolysis of spent brewer's yeast, a residue from the brewing industry, as well as the evaluation of its performance in the precipitation of recalcitrant dyes. The optimum hydrolysis system was accessed by a full 23 factorial design in terms of NaOH concentration, yeast mass, and temperature, followed by a kinetic study. The solid fraction composition of the produced flocculant agent is 46 % of proteins and 29 % of polysaccharides. The performance of the bioflocculant was evaluated in two different systems, real textile wastewater containing rhodamine and a synthetic solution with flavine. The effects of the flocculation variables pH, temperature, agitation, and flocculant agent dosage were taken into consideration. Color removal outcomes above 80 and 90 % were attained for rhodamine and flavine systems, respectively. Further analysis of real textile wastewater for treated and untreated samples in terms of BOD, COD, TOC, and light metals was performed. A biodegradability test showed the employed treatment could increase microbial assimilation of the sample and reduce its persistent compounds. This work shows, for the first time, the feasibility of the bioflocculant from spent brewer's yeast and features its potential applicability to recalcitrant compounds precipitation in textile wastewaters.

Studies related to changes in ionic strength due to addition of sodium chloride to an aqueous solution of cationic dye methylene blue (MB): Electronic spectra analysis for dimerization equilibria

It is well-known that methylene blue (MB),a cationic dye forms dimer and higher aggregates in aqueous solutions. For specific concentration range (1∙10−6–1∙10−4 M), a D⇌2M equilibria has been postulated and well characterized by visible electronic spectroscopy. The dye molecules can lead to formation of stacking (end on end and sandwich) type structures in solution phase stabilized by weak dispersion van der Waals forces and cation-anion-cation ion pairs and triplet interactions usually referred as hydrophobic interactions. Recent literature reports indicate that excess chemical potential of small hydrophobic particles and the strength of hydrophobic pair interactions appear to be linearly related. Our observations about precipitation of dye (MB) at higher concentrations of salt like sodium chloride (NaCl) made us to study the dimerization equilibria in detail since in the Corona health disaster; use of MB to diagnose the type of Covid variants helped Scientists in a great way. Salting-out of proteins is in general used to explain the specific protein aggregation behaviour observed in Huntington's disease. For model compound like tertiary butyl-alcohol, Geiger et al. reported enhancement of hydrophobic contacts which increase with increase in salt concentration. NaCl is an essential ingredient of biological fluids, of which concentration controls the various biological life governing processes. However, such information is non-existent for aqueous solutions of dyes.We therefore reported measured optical absorbance of aqueous solution containing NaCl (0.1–1.0 M) and dye at different concentrations (1∙10−6–1∙10−4 M) at 298 K spectrophotometrically, in the wavelength range of 550–700 nm. The spectrums are compared to those obtained for binary solutions of MB in water. Analysis of the spectral data yielded the dimer dissociation constant and individual characteristic monomer and dimer spectra. Further information about the geometry and twist angle between the dipoles of the MB molecules in the dimer species has been obtained. The results are analyzed for the monomer-dimer equilibria and salting-out effect as well applications of mass action model and exciton theories are discussed.

Silica incorporated cellulose fibres as green concept for textiles with reduced flammability

Safety requirements led to widespread use of textile products with reduced flammability. The global production of nearly 3 million tons of flame retardants generates a substantial environmental burden both during synthesis of the chemicals and disposal of waste textiles. In this work a cleaner technology to impart reduced flammability to viscose fibres is presented, which bases on the incorporation of 20%wt of silica into the cellulose fibre matrix during the stage of fibre formation. Stabilisation of the silica against unwanted leaching during washing procedures was achieved by treatment with aluminate, which reacts with silica under formation of the less soluble aluminosilicate. This treatment successfully was combined with the reactive dyeing step where no precipitation of dyes, losses in colour depth or reduced fastness of the dyeings occurred. Substantial reduction in time of afterglowing (-82%) and in length of destroyed material (-90%) were observed in standard tests for ignitability of bedclothes. The incorporation of silica into regenerated cellulose fibres offers a green alternative to the rather polluting finishing processes used today. The use of these modified fibres is of particular value for textile products worn next to the skin, as leaching of irritating flame retardants to the skin can be avoided.

Efficacy of Chitosan as a Coagulant Aid to Alum Precipitation of Congo Red In Wastewater

The use of chitosan prepared from prawn shells as coagulant aid for congo red (CR) dye removal from wastewater was investigated in this study. Characterisation of the prepared chitosan samples showed characteristics similar to commercially available ones. The coagulation – flocculation experiment was carried out using the jar test procedure. Both chitosan and alum were used separately for the dye precipitation and then combined together. The usage of alum alone showed no precipitating effect on the CR dye molecule, while chitosan was able to considerably reduce the concentration of the dye in solution. When chitosan was used as a coagulant aid in the alum precipitation, the amount (%) of dye removed increased greatly. Optimization of the process via study of effect of pH and flocculation time at optimum alum – chitosan combination indicated that pH 4-5 and settling time of 40 min were suitable conditions for maximum decolourisation of CR dye wastewater with about 98% efficiency. Moreover, study of settling characteristics of the sludge produced from the alum-chitosan synergy was better than that produced from either of them alone. Also, occurrence of redispersion and restabilization of the precipitate was not encountered.

Ionic Liquid-Based Dye for Highly Sensitive Optical Sensing Based on FRET and Ion Extraction System Using Plasticized PVC Membrane

Ionic Liquid-Based Dye for Highly Sensitive Optical Sensing Based on FRET and Ion Extraction System Using Plasticized PVC Membrane

Selective, efficient and complete precipitation of anionic dyes in aqueous solutions using Ag@PbCO3 nanocomposite

This work describes a selective, facile, economic and fast technique using Ag@PbCO3-NPs for 100% precipitation of anionic dyes within 50–100 s from aqueous solutions. The selectivity of the present method was examined for removal of hazardous cationic and anionic dyes. Positive results were obtained only for anionic dyes namely indigo carmine (IC), Congo red (CR), methyl blue (MB), and eriochrome black T (EBT). Removal dyes mechanism by precipitation process is suggested and described. Precipitates are filtered and characterized using FT-IR spectroscopy. This work possessed promising results in anionic dyes industrial water treatment.

Insight into the formation mechanism of azo dye-based hybrid colorant: Physico-chemical properties and potential applications

This paper presents a novel method for preparing organic-inorganic hybrid composites by precipitation of monocarboxylic azo dye (MCD) using aluminum-magnesium hydroxycarbonate (LH) as a host. Secondary ion mass spectrometry (TOF-SIMS), solid state nuclear magnetic resonance (13C MAS NMR), powder X-ray diffraction (XRD), thermogravimetric analysis (TG-DTA) and scanning electron microscopy (SEM) were performed to characterize the structure of the synthesized hybrid colorant. TOF-SIMS displayed the presence of C17H13N4O3−Mg2+ ions in the LH matrix. The X-ray diffraction pattern showed that the formation of azo dye-LH complexes strongly affected the crystal structure of the LH mineral suggesting existence a new organic-inorganic hybrid. Incorporation of the monocarboxylic dye into the LH mineral contributed to the appearance of new peaks in the diffraction pattern, which did not belong to either the azo dye or the LH carrier. The thermostability of the pure dye and LH/pigment was investigated using TOF-SIMS, TG-DTA and UV–Vis spectroscopy. The TOF-SIMS technique was found to be a very promising tool for evaluating the chemical composition of organic-inorganic materials and monitoring their thermal stability. The thermal stability, photostability as well as solvent resistance of the chromophore were enhanced significantly. This is mainly attributed to strong interactions between the carboxylic group in the dye and the Mg2+ in the inorganic matrix. This simple strategy for the preparation of hybrid composites can be easily applied for the design of novel multifunctional organic-inorganic pigments.

Pulse shape discrimination properties of plastic scintillators incorporating a rationally designed highly soluble and polymerizable derivative of 9,10-diphenylanthracene

A highly soluble and polymerizable derivative of 9,10-diphenylanthracene was designed and synthesized specifically to be capable of achieving very high loadings (at least 50wt.%) when copolymerized with a polyvinyltoluene (PVT) matrix. The resulting heavily crosslinked plastics are mechanically hard and robust, and were found to have exceptional clarity with no sign of dye precipitation. Samples of these plastics both with and without added wavelength shifter were characterized for light yield, scintillation decay, and pulse shape discrimination (PSD) performance for α/γ discrimination, and the results were compared to that of a commercially available PSD plastic, EJ-299-34. The best performing formulation, with a primary dye loading of 50wt.%, had a measured light yield of 9950 photons/MeV, and achieved a PSD figure-of-merit (FOM) of 1.05, the latter indicating that while the present material is not suited for practical applications, the overall approach demonstrates a proof-of-concept of PSD in highly loaded plastics stabilized through copolymerization of the primary dye, and suggests that further improvements through better dye choice/design may yet be achievable.

Potential of Melaleuca diosmifolia as a novel, non-conventional and low-cost coagulating adsorbent for removing both cationic and anionic dyes

The potential of dried twigs of Melaleuca diosmifolia as a novel biosorbent for removing three cationic dyes, methylene blue (MB), acridine orange (AO) and malachite green (MG), and an anionic dye, eriochrome black T (EB) was evaluated in a batch adsorption process. Notably, the biosorbent removed 77–99% of both cationic and anionic dyes in a wide ranging pH of 2–10, and the reactions were endothermic. The dye adsorption equilibria were rapidly attained within 3h. The monolayer adsorption capacity of the sorbent added at 5gL−1 was 119.05, 126.8, 116.28 and 94.34mgg−1 for MB, AO, MG and EB, respectively. The water extract obtained from the plant material induced fast decolourization of both categories of dyes followed by gradual flocculation, indicating its potential as a natural coagulant. Gas chromatographic analysis also indicated that the main electrostatic attraction between 1,8-cineole, 1-p-methene-8-thiol and furfural compounds of the biomaterial, and dye molecules resulted in the formation of initial supramolecular complexes which further progressed into strong aggregates, leading to precipitation of dye–biomaterial complexes. Subsequently, the overall complex mechanism of dye removal was confirmed to be a combined process of adsorption and coagulation. Consistent with the batch studies, using selected plant material in real environmental water samples also resulted in effective dye removal, highlighting its potential for use in wastewater treatment.

Preparation of Mg(OH)2 hybrid pigment by direct precipitation and graft onto cellulose fiber via surface-initiated atom transfer radical polymerization

Mg(OH)2 flame retardant hybrid pigment is synthesized through simultaneous solution precipitation and adsorption of anionic dyes (C.I. Acid Red 6). The Mg(OH)2 hybrid pigment bearing vinyl groups after surface silane modification is immobilized onto the surface of bromo end-functional cellulose fiber by atom transfer radical polymerization (ATRP). The morphology and structure of Mg(OH)2 pigments and cellulose fibers grafted with modified pigments are characterized. The thermal properties, flammability and color fastness of cellulose fibers grafted with modified pigments are measured. The results reveal that anionic dye molecules are adsorbed onto Mg(OH)2 crystals and affect the formation of lamella-like Mg(OH)2 crystals. The cellulose fiber grafted with modified Mg(OH)2 hybrid pigment absorbs about four times heat more than original cellulose fiber with about 4% immobilization ratio of pigment, which shortens nearly half of afterflame time and afterglow time.

Rational Design of Latent Fluorophores from Water‐Soluble Hydroxyphenyltriazine Dyes Suitable for Lipase Sensing

AbstractDerivatives of 2‐(2′‐hydroxy‐5′‐dimethylaminobenzyl)‐4,6‐dimethylamino‐1,3,5‐triazine were synthesized by an original multistep protocol that afforded, after quaternization of the N,N‐dimethylaminobenzyl moiety, water‐soluble fluorescent dyes. These fluorophores exhibited excited‐state intramolecular proton transfer and large Stokes shifts (ΔSS > 10000 cm–1). The phenol residue was masked by an enzyme‐labile protecting group based on self‐immolative para‐hydroxybenzyl alcohol. Lipases were used to unveil the fluorescence under physiological conditions (phosphate‐buffered saline, pH 7.2) without aggregation or precipitation of the fluorescent dyes.

Standardization of blood smears prepared in transparent acetate: an alternative method for the microscopic diagnosis of malaria.

BackgroundDue to students’ initial inexperience, slides are frequently broken and blood smears are damaged in microscopy training, leading to the need for their constant replacement. To minimize this problem a method of preparing blood smears on transparent acetate sheets was developed with the goal of implementing appropriate and more readily available teaching resources for the microscopic diagnosis of malaria.MethodsAcetate sheets derived from polyester were used to standardize the preparation and staining of thin and thick blood smears on transparent acetate sheets. Thick and thin blood smears were also prepared using the conventional method on glass slides. The staining was conducted using Giemsa staining for the thick and thin smears.ResultsMicroscopic examination (1,000x) of the thin and thick blood smears prepared on transparent acetate produced high-quality images for both the parasites and the blood cells. The smears showed up on a clear background and with minimal dye precipitation. It was possible to clearly identify the main morphological characteristics of Plasmodium, neutrophils and platelets. After 12 months of storage, there was no change in image quality or evidence of fungal colonization.ConclusionPreparation of thin and thick blood smears in transparent acetate for the microscopic diagnosis of malaria does not compromise the morphological and staining characteristics of the parasites or blood cells. It is reasonable to predict the applicability of transparent acetate in relevant situations such as the training of qualified professionals for the microscopic diagnosis of malaria and the preparation of positive specimens for competency assessment (quality control) of professionals and services involved in the diagnosis of malaria.

Process Balance of Natural Indigo Production based on Traditional Niram Method

In this work, the natural indigo production process from Polygonum tinctorium was balanced based on the traditional Niram method in Korea. A standard procedure was determined considering the conditions of indican extraction from plant material, the amount of alkali for precipitation, storage of extract, etc. The effect of experimental conditions on the yield of crude dye was investigated. The contents of indigo and indirubin of the crude dyes were analyzed by HPLC. Increase of the amount of crude dye was observed within 1-2.5 days of extraction time. Longer extraction beyond 2.5 days resulted in a slight decrease in the amount of crude dye. There was no consistency in terms of indigo content depending on extraction pH. We found that the storage of extract or harvested plants affected adversely to dye yield and dye quality. Based on the lab scale extraction, large scale extraction was performed for 2-2.5 days in water and 2.0-2.5 g/L of <TEX>$Ca(OH)_2$</TEX> was applied for precipitation of indigo dye. We obtained natural indigo dye containing about 15% of pure indigo in scale-up production using whole plant except root.