Dye Transport Research Articles

Environmental Impact of Synthetic Dyes on Groundwater in Malaysia: Sources, Distribution, Transport Mechanisms, and Mitigation Strategies

Synthetic dyes, extracted from natural sources like insects, plants, coal, and ochre, have become prevalent due to their advantages over natural dyes. However, their production has led to increased environmental pollution, particularly in groundwater. Groundwater contamination from synthetic dyes occurs through advection, dispersion, and retardation. This review aims to highlight the environmental impacts of synthetic dyes on groundwater, elucidate the mechanisms of dye transport, and propose effective strategies for monitoring and mitigating contamination. Urban runoff carries dyes from surfaces such as roofs, parking lots, and roads into stormwater systems, while agricultural runoff transports dyes from products like soil conditioners, fertilizers, and seed coatings into water bodies. In groundwater, dyes move through the aquifer via advection, dispersion, and retardation, all influenced by groundwater flow and geological conditions. The advection process involves the bulk movement of groundwater carrying dissolved dyes, while dispersion causes dyes to spread and dilute over time and distance. Retardation, which involves the adsorption of dye molecules onto soil particles, slows dye movement, prolonging their presence in groundwater. Understanding the sources, distribution, and movement of synthetic dyes in groundwater is crucial for developing strategies to protect water resources and reduce environmental and health impacts. The extensive use of dyes in industrial and domestic activities necessitates comprehensive monitoring and management to ensure sustainable groundwater quality.

Investigation of the effect of salts on dye wastewater separation performance in TpPa-1 membrane via molecular dynamics simulation

The rapid progress in science and technology increases the demand for dyes and results in the pollution of dye wastewater. Recently, covalent organic frameworks (COFs) have been suggested as a promising candidate for wastewater treatment. The influence of inorganic salt ions on the transport and separation processes of dye wastewater is poorly understood. In this work, the transport and separation mechanisms of dyes are investigated via nonequilibrium molecular dynamics simulations (NEMD). It is found that the inorganic salts enhance the rejection rate of different dyes in TpPa-1 membranes. The fundamental reason for this phenomenon is the hindrance caused by inorganic salt ions, which change the orientation of dye molecules as they pass through the pore channels of the TpPa-1 membrane. As a result, the dye molecules show a greater tendency to form π–π interaction with the TpPa-1 membrane surface, which accelerates their adsorption.

Adsorption and transport of acid dye through polymer inclusion membrane with Aliquat 336 and TBP

Colour is typically the initial pollutant identified in wastewater. Membrane separation represents a novel approach to separation processes, with expectations of supplanting many traditional separation systems. The aim of this study is to investigate polymer inclusion membranes (PIMs) consisting of tri octyl methyl ammonium chloride as the carrier, tributylphosphate as the modifier, poly-vinyl chloride as the base polymer and 2-Nitro phenyl pentyl ether as the plasticizer for removing an acid dye (Red Erionyl A-3G) from aqueous solution. The dye adsorption on the membrane surface and its transition to the stripping phase was achieved by placing the membrane between two glass cells. Changing the stripping solution ensured both adsorption on the membrane surface and the transfer of all the dye to the stripping stage. Using a mixture of 0.8 M salicylic acid and 0.8 M NaOH, along with stirring at 1000 rpm during the stripping phase, extraction efficiency reached 98% in the feed phase and 53% in the stripping phase. When 1 M NaOH solution was employed as the stripping solution, the membrane absorbed all the dye within 10 minutes, but there was no transition to the stripping phase. The membrane has a durability of 2 days.Graphical abstract

Unveiling the potential of TPA-based molecules to tune the optoelectronic properties and enhance the efficiency of dye-sensitized solar cells.

The world's energy and environmental requirements are changing due to rapid population growth and industrial growth, and solar cells can be used to meet these demands. Dye-sensitized solar cells (DSSCs) are solar cells in which energy conversion occurs via a process similar to photosynthesis in plants. DSSC development is still in its infancy. DSSCs can operate under cloudy conditions and indirect sunlight and have attracted considerable attention due to their low cost and high efficiency. We designed two metal-free TPA-based dyes (Dye2 and Dye3) based on the reference dye Mg207 (Dye1) by increasing the donor strength of the molecule, as such dyes have shown enhanced efficiency in DSSCs. Moreover, the triphenylamine (TPA) moiety has been demonstrated to be a good donor that prevents charge recombination. Intramolecular charge transfer (ICT) from the donor to acceptor moiety was found in the sensitizers, and electrons were promoted to the conduction band (CB) of the TiO2 semiconductor. The negative binding energy of the dye@TiO2 clusters indicated that dye adsorption on the semiconductor surface was stable. The double donor increased the electron injection and electronic coupling constants in Dye2 and Dye3, indicating that these newly designed dyes have superior charge injection capacity. Accordingly, the efficiencies of DSSCs with Dye2 and Dye3 were 9.77% and 9.62%, respectively, and substitution with the TPA unit at the -R1 and -R2 positions in Dye1 resulted in better power conversion compared to the parent compound (9.09%). Increased donor strength improved photovoltaic performance by increasing current density and light-harvesting efficiency. This is a good molecular design approach for preparing targeted donor- -acceptor (D- -A) organic dyes with high DSSC efficiency. To predict the charge transport and optoelectronic characteristics of the TPA dyes, quantum chemical calculations were carried out using Gaussian16. The ground-state (S0) optimized geometries of the sensitizers were computed by utilizing DFT at the B3LYP/6-31G** level. The absorption spectra ( max) were computed by employing TD-DFT with various functionals (B3LYP, PBE1PBE, CAM-B3LYP, and BHandHLYP) in the gas and solvent (DCM) phases. Among the studied functionals, BHandHLYP was found to be best at successfully reproducing the experimental data. Thus, the absorption spectra of the newly designed dyes and dye@TiO2 were calculated at the BHandHLYP/6-31G** level. The dye@TiO2 cluster optimizations were carried out at the B3LYP/6-31G**(LANL2DZ) level.

Managing the Taste and Odor Compound 2-MIB in a River-Reservoir System, South Korea

High concentrations of 2-methylisoborneol (2-MIB) were reported during winter in the Paldang reservoir and North Han River, South Korea. The causes of the unusual taste and odor problems in the regulated river-reservoir system were not understood; however, a short-term solution is to flush out 2-MIB-rich water to secure water sources for over 20 million people. Approximately 150 million tons of water was released from upstream dams for 12 days (late November to early December 2018) to reduce the elevated levels of 2-MIB. Simultaneously, the spatio-temporal variations of the measured concentration of sample 2-MIB from five sites were simulated using a multi-dimensional hydrodynamics-based solute transport model to monitor the flushing effect. A modified environmental fluid dynamics code (EFDC) was adopted as the primary model framework. Five scenarios on the kinetic constants related to the characteristics of 2-MIB transport and behavior, such as conservative, net decay, and net production, were applied, and the results were compared. We found that the simulation errors on the elapsed times to satisfy the Korean drinking water monitoring standard (≤20 ngL−1) were smallest with the conservative dye transport option, indicating that the physical and biochemical characteristics of 2-MIB may not play an essential role.

Nanohybrid photocatalysts in dye (Colorants) wastewater treatment: Recent trends in simultaneous dye degradation, hydrogen production, storage and transport feasibility

Dyes (colorants) are produced globally owing to their need in textile industries and this has led to the release of toxic dye effluents into environment. This is one of the major phenomena causing harmful effects on both human and aquatic organisms. In this review, the simultaneous and sustainable way of dye degradation with both wastewater treatment and hydrogen energy production via photocatalysis was discussed. It was seen that multiple researches were reported on different photocatalysts synthesis and experimentation on dye degradation and hydrogen production. This review further focuses on dyes and their toxicity, photocatalytic materials, hydrogen storage and transport feasibility. Magnetic biochar based photocatalysts showed more than 90% methylene blue degradation efficiency. Metal doped nano catalysts showed 0.072 min−1 rate of organic dye degradation. Hydrogen produced from photocatalysis needs to be safely stored and transported. Containers make and material for effective hydrogen storage and transport needs to be identified in future. This review recommends the future directions to overcome the limitations of existing photocatalysts for simultaneous dye degradation and hydrogen production.

Role of cations in the photovoltaic performance optimization of ternary stannates, MSnO3 (M = Ca, Sr, and Ba) and N2SnO4 (N = Ca, Sr, Ba, and Zn)

Given the tremendous interest in next-generation photoelectric conversion devices, such as tandem solar cells, indoor photoelectric conversion devices, and image sensors, the development of device-specific electron transport materials is essential for achieving high performance. Sn-based semiconductors are one of the edge materials with the potential to satisfy these requirements. In particular, ternary stannate compounds have shown high potential as electron transport electrodes in several impressive studies. However, systematic research on the electronic band structure and chemical bonding characteristics of these materials remains insufficient. In this study, we present the effect of cations on the crystal structure and electronic band structure of ternary stannate compounds, MSnO3 (MSO, M = Ca, Sr, and Ba) and N2SnO4 (N2SO, N = Ca, Sr, Ba, and Zn). Additionally, their potential as electron transport electrodes is verified by application in dye-sensitized solar cells (DSCs). Notably, although BaSnO3 (BSO) and Zn2SnO4 (Z2SO) had inferior dye adsorption properties, they exhibited higher overall performance in DSCs than the other stannate compounds. The origin of the excellent performances of BSO and Z2SO is attributed to their supportive electronic band features, including the lower flat-band potential and conduction band than that of the lowest unoccupied molecular orbital level of N719 dye and excellent charge transport property. This study highlights the decisive impact of the electronic band structure and charge transport ability of stannate compounds on the photoelectric conversion performance and provides design guidelines for developing new charge transport materials.

Investigation on dye separation mechanism in covalent-organic framework membranes with molecular dynamics simulation

Wastewater caused by textile and dyeing industry has become one of sources in water pollution. Membrane technology have been considered as the most promising method to deal with wastewater. Recently, Covalent organic frameworks (COFs) have been employed to construct membranes for dye separation. In this work, nonequilibrium molecular dynamics simulations are employed to investigate the transport and separation mechanism of dye. The effect of TpPa-1 membrane thickness and the structure of dye molecules on rejection rate is also discussed. It is found that the rejection rate of dyes is mainly determined by the adsorption on the surface of TpPa-1 membranes. The thicker TpPa-1 membrane is, the stronger π-π interactions become, which leads to better dye rejection. Particularly, dye molecules with better conjugate planar structures are prone to form π-π interactions with surface of TpPa-1 membrane, which results in the excellent rejection rate of dyes.

A comprehensive methodology to study double emulsion stability

HypothesisThe stability of emulsions requires the fast formation of viscoelastic interfaces between water and oil phases. In double emulsions, two surfactant types (hydrophilic and lipophilic) are present and two interfacial films are involved. Understanding cooperative adsorption of these surfactants and its implication on properties of water/oil/water interfacial films will enable replacing the empirical methodologies used in designing double emulsion systems with a knowledge-based approach. Experiments and modelThe distribution of surfactants between the water/oil interfaces was investigated using single droplet diffusion experiments and simulation of equilibrium surfactant density profiles. The stability of the interfaces against coalescence was characterized by dye transport in a leach cell and coalescence time of single droplets in a model experiment. The conformation of the surfactants at an interface was then examined via surface rheology, sum frequency generation spectroscopy, and dissipative particle dynamics simulation. FindingsTwo selected hydrophilic surfactants combined with a lipophilic surfactant induce very different properties at water/oil interfaces and different dye release behaviour from their corresponding double emulsions. Competitive adsorption of sodium dodecyl sulfate and lipophilic surfactant results in the improvement of encapsulation efficiency, elasticity of the interface, and resistance against coalescence due to the intercalation of surfactant alkyl chains into the oil chains.

Role of organic nanoparticles on transport and fate of various dyes in aqueous solution

This work studies the interaction of organic nanoparticles (ON) with various dyes in aqueous solution, to elucidate the role of ON on transport and fate of dyes in the environment, and on dyes removal from wastewater. Studied dyes are Acid Red 66 (AR66), Methylene Blue (MB), Reactive Black 5 (RB5), and Reactive Violet 5 (RV5). ON are extracted from organic matter of anthropogenic origin through resuspension of its colloidal fraction, and successive filtration and dialysis of the obtained suspension. Mechanisms of interaction are investigated initially through three-dimensional excitation emission matrix (3DEEM) analysis. Obtained data indicate that dynamic interactions occur strongly between dye molecules and ON aggregates. 3DEEM spectra of mixed samples containing ON together with one of the tested dyes, present a shape similar to the one of ON alone, but each of them is characterized by specific differences in terms of peaks quenching and shift. The analysis of these singularities suggests that dye molecules are bound to the functional groups of ON through H-bonds, according to the following steps: i) dyes reach the surface of ON aggregates; ii) the molecules pass through the hydrophilic surface of ON aggregates, and reach their hydrophobic core; iii) the dyes are sequestrated into the hydrophobic core of ON aggregates. Nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopies analysis confirm the formation of supramolecular aggregates with stable micellar hydrophobic structure, mainly consisting of aliphatic fractions of ON, which explain the disappearance of aromatic groups signals from dyes.

Lymphatic cells do not functionally integrate into 3D organotypic brain slice cultures, but aggregate around penetrating blood vessels.

Brain slice culture (BSC) is a well-known three-dimensional model of the brain. In this study, we use organotypic slices for studying neuro-lymphatic physiology, to directly test the longstanding assumption that the brain is not a hospitable milieu for typical lymphatic vessels. An additional objective is to model fluid egress through brain perivascular space systems and to visualize potential cellular interactions among cells in the leptomeninges including alterations of cellular geometry and number of processes. Immortalized lymphatic rat cell lines were used to seed organotypic brain slices. The brain slice model was characterized by monitoring morphologies, growth rates, degree of apoptosis, and transport properties of brain slices with or without a lymphatic component. The model was then challenged with fibroblast co-cultures, as a control cell that is not normally found in the brain. Immortalized lymphatic cells penetrated the brain slices within 2-4days. Typical cell morphology is spindly with bipolar and tripolar forms well represented. Significantly more indigo carmine marker passed through lymphatic seeded BSCs compared to arachnoid BSCs. Significantly more indigo carmine passed through brain slices co-cultured with fibroblast compared to lymphatic and arachnoid BSCs alone. We have developed an organotypic model in which lymphatic cells are able to interact with parenchymal cells in the cerebrum. Their presence appears to alter the small molecule transport ability of whole-brain slices. Lymphatic cells decreased dye transport in BSCs, possibly by altering the perivascular space. Given their direct contact with the CSF, they may affect convectional and diffusional processes. Our model shows that a decrease in lymphatic cell growth may reduce the brain slice's transport capabilities.

Removal of methylene blue dye from aqueous solutions using polymer inclusion membrane technology

The polymer inclusion membranes (PIMs) containing Cellulose triacetate as polymer base, 2-NPOE as a plasticizer, and Calix[4]resorcinarene (RC8) as a carrier were prepared and characterized. Microstructure and surface of PIMs were characterized by scanning electron microscope, FTIR, UV/vis spectroscopy, and Thermogravimetric Analysis, respectively. In order to obtain information on the composition and interactions that may manifest between the constituents of the membrane. The PIMs were applied in the elimination of Methylene Blue (MB) dye from model solution as synthetic aqueous wastewater. Furthermore, the effects of different parameters such as internal and external PIMs environment on the transport performance of MB were also investigated. The results confirming that the content of the carrier and plasticizer in the membrane had a significant impact on the property of PIMs. The transport of dye was in line with the first-order kinetics equation. The highest flux value "8.88 × 10–7 mol.m−2 s−1" was obtained with a calix [4] resorcinarene as a transporter in polymer inclusion membrane at pH 11 in the feed and 0.3 M HCl in the stripping phase when MB initial concentration was 100 mg/L. The membrane has better stability under optimum conditions and maximum transport was observed after 30 h of permeation time.

Stimuli responsive self-assembled structural aggregates of ionic liquid based surfactants as the membrane free microreactors for dyes sequestration and drug encapsulation

Judiciously designed surfactant based protocell models such as micelles, vesicles, gels and coacervates with higher thermal stability, low-toxicity and bio-compatibility found applications in various new age technologies. In our attempt to obtain the membrane free microreactors for accumulating dyes and biomolecules within a single system, herein we had designed ionic liquid (ILs) based simple coacervates. These coacervates were formed by merely changing solution pH of ester functionalized imidazolium and morpholinium based surface active ILs with varied alkyl chain length and anions. On reaching the neutral pH, the large isotropic (micellar and vesicular) phase de-mixes into two conjugate phases; the dense coacervate phase in equilibrium with the dilute phase. Stability of these membrane free microreactors were studied in the presence of mono and divalent salt solution, viscous solution, higher temperature and acidic as well as alkaline solutions for their realistic applications. These newly formulated microreactors were investigated for the membrane free transport of neutral, cationic, and anionic dyes under non-equilibrium conditions. The same coacervate droplets further show excellent encapsulation for the anticancer hydrophobic drug, curcumin; opening an all new avenue in drug delivery. Presently investigated environmentally benign simple coacervates could replace their costly and inefficient natural analogous for multi-purpose applications including biomimetic operations.

Exploring the potential of polypeptide–polypeptoide hybrid nanogels for mucosal delivery

By chain extension of polysarcosine with phenylalanine and cystine, nanogels are formed. The nanogels facilitate the transport of dyes across an artificial mucus coated membrane and their release by reductive bond cleavage.

Removal of Disperse Blue 56 from synthetic textile effluent using ionic flocculation

The textile industry is one of the main generators of industrial effluent due to the large volumes of water containing a wide variety of pollutants, including dyes. Thus, the present study aimed to remove the Disperse Blue 56 dye present in synthetic textile effluent using ionic flocculation through surfactant flocs produced from animal/vegetable fat, assessing the system at different surfactant concentrations and temperatures. The process kinetics, adsorption mechanism and equilibrium were evaluated. The results show that the kinetics was better described by the Elovich model when compared to pseudo-first order and pseudo-second order models, indicating that chemical adsorption occurs during the process. The study of the adsorption mechanism obtained lower outer layer diffusivities than their intra-particle counterparts, demonstrating that the dye transport to the surfactant floc is controlled through the outer layer. The Langmuir isotherm was suitable for equilibrium data and the separation factor calculated showed that the isotherm is classified as favorable. Dye removal efficiency reached 87% after 360 minutes of contact between the effluent and the surfactant flocs, indicating that ionic flocculation is an efficient alternative in the treatment of textile effluent containing disperse dye.

Pyranine‐based Dyes as a Sensitive Tool to Investigate Drug/Food Interactions of Organic Anion Transporting Polypeptides, OATP1B1/3 and OATP2B1

OATPs are exchangers mediating the cellular uptake of hormones, bilirubin, bile acids and various drugs, including antivirals, chemotherapeutics, antibiotics and statins. OATP1B1 and OATP1B3 participate in hepatic elimination of their drug substrates, while OATP2B1 is the most abundant OATP in the intestine. Inhibition of their transport activity e.g., by co-administration of their drug or food component substrates may alter pharmacokinetics or even result in toxicity. Hence the study of hepatic OATPs is recommended during drug development (FDA, EMA and PMDA recommendations). OATP drug interactions are generally measured using radiolabeled substrates. However, the use of fluorescent compounds as test substrates of OATPs (and other transporters) provides a more sensitive tool1,2. Recently we identified Cascade Blue hydrazide (CB) and Alexa Fluor 405 (AF405) pyranine-based dyes as transported substrates of OATPs, applicable in drug interaction tests3. The aim of the current study was to analyze the transport of further pyranine analogs with the aim to map substrate interaction profile of hepatic OATPs, and to find more affordable OATP test substrates4. Transport of the fluorescent dyes was measured in adherent cell lines stably overexpressing OATP1B1, 1B3 or 2B1. Positive hit dyes were further characterized to find optimal assay conditions. The assay based on best performing dyes was validated by measuring uptake in the presence of documented OATP inhibitors. Finally, using the novel assay interaction between a set of flavonoids and OATPs was determined5,6. The developed fluoresce-based assay is a sensitive tool allowing large scale screen of OATP inhibitors and substrates.

Transport of Organic Dyes in Systems Containing Humic Acids

This work is focused on transport organic dyes in systems containing humic acids as active reaction agent. Methylene blue was usedas a model organic dye which can behave as pollutant and influence many processes in nature. Transport of pollutants in nature isstrongly affected by interactions with humic acids or natural organic matter. Their influence is dependent on affinity of pollutant tocontent and strength of active binding sites. Two different humic samples are used in this study in order to compare their propertieson transport of organic dye. Both humic acids are used in original extracted form as well as in the form of samples with selectiveblocked functional groups.

Screening of Additive Formulations Enables Off-Chip Drop Reverse Transcription Quantitative Polymerase Chain Reaction of Single Influenza A Virus Genomes.

The miniaturization of polymerase chain reaction (PCR) using drop-based microfluidics allows for amplification of single nucleic acids in aqueous picoliter-sized drops. Accurate data collection during PCR requires that drops remain stable to coalescence during thermocycling and drop contents are retained. Following systematic testing of known PCR additives, we identified an optimized formulation of 1% w/v Tween-20, 0.8 μg/μL bovine serum albumin, 1 M betaine in the aqueous phase, and 3 wt % (w/w) of the polyethylene glycol-perfluoropolyether2 surfactant in the oil phase of 50 μm diameter drops that maintains drop stability and prevents dye transport. This formulation enables a method we call off-chip drop reverse transcription quantitative PCR (OCD RT-qPCR) in which drops are thermocycled in a qPCR machine and sampled at various cycle numbers "off-chip", or outside of a microfluidic chip. qPCR amplification curves constructed from hundreds of individual drops using OCD RT-qPCR and imaged using epifluorescence microscopy correlate with amplification curves of ≈300,000 drops thermocycled using a qPCR machine. To demonstrate the utility of OCD RT-qPCR, influenza A virus (IAV) RNA was detected down to a single viral genome copy per drop, or 0.320 cpd. This work was extended to perform multiplexed detection of IAV M gene RNA and cellular β-actin DNA in drops, and direct amplification of IAV genomes from infected cells without a separate RNA extraction step. The optimized additive formulation and the OCD-qPCR method allow for drop-based RT-qPCR without complex devices and demonstrate the ability to quantify individual or rare nucleic acid species within drops with minimal processing.

Molecular Tetrahedrons as Selective and Efficient Ion Transporters via a Two-Station Swing-Relay Mechanism

The traditional approach to utilizing an ion-relay mechanism for ion transport requires three or more ion-relay stations. Herein, we describe a novel strategy, incorporating a swing action to reali...

Dye Transport through Bilayers Agrees with Lipid Electropore Molecular Dynamics

Although transport of molecules into cells via electroporation is a common biomedical procedure, its protocols are often based on trial and error. Despite a long history of theoretical effort, the underlying mechanisms of cell membrane electroporation are not sufficiently elucidated, in part, because of the number of independent fitting parameters needed to link theory to experiment. Here, we ask if the electroporation behavior of a reduced cell membrane is consistent with time-resolved, atomistic, molecular dynamics (MD) simulations of phospholipid bilayers responding to electric fields. To avoid solvent and tension effects, giant unilamellar vesicles (GUVs) were used, and transport kinetics were measured by the entry of the impermeant fluorescent dye calcein. Because the timescale of electrical pulses needed to restructure bilayers into pores is much shorter than the time resolution of current techniques for membrane transport kinetics measurements, the lifetimes of lipid bilayer electropores were measured using systematic variation of the initial MD simulation conditions, whereas GUV transport kinetics were detected in response to a nanosecond timescale variation in the applied electric pulse lifetimes and interpulse intervals. Molecular transport after GUV permeabilization induced by multiple pulses is additive for interpulse intervals as short as 50 ns but not 5-ns intervals, consistent with the 10–50-ns lifetimes of electropores in MD simulations. Although the results were mostly consistent between GUV and MD simulations, the kinetics of ultrashort, electric-field-induced permeabilization of GUVs were significantly different from published results in cells exposed to ultrashort (6 and 2 ns) electric fields, suggesting that cellular electroporation involves additional structures and processes.