Rate Of Dye Uptake Research Articles

Methylene blue adsorption by the waste of Abu-Tartour phosphate rock

Phosphate rock (PR) is an abundant ore and represents the basic raw material for the phosphatic fertilizer industry. Prior to industrial processing, PR is concentrated by grinding-and-screening to separate a fine fraction that is very poor in P 2O 5. This fine fraction is a solid waste and represents a disposal problem. The present study shows that the fine fraction of ground-and-screened Abu-Tartour PR can be used as an adsorbent for the removal of methylene blue dye from aqueous solutions. The amount of dye adsorbed was found to vary with initial methylene blue concentration and contact time. Raising the temperature enhances the rate of adsorption but has no effect on the adsorption capacity at equilibrium. The adsorption equilibrium data were found to fit the Langmuir isotherm, indicating monolayer adsorption on a homogeneous surface. The Elovich model can be used to predict the adsorption kinetics at ambient temperatures especially when the initial concentration of MB is relatively high, while Ho’s model deviates from the data as the initial concentration increases. However, as the temperature increases and MB concentration decreases, Ho’s model fits the data better than the Elovich model. On studying the mechanism of adsorption, the results showed that the overall rate of dye uptake is controlled by intraparticle diffusion. The multilinear plots of intraparticle diffusion were modeled by piecewise linear regression and related to pore-size distribution of the adsorbent.

Effects of a pretreatment with N‐methylmorpholine‐N‐oxide on the structures and properties of ramie

AbstractTo improve the dyeing properties of ramie, the ecofriendly organic solvent N‐methylmorpholine‐N‐oxide (NMMO) was used to substitute sodium hydroxide as a ramie‐fiber swelling solvent. Through padding and baking pretreatment, ramie fabric was modified by an NMMO aqueous solution. Ultraviolet–visible spectrophotometry, Fourier transform infrared spectroscopy, X‐ray diffraction, and differential scanning calorimetry were used to investigate the effects of NMMO pretreatment on the structure of the ramie, whereas the color strength (K/S, where K is the light absorption coefficient and S is the scattering coefficient), adsorption isotherm, and dye uptake rate curve were measured to investigate the effects of NMMO pretreatment on the dyeing properties of the ramie. The results show that the ramie fiber experienced a limited and irreversible swelling because of the partial breakage of interhydrogen and intrahydrogen bonds of cellulose molecules in the amorphous area, but the crystal and chemical structure of the ramie fiber did not change obviously under the experimental conditions. The K/S value of the NMMO‐modified ramie fabrics dyed with reactive dyes increased by about 100%, and the dye uptake increased by 27.88% compared to that of the raw sample, whereas the standard affinity and diffusion coefficient value of the reactive dyes on the NMMO‐modified ramie fabric were higher than those of the raw ramie fabric. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Interactions between new multi-anionic surfactants and direct dyes and their effects on the dyeing of cotton fabrics

A series of novel surfactants containing multi-anionic and nonionic hydrophilic moieties have been prepared by reacting fumaric acid with polyoxyethylenated stearyl ether in the presence of a peroxy-type free radical initiator to form addition products featuring a carboxylic acid groups. The critical micelle concentration (CMC) decreased upon increasing the length of the polyoxyethylene chain of the surfactant. The surface excess concentration at the surface and the occupied area per surfactant molecule were calculated. We used spectrophotometric methods to study the interactions between the dyes and the polycarboxylated multi-anionic surfactants. The rate of direct dyeing of cotton was influenced by the degree of aggregation of the dye in the dye bath. Indeed, disaggregation of direct dyes in the presence of the surfactants increased the rate of dye uptake by the cotton fibers. On the other hand, the formation of dye–surfactant complexes retarded the rate of dye uptake on the cotton fabrics.

The Removal of Dye from Aqueous Solution by Adsorption on Low Cost Adsorbents

Removal of color from aqueous solution by using low cost easily available adsorbent was conducted by batch experiment. The potential of the low cost adsorbent (Marble powder‐treated and untreated) to remove methylene red from aqueous solution were assessed at room temperature. Laboratory investigation of the potential of marble powder and sulphuric acid treated marble powder to remove dye color from aqueous solution has been studied. Parameters studied included pH, adsorbent dose, initial dye concentration and contact time. The influence of these system variables were investigated to observe the effect on the rate of dye uptake. Sulphuric acid treated marble powder has shown better adsorptive capacity than untreated marble powder and thus it has become an interesting option for dye removal from industrial effluents.

Kinetic and isotherm studies of the adsorption of Acid Blue 92 using a low-cost non-conventional activated carbon

Abstract Adsorbents prepared from waste plants for the treatment of dyeing effluents have high significance in environmental sustainability. In this research, an attempt is made to analyze the applicability of activated carbon prepared from Euphorbia antiquorum L wood by H 3 PO 4 activation method for the removal of Acid Blue 92 dye. Various kinetic models were used for the analysis of adsorption kinetics and pseudo second-order model fits well for the selected adsorbent–adsorbate system. The moderate rate of dye uptake indicates that the rate-determining step could be physisorption in nature. Langmuir, Freundlich and Dubinin-Raduskevich isotherm models were applied for the analysis of isotherm data. The positive enthalpy of adsorption substantiates that the adsorption process is endothermic in nature.

Sorption of malachite green by eucalyptus bark as a non-conventional low-cost biosorbent

In this work, eucalyptus bark, a forest waste, was evaluated for its ability to remove malachite green (MG) from aqueous solutions. Sorption kinetic experiments were studied in a batch mode operation at various initial dye concentrations, sorbent dosages, and temperatures. The equilibrium sorption data of MG by eucalyptus bark were analyzed by Langmuir and Freundlich isotherm models. The results indicate that both the Langmuir and Freundlich equations provide good correlation of the experimental data, but the Langmuir expression fits the equilibrium data better. The maximum sorption capacity of eucalyptus bark was found to be 59.88 mg g-1 at 20 °C. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to analyze the kinetic data obtained at different concentrations. Among the kinetic models studied, the pseudo-second-order was the best applicable model to describe the sorption of MG by eucalyptus bark. The overall rate of dye uptake was found to be controlled by external ma...

Effects of Plasma Treatment of Wool on the Uptake of Sulfonated Dyes with Different Hydrophobic Properties

A wool fabric has been subjected to an atmospheric-pressure treatment with a helium plasma for 30 seconds. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry confirmed removal of the covalently-bound fatty acid layer (F-layer) from the surface of the wool fibers, resulting in exposure of the underlying, hydrophilic protein material. Dye uptake experiments were carried out at 50°C to evaluate the effects of plasma on the rate of dye uptake by the fiber surface, as well as give an indication of the adsorption characteristics in the early stages of a typical dyeing cycle. The dyes used were typical, sulfonated wool dyes with a range of hydrophobic characteristics, as determined by their partitioning behavior between water and n-butanol. No significant effects of plasma on the rate of dye adsorption were observed with relatively hydrophobic dyes. In contrast, the relatively hydrophilic dyes were adsorbed more rapidly (and uniformly) by the plasma-treated fabric. It was concluded that adsorption of hydrophobic dyes on plasma-treated wool was influenced by hydrophobic interactions, whereas electrostatic effects predominated for dyes of more hydrophilic character. On heating the dyebath to 90°C in order to achieve fiber penetration, no significant effect of the plasma treatment on the extent of uptake or levelness of a relatively hydrophilic dye was observed as equilibrium conditions were approached.

Poly(acrylamide/laponite) nanocomposite hydrogels: Swelling and cationic dye adsorption properties

AbstractSuper adsorbent polyacrylamide (PAAm)/nanoclay (laponite, Lap) hydrogels were prepared by in situ free radical polymerization of AAm in an aqueous solution with clay as a crosslinker. The swelling properties and water‐soluble cationic dye adsorption behaviors of the PAAm/laponite (PAAm/Lap) nanocomposite (NC) hydrogels were investigated. The parameters of swelling and diffusion of water in dye solutions were evaluated for the PAAm/Lap NC hydrogels. The adsorption behavior of the monovalent cationic dyes such as Basic Blue 12 (BB 12), Basic Blue 9 (BB 9), and Basic Violet 1 (BV 1), were studied on the NC hydrogels. The effects of the clay content of the hydrogel on its cationic dye uptake behavior were studied. The adsorption studies indicated that the rates of dye uptake by the NC hydrogels increased in the following order: BB 9 > BB 12 > BV 1. This order is similar to the swelling results of the PAAm/Lap NC hydrogel in the dye solutions. The equilibrium uptakes of the different dyes by the PAAm/Lap NC hydrogel were nearly the same. In the dye absorption studies, S‐type adsorption in the Giles classification system was found for the BB 12 and BV 1 dyes, whereas L‐type was observed for the BB 9 dye. After the heat treatment of PAAm/Lap, the rate of dye uptake and equilibrium dye uptake were increased. The NC hydrogels may be considered as a good candidate for environmental applications to retain more water and to remove dyes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Modelling the solid–liquid adsorption processes using artificial neural networks trained by pseudo second order kinetics

A three-layer feed forward neural network was constructed and tested to analyze the second order kinetics of solid–liquid adsorption process. The pseudo second order kinetics of auramine O onto activated carbon was used to train the artificial neural network (ANN) to model the sorption system for various operating conditions. The operating variables studied are the contact time, initial dye concentration, agitation speed, temperature, initial solution pH and activated carbon mass. The studied operating variables were used as the input to the constructed neural network to predict the dye uptake by pseudo second order kinetics at any time as the output or the target. The dye uptake predicted by ANN trained by pseudo second order kinetics was found to be precise in representing the experimental kinetics of auramine O uptake by activated carbon. The constructed network was also found to be precise in predicting the sorption kinetics of auramine O by activated carbon for the new input data which are kept unaware of the trained neural network showing its applicability to determine the dye uptake rate for any operating conditions under interest. The ANN was also trained using pseudo second order kinetics of sorption of divalent metal ions onto peat particles and also using the second order kinetics of cadmium ions onto tree fern particles. The ANN and pseudo second order kinetics compliment each other to model the studied sorption systems for a wide range of operating conditions.

Equilibrium, kinetics and mechanism of malachite green adsorption on activated carbon prepared from bamboo by K 2CO 3 activation and subsequent gasification with CO 2

In this work, the adsorption of malachite green (MG) was studied on activated carbon prepared from bamboo by chemical activation with K 2CO 3 and physical activation with CO 2 (BAC). Adsorption studies were conducted in the range of 25–300 mg/L initial MG concentration and at temperature of 30 °C. The experimental data were analyzed by the Freundlich isotherm, the Langmuir isotherm, and the multilayer adsorption isotherm. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 263.58 mg/g. The rates of adsorption were found to confirm to pseudo-second-order kinetics with good correlation and the overall rate of dye uptake was found to be controlled by pore diffusion throughout the entire adsorption period. The results indicate that the BAC could be used to effectively adsorb MG from aqueous solutions.

Neural Network Modeling and Simulation of the Solid/Liquid Activated Carbon Adsorption Process

A three-layer feed-forward neural network was constructed and tested to analyze the kinetic dye uptake of a batch activated carbon adsorption process. The operating variables studied are the contact time, initial dye concentration, agitation speed, temperature, initial solution pH, activated carbon mass, and volume of the dye solution treated. The studied operating variables were used as the input to the constructed neural network to predict the dye uptake at any time as the output or the target. The constructed network was found to be precise in modeling the rate of dye uptake for the operating conditions studied. The constructed neural network was found to be highly precise in predicting the dye uptake rate for the new input data, which are kept unaware of the trained neural network showing its applicability to determine the reaction rate for any operating conditions.

Batch removal of malachite green from aqueous solutions by adsorption on oil palm trunk fibre: Equilibrium isotherms and kinetic studies

Oil palm trunk fibre (OPTF) – an agricultural solid waste – was used as low-cost adsorbent to remove malachite green (MG) from aqueous solutions. The operating variables studied were contact time, initial dye concentration, and solution pH. Equilibrium adsorption data were analyzed by three isotherms, namely the Freundlich isotherm, the Langmuir isotherm, and the multilayer adsorption isotherm. The best fit to the data was obtained with the multilayer adsorption. The monolayer adsorption capacity of OPTF was found to be 149.35 mg/g at 30 °C. Adsorption kinetic data were modeled using the Lagergren pseudo-first-order, Ho's pseudo-second-order and Elovich models. It was found that the Lagergren's model could be used for the prediction of the system's kinetics. The overall rate of dye uptake was found to be controlled by external mass transfer at the beginning of adsorption, then for initial MG concentrations of 25, 50, 100, 150, and 300 mg/L the rate-control changed to intraparticle diffusion at a later stage, but for initial MG concentrations 200 and 250 mg/L no evidence was found of intraparticle diffusion at any period of adsorption. It was found that with increasing the initial concentration of MG, the pore-diffusion coefficient increased while the film-diffusion coefficient decreased.

Kinetics and equilibrium studies of malachite green adsorption on rice straw-derived char

In this work, the potential feasibility of rice straw-derived char (RSC) for removal of C.I. Basic Green 4 (malachite green (MG)), a cationic dye from aqueous solution was investigated. The isotherm parameters were estimated by non-linear regression analysis. The equilibrium process was described well by the Langmuir isotherm model. The maximum RSC sorption capacity was found to be 148.74 mg/L at 30 °C. The kinetics of MG sorption on RSC followed the Lagergren's pseudo-first-order model and the overall rate of dye uptake was found to be controlled by external mass transfer at the beginning of adsorption, while intraparticle diffusion controlled the overall rate of adsorption at a later stage. The results indicated that RSC was an attractive adsorbent for removing basic dye from aqueous solutions.

Measurements of dye absorption by cellulose triacetate using matching index of refraction absorption spectroscopy

A simple method of analysis has been devised in which the uptake of disperse dyes in triacetate fabrics can be monitored using ordinary absorption spectroscopy. The experimental technique requires that a sample of triacetate fabric be immersed in a liquid having the same index of refraction as the constituent fibres, thus rendering the fabric transparent to visible light. Under these conditions, a dyed sample of fabric may be placed in the cell compartment of an ordinary ultraviolet/visible spectrometer allowing one to measure the absorption spectrum of the dye molecules located within the constituent triacetate fibres of the fabric sample. Values measured for the absorbance of several dyes incorporated within samples of triacetate fabric are shown to satisfy the Beer–Lambert law, thus enabling one to measure the rate of dye uptake by triacetate fabric samples placed in infinite dyebaths.

Opening of connexin 43 hemichannels is increased by lowering intracellular redox potential

Nonjunctional membrane in many cells contains connexin gap junction hemichannels (or connexons) that can open to allow permeation of small molecules. Opening of Cx43 hemichannels is infrequent in normal extracellular Ca(2+) and enhanced by low Ca(2+), positive membrane potentials, and dephosphorylation of critical residues. Here we report that lowering intracellular redox potential increases Cx43 hemichannel open probability under otherwise normal conditions. We studied dye uptake and single-channel activity in HeLa cells transfected with wild-type Cx43, Cx43 with enhanced GFP attached to its C terminus (Cx43-EGFP), and Cx43 with enhanced GFP attached to its N terminus (EGFP-Cx43). Dithiothreitol [(DTT) 10 mM], a membrane permeant-reducing agent, increased the rate of dye uptake by cells expressing Cx43 and Cx43-EGFP, but not by parental cells or cells expressing EGFP-Cx43. Induced dye uptake was blocked by La(3+), by a peptide gap junction and hemichannel blocker (gap 26), and by flufenamic acid. DTT increased Cx43-EGFP hemichannel opening at positive voltages. Bath application of reduced glutathione, a membrane impermeant-reducing agent, did not increase dye uptake, but glutathione in the recording pipette increased hemichannel opening at positive voltages, suggesting that it acted intracellularly. DTT caused little change in levels of surface Cx43 or Cx43-EGFP, or in intracellular pH. These findings suggest that lowering intracellular redox potential increases the opening of Cx43 and Cx43-EGFP hemichannels, possibly by action on cytoplasmic cysteine residues in the connexin C terminus.

Laser intensity dependence of femtosecond near-infrared optoinjection

We report an experimental study on transient membrane permeabilization of single living bovine aortic endothelial cells (BAEC) by tightly focused femtosecond near-infrared laser pulses. The membrane permeabilization of the BAEC cells was studied as a function of the incident laser intensity. The rate of dye uptake by the cells was analyzed using time-lapse imaging. We found that membrane permeabilization occurs for laser intensities higher than 4.0 x 10(12) W/cm(2). For laser intensity above 3.3 x 10(13) W/cm(2) the cell disintegrates. Within these two limits the rate of dye uptake increases logarithmically with increasing laser intensity. This functional dependence is explained by considering the Gaussian intensity distribution across the laser focal spot. Cell membrane permeabilization is explained by the creation of a plasma within the laser focal spot. The physical understanding of the relationship between dye uptake, pore characteristics, and laser intensity allows control of the concentrations of molecules delivered into cells through the control of pore characteristics.

Kinetics and mechanism of adsorption of methylene blue from aqueous solution by nitric-acid treated water-hyacinth

Kinetics adsorption experiments were conducted to evaluate the adsorption characteristics of a cationic dye (methylene blue, MB) onto nitric-acid treated water-hyacinth (N-WH). Results showed that N-WH can remove MB effectively from aqueous solution. The loading of MB onto N-WH was found to increase significantly with increasing the initial MB concentration, but the residual concentration of MB in solution also increased. A complete removal of MB from solution was only achieved at the lower range of initial MB concentration (less than 286 mg/L). Temperature had a slight effect on the amount adsorbed at equilibrium. The adsorption rate was fast and more than half of the adsorbed-MB was removed in the first 15 min at room temperature, which makes the process practical for industrial application. The adsorption kinetics at room temperature could be expressed by the pseudo second order model, while at higher temperatures (45–80 °C) and low MB concentration (97 mg/L) both Lagergren's model and the pseudo second order model can be used to predict the kinetics of adsorption. The overall rate of dye uptake was found to be controlled by external mass transfer at the beginning of adsorption, then gradually changed to intraparticle diffusion control at a later stage. The initial period where external mass transfer is the rate controlling step was found to increase with increasing initial MB concentration and decrease with increasing temperature. The increase in temperature was also found to increase the rate of adsorption and reduce the time required to reach equilibrium. The initial rate of adsorption, h o, was calculated, it was found to increase with increasing temperature, while the increase in MB concentration decreased h o at the lower concentration range then increased h o again at high concentration. The value of the activation coefficient, E, was found to be 8.207 kJ/mol, which indicates a diffusion controlled process.

Pannexin-1: A P2X 7 ATP Receptor-Activated Pore

Activation of the inflammasome, a complex that processes interleukin-1β (IL-1β), occurs in response to activation of the adenosine triphosphate receptor P2X 7 on macrophages. Activation of P2X 7 also triggers the opening of a nonselective, large pore in the plasma membrane. Pelegrin and Surprenant found that pannexin-1 (panx1), a protein that produces hemichannel currents when ectopically expressed in oocytes, was present in monocytes, macrophages, astrocytes, and various cell lines. Panx1, when expressed in transfected HEK cells, coimmunoprecipitated with the P2X 7 receptor and colocalized with the P2X 7 receptors in ATP-stimulated cells. Using either an siRNA to knock down panx1 or a peptide inhibitor to block the pore function of panx1, the authors showed that dye uptake (a measure of pore opening) in response to P2X 7 required panx1. When overexpressed in cells that lack P2X 7 receptors, panx1 caused constitutive dye uptake, and when overexpressed in cells that contain P2X 7 receptors, panx1 increased the rate of dye uptake in response to ATP but did not cause constitutive dye uptake. Inhibition of panx1 function in macrophages or a monocyte cell line prevented P2X 7 -mediated stimulation of caspase 1 activation and IL-1β release. However, inhibition of panx1 function did not prevent intracellular K + depletion, which has been proposed as an activator of the inflammasome. The authors propose that opening of the pannexin1 channel in response to P2X 7 activation may allow extracellular ATP to enter the cell and the increased intracellular ATP concentration may contribute to the activation of caspase 1. P. Pelegrin, A. Surprenant, Pannexin-1 mediates large pore formation and interleukin-1β release by the ATP-gated P2X 7 receptor. EMBO J. 25 , 5071-5082 (2006). [PubMed]

S-nitrosylation and permeation through connexin 43 hemichannels in astrocytes: Induction by oxidant stress and reversal by reducing agents

Marked increase in cell permeability ascribed to open connexin (Cx)43 hemichannels is induced by metabolic inhibition (MI) of cortical astrocytes in culture, but the molecular mechanisms are not established. Dephosphorylation and/or oxidation of Cx43 hemichannels was proposed as a potential mechanism to increase their open probability. We now demonstrate that MI increases the number of hemichannels on the cell surface assayed by biotinylation and Western blot, and that this change is followed by increased dephosphorylation and S-nitrosylation. The increase in rate of dye uptake caused by MI is comparable to the increase in surface expression; thus, open probability and permeation per hemichannel may be unchanged. Reducing agents did not affect dephosphorylation of Cx43 hemichannels but reduced dye uptake and S-nitrosylation. Uptake was also reduced by elevated intracellular but not extracellular levels of reduced glutathione. Moreover, nitric oxide donors induced dye uptake and nitrosylation of surface Cx43 but did not affect its abundance or phosphorylation. Thus, permeability per channel is increased, presumably because of increase in open probability. We propose that increased dye uptake induced by MI is mediated by an increased number of Cx43 hemichannels in the surface and is associated with multiple molecular changes, among which nitrosylation of intracellular Cx43 cysteine residues may be a critical factor.

Dyeing properties of polyamide super‐microfibre with disperse dyes

The dyeing properties of polyamide super‐microfibres and conventional fibres dyed with disperse dyes have been studied by measuring the adsorption isotherm, the rate of dye uptake, the time of half‐dyeing and the amount of equilibrium adsorption. The thermodynamic analysis shows that the adsorption isotherms of super‐microfibres follow a Langmuir sorption model. The kinetic results show that super‐microfibres have a faster dyeing rate and a higher equilibrium dye uptake compared to conventional fibres. This can be explained by the greater surface area and dye capacity of the super‐microfibres. The wash and light fastness properties of the super‐microfibres dyed with disperse dyes are lower than conventional fibres.