Dual-mode adsorption of cochineal natural dye on wool fibers: Kinetic,equilibrium, and thermodynamic studies

The dual-mode adsorption model was used to investigate the adsorption behavior of cochineal natural dye on wool fibers. Kinetic, thermodynamic, and equilibrium characteristics were investigated in terms of the adsorption isotherm, affinity, enthalpy and entropy changes, dyeing rate, diffusion coefficient, and activation energy of dye diffusion. The results revealed the prominent role of dyeing pH in determination of dyeing mechanism and dye adsorption isotherm type. At pH 4, dual Langmuir-Nernst model with the highest correlation coefficient was found as the most appropriate isotherm model to describe the adsorption behavior of cochineal onto wool fibers while at pH 6, the adsorption isotherm was the Nernst type. Cochineal adsorption onto wool was exothermic which resulted in progressive fall in affinity and equilibrium dye up-take values with increasing temperature. Moreover, dyeing rate steadily increased with temperature. At pH 4, affinity, dyeing rate, and diffusion coefficient demonstrated higher values compared to pH 6 whereas enthalpy and entropy changes, and activation energy showed lower values. Additionally, negative value for activation energy was obtained at pH 6. The results are deliberated based on the different possible interactions between cochineal dye and wool fiber.     

An adsorption study of alum-morin dyeing onto silk yarn

Silk yarn was dyed with morin (2′,3,4′,5,7-pentahydroxyflavone) by using alum as mordant. In order to optimize the process, three methods of dyeing involving: pre-mordanting, simultaneous mordanting, and post-mordanting were assessed and compared with a mordant-free process. The adsorption of alum-morin dye onto silk fibers indicated that the adsorption capacities were significantly affected by pH, the initial dye concentration, and temperature. The initial dye adsorption rates of alum-morin dye on silk before equilibrium was reached increased with higher dyeing temperatures. The pseudo second-order kinetic model was indicated for alum-morin dyeing (simultaneous mordanting) of silk at pH 4.0 with an activation energy (E _a ) of 45.26 kJ/mol. The value of the enthalpy of activation (ΔH ^#) for alum-morin dyeing on silk at pH 4.0 was −31.29 kJ/mol. Also, the free energy (ΔG ^o) and entropy changes (ΔS ^o) for alum-morin dyeing on silk were −17.73 kJ/mol and −45.7 J/molK, respectively, consistent with a spontaneous and exothermic adsorption process.     

Dyeing properties of mixture of ultrafine nylon and polyurethane with different types of dye

The dyeing and color fastness properties of levelling type acid dye, milling type acid dye, metal complex dye and reactive dye on ultrafine nylon, polyurethane fiber/film and their mixtures were investigated. Ultrafine nylon was dyed well with four types of dye at pH 3-6, but levelling type acid dye showed low washing fastness. Amine-rich polyurethane fiber exhibited enhanced dyeability due to amino groups which acted as dyeing sites, compared to regular polyurethane fiber. In simultaneous dyeing with milling type acid dye and metal complex dye, amine-rich polyurethane fiber absorbed more dye molecules than ultrafine nylon, the color difference between two fibers were apparent. Polyurethane-impregnated ultrafine nylon was also prepared and its build-up properties were determined. It was found that polyurethane whose soft segment was composed of polytetramethylene glycol (PTMG) and polypropylene glycol (PPG) showed improved dyeing property and subsequently high color strength.     

Effect of Dye Solution Ionic Strength on Dyeing of Cotton with Reactive Dyes

The controlling effect for dye exhaustion (adsorption) and diffusion (absorption) in a reactive dyeing of cotton is shown to be exerted by ionic strength in the dye solution rather than concentration of inorganic salts used as electrolytes. The study showed that the conclusion applies to both exhaust dyeing for dye exhaustion and pad dyeings for dye diffusion. Further, the addition of an alkali, even though it is not used as an electrolyte, increased the extent of exhaustion (in exhaust dyeing) and diffusion (in pad dyeing) due to increase in ionic strength of the dye solution. Hence, the total ionic strength of reactive dye solution for dye exhaustion and diffusion must be taken into account in order to ensure optimum reproducibility. Means for determining the total ionic strength of exhaust or pad dye solutions for different electrolytes are given.     

Combined use of cationization and mercerization as pretreatment for the deep dyeing of ramie fibre

In order to produce deep shades of colour, ramie fibre was subjected to pretreatment by cationization, caustic mercerization (slack and tension condition), and liquid ammonia mercerization. The untreated and pretreated samples were dyed with 0.5 to 7 % concentrations (on mass of fiber (o.m.f)) of Liyuansol Red FL-2BL reactive dye. The dyeing properties of dye exhaustion, fixation, colour uniformity, wash fastness, and rubbing fastness were investigated. The results indicated that these pretreatments improved dye exhaustion and fixation on ramie fibre, with no loss of fastness. For the untreated and treated substance, the amount of dye mass absorption increased linearly with increased dye o.m.f. Cationic treatment improved performance, with 89 % and 98 % for exhaustion and fixation, respectively, and the maximum K/S values of all fibers receiving pretreatment. The colour uniformity was acceptable and similar for the untreated and treated ramie fibers, with the exception of cationic-treated fabric dyed at 7 % dye o.m.f that showed a high standard deviation value of colour uniformity. The Freundlich and Langmuir adsorption isotherm models were also used to study the adsorption of dye on ramie fibre; all of the adsorption processes fit the Freundlich model.     

Basic study on the two-tone color dyeing of PET and PVC wig fibers by carrier dyeing method

PET or PVC wig fibers are usually colored by the dope dyeing method in which the pigment or color master batch is mixed before the spinning process. However, the colored fibers need to be dyed again to obtain a two-tone color along the longitudinal fiber direction. In this study, PET and PVC fibers were dyed by the carrier dyeing method using a disperse dye, and the dyeing behavior was investigated. The fiber was dyed at various carrier and dye concentrations. The dye uptake increased with increasing carrier concentration or dye concentration. The saturation of the dye uptake was observed in each case. No change of the glass transition temperature (T_g) was observed in the 1st run of the DSC thermogram, however, a decrease in the value of T_g was observed in the 2nd run performed after the 1st run sample was quenched and re-measured. The reduction in the value of T_g implies that the carrier acted as a plasticizer in the fiber and enhanced the segmental mobility of the polymer chains. The dyeing temperature and carrier concentration were varied and the diffusion coefficients of the dye and activation energy were measured. The activation energy was increased at a higher carrier concentration, because the carrier acted as a plasticizer and lowered the energy barrier to the penetration of the dye molecule into the polymer chains.     

Preparation of amidoxime-modified polyacrylonitrile nanofibers immobilized with laccase for dye degradation

A novel approach to preparing multifunctional composite nanofibrous membrane was developed. Polyacrylonitrile (PAN) nanofibrous membrane was fabricated by electrospinning and then the nitrile groups in PAN copolymer was chemically modified to obtain amidoxime modified PAN (AOPAN) nanofiber membrane which was further used as a functional support for laccase immobilization. During the process of reactive dye degradation catalyzed by the AOPAN nanofiber membrane immobilized with laccase, metal ion adsorption occurred at the same time. The chemical modification was confirmed by Fourier transform spectroscopy (FTIR). Scanning electron microscope (SEM) was employed to investigate the surface morphologies of the electrospun nanofibers before and after laccase immobilization. The effects of environmental factors on laccase activity were studied in detail. It was found that the optimum pH and temperature for the activity of immobilized laccase was 3.5 and 50 °C. The relative activity retention of the immobilized laccase decreased dramatically during the initial four repeated uses. After 20 days’ storage, the activity retention of immobilized laccase was still high above 60 %. It has also proved that laccase immobilized on AOPAN nanofiber membrane performed well in dye degradation and metal ion adsorption.     

Use of amino-modified cotton fibers loaded with copper ions for anionic dye removal under batch and fixed-bed systems: A comparative study

Amine-functionalized supports were prepared by chemical modification of cotton fibers using amino compounds namely diethylenetriamine (DET) and 1,4-diaminobutane (DB) in order to be loaded with copper ions. Evidence of attaching amine groups onto cellulosic fibers was confirmed through nitrogen and SEM analysis. Adsorption behavior of Acid Blue 25 from aqueous solutions onto [Cu(II)/DET-cotton] and [Cu(II)/DB-cotton] has been evaluated via batch and column mode systems. During the batch experiments, the effects of temperature and type of adsorbent on dye removal were investigated. Results revealed the formation of ternary complexes of the type [AB25/Cu(II)/adsorbent] with a [5/2:3:1] stoichiometry for DET-cotton and a [1:1:1] stoichiometry for DB-cotton at 20 °C. In the isotherm studies, Langmuir, Freundlich, and Jossens equations were applied and it was found that the experimental data conformed to Jossens model. Thermodynamic parameters such as change in free energy (ΔG ⁰), enthalpy (ΔH ⁰), and entropy (ΔS ⁰) have also been calculated in this paper, and it was found that the adsorption process was exothermic and spontaneous. The column experiments were conducted to study the effect of bed height on adsorption performance of both adsorbents. Results exhibited that the column capacity of [Cu(II)/DET-cotton] complex was found to be higher than that of [Cu(II)/DB-cotton] as was obtained in batch process. BDST model was applied to experimental data in order to predict the breakthrough curves and determine the characteristics parameters of the column useful for process design. Results revealed that the used model was appropriate to fit the experimental data. Desorption studies to recover the adsorbed dye from both adsorbents were performed with NaOH and NH₄Cl solutions.     

Morphological structures of the cellulose hybrids containing polyhedral oligomeric silsesquioxane and their application for removing C.I. Reactive Red 250

Cellulose hybrids containing polyhedral oligomeric silsesquioxane (POSS) were synthesized by crosslinking reaction. The chemical and morphological structures of the hybrids were characterized by elemental analysis, infrared spectrum, scanning electron microscope and atomic force microscope. The hybrids were used for adsorbing C.I. Reactive Red 250 in aqueous solution. Adsorption kinetic and equilibrium isotherm of the cellulose hybrids for the dye were investigated. The hybrids formed new adsorptive positions for dyes because of a nanometer-sized cubic core and numerous organic functional groups (-C-N-). The adsorption capacity of the hybrid materials was significantly higher than that of the control cellulose. The adsorption of the dye on the hybrids was good fit with Langmuir isotherm equation and the second-order model. The apparent activation energy of the dye on the hybrid was 14.87 kJ/mol.     

Synthesis and application of novel high light fastness red dyes for ultra high molecular weight polyethylene fibers

A new series of anthraquinoid red dyes were synthesized with 1-amino-2-bromo-4-hydroxyanthraquinone and nalkylphenols to dye UHMWPE fibers with high light fastness. Their dyeability was examined depending on the length of alkyl chains. As the length of alkyl substituents increases, the dyeability toward UHMWPE fibers improves rapidly from methyl to ethyl substituents and maintains almost same level of color strength, and then decreases from heptyl to octyl groups. The color strength of dyeings increased dramatically with the increase of dyeing temperature from 100 °C to 130 °C. The maximum build-up was shown at around 5 % owf dye amount. From the dyeing rate, equilibrium dyeing was achieved at around 5 h at 130 °C. All kinds of fastnesses were good enough showing higher than ratings 4-5 to washing and rubbing for the longer alkyl substituents. Especially, much improvement was achieved in light fastness showing ratings 4, which was higher than ratings 2 of the previous study.     

Equilibrium and kinetic modeling of the adsorption of indigo carmine onto silk

Quantitative adsorption kinetic and equilibrium parameters for indigo carmine dyeing of silk were studied using UV-visible absorption spectroscopy. The effect of initial dye concentration, contact time, pH, material to liquor ratio (MLR), and temperature were determined to find the optimal conditions for adsorption. The mechanism of adsorption of indigo carmine dyeing onto silk was investigated using the pseudo first-order and pseudo second-order kinetic models. The adsorption kinetics was found to follow a pseudo-second-order kinetic model with an activation energy (E _a) of 51.06 kJ/mol. The equilibrium adsorption data of indigo carmine dye on silk were analyzed by the Langmuir and Freundlich models. The results indicate that the Langmuir model provides the best correlation. Adsorption isotherms were also used to obtain thermodynamic parameters such as free energy (ΔG ^o), enthalpy (ΔH ^o), and entropy (ΔS ^o) of adsorption. The negative values of ΔG ^o and Δ^{H o} indicate the overall adsorption process is a spontaneous and exothermic one.     

Cellulose-based porous adsorbents with high capacity for methylene blue adsorption from aqueous solutions

A novel cellulose-based porous adsorbent with high adsorption capacity for methylene blue (MB) was prepared by free radical polymerization methods. The obtained polymer grafting rate and dye removal efficiency are as high as 338.64 % and 97.74 %, respectively, when the dosage of monomer is 4.5 g, the polymerization condition is 3 h at 70 °C. The cellulose-based adsorbent showed high mechanical properties and good flexibility. The Langmuir isotherm model revealed that the maximum theoretical adsorption capacity of this material for methylene blue was 1734.816 mg g-1 at pH 9.0 at 313 K, which is higher than the values observed for other adsorbents. Scanning electron microscopy (SEM) showed that the cellulose-based adsorbent exhibits a typical well-defined porous and interconnected three-dimensional framework structure, which is benefits to dye adsorption. The adsorption kinetics (pseudo first-order, pseudo-second-order, and intraparticle diffusion models) was also studied, and the pseudo-second-order model fitted MB adsorption better than the pseudo-first-order and intraparticle diffusion models at different initial dye concentrations (500-3000 mg l ^-1). The novel polyacrylic acid-grafted quaternized cellulose (PAA-g-QC) adsorbent is thus potentially useful for the treatment of dye-contaminated wastewater.     

Study on the dyeing of wool fabrics with Phytolacca berry natural dyes

Dyeing of wool fabrics with natural dyes from Phytolacca berries has been studied. The effect of dye concentration, dye bath pH, dyeing time and temperature were discussed. The influence of chitosan application on the dyeing properties of wool fabrics was investigated. The SEM photographs of chitosan treated wool fabrics clearly depict the deposition of chitosan on the fibers. The effect of chitosan concentration, dye bath pH, dyeing time and temperature has been studied by orthogonal experiment. It has been proved that the dyed wool samples pretreated by chitosan have higher color fastness, faster dyeing rate, and better antibacterial properties compared with untreated ones.     

Dyeing properties of nylon 66 nano fiber with high molecular mass acid dyes

Research and development of nano fiber products is very active over the world. Physical characteristics and dyeing properties of nylon 66 nano fiber were investigated in this study. X-ray diffraction, DSC, analysis of amino end group, and water absorption were performed to get information concerning physical properties of nano fiber. Nylon 66 nano fiber was dyed with high molecular mass acid dyes. Effects of dyeing temperature, pH of dyeing solution, and concentration of acid dyes on dyeing properties such as rate of dyeing and the extent of exhaustion, were examined and compared to those of regular fiber. It was found that nano fiber adsorbed acid dyes at lower temperature, got rapidly dyed, and its extents of exhaustion at specific dyeing temperature were higher than regular fiber. It was also observed that nano fiber could adsorb a large amount of acid dye without a significant loss in the extent of exhaustion. Washing fastness of the dyed nano fiber was lower by 1/2∼1 grade, light fastness by 1 grade than the dyed regular fiber.     

Influence of water hardness on acid dyeing with silk

In this paper, the effect of water hardness, expressed in CaCO₃ equivalent, on the dyeing silk with acid dye under acid, alkaline and isoelectric point dyeing conditions was studied by zeta potential method. Under acid condition and in the presence of calcium ion, the positive zeta potential of silk was found to decrease with a reduction in the dye adsorption. Such a phenomenon might be due to the presence of cation which increased the dyeing potential barrier at the interface between fibre and dye solution. This would result in a higher resistance of dye anions passing through the interface. Under alkaline condition, the zeta potential on silk was negative and resulted in a strong potential barrier for the dye anions. The presence of calcium ion would result in a decrease in the absolute value of zeta potential of silk fibre with an overall increase in dye absorption. Under isoelectric point, the zeta potential of silk fibre was found to be near zero and dye adsorption was not influenced by the cations. When studying the effect of calcium ion on the silk dyeing with acid dye under acid, alkaline and isoelectric point dyeing conditions, it was found that calcium ions influenced dye exhaustion and fixation greatly under acidic and alkaline dyeing conditions, which such influence became much smaller when the pH of dyebath was at the isoelectric point of the fibre. These results showed that calcium ion could produce strong electrolytic effect on dyeing even under very low concentrations.     

Dyeing and fastness properties of a reactive disperse dye on PET, nylon, silk and N/P fabrics

Dyeing and color fastness properties of a reactive disperse dye containing an acetoxyethylsulphone group on PET, Nylon, silk and N/P fabrics were examined. The reactive disperse dye exhibited almost the same dyeing properties on PET fabric as a conventional disperse dye except the level of dye uptake. The most appropriate pH and dyeing temperature for the dyeing of Nylon fabric were 7 and 100°C respectively. The build-up on Nylon fabric was good and various color fastnesses were good to excellent due to the formation of the covalent bond. Application of the reactive disperse dye on silk fabric at pH 9 and 80°C yielded optimum color strength. The rate of dyeing on Nylon fabric was faster than that on PET fabric when both fabrics were dyed simultaneously in a dye bath, accordingly color strength of the dyed Nylon was higher. The reactive disperse dye can be applied for one-step and one-bath dyeing of N/P mixture fabric with good color fastness.     

Dyeing behavior of low temperature plasma treated wool

In this paper, the effects of low temperature plasma (LTP) treatment on the dyeing properties of the wool fiber were studied. The wool fibers were treated with oxygen plasma and three types of dye that commonly used for wool dyeing, namely: (i) acid dye, (ii) chrome dye and (iii) reactive dye, were used in the dyeing process. For acid dyeing, the dyeing rate of the LTP-treated wool fiber was greatly increased but the final dyeing exhaustion equilibrium did not show any significant change. For chrome dyeing, the dyeing rate of the LTP-treated wool fiber was also increased but the final dyeing exhaustion equilibrium was only increased to a small extent. In addition, the rate of afterchroming process was similar to the chrome dyeing process. For the reactive dyeing, the dyeing rate of the LTP-treated wool fiber was greatly increased and also the final dyeing exhaustion equilibrium was increased significantly. As a result, it could conclude that the LTP treatment could improve the dyeing behavior of wool fiber in different dyeing systems.     

Thermodynamics of adsorption of laccaic acid onto chitosan and associated dye toxicity studies

The thermodynamics of adsorption of laccaic acid (lac dye) onto chitosan were investigated under acidic condition over various concentrations (20–293 mg/l). Langmuir, Freundlich, and Temkin isotherms were used to analyze the equilibrium data at different temperatures, with the Freundlich isotherm fitting the experimental data significantly better than the other isotherms. The effect of temperature on the adsorption isotherm was studied by carrying out a series of isotherms at 10, 20, 40, and 60 °C. It was found that more dye was strongly adsorbed by chitosan when the temperature of the dye solution increased. Thermodynamic parameters such as free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) were also evaluated. The negative value of ΔG° and positive value of ΔH° indicated that the laccaic acid adsorption process is a spontaneous and an endothermic one. Attenuated total reflectance Fourier transform infrared spectroscopy confirmed the functional groups of chitosan that affected the laccaic acid adsorption. Therefore, laccaic acid molecules could interact with the chitosan via electrostatic forces, hydrogen bonding, and ion-dipole interactions under acidic condition. From the toxicity study, the dye solution with the initial dye concentrations of 40 and 120 mg/l before dye removal showed significant mortality to earthworm Diplocardia communis (P<0.01).     

Preparation of nano disperse dyes from nanoemulsions and their dyeing properties on ultramicrofiber polyester

Six nano disperse dyes were prepared using corresponding O/W nanoemulsions which were obtained with sodium laurylsulphate and caprylic triglyceride. The average particle size of the dyes prepared were in the range of 110–130 nm. Exhaust dyeing using nano dyes resulted in low exhaustion yields of 17–26 % on regular polyester fiber and 28–38 % on ultramicrofiber polyester. The observed low exhaustion yields of nano disperse dye can be explained by the solubilization of dye particles into surfactant micelles as well as the high stability of the nanoemulsions, these might reduce the capacity of dye uptake onto the fibers. However, higher K/S values of dyeings with nano dyes on ultramicrofiber sites compared to those on regular polyester sites suggested their potential to be more efficient dyes for finer denier microfiber polyesters.     

Dyeing properties of nylon,PET, and N/P mixture fabric with reactive-disperse dyes having a sulfatoethylsulfone group

The dyeing and color fastness properties of two reactive-disperse dyes containing a sulfatoethylsulfone group on nylon, PET and N/P mixture fabrics were examined. The rate of dyeing on nylon fabric was greatly dependent upon dye bath pH. The final dye uptakes at all pH, however, were as high as 97 %. Color strength of the dyed nylon fabric linearly increased up to 0.5 %owf and then slowed down over 1 %owf dyeing. Washing and rubbing fastness of the dyed nylon fabric were excellent, but grade of light fastness was moderate. Dyeability of the reactive-disperse dyes on PET fabric was not much affected by pH, and K/S values of PET fabric dyed at pH 5–8 were lower than those of nylon fabric at all pH examined. Buildup and color fastnesses properties on PET fabric showed the same tendency with nylon fabric. The rate of dyeing of the reactive-disperse dyes on nylon fabric was faster than on PET fabric when both fabrics were dyed simultaneously in the same dye pot, resulting in higher color strength of nylon than PET. The reactive-disperse dyes were found to be adequate to the one-bath, one-step dyeing of N/P mixture fabric when applied at pH 5 and 120 °C.