Reactive Dyes Research Articles

Comprehensive analysis of dye adsorption and supramolecular interaction between dyes and cotton fibers in non-aqueous media/less water dyeing system

Cotton textile dyeing consumes large amounts of energy and water and discharges large amount of wastewater and pollutants. Zero or less discharge of the wastewater and contaminants from the cotton textile dyeing has been under high demands from textile industry. Recently, a novel reactive dyeing technology of using a non-aqueous medium with little water (NMLW) was developed for cotton fabrics. However, the use of high concentration of reactive dyes in the system triggers aggregation of the dyes in cotton fibers, influencing the quality of dyed cotton textiles. In this investigation, adsorption, diffusion, and aggregation behavior of reactive dyes in cotton fibers were studied. Compared to traditional water-based dyeing system, cotton fabrics demonstrated superior color depth, as long with higher rates of dye uptake and fixation for reactive dyes. At low dye concentrations, the maximum absorption wavelengths of reactive dyes were unchanged, and complied with the Lambot-Beer law. However, when the dye concentration was excessively high, reactive dyes with different molecular structures, as well as multi-layer dye aggregates with π-π stacking and hydrogen bonding interactions, showed different light absorption spectral characteristics and photophysical properties. Moreover, the dye particle size and dye ionization were influenced by the dye concentration, molecular weight, molecular configuration, etc. Analysis of the molecular dynamics of reactive dyes revealed that the maximum dye aggregation size was predominantly dimer at low dye concentration. However, the dimer ratio significantly decreased, while the trimer ratio increased, and higher-order aggregates were observed at a higher dye concentration. The strength of hydrogen bonds between dye molecules and water molecules, as well as the number of water molecules surrounding dye molecules, was influenced by dye concentration and alkali. This study provides a foundation for understanding the micro-aggregation behavior of reactive dyes and offer guidance for optimizing the dyeing process in practical production settings.

Green synthesized nano-TiO2 from Tamarindusindica leaf extract for photo-degradation of combination of dyes by suspension and immobilization on inert supports

ABSTRACT The present study aims to use green synthesized TiO2 as a photocatalyst in suspended and immobilized form under UV light to efficiently degrade a combination of reactive dyes, namely titan yellow, methyl orange, rhodamine B, and methylene blue. TiO2 nanoparticles (NPs) were synthesized using Tamarindus indica leaf extract and were utilized to parametrically study photo-degradation at room temperature. The green synthesized NPs were characterized by Powder XRD, SEM, and FTIR techniques to understand the crystalline phase/purity, morphology, and functional groups respectively. The TiO2 in suspension under UV light showed >90% degradation towards a 10 ppm composite dye at a loading of 1.5 gL−1, pH 7, and an irradiation time of 120 min. Subsequently, TiO2 was further immobilized in-situ, on inert supports of perlite granules and glass and studied for catalytic activity in batch and continuous modes. The TiO2 nanoparticles immobilized on perlite granules and glass showed 59 and 48% degradation in batch operation under the same conditions as in suspended form. In continuous mode, the highest degradation activity was recorded at 2 Lh−1 after 4 passes. Further, kinetic studies reveal that the degradation reaction is best described by Langmuir Hinshelwood kinetics for both suspended and immobilized TiO2.

Environmental modification of cellulose fibers for reducing dye diffusion rate by anionic polyacrylamide

Reactive dyeing is the primary method for coloring cellulose fibers due to its vibrant colors, various hues, excellent colorfastness, and cost-effectiveness. However, this process consumes a large amount of water and chemicals, leading to significant environmental concerns due to the wastewater. Non-aqueous media/less water dyeing has emerged as a cleaner alternative, showing promising results in dyeing cotton fibers with reactive dyes. Nevertheless, the rapid adsorption rate of dyes can impact the evenness of dyeing. This study explores the use of anionic polyacrylamide (APAM) in the modification bath to reduce dye adsorption rate and enhance dye desorption during cellulose fibers dyeing. Fourier transform infrared spectroscopy (FT-IR) and field-emission scanning electron microscope (FSEM) analysis revealed effective interaction between APAM and cellulose fibers. Thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and breaking strength tests indicated minimal impact on the thermal stability and physical properties of cellulose fibers with APAM modification. Zeta potential testing demonstrated that APAM modification reduced the surface potential of cellulose fibers and increased their negative charge. The adsorption rate of reactive dye decreased with APAM modification, while dye fixation, washing, and rubbing fastness remained largely unaffected. Adsorption isotherm results supported the weakening of the affinity between dyes and fibers after APAM treatment. Furthermore, the electrostatic potentials of fibers decreased after APAM modification. Compared to salt-free dyeing in non-aqueous media dyeing systems, anionic polymer modification not only improves the level dyeing performance of cotton fiber and reduces 0.9% in dyeing costs, but also increases production efficiency.

Ecofriendly one-bath waterless dyeing: Systhesis of novel pyrazolone benzothiazole disperse dyes suitable for cotton-containing fabircs in supercritical CO2

Traditional dyeing utilizes a substantial amount of water and necessitates the incorporation of significant quantities of dyes, auxiliaries, and salts, leading to the discharge of highly concentrated organic wastewater and severe water pollution issues. In this study, a novel pyrazolone benzothiazole disperse dye and its triazine disperse reactive dye were designed with the same yellow shade and synthesized. The results showed that the synthesized dyes could successfully realize one-step dyeing of cotton, polyester, and polyester-cotton in supercritical CO2. At 100℃, 24 MPa, 60 min, and 2.5 % (o.w.f.) of dye concentration, the K/S value of polyester-cotton fabric was 8 by using the same amount of disperse dye and disperse reactive dye. When disperse reactive dye was used at 100℃, 24 MPa, 60 min, and the concentration of 1.5 % (o.w.f.), the K/S value of cotton fabrics can reach 7.3, and their σK/S values were less than 0.03 and 0.006, respectively. Moreover, polyester reached the maximum K/S value of 15.96 at 120°C, 24 MPa, 60 min, and a dye concentration of 2.0 % (o.w.f.) with disperse dye. The σK/S value was below 0.045. The fastness of washing and rubbing was above 4. This study provides novel disperse dye structures and dyeing methods for ecofriendly textiles dyeing in supercritical CO2, especially for one-bath low temperature dyeing polyester-cotton fabrics.

Assembly of S-Scheme heterojunction In2S3/Zr-bcu-22bipy44dc: Optimize the optical-electronic properties for highly efficient photochemical decontamination of Cr(VI) ions and dyes

Zr-bcu-22bipy44dc, which features a LUMO positioned closer to the VB of In2S3, was utilized to assemble a S-Scheme heterojunction IS-Zr-MOF. Due to the appropriate band structure dislocation, the optical-electronic properties have been notably optimized. The photocatalytic reduction efficiency of IS-Zr-MOF-2 for Cr2O72- has achieved 98.6 % just within 30 min, under 500 W xenon lamp. It also displays effective degradation ability towards reactive dyes RB13, RB21 and RR15, under 500 W mercury lamp. This study presents a practical approach to create novel bi-functional photocatalysts for remediation of water environment.

Influence of water on liquid ammonia-based sustainable dyeing of ramie fiber

Liquid ammonia dyeing emerges as an environmentally benign and sustainable option for the textile industry, characterized by a minimal ecological impact. However, its adoption is hampered by certain limitations, such as suboptimal dye exhaustion and issues with color uniformity, which present significant hurdles to its widespread industrial application. Building on the premise that the addition of water to an ethanol solvent can enhance reactive dye exhaustion in cotton fiber dyeing, this study delves into the dyeing behavior of ramie fiber using a water-liquid ammonia mixture with Reactive Red 195. The incorporation of water into the liquid ammonia solution was observed to marginally decrease the color strength (K/S value) of the dyed ramie fiber, compared to the dyeing with anhydrous liquid ammonia. This reduction is likely due to the diminished expansion of the amorphous regions within the fiber. However, the color levelness of the dyed ramie fiber was enhanced by the addition of water to the liquid ammonia. To decipher the influences on the dyeing process, the Taguchi method, utilizing an orthogonal array (L16), was applied. The analysis revealed that the dye mass factor was the predominant influencer (79.08 %), followed by the liquor ratio factor (18.53 %), with both factors demonstrating statistically significant effects (p < 0.05). A multifaceted analysis of the samples was conducted using advanced techniques such as XRD (X-ray diffraction), FTIR (Fourier transform infrared), TGA (thermogravimetric analysis), and SEM (scanning electron microscopy). These analyses confirmed that the water-liquid ammonia treatment induced changes in the samples’ properties. The treated samples exhibited lower barium activity numbers and breaking force values, indicating structural alterations. Furthermore, the molecular structure of Reactive Red 195 remained intact throughout the dyeing process in the water-liquid ammonia mixture, thereby affirming its viability for practical applications in the textile industry.

A functionalization approach of decorative poplar veneer accomplished via reactive dyeing followed by in-situ synthesis of ZnO-Ag nanoparticles

Fast-growing wood has been widely used in manufacturing decorative material for wood-based panels. However, the deterioration of the decorative quality of the decorative material is still a hard nut to crack. The single decorative function of this material also makes it challenging to meet the requirements of the current consumer market. In this study, a novel method for the preparation of decorative poplar veneer that integrated multiple functions was proposed. It was accomplished via reactive dyeing of poplar veneer followed by in-situ synthesis of ZnO-Ag nanoparticles (NPs) at room temperature. The critical functional parameters and preparation mechanism of the functional decorative material were systematically analyzed. Results demonstrated that ZnO and Ag NPs were synchronously formed through the in-situ redox of metal ions and subsequent self-assembly in an alkaline medium. The ZnO-Ag NPs were uniformly distributed on the surface of dyed wood. The color change of the prepared decorative material was reduced by at least 40 % due to the physical obstruction of the ZnO-Ag NPs layer. More importantly, the antibacterial, hydrophobic, and flame retardant properties of the prepared material were also synchronously improved. This study provided a new approach to improving the quality of wood-based decorative materials.

A novel green approach for reactive printing of cotton/cellulosic regenerated blended fabrics using trisodium nitrilotriacetate

Owing to their comfort, handle, and aesthetic characteristics, cotton fabrics will always be the first and primary choice for clothing and apparel. In recent years, regenerated cellulosic fabrics like bamboo, Tencel, and modal fabrics have had many natural advantages. Fabrics based on blending cotton fibres with regenerated cellulosic fibres are considered promising products in textile industry sectors. Use of urea poses ecological problems associated with the high nitrogen content of the printing effluent. Therefore, urea reduction or elimination in reactive dye print pastes is of ecological interest. We report the use of trisodium nitrilotriacetate as a complete substitution of urea and alkali in the conventional reactive printing of cotton/cellulosic regenerated blended fabrics. CI Reactive Black 5 was selected for the present study. Three different print pastes containing urea/alkali, trisodium nitrilotriacetate/alkali and trisodium nitrilotriacetate without alkali were thoroughly investigated. Different factors that may affect the printability of cotton/cellulosic regenerated blended fabrics, such as the concentrations of dye, trisodium nitrilotriacetate, urea, absence or presence of alkali and steaming time in the prints obtained, were evaluated concerning colour strength, dye fixation, dye penetration, levelling, colure, and fastness properties. All printed fabrics using three print pastes obtained excellent to good fastness. The results proved the viability of using TNA as an environmentally friendly approach for urea/alkali-free printing of cellulosics with reactive dyes.

Efficacy of white rot fungal biomass of Phanerochaete chrysosporium for adsorption and removal of reactive red and reactive blue dyes from water

Water pollution has become a worldwide issue, particularly in developing countries. This study aimed to cleanse water contaminated with reactive red (RR-198) and reactive blue (RB-19) dyes via adsorption onto nonliving white rot fungal biomass Phanerochaete chrysosporium under different operational conditions. It was found that P. chrysosporium removed more of RB-19 than RB-198. The conditions of pH 3, temperature 50 °C, adsorbent dosage 0.6 g, particle sizes of adsorbent (0.25 mm), and contact time (30 min) were optimum for removal of the dyes. RR-198 and RB-19 were removed with levels of 78.4% and 86.4%, respectively at pH 3; 79.6% and 90.0%, respectively using 0.6 g of adsorbent dosage; 82.0% and 87.0%, respectively at 30 min; and 82.0% and 87.2%, respectively at 50 °C. Thus, dead P. chrysosporium biomass was shown to be a biosorbent for the uptake of RB-19 and RR-198 dyes.

Donor–π bridge-acceptor dyes featuring dual chromophoric groups for enhanced sensitivity in wearable sweat sensor

The pH value of human sweat serves as a crucial biomarker for disease diagnosis, rendering wearable sweat sensors an innovative tool for monitoring human health. However, the commercialization of these devices is seriously impeded by their low sensitivity, poor wearing comfort, and limited reusability. In this work, a reactive dye capable of color change under pH change has been synthesized. Due to the unique molecular structure, the dye molecule exhibits remarkable color change recognition and high sensitivity. To fabricate a wearable pH sensor, screen printing technology was employed for depositing the color-changing dye onto cotton fabric. The resulting sensor demonstrated excellent performance attributes including high color sensitivity, robust cyclic stability in response to pH changes, and exceptional resistance against washing, friction, and sunlight-induced fading. Therefore, this study presents a highly promising approach for achieving real-time monitoring of human sweat pH levels.

Preparation of grafted starch‐based cationic flocculants and its removal of reactive and disperse dyes

AbstractIn this paper, a starch‐based flocculant (ADSt) with medium and low temperature solubility and enhanced flocculation effect was synthesized using corn starch, acrylamide, and dimethyldiallyl ammonium chloride as main materials by the ethanol‐alkali method and grafting method. The main mechanism of ADSt's flocculation was electrical neutralization and bridging. The flocculation performance of ADSt was verified by using it along with polymeric aluminum chloride (PAC) as coagulant/flocculant, dispersible dye (dispersible yellow RGFL), and reactive dye (active trimeric blue KN‐G) to simulate dye wastewater. For the dispersed yellow water sample and active emerald blue water sample, the dosage of PAC was 40 and 35 mg/L respectively. When the dosage of ADSt was 10 mg/L with a dye content of 100 mg/L, the decolorization rates for both dyes reached up to 96.2% and 94.4% respectively. The properties of the flocs such as size and two‐dimensional fractal structure were described. The prepared ADSt maintained a good flocculation effect in the pH range of 5–9 due to its excellent water solubility achieved through the ethanol‐alkali preparation process, where its solubility reached 86.7% at 30°C. Overall, the preparation process for ADSt is simple, cost‐effective, while providing an effective solution for treating printing and dyeing wastewater.

Energy band gap tuning of Ba-Ca hexagonal ferrite by Dy3+ ion substitution (0 ≤ x ≤ 0.2) to improve spectral, structural, dielectric and photocatalytic properties

In the present study, Dy3+ substituted M-type Ba0.5Ca0.5DyxFe12-xO19 (0.00 ≤ x ≤ 0.20) hexagonal ferrites were synthesized using sol-gel auto-combustion method with lemon extract as a fuel. The single hexaferrite phase with space group P63/mmc is revealed by the X-ray powder diffraction (XRD) patterns. The Field emission scanning electron microscopy (FESEM) exhibits the agglomeration of nanoplates with vacancies at some places. Energy dispersive X-ray photoelectron spectroscopy (EDAX) mapping confirmed the presence of Ba, Ca, Fe, O, and Dy in the hexaferrite. Fourier Transform Infrared (FTIR) spectroscopy exhibits two characteristic bands at 579 and 429 cm−1 corresponding to tetrahedral and octahedral metal ions-oxygen stretching, revealing the occurrence of the ferrite phase. The optical energy band gap calculated using the Tauc plots was found to increase with the increase in dysprosium substitution to fall within the range of 2.8–3.5 eV. The Raman spectra confirmed the Raman vibration modes and M-type structures of hexagonal ferrites (HFs). The dielectric constant values drop rapidly with increasing frequency up to a few KHz and then gradually for the further higher frequencies. The occurrence of Ba and Ca with 2+, while Dy, and Fe with 3+ oxidation states is confirmed using X-ray photoelectron spectroscopy (XPS). The HFs exhibit remarkable efficiency by degrading the Reactive Brown dye to 99.3 % in just 15 min, equivalent to a high degradation reaction rate constant (k) value of up to 0.0396 min−1. Consequently, the catalyst shows promising potential for environmental remediation.

Assembly of Eosin Y in-situ intercalated Zr-MOF composite for decontaminating Cr(VI) and reactive dyes via physical capture and photochemical purification

Post-modification based on highly water stable Zr-MOF introduces a novel dimension of functional regulation, offering a fresh perspective for the advancement of pragmatic photocatalysts in the water treatment field. In this study, an entirely novel Zr-MOF (NU-1400-py), featuring a topological network identical to that of NU-1400, has been assembled. The main difference is the replacement of TPTC's central benzene ring with a pyrimidine ring. Utilizing the inherent porosity and semiconducting properties, this Zr-MOF possesses the capability to physically trap Cr2O72- ions (136.43 mg/g), achieving photochemical purification of Cr(VI) and K-, X-, M-type reactive dyes from water. Moreover, another novel heterojunction material EY@Zr-MOF, has been fabricated via in-situ intercalation of luminescent Eosin Y (EY) species within Zr-MOF. Due to the sensitization of embedded EY molecules, EY@Zr-MOF exhibits significantly optimized interface resistance, transient photocurrent intensity and carrier migration efficiency compared to pristine Zr-MOF. Notably, the photochemical purification efficiencies of EY@Zr-MOF towards Cr2O72- (99.66 %, 30 min), RB13 (90.18 %, 120 min), RR2 (92.40 %, 300 min) and RR11 (84.80 %, 90 min) have been dramatically elevated, offering the considerably accelerated reaction kinetics of 1.24, 4.82, 2.48 and 6.23 times, respectively, compared to pristine Zr-MOF, the photochemical purification efficiencies of Zr-MOF towards Cr2O72- (97.88 %, 30 min), RB13 (85.55 %, 450 min), RR2 (71.38 %, 450 min) and RR11 (53.16 %, 240 min). Additionally, its photocatalytic REDOX mechanisms in eliminating target contaminants were proposed tentatively. This contribution offers a viable pathway for designing multi-functional materials aimed at solving some intractable environmental issues caused by Cr(VI) and reactive dyes.

Bio-Adsorbent for Elimination of Reactive Dye from Aqueous Solution: Kinetic and Statistical Modelling Study

Introduction/Background: The use of various dyes to colour products is a general practice in various industries. The occurrence of these dyes in water, even at small concentrations, is highly noticeable and aesthetically objectionable. In the present study, the applicability of inexpensive and eco-friendly bio-adsorbent has been tested as an alternative substitution of the commercially available activated carbon for the removal of reactive dye from the aqueous solution. Materials and Methods: Bio-adsorbent prepared from pomegranate peel was successfully used to remove the reactive dye (Reactive Black 5) from the aqueous solution. The effects of major parameters such as pH, adsorbent dosage, and contact time on dye removal efficiency were studied. Statistical models were articulated based on selected variables to optimize the decolourisation efficiency of the adsorption process using a full factorial central composite design. Results: Dye removal efficiency of close to 100% was observed at a pH 12 using 1 g adsorbent/ 200 mL dye solution within a contact time of 60 min., yielding a virtually colourless solution. A fixed-bed column study with an initial dye concentration of 100 mg/L at bed depths of 4 cm, 8 cm, and 12 cm yielded a breakthrough time of 300 min, 570 min, and 780 min, respectively. Discussion: Langmuir, Freundlich, and Temkin isotherm models were applied to analyze the sorption equilibrium parameters. The experimental results of the analysis revealed that the Langmuir isotherm fits better than the other isotherms with a linear regression coefficient (R2) of 0.99. The high correlation coefficient (R² &gt; 0.95) and low p-values (&lt; 0.0001) indicate that the model and its terms are significant, making it effective for optimizing operational parameters and accurately predicting the response. Conclusion: The breakthrough curve serves as a tool to evaluate the effectiveness of the prepared adsorbent in real-world applications. The present work not only provides an alternative to commercially available activated carbon for dye wastewater colour removal but also emphasizes the importance of repurposing fruit residues, which could otherwise become environmental pollutants if improperly disposed of.

Synthesis of Montmorillonite-Silica Nanocomposite Using Millet Husk and Montmorillonite Clay and Optimization of Adsorption Parameters for Congo Red Dye Adsorption

Dyes are substances that, when applied to a substrate provides color by a process that alters, at least temporarily, any crystal structure of the colored substances The discharge of these effluents into the receiving environments results in hazardous health problems as most of these dyes have carcinogenic effects on the living organisms. Generally, dyes are classified into three categories: a) anionic: direct, acid, and reactive dyes; b) cationic: basic dyes; and c) non-ionic: disperse dyes. The chromophores in anionic and non-ionic dyes mostly consist of azo groups or anthraquinone types. However, Congo red, are difficult to biodegrade due to their complex aromatic structures, which provide them with physico-chemical, thermal, and optical stability. This study is aimed at synthesizing Montmorillonite-silica nanocomposite, a cost effective adsorbent from millet husk and Montmorillonite-clay with the determination of its optimum adsorption parameters for Congo Red Dye adsorption. Here, synthesis of Montmorillonite-silica nanocomposite and optimization parameters were carried out using standard procedures. The unbiased result demonstrated that the percentage yield was found to be 94.51 %. The optimum adsorption parameters studied were adsorbent dose, adsorbate concentration, pH and Kinetics studies. The optimum adsorption parameters were found to be 8.0 g/L, 2.0 mg/L, 8 and 30 minutes, respectively. Hence, the synthesized Montmorillonite-silica nanocomposite obtained from montmorillonite clay and millet husk ash can serve as a cost-effective adsorbent for the removal of Congo Red Dye from waste waters.

Limonene biosolvent-based non-aqueous dyeing medium for salt-free and alkali-free rhamnolipid (RL) biosurfactant reverse micellar dyeing of cotton fabric with reactive dyes

The feasibility of using different forms of limonene biosolvents as dyeing medium in rhamnolipid (RL) biosurfactant-based reverse micellar dyeing system for cotton fabrics is investigated, with different dyeing profiles. Experimental results reveal that limonene-dyed fabrics can achieve generally higher colour yield than water-dyed fabrics while samples dyed by one-step dyeing method could obtain higher colour yield, but poorer relative unlevelness index (RUI) values when compared with samples dyed by two-step method. The CIE L*a*b* value and reflectance of water-dyed and limonene-dyed samples were examined. The pH value of aqueous and non-aqueous dye liquor was measured. SEM images of limonene-dyed cotton fabrics and TEM images of reverse micelle morphology were evaluated. Washing and crocking fastness of the dyed samples were also assessed. The resulting evidence validate that limonene is feasible for reverse micellar reactive dyeing of cotton fabric with the use of RL biosurfactant and it can be one of the alternative solvents, making the dyeing process more natural, more biodegradable and environmentally more sustainable.

Cotton Fabric Coating by Cationic Starches to Aim for Salt‐Free Reactive Dyeing

AbstractCationic starch (CatS) coating of cellulose fabrics enables salt‐free reactive dyeing. However, the relation of the degree of substitution and CatS concentration in the dyeing procedure are open issues. Accordingly, three cationic starches of increasing degree of substitution were used at different concentrations for the coating of cotton fabrics. Fabrics were evaluated for stiffness, dye uptake, dye exhaustion, wash fastness and nitrogen content.With an increasing degree of substitution coating solutions become more viscous, resulting in increased wet pick‐up and less stiff coated fabrics. These fabrics show increasing dye absorption and color generation. Due to the molecular size of the cationic starch, yarn/fiber ring dyeing is supposed present. Specifically, color generation can be adjusted by initial cationic starch coating concentration. Above 5 % CatS concentration ceases to have an increasing coloration effect. Pre‐treating a cellulose fabric with approximately 2.2 % CatS (Ds=0.7) enables similar coloration to a standard reactive dyeing protocol. Light fastness is reduced by 1–1.5 compared to salt‐based reactive dyeing. Rub fastness decreases by 1–2 only for higher substituted cationic starches (Ds=0.7). Nitrogen analysis reveals that a share of the CatS elutes off the fabrics into the dye bath.

Salt-free neutral dyeing of cotton fiber with monochlorotriazine type reactive dyes

In this paper, we present the modification of cotton with glycidyltrimethylammonium chloride (GTA), demonstrating its capability not only for salt-free dye adsorption but also for achieving fixation reactions with monochlorotriazine-type reactive dyes under neutral conditions. The results of adsorption kinetics and isotherm experiments indicate that the adsorption of reactive dyes by modified cotton is chemisorption. Color-stripping experiments conducted on modified cotton dyed with different dyes revealed that GTA-modified cotton underwent fixation reactions with monochlorotriazine-type reactive dyes under neutral conditions. The reaction sites of modified cotton with reactive dyes were determined by measuring the 1H NMR of the model reaction products. Mechanism investigation using Density Functional Theory (DFT) on the fixation reaction revealed that the hydroxyl groups on the modification agent chain exhibit a lower pKa value and carry more negative charge, resulting in a lower reaction barrier with monochlorotriazine-type reactive dyes. Our research findings demonstrate that GTA-modified cotton fiber enhance the reactivity of cotton, providing significant guidance for the development of novel modifiers.

One-bath dyeing and antibacterial finishing of cotton fabric using reactive dye and silver chloride: a sustainable approach

One-bath dyeing and antibacterial finishing of cotton fabric using reactive dye as colorant and silver chloride (AgCl) as an antibacterial agent was conducted to streamline the process and enhance its economic efficiency. The effectiveness of the antibacterial agent in reactive dyeing of cotton fabric, was evaluated through exhaust method with 0.5% AgCl and continuous (pad dry cure) method with 5 g/l of AgCl, utilizing various dye concentrations (1%, 3%, 5% for exhaust; 1g/l, 3g/l, 5g/l for pad dry cure) according to a standard reactive dye recipe. Characterization of the one-bath dyed, and antibacterial finished cotton fabric was performed using K/S values to determine the optimal dye shade concentration and antibacterial activity was evaluated using agar diffusion method. It was observed that the exhaust method revealed an optimum dye concentration at (AgCl 0.5% and dye 5%), while pad dry cure method showedoptimal dye concentration at (AgCl 5g/l and dye 5g/l). Antibacterial tests were conducted on the optimal specimens from both methods (AgCl 0.5%, 0.2%, dye 0.5% for exhaust; dye 5g/l, AgCl 5g/l, 2g/l for pad dry cure), showcasing resistance against bacterial growth. While inhibition zones were observed on treated specimens of the exhaust method, whereas the treated specimens of the pad dry cure method exhibited complete resistance to bacterial growth around the specimen.

Spent Tea Leaves as an Adsorbent Material: Preparation, Characterization, and Application

The adsorption of Congo Red (CR) on the surface of Spent Tea Leaves (STL) was evaluated in an aqueous system. The study was carried out for the establishment of a standard wastewater treatment method that would remove reactive dyes by employing spent tea leaves as a bio-adsorbent. The effect of various parameters like amount of adsorbent, contact time, concentration of dye, and pH on the adsorption was studied. The adsorption capacity was monitored with a UV-visible spectrophotometer. The maximum adsorption of dye was observed at adsorbent mass of 3.5g /100 mL, at 8×10-5 M CR concentration, at pH = 9.72 and 50 minutes of contact time. The experimental results suggest that the adsorption of CR on the surface of STL is an exothermic process. The adsorption of CR on STL is found to follow pseudo first order kinetics. Based on the findings, it’s feasible to draw the conclusion that spent tea leaves would be a better adsorbent for the removal of reactive dyes from the wastewater.