Conventional Dyes Research Articles

Rapid Degradation Of Dye Effluents With A SnS Catalyst: A Sustainable Approach Using Natural Light Under Ambient Conditions.

Dye degradation presents a persistent challenge in addressing water pollution. While several methods, including adsorption, biodegradation, and advanced oxidation processes, have been extensively explored, photocatalysis remains one of the most effective techniques. Conventional photocatalytic dye degradation processes often rely on expensive light sources and are time-intensive. Herein, we synthesized a SnS catalyst using solvated metal atom dispersion (SMAD) method, using Sn foil and sulfur powder. The catalyst exhibited remarkable performance, achieving complete degradation of methylene blue within 2 minutes under ambient room light, without the need for any external light source. Similar degradation efficiency was achieved for methyl orange. To evaluate the role of light for the degradation, control experiments were conducted in the dark using methylene blue as a model dye. Although the degradation rate was slightly reduced, the catalyst still facilitated dye degradation in the absence of light. Additionally, the catalytic performance was tested with four other dyes under natural light, all of which yielded promising results, demonstrating the versatility and effectiveness of the SnS catalyst in dye degradation. This work highlights the potential of the SnS catalyst for efficient and rapid dye degradation under both light and dark conditions, offering an energy-efficient solution for wastewater treatment.

The Environmental Impact of Low-Pressure Anhydrous Dyeing Technology for Polyester: Carbon Footprint Quantification and Evaluation

Many emerging dyeing technologies have recently entered laboratory research or industrial production phases. However, only a few studies have evaluated and compared the environmental impact of different dyeing systems. This study calculated the carbon footprint of low-pressure anhydrous dyeing for polyester and compared with conventional water bath dyeing. The results showed that the carbon footprint of the anhydrous dyeing process was 1670 kgCO2 eq/1000 kg polyester. Steam occupied the most significant proportion, accounting for 55.5%, followed by electricity at 35.5%. The waste has the lowest environmental impact, with 0.55%. Uncertainty analyses showed that the data and results in this article were reliable. The results of the sensitivity analyses indicated that more attention should be paid to the data quality of steam and electricity. Compared with the traditional water bath dyeing process, the low-pressure anhydrous dyeing system can reduce greenhouse gas emissions by more than 30% and, more importantly, can avoid almost all the consumption of clean water. This anhydrous dyeing system can save water and reduce carbon emissions, which is of positive significance to the sustainable development of the textile and fashion industry. Further studies could use the water footprint as an indicator to evaluate this dyeing system in terms of water consumption and potential environmental impact.

Dyeing kinetics and thermodynamics of mono-chlorotriazine reactive dye in recycled wastewater

Purpose This study aims to elucidate the dyeing kinetics and thermodynamic relationships of CI Reactive Red 24 (RR24) on cotton fabrics, achieve the recycling of inorganic salts and water resources and obtain comprehensive data on color parameters, fastness and other characteristics of fabrics dyed with the recycled dyeing residual wastewater. Design/methodology/approach The dyeing wastewater obtained through advanced oxidation technology was used as a medium for dyeing cotton fabrics with RR24. The absorbance value of the dyeing residue served as an evaluation index, and the relevant kinetic and thermodynamic parameters were calculated based on this absorbance. The color parameters and fastness of the fabric samples were measured to compare the performance of different dyeing media. Findings Dyeing cotton with RR24 in both media follows pseudo-second-order kinetics. When dyeing with wastewater media, the dye adsorption in the first 45 min increased by 0.082–1.29 g/kg compared with conventional dyeing. Furthermore, the half-dyeing time was shortened by 4.19–11.99 min and the equilibrium adsorption amount was reduced by 0.277–0.302 g/kg. The adsorption of RR24 on cotton fabrics conformed to the Freundlich model. Fabrics dyed using recycled wastewater exhibit a deeper color, with reduced red light and enhanced blue light, resulting in an overall deeper apparent color. Originality/value These dyeing kinetics and thermodynamic properties are beneficial for comprehending and interpreting the dyeing performance and behavior of reactive dyes in dyeing wastewater. They lay a theoretical foundation for the treatment and recycling of dyeing wastewater.

Mercerisation Followed by Wet on Wet Reactive Dyeing of Cotton Fabric

The commonly employed textile wet processing methods are singeing, de-sizing, scouring, bleaching, mercerising, dying, printing, and finishing. However, these methods are more time-consuming and require a lot of energy, manpower, and chemicals. Therefore, this research aims to develop a semi-continuous processing route that minimizes these problems. In this study, two dying routes were employed. The first is a control group, which was done by conventional mercerisation and dyeing procedures, whereas the second is a semi-continuous experimental group, which has been employed by mercerisation followed by wet-on-wet (WOW) reactive dying. That is, after mercerisation, the fabric, which contains the optimum alkali concentration, goes to dyeing without washing. Washing and titration were performed to determine the optimum alkaline concentration in the fabric at a specific washing cycle. Fabrics that were washed at different cycles after mercerisation were dyed, and their washing fastness, degree of dye exhaustion, fixation, and colour strength were evaluated, and they had a slightly greater colour strength than conventionally dyed fabrics. This is because with a wet-on-wet dyeing procedure, the fabric is relaxed after mercerisation, which allows it to absorb more dye, and the leftover alkali in the fabric is used to fix the dye to the cellulose. The study shows that the optimal washing cycle for passing the optimum alkali concentration is one. Furthermore, the optimal amount of alkali remaining in the fabrics is 3–3.5%. As compared to the conventional dyeing process, this process is economical.

Unveiling the Influence of Brightness Heterogeneity in Fluorescence Correlation Spectroscopy of Perovskite Nanocrystals.

Nanoparticles (NPs), including perovskite nanocrystals (PNCs) with single photon purity, present challenges in fluorescence correlation spectroscopy (FCS) studies due to their distinct photoluminescence (PL) behaviors. In particular, the zero-time correlation amplitude [g2(0)] and the associated diffusion timescale (τD) of their FCS curves show substantial dependency on pump intensity (IP). Optical saturation inadequately explains the origin of this FCS phenomenon in NPs, thus setting them apart from conventional dye molecules, which do not manifest such behavior. This observation is apparently attributed to either photo-brightening or optical trapping, both lead to increased NP occupancy (N) in the excitation volume, consequently reducing the g2(0) amplitude [since g2(0) α 1/N] at high IP. However, an advanced FCS study utilizing alternating laser excitation at two different intensities dismisses such possibilities. Further investigation into single-particle blinking behaviors as a function of IP reveals that the intensity dependence of g2(0) primarily arises from the brightness heterogeneity prevalent in almost all types of NPs. This report delves into the complexities of the photophysical properties of NPs and their adverse impacts on FCS studies.

Carbon quantum dots for the diagnosis and treatment of ophthalmic diseases.

Carbon quantum dots (CQDs), an emerging nanomaterial, are gaining attention in ophthalmological applications due to their distinctive physical, chemical, and biological characteristics. For example, their inherent fluorescent capabilities offer a novel and promising alternative to conventional fluorescent dyes for ocular disease diagnostics. Furthermore, because of the excellent biocompatibility and minimal cytotoxicity, CQDs are well-suited for therapeutic applications. In addition, functionalized CQDs can effectively deliver drugs to the posterior part of the eyeball to inhibit neovascularization. This review details the use of CQDs in the management of ophthalmic diseases, including various retinal diseases, and ocular infections. While still in its initial phases within ophthalmology, the significant potential of CQDs for diagnosing and treating eye conditions is evident.

Investigate the utilization of novel natural photosensitizers for the performance of dye-sensitized solar cells (DSSCs)

Dye-sensitized solar cells (DSSCs) offer a promising route for sustainable energy conversion, with natural photosensitizers emerging as attractive alternatives to conventional synthetic dyes due to their abundant resources, cost-effectiveness, and eco-friendly materials. However, the efficiency of DSSC utilizing natural photosensitizer remains low. In this study, we investigate the utilization of novel natural photosensitizers extracted from gambier leaves, gambier branches, cinnamon, and petiole of tectona leaves, which contain flavonoids/tannins, chlorophyll, and anthocyanins, aiming to achieve high-performance DSSCs. Five different solvents—ethanol, isopropanol, distilled water, methanol, and Zamzam water—are explored to optimize the extraction process of the natural dyes. The doctor blade technique is employed to coat TiO2 nanomaterials onto ITO glass substrates. UV–Vis spectrophotometry and FTIR spectroscopy are used to characterize the optical properties and structural composition of the dyes, revealing that flavonoid/tannin groups are the primary compounds responsible for light harvesting. The DSSC performance is evaluated under a 30 W lamp, adjusted to light intensity of 10 mW/cm2. As a result, the DSSCs using gambier leaf extract as photosensitizer demonstrate the highest recorded efficiency of 4.71 %, with a Jsc of 2.95 mAcm−2 and a Voc of 0.64 V. These findings contribute to advancing DSSC technology by leveraging the potential of natural photosensitizers for sustainable energy conversion applications.

Construction of “ant-like tentacle” structure for ultra-sensitive detection of low-concentration ammonia through colorimetric fluorescent dual-signal gas-sensitive cotton fabric

Detection and monitoring of ammonia (NH3) are crucial in various industries, including plant safety management, food freshness testing, and water pollution control. Nevertheless, creating portable, low-cost, highly sensitive, and easily regenerated ppm-level NH3 sensors poses a significant challenge. In this investigation, an innovative “ant-like tentacle” fabrication strategy was proposed, and a colorimetric fluorescent dual-signal gas-sensitive cotton fabric (PAH-fabric) for NH3 detection was successfully prepared by conventional dyeing using suitable molecular-level photoacid (PAH) sensitive units. The visual recognition lower detection limit of the ultra-low is 1.09 ppm-level. PAH-fabric is not only straightforward, convenient, and cost-effective to prepare, but it can also be efficiently regenerated and recycled multiple times (maintaining excellent gas-sensitive performance even after 100 cycles) by strategically leveraging volatile acid fumigation. Detailed molecular reaction mechanisms involved in the NH3 response and PAH-fabric regeneration are elucidated. PAH-fabric, available either as a portable kit or an alarm system, offers a promising approach for ultra-low NH3 detection. The demonstrated “ant-like tentacle” fabrication strategy introduces numerous possibilities for designing and developing sensors with adjustable response thresholds, particularly those requiring high sensitivity.

Nitrogen-Doped Carbon Dots: A New Powerful Fluorescent Dye with Substantial Effect on Bacterial Cell Labeling.

Carbon dots (CDs)-minute carbon nanoparticles with remarkable luminescent properties, photostability, and low toxicity-show potential for various applications. CDs synthesized using citric acid and urea are the least toxic to biological environments. Here, we aimed to explore the effect of CDs synthesized using citric acid and urea at 50, 33, and 25% (CDs 1/1, 1/2, and 1/3, respectively) weight ratios in a microwave on bacterial cell fluorescence sensing and labeling. The nanoscale properties of CDs were investigated via transmission electron microscopy and dynamic light scattering particle size analysis. X-ray powder diffraction confirmed the graphitic structures of CDs. X-ray photoelectron spectroscopy revealed that the nitrogen content increased gradually with increasing urea ratios, indicating functional group changes. Transient photoluminescence decay periods demonstrated superior fluorescence intensity of CDs 1/3 under blue, green, and red lights. The use of CDs was notably more efficient than traditional methods in staining bacterial cells. Fluorescence microscopy of 10 g-positive and 10 g-negative bacteria revealed enhanced staining of Gram-positive strains, with CDs 1/3 presenting the best results. The CDs exhibited excellent photostability, maintaining poststaining fluorescence for 100 min, surpassing the performance of conventional dyes. CDs could serve as potential fluorescent dyes for the rapid discrimination of Gram-positive and Gram-negative bacteria.

Enzymatic coloration of wool fabrics and its comparison with conventional dyeing

Enzymatic coloration of wool fabrics and its comparison with conventional dyeing

Nylon dyeing with reactive dyes by intermittent exposure to microwave irradiations to improve leveling

Purpose Reactive dyes are believed to have great potential for nylon dyeing, but these anionic dyes tend to rush toward the nylon at the beginning of the process, resulting in uneven dyeing. Achieving uniformity gets even harder when the dyeing is performed under exposure to eco-friendly technique microwave irradiations. This study aims to achieve rapid and homogenous results by intermittent shaking and non-continuous exposure to microwave. Design/methodology/approach A set of reactive red dyes, based on the same chromophore and different substituents in the auxochrome part, was applied to the nylon fabric without any leveling agent. A series of experiments were designed to investigate the effect of different dye structures, exhaustion pH, liquor ratio, exhaustion time and fixation time to obtain an optimum recipe under the microwave dyeing technique. Findings Dyeing performance was characterized based on the color strength, exhaustion and fixation percentages and color fastness values. The characterization showed that better results can be achieved at a liquor ratio of 1:15 at exhaustion pH 2.7 which is also the isoelectric point of nylon, with 5.5 to 7 min of exhaustion and 6 to 8 min of fixation time for different dyes. Microwave dyed samples secured higher color strength values and provided better exhaustion and fixation than the conventional dye samples. Furthermore, the X-ray diffraction results verified that there was no considerable difference in the morphological structure of nylon with microwave exposure. Originality/value An applied technique is disclosed in this work to achieve uniform dyeing on nylon 66 with reactive dyes without any leveling agent under exposure to eco-friendly rapid heating microwave irradiations.

Early Detection and Noninvasive Staging of Kidney Dysfunction by a PEGylated Conventional Fluorophore via GFR-Sensitive Renal Transport.

Noninvasive fluorescence imaging of renal function is a valuable technique for understanding kidney disease progression and the development of renal medicine. This technique requires sensitive imaging probes for reporting renal dysfunction accurately at early stage. Herein, a molecularly engineered imaging probe (800CW-PEG45-COOH) was synthesized by simply PEGylating conventional near-infrared fluorophore IRDye800CW with NH2-PEG45-COOH (molecular weight ∼2100 Da) for early detection and staging of renal dysfunction through noninvasive real-time kidney imaging. 800CW-PEG45-COOH not only cleared through the kidney efficiently (>90% injection dosage at 24 h postinjection) but was also found to be freely filtered by glomeruli without renal tubular reabsorption and secretion. Despite this simple construction strategy, the transport of 800CW-PEG45-COOH within the kidneys was extremely sensitive to the alteration of the glomerular filtration rate (GFR), which enabled it to detect renal dysfunction much earlier than commonly used serum biomarkers and stage kidney function impairments (mild vs severe dysfunction) via imaging-based kidney clearance kinetics. This work not only provides a promising optical imaging probe for the noninvasive evaluation of kidney function but also highlights the utility of PEGylation in enhancing the performance of conventional organic dyes in biomedical applications.

An ultrasensitive fluorescence sensing platform for HCV detection based on the T7 isothermal amplification combined with aggregation-induced emission luminogens strategy

Hepatitis C virus infection constitutes a significant global public health concern. Fluorescence technique (FL) is a promising biosensor, however, many conventional dyes exhibit reduced fluorescence or no emission at high concentrations. To break through this shackle, an ultrasensitive AIE-based (aggregation-induced emission) FL sensing platform was developed for HCV detection by using the FLRNAs-based T7 isothermal transcription amplification RNA diagnosis combined with AIE luminogens (FTAR) strategy. In the FTAR strategy, the T7 transcription amplification process was responsible for the recognition of the target HCV and produced Pepper aptamer, which could form aggregates of nanoparticles with the HBC, an AIEgen, to produce high-intensity FL. The multi-integrated signal amplification strategy led to ultrasensitivity. Moreover, under the optimal experimental conditions, HCV could be assayed in the range of 100aM-100pM. The proposed strategy has been successfully applied in detecting HCV in clinical samples. In summary, this research was the first to utilize aptamer restriction of AIEgens internal rotation to achieve aggregation-induced emission and presented the successful development of a specific, sensitive and rapid FTAR assay for HCV diagnosis. The proposed FTAR platform with facile operation, short analysis time, low-cost as well as excellent quantification ability could provide a promising tool for point-of-care testing (POCT).

Carbon Footprint for Jeans’ Circular Economy Model Using Bagasse

To date, clothing has been produced and disposed of in large quantities. It is also known that each process, from the procurement of raw materials to production, transportation, sales, laundry, and disposal, has a significant environmental impact. According to the Global Fashion Agenda, greenhouse gas (GHG) emissions from the fashion industry account for 4% of the global total. Therefore, apparel makers are shifting from a linear economy to a circular economy. For example, the Japanese start-up Curelabo Co., Ltd. (Okinawa, Japan) developed jeans (bagasse washi jeans) made from bagasse, which is a residual material derived from sugarcane after the extraction of cane juice. Furthermore, the use of improved dyeing reduces boiler fuel consumption and eliminates the need for detergents and acid. For disposal, the used jeans and their production waste are processed into biochar for carbon sequestration. In this study, we attempted to calculate GHG emissions using life cycle assessment (LCA) for the circular economy model developed by Curelabo Co., Ltd. GHG emissions from the production of bagasse washi jeans were 1.09 × 101 kg-CO2e. Dyeing, bleaching, and fabric finishing, known as the wet processes, were found to contribute a large proportion of GHG emissions due to their high energy consumption. Furthermore, the entire lifecycle of GHG emissions from bagasse washi jeans, including transport, sales, laundry, and disposal, were 1.53 × 101 kg-CO2e. First, the use of bagasse washi yarn for the weft reduced by 2.99 × 10−1 kg-CO2e compared with the use of conventional 100% bleached cotton yarn. Second, compared with conventional dyeing, GHG emissions from the improved dyeing process were reduced by 2.78 kg-CO2e. Third, the disposal of the used jeans and their production waste into biochar reduced GHG emissions by 9.01 × 10−1 kg-CO2e. Additionally, GHG emissions can be reduced by re-inputting waste in the paper-making process and by using liquefied natural gas as boiler fuel in the dyeing process.

Investigating the optimum conditions for azo dye (methyl orange and methyl red) decolorization from aqueous solution using oyster mushroom (Pleurotus ostreatus): a mycoremediation approach

Since conventional dye removal techniques require a substantial amount of energy and chemicals, this study evaluated the utilization of Pleurotus ostreatus, a species of fungus, in an environmentally beneficial mycoremediation approach to decolorize two azo dyes, methyl orange (MO) and methyl red (MR), in a liquid medium. Pleurotus ostreatus was utilized under standard circumstances in the solutions containing 0.05% (w/v) MO and 0.05% (w/v) MR, without undergoing any genetic modifications. By analyzing the effects of time (6, 12, and 18 days), temperature (15 °C to 40 °C), pH (4 to 7), and inoculum volume (1 to 25 mL) on the decolorization rate of P. ostreatus, the ideal environment for the decolorization of MO and MR was determined. The highest rate of decolorization was evident at 25 °C temperature, pH 7 within 18 days of incubation, P. ostreatus could decolorize 0.05 g MO up to 97% when added in 10 mL inoculum volume on the other hand 0.05 g MR up to 93% in 15 mL inoculum volume at pH 6. Furthermore, the dye uptake rate after 18 days for MO was 59.25% and MR was 53.97% which indicated that P. ostreatus had a better uptake efficiency for MO than MR. Based on its ability to decolorize both MO and MR under suitable circumstances, the study concludes that P. ostreatus offers an appreciable mycoremediation approach for removing dye pigments from industrial wastewater.

Performance enhancement of reactive foam dyeing for cotton fabric through different foaming agents and stabilizers

Purpose In the textile dyeing industry, the foam dyeing has been recognized as a significantly sustainable alternative for the cotton fabrics. However, this efficient technology undergoes the many issues related to the foam generation, foam optimization and the required performance of the resultant fabrics. The purpose of this paper is to address these issues through the development and optimization of the novel reactive foam dyeing recipes for the cotton fabrics. Design/methodology/approach The foam dyeing recipes were generated and optimized using the different stabilizers, foaming agents and three primary colors of reactive dyes. The different recipes were applied onto the cotton fabric using laboratory scale foam coating machine. The performance of the foam coated and padded fabrics was evaluated using different criteria including the shade depth, rubbing fastness, air permeability, washing fastness, perspiration fastness, light fastness and tear strength. Then, a complex decision-making approach, namely, analytic hierarchy process (AHP), was applied for the ranking of the key recipes based on the main criteria. Findings The newly optimized foam dyeing recipes were found very competitive with the conventional pad dyeing process with respect to the shade-depth and the other performance properties. The optimization of foaming parameters and addition of stabilizers have advanced the foam dyeing process, which would accelerate the implementation of foam dyeing methods in the textile industry. Furthermore, significant water and energy savings would be achieved as compared to the conventional foam dyeing. AHP model offered a comprehensive and rational way to identify the most important recipes amongst the selected recipes. Originality/value In this research, novel foam dyeing recipes have been developed for the cotton fabrics through the optimization of the different stabilizers, foaming agents and the three primary colors of reactive dyes. Until now, the exiting literature has not reported the combination of these stabilizers with the different foaming agents and three primary reactive dyes for the improvement of sustainable foam cotton dyeing process.

Solvent-assisted salt-free reactive dyeing of cotton fabric

The objective of this study was to establish a solvent-assisted salt-free dyeing method for cotton fabric utilizing commercially available reactive dyes. In this study, the feasibility of substituting water as the dyeing medium with environmentally friendly solvents, specifically ethanol (EtOH), isopropyl alcohol (IPA), and propanol (PrOH), was investigated. Eight commercial reactive dyes, each possessing distinct chemical structures, were examined with various dyeing characteristics including exhaustion, fixation, and fastness properties, in the presence of various alcohols. However, solvent-assisted dyeing exhibited comparable or enhanced color strength (K/S) values, exhaustion, and fixation rates compared to conventional aqueous dyeing. For instance, the RR35 dye demonstrated a substantial increase in K/S values with PrOH, EtOH, and IPA, ranging from 115 to 369% improvement. The substitution of alcohol for water did not affect the wash, rub, and light-color fastness properties, as these properties remained consistently excellent. Solvent-assisted salt-free dyeing of cotton fabrics offers a promising solution to address the environmental impacts of traditional water-based dyeing methods by eliminating the requirement for water and salt. Overall, this study presents a solvent-assisted salt-free dyeing technique and contributes to the field by offering detailed insights into its mechanisms and performance. Our research has the potential to reduce water consumption, eliminate salt usage, and mitigate environmental pollution.

User-Friendly Multifunctional Red-Emissive Carbon Dots for Rapid Cell Nucleus Staining via Targeting Nuclear Proteins.

Cytoarchitectural staining is of great importance in disease diagnosis and cell biology research. This study developed user-friendly multifunctional red-emissive carbon dots (R-CDs) for rapid cell nucleus staining via targeting nuclear proteins. R-CDs, simply prepared by electrochemical treatment of 1,2,4-benzenetriamine, exhibit strong emission at 635 nm when excited at 507 nm. The R-CDs can rapidly stain the nucleus of human SH-SY5Y, HepG2, and HUH-7 cells with a high signal-to-noise ratio owing to fluorescence enhancement after entering the nucleus. Compared to conventional cytosolic dyes such as Hoechst and DAPI, R-CDs are cheaper, more highly dispersed in water, and more stable (requiring no stringent storage conditions). The R-CDs show stable optical properties with insignificant photobleaching over 7 days and salt resistance up to 2 M of NaCl. More importantly, R-CDs, possessing a positive charge, allow rapid staining of live cells (3 min) and dead cells (10 s) in saline. According to kinetic variation, R-CDs can distinguish live cells from dead cells. Staining exhibits high efficiency in onion epidermal cells, Aspergillus niger, Caenorhabditis elegans, and human spermatozoa. The mechanism for efficient staining is based on their fast accumulation in the nucleus due to their small size and positive charge and strong interaction with nuclear proteins at amino acid residues of histidine and arginine, resulting in fluorescence enhancement by dozens of times. The developed R-CDs do not bind to DNA and would not cause genetic damage and will find various safe applications in biological and medical fields.

Waterless Dyeing of Polyamide 6.6.

Waterless dyeing of polyamide 6.6 using scCO2 (supercritical carbon dioxide) was investigated. PA (polyamide) fibers can be dyed with various dyes, including disperse dyes. The conventional aqueous dyeing process uses large amounts of water and produces polluted water. Considering these environmental issues, waterless dyeing of fibers is a forefront issue, and utilization of supercritical carbon dioxide (scCO2) is a commercially viable technology for waterless dyeing. This study tested PA6.6 (polyamide 6.6) dyeing in scCO2 at 100 °C 220 bar pressure for 45 min. Color measurements and color fastness tests were performed, as well as tensile strength, scanning electron microscope (SEM) analysis, and Fourier transform infrared spectroscopy (FTIR) analysis. PA6.6 fabrics yielded higher K/S (color strength, the Kubelka-Munk equation) values with larger molecular weight dye and almost the same color strength with medium and small-sized dyes, demonstrating the ability of dyeing in a supercritical environment without water as a more environmentally friendly dyeing option compared to conventional dyeing.

Cleaner reactive dyeing with the recycled dyeing wastewater

In order to recycle water and inorganic salts, sodium persulphate (SPS) was used to degrade the C.I. Reactive Red 195 (RR195) dyeing wastewater. The thermodynamic and kinetic relationships of RR195 dyeing in cleaner and conventional dyeing processes were analyzed and compared. The feasibility of the one-bath cyclic dyeing in the recycled dyeing wastewater was confirmed through the properties of dye utilization, color parameters and energy conservation. The appropriate conditions were 0.3 g/L of SPS and treatment at 95 °C for 30 min, which resulted in a decolorization rate of 99.7% for the dyeing wastewater, mainly due to the action of radical sulfate. When cotton fabric was dyed with the cleaner dyeing, the kinetic was pseudo-second-order and the thermodynamic was Freundlich adsorption. There was a 47.5% reduction in half dyeing time, a greater diffusion coefficient and standard affinity, and lower entropy and enthalpy values when dyeing in reused wastewater. Cotton fabrics were dyed with the proposed cleaner dyeing process, which reduced the amount of water and inorganic salt by 95.8% and 89.8%, respectively. The total organic carbon (TOC), biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) were 53.6%, 69.8% and 42.6% lower than the conventional dyeing process, respectively. The recommended technology not only reduces the amount of dyeing wastewater but also enables the recycling of inorganic salts and water, which makes great progress in the textile industry.