The influence of caustic mercerization (CM) and liquid ammonia (LA) treatments on the properties of reactively dyed cotton fabrics were schematically studied. The cotton fabrics were dyed using different commercial reactive dyes such as Reactive Red 2 (R2), Reactive Blue 21 (B21), and Reactive Orange 5 (O5) via industrial dyeing procedures. The dyed fabrics were then treated using 260 g·L−1 of caustic soda solution at 23 °C for 180 s and pure LA at −40 °C for 3 min in slack and tension conditions. The dyeing properties of the fabrics such as dye removal percentage, color strength, color uniformity, reflectance, and fastness properties (washing, rubbing, hot pressing and light) were examined. The changes in tensile strength, elongation, bending property, decomposition temperature, crystal structure, and surface morphology of the samples were also investigated using a tensile strength tester, thermogravimetric analyzer (TGA), scanning electron microscope (SEM), and an X-ray diffractometer (XRD). Results revealed that the fabric dyed with O5 showed the best stability in CM and LA treatment, and the color strength and color uniformity of the dyed fabrics increased extensively after both treatments, while the reflectance of the fabrics decreased. The washing and rubbing fastness of the fabrics were also improved, which was mainly attributed to the diffusion of the dye molecules inside the fibers and enhanced bonding between fiber and dye molecules. The fastness to hot pressing and light was unaffected and all the samples retained fastness rating between 4 and 5 after being post-treated with the CM and LA, respectively. The tensile strength of the fabrics improved from 287 to 291 and 301 N, and the elongation at break increased from 11 to 21.5 and 26% after CM and LA treatment in slack conditions, respectively. Additionally, the tensile strength of the fabrics improved from 287 to 312 and 330 N, and the elongation at break increased from 11 to 12% after applying tension during both treatments. However, the total bending length and total flexural rigidity of the samples slightly increased after both the treatments either treated with or without tension, which was mainly attributed to the orientation of the cellulose microfibril angle along the fiber axis. The surface morphology and X-ray diffraction examination revealed that the treated samples consisted of smooth rod-like structure and the cellulose I allomorph was converted to cellulose II and cellulose III after CM and LA treatments. This developed treatment method could have application potential within the textile wet-processing industry, as it could be used to improve the dyeing properties and mechanical properties of cotton fabrics.

Post-treatment of reactive dyed cotton fabrics by caustic mercerization and liquid ammonia treatment

Clothing, one of the basic needs, demands the growth of textile industries worldwide, resulting in higher consumption and pollution of water. Consequently, it requires extensive treatment of textile effluent for environmental protection as well as reuse purposes. Primary treatment, secondary treatment, and tertiary treatment are the three major phases of textile wastewater treatment. Secondary treatment under aerobic and anaerobic circumstances is carried out to decrease BOD, COD, phenol, residual oil, and color, whereas primary treatment is utilized to remove suspended particles, oil, grease, and gritty materials. However, biological treatment is not fully capable of treating water according to discharge/reuse standards. Hence, tertiary treatment is used to remove final contaminants from the wastewater. Adsorption is regarded as one of the most feasible processes for dye and metal removal in consideration of cost and variation in the adsorbent. Though membrane filtration is an efficient process, the cost of operation limits its application. It’s unfortunate that there isn’t a universally applicable treatment solution for textile effluents. Therefore, the only flexible strategy is to combine several therapy modalities. Treatment of complicated, high-strength textile wastewater depending on pollutant load will be more successful if physical, chemical, and biological approaches are used in tandem. Enforcement of stringent environmental regulation policies, increasing costs and demand for freshwater, and the rising costs and difficulties associated with wastewater disposal are accelerating efforts toward achieving ZLD. Additionally, research into methods for extracting useful materials from wastewater has blossomed in recent years. As such, the purpose of this analysis is to give a holistic overview of textile wastewater treatment systems, with a focus on zero liquid discharge (ZLD) and efficient resource recovery, both of which may hasten the transition to more sustainable water management.

/pdf/a-comprehensive-review-on-the-sustainable-treatment-of-2w6s9y0l.pdf

A Comprehensive Review on the Sustainable Treatment of Textile Wastewater: Zero Liquid Discharge and Resource Recovery Perspectives

The conventional dyeing process requires a substantial amount of auxiliaries and water, which leaches hazardous colored effluents to the environment. Herein, a newly developed sustainable spray dyeing system has been proposed for cotton fabric in the presence of reactive dyes, which has the potential to minimize the textile dyeing industries environmental impact in terms of water consumption and save significant energy. The results suggest that fresh dye solution can be mixed with an alkali solution before spray dyeing to avoid the reactive dye hydrolysis phenomenon. After that, drying at 60-100 °C, wet fixation treating for 1-6 min, and combined treatments (wet fixation + drying) were sequentially investigated and then dye fixation percentages were around 63-65%, 52-70%, and above 80%, respectively. Following this, fixation conditions were optimized using L16 orthogonal designs, including wet fixation time, temperature, dye concentration, and pH with four levels where the "larger-the-better" function was selected to maximize the dye fixation rate. Additionally, the color uniformity and wash and rubbing fastnesses were at an acceptable level when both treatments were applied. Finally, the dyes were hydrolyzed after wet fixation, and the hydrolysis percentages were enhanced after the drying process.

/pdf/combination-of-wet-fixation-and-drying-treatments-to-improve-3w2uftyp82.pdf

Combination of wet fixation and drying treatments to improve dye fixation onto spray-dyed cotton fabric.

Using an environmentally friendly approach for eliminating methylene blue from an aqueous solution, the authors developed a unique electrospun nanofiber membrane made of a combination of polyethersulfone and hydroxypropyl cellulose (PES/HPC). SEM results confirmed the formation of a uniformly sized nanofiber membrane with an ultrathin diameter of 168.5 nm (for PES/HPC) and 261.5 nm (for pristine PES), which can be correlated by observing the absorption peaks in FTIR spectra and their amorphous/crystalline phases in the XRD pattern. Additionally, TGA analysis indicated that the addition of HPC plays a role in modulating their thermal stability. Moreover, the blended nanofiber membrane exhibited better mechanical strength and good hydrophilicity (measured by the contact angle). The highest adsorption capacity was achieved at a neutral pH under room temperature (259.74 mg/g), and the pseudo-second-order model was found to be accurate. In accordance with the Langmuir fitted model and MB adsorption data, it was revealed that the adsorption process occurred in a monolayer form on the membrane surface. The adsorption capacity of the MB was affected by the presence of various concentrations of NaCl (0.1–0.5 M). The satisfactory reusability of the PES/HPC nanofiber membrane was revealed for up to five cycles. According to the mechanism given for the adsorption process, the electrostatic attraction was shown to be the most dominant in increasing the adsorption capacity. Based on these findings, it can be concluded that this unique membrane may be used for wastewater treatment operations with high efficiency and performance.

/pdf/one-step-fabrication-of-novel-polyethersulfone-based-2ewfzmx5.pdf

One-Step Fabrication of Novel Polyethersulfone-Based Composite Electrospun Nanofiber Membranes for Food Industry Wastewater Treatment

The aerial parts of the Argy Worm Wood (AWW) plant have been used in different Chinese foods as a colorant and a taste enhancer for a long time. Despite its application as a food colorant, it has rarely been considered for the coloration of textiles. Keeping in mind the variation in color strength due to the change in phytochemical contents by seasonal change and other variables, the extraction of AWW aerial parts was optimized using the Taguchi method. Optimization was performed on the basis of total phytochemical contents (phenols, flavonoids, and tannins) in the extracted solutions. For this purpose, two different solvent systems, namely sodium hydroxide/water (NaOH/water) and ethanol/water (EtOH/water), were applied through a simple aqueous extraction method at varying levels of solvent concentration, and extraction temperature and duration. Maximum phytochemicals yield of 21.96% was obtained using NaOH/water system with 9 g/L NaOH/water at 85 °C for 20 min and 25.5% with 75% aqueous ethanol at 85 °C for 40 min. Optimized extracts were characterized by UV-Vis and FTIR spectrophotometry, which showed the presence of multiple phytochemicals in the extracts. The dyeing temperature and time were also optimized. Dyed cotton fabrics showed medium to high colorfastness to washing and excellent antibacterial and UV radiation absorption properties. The effect of pre-mordanting with salts of iron and copper was also studied on the color fastness properties. Cotton fabrics dyed with two different solvent system extracts displayed various shades of brown with NaOH/water, and green with aqueous ethanol with and without pre-mordanting. The present study provides the textile industry with a promising source of functional bio-colorant and a value-adding approach for the AWW plant industry.

Extraction of Natural Dye from Aerial Parts of Argy Wormwood Based on Optimized Taguchi Approach and Functional Finishing of Cotton Fabric.

Natural dyes exhibit a low dye uptake when cellulosic fiber dyeing is carried out using a conventional water bath dyeing process. In this research, cotton fabric was exhaust dyed in a microemulsion dyebath containing cacao husk extracts dye and decamethylcyclopentasiloxane (D5) to achieve higher dye exhaustion percentage on cotton fiber, which is an environmentally beneficial dyeing process. The adsorption behavior of cacao husk extract dye in a D5 microemulsion system was investigated under conditions of varied dye mass (1–8% o.w.f), dyeing time (5–500 min), and dyeing temperatures (333–373 K). Kinetic modelling of cacao husk extracts dye/D5 adsorption on cotton fiber was studied by fitting experimental data to pseudo first-order and pseudo second-order kinetics, and the intraparticle diffusion model. Early results indicated that the kinetic model of adsorption of cacao husk extracts dye on cotton fiber followed the pseudo second-order model. Langmuir, Freundlich, and Dubinin–Radushkevich adsorption isotherm models were employed to analyze the adsorption isotherms, and the results showed that the adsorption process fit well with the Langmuir model compared to the Freundlich isotherm. The mean adsorption energy from the Dubinin–Radushkevich isotherm model implied that adsorption of the cacao husk extracts onto cotton was accompanied with a physical process. The values of standard enthalpy (ΔH° > 0), standard entropy (ΔS° > 0), and Gibbs free energy (ΔG° < 0) strongly reflected that the adsorption of the cacao husk extracts onto cotton was thermodynamically favourable and feasible. Thus, waterless dyeing of cotton fabric using a natural dye/D5 system explores a sustainable dyeing technology with higher dye exhaustion percentage.

Xiaojun Yang

Papers

Adsorption, kinetics, and thermodynamic studies of cacao husk extracts in waterless sustainable dyeing of cotton fabric