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This study aims to demonstrate that orange-derived and lemon-derived systems can be used in continuous processes as efficient adsorbents to the entrapment of some anionic and cationic dyes in the textile dyeing wastewater effluents.

Physically and chemically modified orange and lemon mesocarps are used as natural adsorbents for the cationic dyes Basic Blue 3, Basic Yellow 21, Basic Red 18 and Basic Green 4 and the anionic dyes Acid Blue 264, Acid Yellow 49 and Acid Red 337, all commonly used in the textile dyeing industry. Adsorption capacities of the orange-derived and lemon-derived adsorbents on the dyes are studied simulating a batch and continuous industrial processes.

Results demonstrate that treated orange mesocarp (orange-derived adsorbent) can adsorb up to 97% of cationic Basic Green 4 in 30 min, whereas the lemon mesocarp (lemon-derived adsorbent) can retain up to 88% within the same time. In the case of anionic, 91% Acid Blue 264 is adsorbed by the orange mesocarp in 15 min, whereas 92% is adsorbed by the lemon homologue within the same time.

As far as the authors know, physically and chemically modified orange and lemon mesocarps have not been used on the removal of cationic (Basic Blue 3, Basic Yellow 21, Basic Red 18 and Basic Green 4) and anioinic (Acid Blue 264, Acid Yellow 49 and Acid Red 337) dyes of textile dyeing wastewater industry. It is a costless and efficient treatment that supposes, on the one hand, an eco-friendly and feasible process for discolouration of wastewater and, on the other, a valorisation (upcycling) of orange and lemon peels, which are not currently used.

This study’s aim is to introduce a high-performance sorbent for the removal of both anionic (Congo red; CR) and cationic (methylene blue; MB) dyes from aqueous solutions.

Sodium silicate is adopted as a substrate for GO and AgNPs with positive charge are used as modifiers. The synthesized nanocomposite is characterized by FTIR, FESEM, EDS, BET and XRD techniques. Then, some of the most effective parameters on the removal of CR and MB dyes such as solution pH, sorbent dose, adsorption equilibrium time, primary dye concentration and salt effect are optimized using the spectrophotometry technique.

The authors successfully achieved notable maximum adsorption capacities (Qmax) of CR and MB, which were 41.15 and 37.04 mg g⁻¹, respectively. The required equilibrium times for maximum efficiency of the developed sorbent were 10 and 15 min for CR and MB dyes, respectively. Adsorption equilibrium data present a good correlation with Langmuir isotherm, with a correlation coefficient of R2 = 0.9924 for CR and R2 = 0.9904 for MB, and kinetic studies prove that the dye adsorption process follows pseudo second-order models (CR R2 = 0.9986 and MB R2 = 0.9967).

The results showed that the proposed mechanism for the function of the developed sorbent in dye adsorption was based on physical and multilayer adsorption for both dyes onto the active sites of non-homogeneous sorbent.

The as-prepared nano-adsorbent has a high ability to remove both cationic and anionic dyes; moreover, to the high efficiency of the adsorbent, it has been tried to make its synthesis steps as simple as possible using inexpensive and available materials.

The main purpose of this paper is to investigate the adsorption properties of CoFe_1.9Mo_0.1O₄ magnetic nanoparticles (CFMo MNPs) using, anionic dye “congo red (CR)” as a model of water pollutants.

The magnetic nano-adsorbent was synthesized via sol-gel process. Different techniques including; Fourier transform infrared spectroscopy, point of zero charge, scanning electron microscope and X-ray powder diffraction were used to characterize the prepared adsorbent. Adsorption experiments were conducted in batch mode under various conditions (contact time, shaking speed, initial dye concentration, initial solution pH, solution temperature and adsorbent amount) to investigate the adsorption capability of CFMo MNPs for CR.

The results showed that, CFMo MNPs could successfully remove more than 90% of CR dye within 20 min. Adsorption kinetics and isotherms were better described using pseudo-second-order (PSO) and Langmuir models, respectively. The maximum adsorbed amount (q_max) of CR dye was 135.14 mg/g. The adsorption process was found to be endothermic and spontaneous in nature as demonstrated by the thermodynamics ( ΔGo, ΔHoand ΔSo).

This study provided a good example of using an easily separated magnetic nano-adsorbent for fast removal of a very toxic organic pollutant, congo red, from the aquatic environment

The employment of Mo-doped cobalt ferrite for the first time for removing hazardous anionic dyes such as congo red from their aqueous solutions.

This paper aims at studying the oxygen plasma treatment and the previously prepared and fully characterized chitosan nanoparticles (CNPs) as a green and eco-friendly strategy for surface modification of viscose fabric. This was done to render viscose fabric dye able with two types of acid dyes that do not have direct affinity to fix on it via improving the fabric wettability.

To achieve the goal, viscose fabric was activated with oxygen plasma at optimum conditions and coated with different concentrations of CNPs solution via conventional pad dry cure technique. The untreated and plasma-treated fabrics with CNPs were dyed with two types of acid dyes, namely, Acid Orange 7 and Methyl Red under determined conditions. The color strength (K/S), fastness properties to light, rubbing and perspiration, add on %, tensile strength, wettability and durability of the dyed samples were determined and compared.

The results divulged that oxygen plasma-treated fabric with CNPs and the aforementioned dyes in question could improve the flowing properties in comparison with untreated fabric: (a) the fabric wettability expressed as wetting area mm²; (b) the dye ability and fastness properties of viscose fabrics expressed as K/S and fastness properties; and (c) the strength properties and add on % of the treated fabric. On the other hand, the durability of the plasma-treated fabric decreased with increasing washing cycles.

The novelty addressed here was using plasma treatment as an eco-friendly pre-treatment approach for attachment of CNPs as a multifunctional green bio-nano polymer onto viscose fabric, which improved the dyeing properties of the fabric with acid dyes that do not have direct affinity to fix onto it.

Water is a vital natural resource without which life on earth would be impossible. Properties of synthetic dyes like high stability and noxious nature make it difficult to remove them from the effluent. This review focuses on the removal of synthetic dyes using nanoparticles (NPs) based on the adsorption principle.

Adsorption technique is widely used to remove synthetic dyes from their aqueous solution for decades. Synthetic dye removal using NPs is promising, less energy-intensive and has become popular in recent years. NPs are in high demand for treating wastewater using the adsorption principle due to their tiny size and vast surface area. To maximise environmental sustainability, the utilisation of green-produced NPs as efficient catalysts for dye removal has sparked attention amongst scientists.

This review has prioritised research and development of optimal dye removal systems that can be used to efficiently remove a large quantity of dye in a short period while safeguarding the environment and producing fewer harmful by-products. The removal efficiency of synthetic dye using different NPs in wastewater treatment varies mostly between 75% to almost 100%. This review will aid in the scaling up of the wastewater treatment process.

There is a lack of research emphasis on the safe disposal of NPs once the reuse efficiency significantly drops. The relevance of cost analysis is equally critical, yet only a few papers discuss cost-related information.

Comprehensive and planned research in this area can aid in the development of long-term wastewater treatment technology to meet the growing need for safe and reliable water emphasising reuse and desorption efficiency of the NPs.

Fibre reactive dyes are very popular for cellulosic garments as they are environmentally safe and having good overall fastness properties. But application of these dyes requires a very high concentration of salt. The salt released from garment dyeing increases salinity in drain water stream which has a negative impact on environmental ecology. The present work aims to eliminate the usage of salt during dyeing of cotton goods with reactive dyes.

The methodology adopted here, for the elimination of salt in cotton dyeing, was based on the principle of cationisation (to develop a positive charge) of cotton. The same was achieved by subjecting the caustic pretreated cotton fabric samples to a treatment of 1, 2 dichloroethane followed by methylamine to introduce amino groups in the cellulose structure. The treated cotton when dyed from slightly acidic bath generates positive sites due to protonation in the amino group. The reactive dyes being anionic (negatively charged) in solution get attracted to the positive charges on the fibre which eliminates the salt requirements for satisfactory dye exhaustion.

The investigation was conducted for cold brand, hot brand and highly exhaustive reactive dyes. The modified cotton showed excellent dye exhaustion for all the dyes in the absence of salt. The treatment was found to improve the dye fixation also. The modification was assessed through elemental analysis.

This study may be further extended to viscose material after suitably modifying the treatment conditions.

A pretreatment to cotton which could eliminate the usage of salt in its dyeing with reactive dyes is revealed.

The study explored a newer technique of cotton dyeing without salt usage. Both garment dyeing units and fabric/yarn finishing industries would thus be helpful.

Sulphur dyes provide an inexpensive medium to dye cellulosic fibres with heavy shade depths. They offer moderate to good fastness to light and wet treatments. However, owing to the environmental hazard produced by the use of sodium sulphide, the practical implication of these dyes is steadily decreasing. Moreover, these dyes are prone to oxidation causing pronounced fading on exposure to laundering. This paper aims to present the green processing of sulphur dyes by using a biodegradable reducing agent in place of sodium sulphide to dye cotton fabrics. The study also proposes after-treatments with tannin to improve the fastness properties of the dyeings.

In this study, dyeings were produced on cotton fabric with a range of C.I. Leuco Sulphur dyes, which were reduced with sodium sulphide and glucose. Sulphur dyeings were after-treated with an environment-friendly tannin-based product (Bayprotect CL (BP)); subsequently, the after-treated samples were evaluated for colour strength, wash, light and rubbing fastness.

A novel after-treatment method was developed, which substantially improved the wash fastness of C.I. Leuco Sulphur Black 1 dyeing to ISO 105 C06/C09 washing. However, the degree of this improvement varied for the other sulphur dyes used. The surface morphology and the possible mechanisms for the improved fastness properties were also discussed.

The effect of after-treatment was significant for improving the wash fastness of sulphur black dyeings in particular, while the effect on other colours was minor. Significant improvements were observed for light and wet rub fastness for most of the dyeings, which signifies the importance of tannins as a finishing agent.

It is observed that the tannin-based product, BP, is found to provide the photoprotective effect by improving the lightfastness of the dyeings. Future research may involve the exploration of various tannins as a finishing agent to sulphur dyeings.

This novel finishing technique is found significant for improving the wash fastness of sulphur black 1 dyeings for both the reducing systems. Improvements were also observed for light and wet rub fastnesses for most of the dyeings.

The purpose of this paper is to give compiled information on previously applied cotton fabric surface modifications. The paper covered most of the modifications done on cotton fabric to improve its properties or to add some functional properties. The paper presented mostly studied research works that brought a significant surface improvement on cotton fabric.

Different previous works on surface modifications of cotton fabrics such as pilling, wrinkle and microbial resistance, hydrophobicity, cationization, flame retardancy and UV-protection characteristics were studied and their methods of modification including the main findings are well reported in this paper.

Several modification treatments on surface modification of cotton fabrics indicated an improvement in the desired properties in which the modification is needed. For instance, the pilling tendency, wrinkling, microbial degradation and UV degradation drawbacks of cotton fabric can be overcome through different modification techniques.

To the best of the author’s knowledge, there are no compressive documents that covered all the portions presented in this review. The author tried to cover the surface modifications done to improve the main properties of cotton fabric.

The purpose of this study is to undertake surface graft copolymerization of viscose fabric via altering its fibrous properties by using acrylic acid (AA) as a carboxyl-containing monomer and peroxydisulfate (PDS) in presence of ferrous sulfate as a novel redox pair for initiating grafting. The latter process acted as an energy-saving process with respect to the reduction in polymerization temperature and maximizing the graft yield %, in addition to rendering the grafted viscose fabrics dye-able with cationic dye (crystal violet), which has frequently no direct affinity to fix on fabric.

To make graft copolymerization more efficient and economic, the optimum conditions for graft copolymerization were established. The graft yield % was determined as a function of initiator, catalyst and monomer concentrations and the material to liquor ratio, in addition to polymerization time and temperatures. Metrological characterizations via Fourier transform infrared spectroscopy and scanning electron microscopy of topographic morphological surface change have also been established in comparison with the ungrafted samples.

The maximum graft yield of 70.6% is obtained at the following optimum conditions: monomer (150 % based on the weight of fabric), PDS (50 m mole), ferrous sulfate (80 m mole) and sulfuric acid (30 m mole) at 40° C for 1.5 h using a liquor ratio of 30. Remarkably, grafting with AA enabled a multifold upsurge in color strength, with improvements in the fastness properties of cationically dyed grafted viscose fabric measured on the blue scale in comparison with untreated viscose fabric.

The novelty addressed here is undertaken with studying the effect of altering the extent of grafting of poly (AA)-viscose graft copolymers expressed as graft yield % in addition to carboxyl contents on cationic dyeing of viscose fabric for the first time in the literature. Moreover, rendering the viscose fabrics after grafting is dye-able with cationic dye with high brilliance of shades, which has regularly no direct affinity to fix on this type of fabrics.

The conventional textile dyeing process requires various operational characteristics, and determining the most reliable factor in dyeing performance has always been a challenge for the textile industry. Thus, the present paper aimed to evaluate the process sensitivity of C. I. Reactive Blue 194 dyeing of cotton fabric using a statistical technique.

An L₂₇ orthogonal array-based Taguchi's methodology was used with six parameters and three levels of each parameter. The signal-to-noise (S/N) ratio and analysis of variance were studied using total fixation efficiency (T%) as the response of the process sensitivity.

Results showed that dyebath pH was the most influential factor on the process and total fixation efficiency (p-value = 0.00 and contribution percentage 45.03%), followed by dye-fixing temperature, dye mass, electrolyte concentration, dye-fixing time and material to liquor ratio.

Overall this study provides a foundation for the determination of dyeing process sensitivity that will be useful in textile industries toward further development.