The employment of sustainable chemicals, such as citric acid, represents a possibility for the development of textile dyeing processes. This study aimed to analyze the possibility of replacement of acetic acid (commonly used in textile processing) by citric acid in polyester and polyamide 6 dyeing processes. The utilization of citric acid as leveling agent for disperse dyestuffs was also investigated. Dyeing processes in turquoise color for these fabrics were performed employing citric and acetic acid. Color differences between dyeing processes and color fastness to water were evaluated. All the color dyeing differences were not significant and there was no transference in color fastness tests (grade 5). Otherwise, the differences among polyamide dyeing processes could be related to the efficiency of citric acid solution as sequestering agent. Notwithstanding citric acid to be more expensive than acetic acid and the need of previous dissolution by stirring, it could be advantageous for some formulations.
Textile industry involves processing or converting raw material into finished textile materials via several processes which consume large amount of water and generate polluting waste effluents containing nonbiodegradable and dissolved toxic substances [
Dyeing is the process of adding color to textile products like fibers, yarns, and fabrics. It is normally done in a solution containing dyes and chemicals. The dyeing process of fibers and/or textiles comprises four processes: diffusion of dye in the solution, adsorption at the fiber surface, diffusion into the fiber and fixation of the dye to the fiber. The diffusion of dye into fiber depends on pH, temperature and employs auxiliary agents as well [
Although the majority of commercial textile dyes are water soluble, some dyes present hydrophobic behavior, especially the disperse dyes that are used for dyeing polyester fabrics [
Environmental issues are being increasingly taken into account in textile dyeing and finishing processes because of strict legislations and a growing ecological concern [
On the other hand, during the production process controlling pollution is as vital as making a product less harmful and with ecological benefits to the environmental. A number of sustainable and ecofriendly practices have been implemented by various textile processing industries, such as: ecofriendly bleaching; peroxide bleaching; ecofriendly dyeing and printing; low impact dyes; natural dyes; azo free dyes; phthalates free printing [
Additionally, input material change involves substituting one material for another, which is less harmful to the environment, more feasible to use and has the same or better technical requirements [
Acetic acid, toxic in high concentration, is generally used for adjusting the dyebath pH value in dyeing process [
Citric acid is a weak organic acid that is found in many fruits and vegetables especially citrus. The compound is produced by fermentation and used primarily in the foods, beverages, pharmaceutical, chemical, textile and electroplating industries. This acid is widely used in food industry, but it also finds applications as a function of additive detergents, pharmaceuticals, cosmetics and toiletries [
Thus, articulating the requirements for industrial application of sustainable chemistry, the use of citric acid in textile dyeing technologies can be a viable alternative. It is important to mention that in textile industry many employed empirical methods and practices have not been yet subjected to strict scientific studies and published in literature. In this way, despite of the employment of citric acid in textile processes is not novel; the present authors did not found reports in literature on the use of citric acid in polyamide dyeing. In this context, the present study reports the possibility of substituting acetic by citric acid in textile dyeing process. Considerations about employment possibilities and environmental impacts were accomplished according literature data.
The fabric samples were obtained from local market in Sao Paulo State: i) jersey knitted fabric-100% polyester previously scoured (Conformatec Textile Industry, Brazil) and ii) jersey knitted fabric-100% polyamide 6 previously scoured (Brazilian Service for Industrial Apprenticeship-SENAI, Brazil).
Lactic acid (98.0%), malic acid (99.0%), tartaric acid (99.0%), glacial acetic acid (99.5%), sodium hydroxide and calcium chloride were obtained from Quimesp Quimica Ltda (Brazil). Turquoise disperse dye Quimacron C-2GN-200 and turquoise acid dye Quimanylon N-5G were purchased from Quimanil Produtos Quimicos Ltda (Brazil). Sequestering agent Ladiquest 1097 and polyamide fixer agent Nylofixan PAN were acquired from Clariant (Brazil). Disperse dyestuff levelling agent Setamol WS (based on sulfonated naphthalene) and anhydrous citric acid 99.5% were purchased from BASF S/A (Brazil) and Casa Americana de Artigos para Laboratorios (CAAL, Brazil), respectively. Distilled water was used as solvent for preparation of reagents.
A 1 g sample of tested sequestering agent was dissolved in 80 mL of distilled water and 10 mL of calcium carbonate solution 2%. The pH was adjusted to 11 with a sodium hydroxide solution 2%. The resulting solution was titrated with a solution of dihydrate calcium chloride 48.7 g/L. The determination of sequestering power was determined according to the Hampshire test [
1mgCaCO 3 = 33.15 × ( spentvolumeofCaCl 2 ) sampleweight (1)
In this qualitative test, the dyeing process was carried out without textile substrate. The dyeing solution was prepared with turquoise disperse dye (Quimacron C-2GN-200, 3 g/L) and disperse dyestuff levelling (Setamol WS, 2 g/L). The pH of the dyebath was adjusted to 4.0 employing aqueous solutions of acetic or citric acid. The dyebath was heated until 130˚C and kept at this temperature for 30 min. Afterwards, the bath was cooled to 80˚C and the solution was vacuum filtered through a filter membrane of 0.45 µm pore size. The parameters are shown at
Dyeing experiments were carried out with polyester and polyamide fabrics in two types of dyebath: i) water with a hardness of CaCO3 200 ppm and ii) potable water for public consumption (containing chlorine near 0.2 mg/L and fluorine 0.7 mg/L) [
The colorimetric parameters of the dyed fabrics were determined by reflectance spectrophotometer VIS (Konika Minolta CM 3600 d) in order to check the possible color differences between the obtained results from dyeing experiments employing the CIELab system [
Experiments | 1 | 2 | 3 | 4 |
---|---|---|---|---|
Acetic Acid | pH 4.0 | pH 4.0 | ----- | ----- |
Citric Acid | ----- | ----- | pH 4.0 | 0.5 g/L |
Setamol WS | ----- | 2.0 g/L | 2.0 g/L | ----- |
Type of water | Public supply water | Water with CaCO3 200 ppm | ||||
---|---|---|---|---|---|---|
Experiments | Control | (1) | (2) | (3) | (4) | (5) |
Citric Acid | ----- | 0.5 g/L | ----- | ----- | 0.5 g/L | ----- |
Acetic Acid | 0.5 g/L | ----- | 0.5 g/L | 0.5 g/L | ----- | 0.5 g/L |
Sequestering agentc | ----- | ----- | 0.5 g/L | ----- | ----- | 0.5 g/L |
aTurquoise disperse dye Quimacron C-2GN-200 (Quimanil, Brazil) (2.0 %) for polyester dyeing. bTurquoise acid dye Quimanylon N-5G (Quimanil, Brazil) (2.0 %) for polyamide 6 dyeing. cLadiquest 1097 (Clariant, Brazil).
For the determination of differences between dyeing results, it is calculated the DE* value applying Equation (2):
Δ E * = [ ( Δ a * ) 2 + ( Δ b * ) 2 + ( Δ L * ) 2 ] 1 / 2 (2)
The equation allows to calculating de Euclidian distance between two colors in the CIELab space, described as:
• a*-red/green axis-meaning if the value is positive the sample is redder, or negative, greener;
• b*-blue/yellow axis-meaning if the value is positive the sample is yellower, or negative, bluer and;
• L*-white/black axis-meaning if the value is positive the sample is clearer, or negative, darker.
Color fastness tests to water were carried out on turquoise dyed polyester and polyamide 6 fabric samples according the test method ABNT NBR ISO 105-E01: 2014-Textiles-Tests for color fastness Part E01: color fastness to water [
The values for acetic, citric, lactic, malic and tartaric acid tested on the sequestering power evaluation of the Hampshire test were: zero; 366.71; 19.84; 54.06; and 17.28 mg CaCO3/(g of product) respectively. The results showed that acetic acid has no presented sequestering action whereas citric acid has a similar complexing action of the calcium ions as compared to the commercial sequestering agent tested (Ladiquest 1097) correspondent to 231.1 mg CaCO3/(g of product).
The experiments were carried out in order to simulate the normal conditions of polyester fabric dyeing solution preparation with the use of auxiliary chemicals in a process with a range of pH 4.5 - 5.5. However, instead of being employed for dyeing textile substrate, they were filtered. The dyebaths were vacuum filtrated in filter membrane of 0.45 µm pore size. The orifice marks formed in membranes upon filtration were circular with dark turquoise color. Dispersion test results represented by these orifice marks in membranes are presented in
Color differences in dyed samples could not be observed accurately by visual comparison. In this way, separately for polyester and polyamide 6 analysis, spectrophotometry was utilized to measure the color parameters in three dyed fabric samples (two verifications in each one), resulting in six color results. A reference sample containing only the dye and acetic acid solution (0.5 g/L) in dyeing process was used as control. For the determination of differences between dyeing results, DE values were calculated. Averages and standard deviations are presented in
In
However, for polyamide 6 dyeing processes all probabilities for no difference among the averages were inferior to 5%, exception the comparisons between (2) public supply water with acetic acid 0.5 g/L and sequestering agent 0.5 g/L and (3) hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L (probability of 24.4%); and between (3) hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L and (5) hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L and sequestering agent 0.5 g/L (probability of 8.4%) (
Additionally, the visual observation of all samples (polyester and polyamide 6) has not found failures in the dyeing processes, as stains or fades, which could cause irreparable damage to the appearance of fabrics (data not shown).
Dyeing | Polyamide 6 | Polyester |
---|---|---|
(1) Public supply water with citric acid 0.5 g/L | 0.50 ± 0.21 | 0.39 ± 0.11 |
(2) Public supply water with acetic acid 0.5 g/L and sequestering agenta 0.5 g/L | 0.84 ± 0.16 | 0.29 ± 0.08 |
(3) Hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L | 0.94 ± 0.11 | 0.24 ± 0.06 |
(4) Hard water (with CaCO3 200 mg/L) with citric acid 0.5 g/L | 0.77 ± 0.10 | 0.26 ± 0.02 |
(5) Hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L and sequestering agenta 0.5 g/L | 1.07 ± 0.13 | 0.31 ± 0.05 |
aLadiquest 1097 (Clariant, Brazil).
Comparison of results from different dyeing processes | Test t probability (%) | |
---|---|---|
Polyamide 6 | Polyester | |
(1) Public supply water with citric acid 0.5 g/L X (2) Public supply water with acetic acid 0.5 g/L and sequestering agenta 0.5 g/L | 1.0 | 7.9 |
(1) Public supply water with citric acid 0.5 g/L X (3) Hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L | 0.1 | 1.4 |
(1) Public supply water with citric acid 0.5 g/L X (4) Hard water (with CaCO3 200 mg/L) with citric acid 0.5 g/L | 1.7 | 1.4 |
(1) Public supply water with citric acid 0.5 g/L X (5) Hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L and sequestering agenta 0.5 g/L | 0.02 | 11.9 |
(2) Public supply water with acetic acid 0.5 g/L and sequestering agenta 0.5 g/L X (3) Hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L | 24.4 | 29.0 |
(2) Public supply water with acetic acid 0.5 g/L and sequestering agenta 0.5 g/L X (4) Hard water (with CaCO3 200 mg/L) with citric acid 0.5 g/L | 3.8 | 38.9 |
(2) Public supply water with acetic acid 0.5 g/L and sequestering agenta 0.5 g/L X (5) Hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L and sequestering agenta 0.5 g/L | 2.0 | 53.3 |
(3) Hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L X (4) Hard water (with CaCO3 200 mg/L) with citric acid 0.5 g/L | 1.9 | 55.0 |
(3) Hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L X (5) Hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L and sequestering agenta 0.5 g/L | 8.4 | 5.1 |
(4) Hard water (with CaCO3 200 mg/L) with citric acid 0.5 g/L X (5) Hard water (with CaCO3 200 mg/L) with acetic acid 0.5 g/L and sequestering agenta 0.5 g/L | 0.1 | 2.6 |
aLadiquest 1097 (Clariant, Brazil).
As presented in
in accordance with Miljkovic et al. [
Both acetic and citric acid are biodegradable. However citric acid (COD = 0.75 g O2/g) demands approximately 70% of oxygen required for biodegradation of the organic matter when compared to acetic acid (COD = 1.07 g O2/g). Chemical oxygen demand (COD) is defined as the amount of dissolved oxygen to oxidize and stabilize a sample when organic or inorganic matter of sample solution is responsive by a strong chemical oxidant. The COD value indicates the mass of oxygen consumed per liter of solution and expressed in milligrams per liter (mg/L). The higher the chemical oxygen demand, the higher the amount of pollution in the water sample. However, COD is considered one of the important quality control parameter of an effluent in wastewater treatment facility [
In adsorption experiments, the affinity of citric acid to soil adsorption sites was greater than acetic acid and this is relevant to the biodegradation of organic pollutants [
The textile industry consists of several processes including dyeing in which due to the nature of the work and its exposures, workers may frequently complain about respiratory symptoms. Studies indicated that system respiratory of textile-dyeing workers presented acute and chronic respiratory symptoms more prevalent [
Diluted acetic acid, such as in the same degree of vinegar (near 5%), is not harmful. However, the acetic acid for textile industry is marketed, stocked and handled before and during dilution in glacial form (<99.5%), which is harmful (by inhalation, skin contact or ingestion), corrosive and inflammable. The exposure and handling of glacial acetic acid without appropriate Personal Protective Equipment (PPE) can cause injuries and other damages to worker health. On other hand, citric acid stocking and handling is safe and does not need PPE [
The Brazilian Labor Legislation Standard, known as Brazilian Regulatory Rule Number 15 (NR-15) [
In addition, according to the Brazilian Law 10357/2001 [
In this way, it is evidenced that the alternative employment of citric acid in textile industry could reduce the toxicity and insalubrity associated to the exposure and handling of other toxic and harmful chemicals.
Textile industry employs generally commercial grade reagents. In this way, respect the comparison of commercial grade citric and acetic acid prices, citric acid is from one-third to one-half more expensive [
At the same time, probably much more significant than the cost difference, there are other resistance aspects related to the plain conventionality (without considering the possible options) of the employment of acetic acid solution in textile processes and, in the case of alternative employment of citric acid, the necessity of previous dissolution of this acid from the solid state to a liquid solution by agitation. However, it should be pointed that, despite of easier dissolution, acetic acid need be also diluted before its employment in these processes. On the other hand, notwithstanding additional cost and the need of previous dissolution by stirring, citric acid could be advantageous for some formulations. Furthermore, doubtless citric acid is safer regarding work occupational health and environmental aspects.
However, it is noteworthy that, despite of these preliminary considerations, only the analysis of real and representative industrial scale results could validate the cost and other possible advantages provided by the use of citric acid.
The results of present study showed that citric acid could be a promising alternative to chemical textiles, mainly, for acetic acid replacement in dyeing process. Both ones, acetic and citric acid, can be utilized in adjustment of pH in dye bath. The dyeing experiments showed that there were no significant commercial color differences between the fabrics of polyester and polyamide 6 dyed employing acetic or citric acid. There was no statistically significant difference among polyester dyeing processes. Otherwise, the differences observed for polyamide 6 dyeing processes could be related to the efficiency of citric acid as a sequestering agent, meanwhile, the insurance on the accuracy and repeatability of the data about complex ion formation, disperse dye levelling and sequestering action should be confirmed in future studies mainly taking in account industrial scale up. Citric acid is a product of easy commercial acquisition. However, citric acid employment in textile processes is economically more expensive than acetic acid. On the other hand, notwithstanding additional cost and the need of previous dissolution by stirring, citric acid could be advantageous for some formulations.
Carmo, R.S.A., Arauz, L.J., Rosa, J.M. Baruque-Ramos, J. and Araujo, M.C. (2017) Dyeability of Polyester and Polyamide Fabrics Employing Citric Acid. Journal of Textile Science and Technology, 3, 31-44. https://doi.org/10.4236/jtst.2017.33003