Ecofriendly Dyeing of Textile Materials with Natural Colorants from Date Palm Fiber Fibrillium

Abstract

Natural dyes have become an interesting subject of study because of their superior ecological properties in comparison to their synthetic counterparts. This explains the great amount of research developed in this regard, especially when the dye used was derived from a natural product’s waste. This research aims to evaluate the affinity of the dye extracted from date palm fibrillium to a multifiber fabric. This choice was made to investigate a comparison of the dyeability of many kinds of textile fibers with the obtained colorant from the date palm fibrillium. It was shown that the different types of fibers were well-dyed. The darkest dyes were obtained especially by using wool and nylon fabrics. In view of these results, wool and nylon fibers were selected for developing a dyeing investigation. The effect of the most important operational conditions such as temperature, pH, and dyeing time on the dyeing quality results has been investigated. Color yield (K/S) and CIELab values (L*, a*, b*, C*, h*) were used to evaluate the dyeing properties. The utilization of durable chemicals and bio-mordants both pre and post-dyeing resulted not only in new dyes but also in improved speed rates.

1. Introduction

The use of natural coloring materials goes back much further than the appearance of the first traces of writing. Indeed, man has appropriated very early the coloring properties of plant, animal, and mineral origin, used for the realization of paints, lacquers, and essentially dyes. Until the end of the 19th century, the dyeing of fabrics was carried out using vegetable dyes. In 1856, the accidental discovery of the first synthetic industrial dye called Mauvein by William Henry Perkin started the disappearance of the traditional art of natural dyeing, especially since it was difficult to standardize and reproduce the results.

Thus, the transition to synthetic dyes was rapid since these dyes were safe and especially less expensive at the industrial level [1,2]. Nevertheless, several studies have now shown that textile dyes of synthetic origin not only cause allergies in [3] but have also confirmed that their discharge is often polluted and non-biodegradable [4]. This has led to a renewed interest among dyers in the application of natural dyes. In fact, natural dyes are more biodegradable and generally more compatible with the environment [5,6,7]. Various works have been written on the dyeing of synthetic and natural fibers with different sources of natural colorants in recent years. Dyer’s oak and barberry [8], eucalyptus leaves [9], and madder [10] are some examples.

The agriculture, food and wood industries produce large amounts of wastes in solid and liquid forms from their production cycle. These wastes pose increasing problems of disposal and potentially serious pollution and result in a loss of valuable nutrients and biomass. On the contrary, these residues have been considered by scientists as a real source of textile dyes in their quality of abundance and availability at a reduced cost [11,12].

Phoenix dactylifera L. (date palm) is known as the tree of the desert regions of the world, known for their hot and dry climate. It is located throughout the Afro-Asian dry strip, which encompasses North Africa and the Middle East. In the Maghreb region, and particularly in Tunisia, the oases have an area of about 40,000 ha. Owing to its food, ecological, social, and economic benefits, the date palm is the most valued fruit tree by the oasis populations [13].

The date, since time immemorial, has been an important element of both human and animal diets. It is an excellent food, with high nutritional and energy value. Date palms provide huge amounts of agricultural waste. One estimate indicates that each date palm produces an average of 25–30 kg of residue from the leaves and surfacing fibers around the trunk, as well as an additional 10–15 kg of residue from the fruiting clusters [14]. Some research has focused on the valorization of this date palm residue for the production of biochar, bioethanol, or even for water treatment. Many studies are devoted to the use of date palm fibers as reinforcing elements in composite materials. To the best of our knowledge, no data about the application of date palm fibrillium residue as a natural source for textile dyeing is available in the literature.

The subject of this research was to study the possibility of dyeing different textile fibers with the brownish extract obtained from date palm fibrillium powder. The fibers with high levels of dye affinity (wool and nylon) were then retained to be screened and tested for all dyeing parameters. The influence of a number of experimental conditions on the dyeability of textile fabrics was explored. Dyeing with and/or without mordants was analyzed, evaluated, and discussed.

2. Materials and Methods

2.1. Raw Materials

The fibrillium material was collected in December 2021 in the Gabes region, a city in southeastern Tunisia with an oasis of hundreds of thousands of palm trees (Figure 1). Samples are finely chopped to remove decomposed parts and washed with water to remove dirt and dust. They were then dried and finely ground into a powder.

2.2. Materials and Chemicals Used

A multi-fiber fabric consisting of different fibers and containing fabric strips (acetate, cotton, nylon, polyester, acrylic, and wool) was used for testing affinity (VIBRATECH DW ISO 105-F10) [15].

100% washed and bleached wool fabrics (200 g/m²) and bleached polyamide knit fabrics (150 g/m²) have been used to investigate the overall dyeing parameters.

Alum (Al₂K₂(SO₄)₄.24H₂O, Fluka, Germany), ferrous sulfate (FeSO₄.7H₂O, Riedel-de-Haen, Germany) and tannic acid were laboratory reagents grade and were used without further purification. Commercial Mimosa extract was obtained from Silvateam (Italy).

2.3. Extraction of Coloring Components

Extraction of dyestuffs from natural sources is a fundamental task in fabric dyeing to maximize the performance of the dyeing. In the current study, 50 g of ground date palm plant was boiled for 1 h in 1 L of distilled water. The resulting solution was then filtered to remove plant debris and used for dyeing (Figure 2).

2.4. Affinity Test Method

The goal of this section is to test the affinity of various fiber types (acetate, cotton, nylon, polyester, acrylic, wool) to the extracted material under various operating conditions. A strip of multifilament fabric was dyed for 1 h at 90 °C in a liquor ratio of 1:40. All experiments were developed at three pH values (4, 7, and 9).

2.5. Dyeing and Mordanting Methods

The wool and polyamide samples were dyed in acidic bath (pH 4) in a laboratory dyeing machine (Ahiba Datacolor International, Trenton, NJ, USA) at different temperature levels (40–100 °C) for different times (30–90 min).

We used a variety of biomordants and sustainable metal mordants to improve fastness and color strength values, rendering the process more perennial and more respectful of the environment.

In case of mordanting, pre-mordanting was chosen as the most suitable process. Various types of biomordants (Mimosa pudica extract and tannic acid) and sustainable metal mordants (alum (Al₂(SO₄)₃) and ferrous sulfate (FeSO₄)) as described in Figure 3. Mordants were used with a concentration of 3% (w/w with respect to the fabric) [16,17].

2.6. Evaluation of Dyeing Quality

Colorimetric parameters of the dyed samples were evaluated using a Datacolor 800–9 mm spectrophotometer, with D65 illumination and a 10-degree standard observer. Colors are expressed in CIEL*a*b* coordinates: L* refers to the brightness (100 = white, 0 = black), a* refers to the red-green coordinate (+ = red, − = green), b* refers to the yellow-blue coordinate (+ = yellow, − = blue), C* refers to color purity, vividness, or dullness (100 = vivid, 0 = dull), and h0 refers to hue angle [17].

In parallel, the color yield (K/S) of dyed fabrics was investigated. The Kubelka-Munk equation described below was used to calculate the K/S values:

$$\raisebox{1ex}{$\mathrm{K}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{S}$}\right.=\frac{\left(1-\mathrm{R}\right)^2}{2\mathrm{R}}$$

with: K is the absorption coefficient,

• S: is the diffusion coefficient,
• R: is the reflectance [18].

2.7. Colorfastness Test

The colorfastness characteristics were evaluated in accordance with the standard procedures. The tests were given as follows: ISO 105-C02:1989 for washing fastness, ISO 105-X12:1987 for rubbing fastness, and ISO 105-B02:1988 for light fastness (carbon arc) [19].

2.8. Phytochemical Study

The bioactive compounds present in fibrillium have been analyzed through phytochemical studies. Reaction with cyanidin was used to emphasize the flavonoids. Notably, 3 mL of HCl/MeOH (50/50% by volume) and some magnesium fragments were added to the extract (5 mL). Addition of 1 mL of amylic acid intensified the pink-orange or purple color, confirming the presence of flavonoids. Catechin tannins were identified using reagents from STIASNY (30% formaldehyde, concentrated hydrochloric acid). A total of 15 mL of STIASNY’s reagent was mixed with the extract. The obtained mixture was kept at 80 °C for 30 min. The observation of coarse, flaky precipitates is characteristic of catechin tannins. A few drops of neutral ferric chloride solution (0.5%) were added to 2 mL of extract. Formation of a dark green color indicates the presence of phenolic compounds [20].

2.9. Total Phenolic Content (TPC)

With the Folin-Ciocalteau reagent, total phenolic compounds were determined. Following 30 min, the absorbance was read at 765 nm. Monohydrate gallic acid was used as our standard [21,22].

2.10. Total Flavonoid Content (TFC)

A quantity of 250 μL of each extract was combined with 75 μL of 5% NaNO₂ and 1.25 mL of distilled water. A volume of 150 μL of 10% AlCl₃-H₂O solution was then added after about six minutes. Five minutes thereafter, a volume of 0.5 mL of 1M NaOH solution and a volume of 225 μL of distilled water was added to the solution. The absorbance was detected at 510 nm [23].

2.11. Condensed Tannins (CT)

A 50 μL volume of each extract was admixed with 1.5 mL of 4% vanillin. An amount of 750 μL of concentrated HCl was then added. The obtained sample solution was then incrementally incubated at room temperature in the dark for 15 min. Absorbance was then read at 500 nm [24].

3. Results and Discussion

3.1. Phytochemical Study

The phytochemical analysis tests were partly based on the qualitative analysis of the formation of insoluble complexes using precipitation reactions or the generation of colored complexes, using staining reactions.

The phytochemical screening was applied as a qualitative test. The bioactive compounds present in the fibrillium date palm aqueous extract were identified.

The determination of total phenolic content, total flavonoid content, and condensed tannin content indicates a high amount of antioxidant components in date palm fibrillium. Polyphenols were the most abundant (90 mg GAE/mg extract DW) followed by flavonoids (75 mg CE/mg extract) and condensed tannins (64 mg CE/mg extract).

Figure 4 illustrates the results of the phytochemical analysis.

The existence of saponins was determined by the generation of a stable froth after a vigorous agitation of 2 mL of date palm fibrillium aqueous extract.

The occurrence of tannins and phenols in the aqueous extract of fibrillium was found by the generation of a blue-black color when 2 mL of 2% iron (III) chloride solution and 2 mL of the extract were added.

The presence of flavonoids was indicated by the generation of a red color when zinc dust was present in the aqueous extract of date palm fibrillium, followed by the dropwise introduction of hydrochloric acid concentrate.

The existence of glycosides is affirmed by the brown ring formation at the interphase after the addition of 2 mL of aqueous extract and 2 mL of glacial acetic acid and 2 drops of 2% iron (III) chloride solution are added to 2 mL of concentrated sulfuric acid.

3.2. Testing the Dye Affinity

In this part, extracted colorant affinity with various fibers was studied. Photographs of the samples are given in Figure 2.

It can be seen from Figure 5 that the extracted dye has a high affinity with wool and polyamide fibers. On the contrary, the colorant has a low or no affinity with cotton, acetate, acrylic, and polyester. At a pH level of 4, the darkest shades are found in wool and polyamide fibers. From these findings, the wool and polyamide fibers that showed the highest K/S were then selected for a more detailed study in an acidic medium.

3.3. Influence of Dye Concentration

Table 1. Results of fabrics dyeing with different dye concentrations.

	Wool				Polyamide
Dye Concentration (%owf)	K/S	L*	a*	b*	K/S	L*	a*	a*
1	3.25	58.23	7.25	12.98	1.52	61.47	3.21	3.62
3	4.98	55.32	8.87	13.25	3.85	59.74	4.81	3.45
5	7.32	48.24	8.98	13.89	5.76	54.62	4.86	3.73
7	12.89	44.98	10.25	15.84	7.12	49.23	6.54	4.85
9	12.98	43.87	10.97	15.86	7.45	48.13	6.78	4.97

represents the evolution of the color yield and colorimetric parameters of dyed fabrics (wool and polyamide) in the function of a dye concentration.

We can see in Table 1 that the dye concentration has an inevitable effect on the dye uptake for the two fabrics. The accessibility of dye molecules in the dye bath also increased correspondingly, and more dye molecules could bind to the fiber, resulting in a higher color yield value. With increasing the dye concentration between 1% and 7%owf, the K/S was increased considerably, and then it was increased a little more by increasing the dye concentration to 9%owf. This demonstrates that the fibers reached saturation at this dye concentration.

3.4. Influence of Dyeing Temperature

The dye bath temperature impact on the performance of dyeings obtained from both wool and polyamide fibers was explored.

Table 2. Results of fabrics dyeing under different dyeing temperatures.

	Wool				Polyamide
Temperature (°C)	K/S	L*	a*	b*	K/S	L*	a*	b*
40	5.35	50.25	2.51	14.81	1.32	62.98	2.31	13.23
60	7.20	48.25	6.17	15.05	4.05	52.47	3.01	13.52
80	9.28	42.36	6.08	16.92	6.61	47.63	3.84	13.37
100	11.95	36.98	8.15	17.44	8.12	41.87	5.45	14.15

clearly shows that the K/S rises along with the dyeing temperature and achieves its maximum at a temperature of 100 °C for both fibers (wool and polyamide). This increase in dyeing strength (K/S) could be attributed to the enhancement of fiber puffing and the diffusion rate of dye substances into the fiber when the temperature of the dye bath increases [25], especially in the case of natural fibers. In addition, for polyamide, the temperature has significant factors. When it exceeds the glass transition temperature, a good penetration of the dyes may have taken place.

3.5. Influence of Dyeing Time

The samples of wool and polyamide have been dyed for various durations ranging from 45 to 90 min (

Table 3. Results of color yield and colorimetric parameters of wool and polyamide fabrics under different dyeing duration.

	Wool				Polyamide
Dyeing Duration (Minutes)	K/S	L*	a*	b*	K/S	L*	a*	b*
45	4.52	51.20	9.20	14.81	2.28	63.89	0.14	1.24
60	6.82	47.26	10.72	15.51	4.05	58.03	2.71	1.58
75	10.21	42.02	10.88	15.98	6.68	47.93	2.96	2.79
90	13.09	38.65	12.58	17.04	8.23	44.65	4.42	5.54

). This table reveals that the hue of all the dyed samples is in the red-yellow range (a* and b* have positive values). Further, it is also revealed that the K/S values of the dyed samples increase with the dyeing time. The recorded K/S values after 90 min of dyeing were 13.09 and 8.23 for wool and polyamide fabrics, respectively.

3.6. Mordanting and Colorfastness Improvement

The mordanting stage is an essential part of the natural dyeing process. As such, the mordants not only provide an affinity to the dye, but in many instances, they produce different shades and enhance the fastness of the dye as well. In this regard, several metallic mordants and bio-mordants were tested in this study.

3.6.1. Metallic Mordants

Various metallic mordants are normally used for natural dyeing, in order to improve dye fixation and fastness properties (wet treatments and light). The most commonly used mordants in natural dyeing are potassium aluminum sulfate, potassium dichromate, stannous chloride, copper sulfate, and ferrous sulfate [26]. The salts of chromium, stannus, and copper are considered potentially toxic. For this reason, two eco-friendly metallic mordants, namely, ferrous sulfate and alum, were used in this study.

The obtained values of color yield and color coordinates when using various mordants are shown in

Table 4. Effects of various mordants on color yield and colorimetric coordinates of dyed samples (wool, polyamide).

	Wool				Polyamide
	K/S	L*	a*	b*	K/S	L*	a*	b*
Without mordant	5.20	50.81	20.08	22.85	4.05	58.75	15.21	18.25
Alum	4.62	46.42	18.12	24.31	3.72	54.88	14.08	22.94
Ferrous sulphate	7.88	41.86	11.29	13.18	6.11	43.49	12.91	14.32
Tannic acid	6.56	48.84	17.71	22.53	4.27	57.58	14.08	20.29
Mimosa extract	4.21	55.88	13.52	16.61	3.19	60.24	17.81	15.03

. From the obtained results, it is apparent that the use of the mordant has a significant influence on the color of the dyed samples. The K/S values of the samples dyed and mordanted with FeSO4 are higher than those of the samples dyed and mordanted with alum. In addition, it was observed that the use of metal salts induced a noticeable change in the color coordinates.

In addition, the effects of each mordant on rubbing, washing, and light fastness were also evaluated. Obtained results are presented in

Table 5. Fastness properties using various mordants.

	Wool				Polyamide
	Rubbing Fastness		Wash Fastness	Light Fastness	Rubbing Fastness		Wash Fastness	Light Fastness
	Dry	Wet			Dry	Wet
Without mordant	4	3–4	4	2	4	3–4	4	2
Alm	4–5	4	4	3	5	4	5	3
Ferrous sulphate	4–5	4	4–5	4–5	5	4	5	4
Tannic acid	4–5	4	4	4–5	5	4	5	4–5
Mimosa extract	4–5	4	4–5	5	5	4	5	5

. Note the improved rubbing fastness and washing fastness. A significant improvement in lightfastness was observed (reaching 4–5 using FeSO₄) compared to the results without mordanting (1–2).

3.6.2. Biological Mordants

Considerable research is being conducted today regarding the utilization of biowaste and by-products from the beverage, agriculture, food, and other industries for the production of natural colorants. A lot of research has also been conducted to upgrade these by-products in a beneficial and environmentally friendly way [27]. Natural dyeing operations typically produce toxic metal ions in wastewater. These metals have adverse effects on the environment and public health. Replacing metal mordants with bio-mordants is an area of interest and popularity for some researchers [28,29]. In this study, he also used two natural bio-mordants, namely acidic tannins and mimosa extracts with high tannin and metal content. The pre-mordanting method was used for each of the natural mordants to assess their colorimetric and fastness properties. The color development and color coordinate values obtained using the two natural stains were presented in Table 4.

The result was quite a change in the shade after using the mordants. For example, pre-mordanting with mimosa extract tends towards a lighter beige pattern color. The color fastness values obtained after organic dyeing with two natural dyes (tannic acid and mimosa extract) are summarized in Table 5.

These results mentioned that the light fastness increase with using biomordants. Light fastness produces values of 5 and 4–5 using mimosa extract and tannic acid, respectively. As it is well known, mimosa extract and tannic acid contain polyphenolic compounds such as gallic acid. The latter is a widely used antioxidant to upgrade light fastness. In conclusion, it can be said that the biomordants used varied the shades obtained from the dyed samples. They also improved their color fastness, especially their light fastness, owing to their chemical arrangements.

4. Conclusions

The target of this work was the search for greener alternatives to satisfy consumer demand for eco-friendly and sustainable products. Progress has been made with this study in the use of date palm by-product (fibrilium) extracts for dyeing wool and polyamide fabrics.

The best results for wool and polyamide dyeing were achieved when a temperature of 100 °C at a duration of 90 min and a dye concentration of 9% were employed.

The wash and dry rubbing fastness of the dyed fabrics ranged from good to excellent, while light and wet rubbing fastness ranged from fair to good. The use of mordants in conjunction with extracts enhances the dyeability and the fastness properties.