Extraction and Characterization of Natural Dye Stuff from Spent Coffee Ground and Bio-Mordant from Mango Bark

ABSTRACT

Synthetic colorants used for dye and mordant purposes in textile industries are currently causing environmental problems in the world. The usage of these synthetic colorants is a major health problem and harms the environment. For this reason, synthetic colorants should be replaced by natural colorants. Therefore, this study aimed to extract natural dye stuff from spent coffee ground and bio-mordant from mango bark. The raw materials were collected, washed, dried, crushed and their physico-chemical properties were determined. Finally, the samples were extracted by using the solvent extraction method. During the extraction process, the central composite design method (CCD) was used to analyze and optimize the effect of dosage (g/l), temperature (℃) and time (min). The maximum natural dye yield value of 18.41% was obtained at a dosage of 60 g/l, temperature of 70°C and time of 90 min. Also, the highest natural mordant yield of 19.03% was achieved at the value of 45 g/l, 70°C and 90 min. The fastness properties of dyed and mordanted cotton fabric results were within a range of acceptable standard values. Therefore, using spent coffee grounds for natural dyes and mango bark for natural mordant can be a feasible commercial alternative to synthetic dyes in textile and dyeing industries.

摘要

纺织工业中用于染料和媒染剂目的的合成着色剂目前正在世界范围内引起环境问题. 这些合成着色剂的使用是一个主要的健康问题，并危害环境. 因此，合成着色剂的最佳解决方案之一应该被天然着色剂所取代. 因此，本研究旨在从废咖啡渣中提取天然染料，并从芒果皮中提取生物媒染剂. 对原料进行收集、洗涤、干燥、粉碎，并测定其物理化学性质（水分含量、灰分含量和溶解度）. 最后，采用溶剂萃取法对样品进行了萃取. 在提取过程中，使用设计专家13.1.0.1软件包中的中心复合物设计方法（CCD）分析并优化了用量（g/l）、温度（℃）和时间（min）对提取产率的影响. 在用量为60 g/l、温度为70°C、时间为90 min的条件下，天然染料的最大得率为18.41%. 在45 g/l、70°C、90 min的条件下，天然媒染剂的收率最高，达19.03%. 染色和媒染后的棉织物的牢度在可接受的标准值范围内. 因此，在纺织和染色行业中，使用废咖啡渣作为天然染料，使用芒果皮作为天然媒染剂，可以成为合成染料的可行商业替代品.

KEYWORDS:

• Dye
• cotton fabric
• fdastness properties
• ground
• mordant

关键字:

• 染料
• 棉布
• 紧固特性
• 地
• 媒染剂

Introduction

The textile dyeing industry is one of the biggest consumers of chemical dyes (Berhanu and Gopalakrishnan 2018). During the dyeing process, approximately 1.7 million tons of various chemical dyestuffs are used annually in the global textile dyeing industry. Each year, an estimated 0.8 million tons of chemical dyes are generated (Nam and Xiang 2019). This results in increased pollution, toxicity, sources of skin cancer, and allergic contact dermatitis (Adeel et al. 2022). Due to this reason, the researchers are appreciating natural dye sources due to their environmentally friendly, nontoxic, nonhazardous, and biodegradable nature (Adeel et al. 2023). Food wastes are responsible for 21% of greenhouse gas emissions due to the excessive use of natural resources and wastage. The whole food system loses or wastes 30% of all produced foods and all stakeholders are responsible for preventing these food losses (Campos et al. 2020).

Natural dyes are bio-colorants that are extracted from natural sources like plants, animals and minerals (Adeel et al. 2019). The majority of natural dyes are derived from plant sources such as roots, berries, skin, barks, leaves, wood, and other organic sources such as fungi and lichens (Guha and Guha 2019). Many researchers reported different results on the extraction of color components from different color-bearing biomass species, but still, many species remain unexplored. From plant sources, coffee is one of the most important agricultural products in the world. In particular, Ethiopian coffee production has increased over the last three years and it is expected to reach 7.62 million bags (457,200 MT) in 2021/22 (Tefera 2021).

During the production of coffee, a beverage creates a solid residue which is known as spent coffee ground (SCG). It is an excellent biodegradable waste and contains high organic compounds such as caffeine, tannins, polyphenols and phenolic components (Bae and Hong 2019; Mongkholrattanasit, Nakpathom, and Vuthiganond 2021). Due to this reason, they are a major cause of environmental pollution since they produce a large amount of methane gas which harms the environment (Zabaniotou and Kamaterou 2019). The effect of methane gas is 2.5 times worse than carbon dioxide (Bae and Hong 2019). For this reason, SCGs could be useful for functional textile dyeing applications because these compounds exhibit multiple biological effects including antioxidant activity, as well as an attractive textile coloring effect. Mordant is commonly used for the dyeing process using natural dyes. Mordant is a substance that binds dyes to the fabric. It’s derived from metallic salt including alum, chrome, stannous chloride, copper sulfate, and ferrous sulfate (Özomay and Akalın 2020).

With these points, the best alternatives are to replace artificial or manufactured components with natural materials known as bio-mordant, which refers to compounds that can be found in nature (Hosseinnezhad et al. 2022). Using bio-mordant extracted from mango bark tree (Mangifera indica L.) is a better option for mordanting cotton fabric. It has been biodegradable, environmentally friendly, durable, non-toxic to humans and has a non-allergic reaction when compared to synthetic ones (Baseri and Baseri 2021). This extracted material applied on cotton fabric is better for other textile materials because it contains dye classes and cellulosic fabrics that are usually derived from the functional groups (−OH) already present in the fiber (Thakker and Sun 2022). For applied dye and mordant on the cotton fabric were obtained from good to excellent wash, light, and rubbing fastness test results (Sayem et al. 2021). Therefore, this study aimed to extract natural dye stuff from spent coffee ground and natural mordant from mango bark and to optimize extraction parameters (dosage, temperature and time) as an upcoming raw material for the production of natural dyes. At the end of dyed and mordanted cotton fabric determine the fastness property (wash fastness, lightfastness and rubbing fastness) by using standard test methods. Moreover, the extraction process produced some novel solid residues from the raw materials. This solid product can be utilized for many applications such as solid fuel, biodiesel, bioethanol and carbon active.

Materials and methods

Material collection

Spent coffee ground (SCG) was collected from the coffee house damping site located in Kombolcha town. The mango bark (MB) was collected from Wuchale town, South Wollo, Ethiopia. Also, a commercially prepared ready-to-dye cotton fabric was obtained from Kombolcha Textile Share Company. The purposive/expert sampling technique was used during the collection of raw materials (Zubairu and Mshelia 2015). Analytical grades of Ethanol (C₂H₅OH), Sodium carbonate (Na₂CO₃), sodium chloride (NaCl) and Acetic acid (CH₃OOH) were used during the experiment.

Methods

Raw material preparation

Spent coffee ground and mango bark were washed by using distilled water to remove soil and dust particles. Next, the raw samples were dried using an oven at 105°C for 24 hr. After that, the dried raw samples were converted to fine powder form by using a laboratory ground machine (ultra-fine grinder) and sieved with sieving processes to keep the particle sizes obtained at 63, 125, 180, 250, 355, 425, 500 and 710 µm. The particle size of 500 µm was selected due to 63–425 µm was insufficient and the reset was coarser and creating a problem of blocking the mesh (Boonsong, Klaypradit, and Wilaipun 2016).

Physio-chemical analysis

The physio-chemical analysis of spent coffee ground and mango bark was conducted according to the American Standard Testing Method (ASTM). The proximate analysis of the raw sample was carried out to determine the moisture content, ash content and solubility.

Natural dye extraction

Firstly, a solvent extraction method was applied to extract natural dye from spent ground coffee (SCG) by using the Soxhlet apparatus. The spent coffee ground powder (20, 40 and 60 g/l) was used in the Soxhlet extractor thimble. 80% ethanol used as a solvent with 1:40 (mass to liquor ratio) was put into the round bottom flask. After that, the flask was heated for the time of 60,90 and 120 min and temperatures of 50, 70 and 90°C (Baaka et al. 2015). After the extraction process, it was filtered by using Whatman filter paper and the ethanol solvent was removed by using simple distillation at 78°C for 30 min (Thummajitsakul, Boonburapong, and Silprasit 2022). The effect of extraction factors, optimization factors and levels were designed by using the central composite experimental design method from the Design Expert 13.1.0.1 software package (Table 1).

Table 1. Factors and levels of the experimental design.

Factors	Units	Symbols	Levels
			−1	0	1
Dosage	g/l	A	20	40	60
Temperature	℃	B	50	70	90
Time	min	C	60	90	120

Bio-mordant extraction

The solvent extraction method was applied to extract bio-mordant from mango bark by using a Soxhlet extractor and 80% ethanol was used as a solvent. The extraction was carried out using different combinations of dosage (20, 40 and 60 g/l), temperature (50, 70 and 90°C) and time (60, 90 and 120 min) with a 1:40 material-to-liquor ratio (MLR) (Aung, Htoo, and Lwin 2020). At the end of the extraction process, the mordant solution was filtered through Whatman filter paper and the ethanol was removed by using simple distillation. Therefore, the pH of each dye and mordant solution is maintained between 6 and 8.

Experimental design and characterization

For this study, the Design Expert 13.1.0.1 software package was used and the experiment was designed with the central composite design method (CCD). The experimental runs were performed as a completely randomized design. The design was applied to evaluate the effect of dosage, temperature and time on extracted yield. To investigate the characteristics of dye compounds contained in the aqueous extract, the spent coffee ground and mango bark solutions were analyzed in the wavelength region of 200–800 nm using a UV-Visible Spectrophotometer (Biochrome LTD, Cambridge CB4 of J England). The infrared spectra (Perkin Elmer Spectrum V770 spectrophotometer, Japan) for spent coffee ground and mango bark were also analyzed in the wavenumber range 4000–400 cm⁻¹ by using the KBr pellet method.

Dyeing and mordanting process on cotton fabric

3 g of cotton fabric was immersed into a dye bath solution at a natural mordant concentration (12%, 16% and 20%), natural dye concentration (6%, 8% and 10%), temperature (90°C) and time (60 min) with 1:20 material to liquor ratio (MLR). In addition, NaCl (10 g/l) and NaCO₃ (5 g/l) were used to increase exhaustion and fixation of dye into the cotton fabric (Hasan et al. 2015; Kaushik 2016). The pH of each dye and the mordant solution was maintained between 6 and 8 with 2–5% w/w of acetic acid (40% solution). Finally, the fabrics were washed several times with cold water and dried at room temperature.

Determination of fastness properties

Dyed and mordanted cotton fabric samples were tested for wash, light, and rubbing fastness properties by using different methods. The washing fastness was tested according to ISO 105 C06: 2010 standard method. The dyed and mordanted cotton fabric was soaked into a composite specimen containing 5 g/l soap solution. After the process, the washing cotton fabric was taken out from the composite specimen and it was dry at room temperature for 10 min. The rubbing fastness was performed by rubbing the dyed cotton fabric put on the crocking machine discoloration as a result of friction, the procedure was repeated for allowed fifteen times. After the process, the rubbing cotton fabric was determined according to the ISO 105-X12:2016 standard testing method. Finally, to evaluation of the light fastness of dyed and mordanted cotton fabric was conducted using solar box 1500. The color variations (fading) of dyed and mordanted cotton fabric were tested according to ISO 105–B06:2020 standard method.

Results and discussion

Physico-chemical analysis

The raw material was characterized in terms of moisture content, ash content and solubility results. The moisture content values of the SCG and MB are presented in Table 2. Therefore, those samples had 10.56 ± 0.096% and 9.53 ± 0.04% moisture contents, respectively. The moisture absorbed by dye and mordant powder from the storage container was considered susceptible to spoilage by microbes otherwise not spoiled (so, does have a longer shelf life). Similarly, the moisture content of SCG and MB was listed with the range of selected values of results mentioned in the literature (Mutua, Imathiu, and Owino 2016). The total ash content which signifies the occurrence of inorganic and mineral matter in SCG and MB composition was 1.5 ± 0.05% and 2.54 ± 0.05%, respectively. The solubility of SCG and MB was another key physicochemical parameter.

Table 2. Physico-chemical characteristics of spent coffee ground and mango bark.

		Mean ±SD value
S. No	Physico chemical properties	SCG	MB
1	Moisture content	10.56 ± 0.096%	9.53 ± 0.04%
2	Ash content	1.5 ± 0.05%	2.54 ± 0.05%
3	Solubility in 50% of ethanol	89.65 ± 0.05%	79.06 ± 0.045%
4	Solubility in 50% of methanol	82.56 ± 0.07%	77.56 ± 0.04%
5	Solubility in 50% of hexane	51.39 ± 0.1%	48.79 ± 0.025%

Solubility in the solvent is necessary for the good application of dye and mordant in an aqueous solution. If the dye and mordant as poor solubilities such as undissolved natural dye and natural mordant residue are present in the solution (Yin, Fei, and Wang 2018). Uneven coloration, spots, and poor color durability can be obtained, resulting in serious defects and cost complaints. In this case, the solubility of natural colorants in various solvents (50% methanol, 50% hexane and 50% ethanol) was gravimetrically tested and the result is summarized in Table 2.

The solubility of SCG and MB in 50% methanol was 82.56 ± 0.07% and 77.56 ± 0.04% respectively, whereas the minimum in 50% hexane of SCG and MB was 51.39 ± 0.1% and 48.79 ± 0.025%, respectively. Similarly, the solubility of SCG and MB was highest in 50% ethanol (89.65 ± 0.05% and 79.06 ± 0.045%). The related result was noted in the previous research work on the solubility of natural dye varies in different solvents. The solubility of natural dye produced from fungi in various solvents (95% ethanol, methanol, distilled water, ethyl acetate and acetone) and reported the highest solubility to be in ethanol. They stated that the polarity of components in the natural dye affects the solubilization of solvents in which polar components tend to be dissolved in polar solvents while nonpolar components can be dissolved in nonpolar solvents. The higher solubility of the natural colorants in ethanol was also observed (Suwannarach et al. 2019). This is because ethanol increases dye molecules in easy penetration of solvent and thus increases the swelling of natural colorants.

Characteristics of extracted spent coffee ground and mango bark

UV-Visible spectrophotometer analysis

The color absorbance of spent coffee ground and mango bark was recorded by UV-Visible spectrophotometer and the result is shown in Figure 1. The maximum absorbance with wavelength (nm) of spent coffee ground and mango bark were 0.79 at 302 nm and 0.84 at 298 nm respectively. These wavelength values showed its very good absorbance character expecting less effect of light on the fastness properties of coloring material (Dhanania, Singhee, and Samanta 2021). The absorbance was low, this implies fewer molecules were available to interact with light.

Figure 1. Uv/visible absorbance spectra of extracted spent coffee ground and mango bark.

Fourier Transformation Infrared Spectroscopy (FTIR) analysis

The FT-IR spectrum of spent coffee ground (SCG) displays bands in the regions of 3482, 1715, 1638, 1075 and 950 cm⁻¹ corresponding to – OH, –C=O, C=C, –C – O and – CH functional groups respectively (Figure 2). The FT-IR spectrum of mango bark (MB) displays bands in the regions of 3225, 1607, 1420, 1190 and 725 cm⁻¹ corresponding to – OH, –C=O, C=C, –C – O and – CH functional groups respectively (Figure 2). These functional groups indicate the presence of flavonoids, phenolic, carbonyl, aromatic, and alkoxyl fragments in the dye structure. This observation agreed with the findings made by different researchers (Amir et al. 2018; Jabar, Ogunmokun, and Taleat 2020; Mongkholrattanasit, Nakpathom, and Vuthiganond 2021) in natural dyes for textile dyeing. The presence of these fragments in the dye and mordant indicated that the extract had chromophores (color-bearing groups) and auxochromes (color-intensifying group) functional groups in the chemical structure (Batool et al. 2022; Jabar, Ogunmokun, and Taleat 2020). These were good characteristics of natural colorants responsible for textile dyeing properties and help the dye molecule to bind with the functional group of the fabrics (Adeel et al. 2022; Batool et al. 2022).

Figure 2. FTIR analysis of extracted spent coffee ground (SCG) and mango bark (MB.

Yield of dye and mordant

Analysis of variance (ANOVA)

The ANOVA of yields on extracted dye and mordant are reported in Tables 3 and 4 respectively. A term was considered significant if the P-value was less than 0.05 and the F-value was high. The result was significant with a P-value <.0001. The effect of dosage and temperature on yield was also statistically significant (P-value <.0001). Therefore, a change in dosage and temperature had a significant effect on the extraction of color (yield). However, the extraction time had a less significant effect relative to dosage and temperature.

Table 3. ANOVA table for dye yield.

Source	Sum of Squares	Df	Mean Square	F-value	p-value
Model	88.75	9	9.86	628.25	<0.0001	Significant
A-Dosage	40.68	1	40.68	2591.87	<0.0001
B-Temperature	8.52	1	8.52	542.76	<0.0001
C-Time	0.0828	1	0.0828	5.28	0.0445
AB	0.1275	1	0.1275	8.12	0.0172
AC	2.05	1	2.05	130.62	<0.0001
BC	0.0528	1	0.0528	3.36	0.0465
A^2	0.9840	1	0.9840	62.69	<0.0001
B^2	11.88	1	11.88	756.66	<0.0001
C^2	0.3528	1	0.3528	22.48	0.0008
Residual	0.1570	10	0.0157
Lack of Fit	0.1303	5	0.0261	4.88	0.0533	not significant
Pure Error	0.0267	5	0.0053
Cor Total	88.91	19

Table 4. ANOVA table for mordant yield.

Source	Sum of Squares	Df	Mean Square	F-value	p-value
Model	60.72	9	6.75	105.95	<0.0001	Significant
A-Dosage	21.61	1	21.61	339.35	<0.0001
B-Temperature	11.58	1	11.58	181.82	<0.0001
C-Time	2.04	1	2.04	32.08	0.0002
AB	0.3872	1	0.3872	6.08	0.0333
AC	0.3445	1	0.3445	5.41	0.0424
BC	3.10	1	3.10	48.68	<0.0001
A^2	1.85	1	1.85	29.04	0.0003
B^2	1.99	1	1.99	31.20	0.0002
C^2	1.59	1	1.59	24.94	0.0005
Residual	0.6368	10	0.0637
Lack of Fit	0.5292	5	0.1058	4.92	0.0525	not significant
Pure Error	0.1075	5	0.0215
Cor Total	61.36	19

Diagnostics plot

Figure 3(a,b) shows the residuals of normal % probability distribution fitted to the straight line, which indicates that the quadratic polynomial model satisfies the assumptions of the analysis of variance was no deviation of variance i.e., the error distribution was roughly normal.

Figure 3. Normal residuals plots of (a) dye yield (b) mordant yield.

The plot of projected against actual vs predicted value was another crucial factor. The scatter of the plot practically touches the diagonal line, this indicates that the model was well designed the experimental data and predicted data by the models were closely related. The actual vs predicted value of dye yield is shown in Figure 4(a,b). The points closely each run actual and predicted values converge on a straight line. This implies that the actual and predicted values were more closely matched.

Figure 4. Actual versus the predicted value of (a) dye yield (b) mordant yield.

Individual effect of extraction parameters on dye and mordant yield

Figure 5(a) shows the effect of dosage on dye yield. When the dosage rapidly increased from 20–40 g/l, the dye yield becomes increased from 14.22–16.86%. With a further increment of dosage from 40–60 g/l, the dye yield becomes slightly increased. As a result, the maximum dye yield of 18.25% was achieved at 60 g/l, due to the high surface area. After 60 g/l, the graph showed that dye yield slightly decreased. Because the amount of dye concentration more than 60 g/l is not easily soluble (Baaka et al. 2015). From the previous report, the dye yield was obtained at 1 g for 45°C and 60 min from red rose (6.7%), plumed cockscomb (1.43%), desert rose (3.3%), and border plant (2.67%) (Zumahi et al. 2020).

Figure 5. Effect of (a) dosage (b) temperature (c) time on dye yield.

Figure 5(b) shows the effect of extraction temperature on the dye yield. As shown from the plot dye yield was very sensitive to the extraction temperature (Adeel et al. 2022, 2023). The dye yield rapidly increased from 13.91% to 17.1% as the temperature increased from 50°C to 70°C. The optimum yield was obtained at around 70°C of extraction temperature. Due to the increment of dye solubility in solvent as temperature increased between the stated ranges. 13.91% of the dye yield was low at a temperature of 50°C because the temperature was not sufficient for the solubility of the dye on the organic solvent. In the other case, the amount of dye yield was slightly decreased from 70°C to 90°C. After 90°C, the yields decreased due to the raw material is denatured and increased loss of solvent. According to the literature report, the dye was extracted from Bombax malabarica flowers (2.8–38.5%) under different operating conditions such as time and temperature are 60–90 min and temperature of 90–95°C (Swamy 2019).

Figure 5(c) illustrates the effect of extraction time on the dye yield. The dye yield slightly increased from 16.70% to 17.01% at the time duration raised from 60 min to 90 min. Further increase in the time up to 120 min, the dye yield dropped to 16.49%. Because the extraction time becomes increased the raw materials were more soluble (Kaushik 2016). But beyond 90 min, the extracted yields were slightly reduced this is due to raw material (spent coffee ground and mango bark) of color components (dye and mordant) being slightly denatured and increased loss of solvent (El-Kammah et al. 2022). Therefore, the maximum dye yield was obtained at 90 min which takes a duration of time to reach equilibrium. Similarly, natural dye yield extracted from date palm pits (Phoenix dactylifera) increases from 12% to 17.5% for extraction times of 60 min to 90 min, respectively. After 90 min, the dye yield decreases with a minimum value of 150 min (Souissi, Guesmi, and Moussa 2018).

Figure 6(b) illustrates the impact of extraction temperature on the mordant yield. The molecular structure expands as the temperature rises, making mordant uptake easier (Adeel et al. 2022). For these reasons, a higher mordant yield was achieved. The temperature increased from 50–70°C and as a result, the mordant yield rapidly increased from 16.38 to 18.31% due to the increment of mordant material solubility in solvent as temperature increased between the stated ranges. The other case is the amount of mordant yield was slightly increased up to 18.53% at a range of temperature from 70°C to 90°C. After 90°C, the yields became decreased due to the degradation of the color components from plant materials (Souissi, Guesmi, and Moussa 2018).

Figure 6. Effects of (a) dosage (b) temperature (c) time on mordant yield.

Figure 6(c) shows the effect of extraction time on mordant yield. The mordant yield slightly increased from 17.09% to 18.32% as the extraction time increased from 60 to 90 min. This implies that the solvent penetrates mordant and more soluble bearing raw materials. For the other case, the amount of mordant yield slowly decreased up to 17.99% at a time range of 90–120 min. After 120 min, the yield became deceased due to the mordant component being degraded and more rise loss of solvent (Hussaan et al. 2023).

Interaction effect of extraction parameters on dye yield

Figure 7(a) illustrates the interaction effect of dosage and temperature with the optimum value of dye yield of 18.31% achieved at a dosage of 60 g/l and a temperature of 70°C. The low temperature was appropriate for higher dye yield. Increasing the extraction temperature from 50 to 70°C caused a decrease in the extraction of the required component (Adeel et al. 2023). With higher dosages and low extraction, the temperature improved the extraction of the coloring component. This comment can be associated with the idea that the saturation point for coloring component was achieved at a medium temperature. Dye and bio-mordant yield reduced as extraction temperature increased beyond 70°C, because the partial degradation (break down into smaller units) of dye and mordant molecules became colorless compounds (Jabar et al. 2023). The degradation of dye components happened at further increments of extraction temperature (Nguyen and Saleh 2020).

Figure 7. 3-D interaction effect of (a) dosage, temperature (b) dosage, time (c) temperature, time on dye yield.

Figure 7(b) shows the interaction effect of dosage and time on dye yield. The dye yield raised from 14.32% to 18.49% at a dosage of 20–60 g/l and for the time of 60–120 min. The dye yield value of 18.49% increased with increasing dosage of 60 g/l and optimum value for a time of 90 min. As the extraction time increased, the interaction between plant materials and extracting solvent increased, hence leading to an increased yield of natural dye in extraction media. However, a further increase in extraction time of 90 min resulted in a decrease in dye yield values. Because of the partial degradation of the dye (coloring) component at constant heating for a longer extraction time (Shahi et al. 2009).

Figure 7(c) illustrates the interaction effects of extraction temperature and time on dye yield. The graph shows the dye yield obtained from 13.56 to 17.01% at a temperature of 50–90°C and for the time of 60‐120 min with a fixed value of dosage. The increment of extraction temperature of 90°C and for an extraction time of 120 min showed the higher dangers of dye bond breakage (Che Sulaiman et al. 2017). This implies that extraction temperature and time had a close relationship with the extracted dye yield. The extraction of dye was highly dominated by extraction temperature with a significant interaction effect (Yin, Fei, and Wang 2018). Therefore, dye extraction should be neither too low at 50°C for 60 min nor too high at 90°C for 120 min.

Interaction effect of extraction parameters on mordant yield

Figure 8(a) illustrates the effect of dosage and temperature on mordant yield. The optimum value of mordant yield of 18.31% was achieved at a dosage of 45 g/l and temperature of 70°C. At maximum extraction, temperature caused a decreased extraction of the required component. The maximum dosage and minimum extraction temperature improved the extraction of the coloring component. Rose beyond 45 g/l, the yields of dye and mordant decreased because it could be attributed to the fact that any additional amount of concentration more than 45 g/l is insoluble, and also, an excess amount of solvents is needed. This comment can be associated with the idea that the saturation point of the coloring component was achieved at a medium temperature (Jabar et al. 2023). The mordant component of bond breakage happened due to further increments in the temperature.

Figure 8. Interaction effect of (a) dosage, temperature (b) dosage, time (c) temperature, time on mordant yield.

Figure 8(b) shows the effect of dosage and time on mordant yield. The maximum mordant yield value of 18.12% was achieved at a dosage of 45 g/l and for a time of 90 min. The fact that as the extraction time increased, the interaction between plant materials and extracting solvent increased leading to increased extracted yield. However, further increment of extraction time for above 90 min achieved less amount yield, because of the partial degradation of the mordant component at constant heating for a longer extraction time (Batool et al. 2022).

Figure 8(c) shows the interaction effects of extraction temperature and time on mordant yield. The graph shows the mordant yield was achieved from 13.56–17.01% at a temperature of 50–90°C and for the time of 60–120 min with a fixed amount of dosage. The maximum mordant yield value of 18.12% was achieved at a dosage of 70°C and for a time of 90 min. The further increment of extraction temperature of 90°C and for an extraction time of 120 min shows the higher dangers of color component bond breakage, for this reason, less amount of yield was obtained (El-Kammah et al. 2022).

Determination of fastness properties on dyed and mordanted cotton fabric

The wash, rubbing and light fastness values of dyed and mordanted cotton fabrics are given in Table 5. These results were evaluated according to the ISO standards method with the grayscale values (rating 3/4–5, 3/4 = good, 5 = excellent) for washing fastness and rubbing fastness and the blue scale values for light fastness (rating 5–8, 5 = good, 8 = excellent).

Table 5. Evaluation of fastness properties of dyed and mordanted cotton fabric.

	Mordant concentration	Dye concentration	Fastness properties
Run	(%)	(%)	Wash fastness	Rubbing fastness	Light fastness
1	16	8	4	4	6
2	12	8	3/4	3	5
3	16	10	3/4	4	6
4	20	6	3	3/4	5
5	20	10	5	4	7
6	12	10	3	4	5
7	12	6	3	3	5
8	16	6	3/4	3/4	6
9	20	8	4	5	6

Wash fastness

The evaluated value for dyed and mordanted cotton fabric obtained from good to very good results (3/4–5). From this fabric sample, the wash fastness testing of dyed and mordanted cotton fabric value was obtained from very good to excellent results (4–5). Because the dye solution has penetrated to fabric sufficiently or dyes that hold strong covalent bonds between dye molecules and fabric.

Rubbing fastness

The acceptable standard range rubbing fastness value of dyed and mordanted cotton fabric has been obtained from good to excellent values 3/4–5. The rubbing fastness value achieved better results between very good to excellent results (4–5). When the fiber was complexed with a mordant, the dye was rendered due to the effect of the insoluble dye.

Light fastness

The outcomes of light fastness for the dyed and mordanted cotton fabric were obtained from good to excellent results (5–8). The acceptable range of light fastness of dyed and mordanted cotton fabric value read from grayscale rating. The light fastness value of dyed and mordanted cotton fabric was obtained from very good to excellent results (5–7). This implies that stronger intramolecular H-bonding which takes the bond in the form of six-membered rings gives dyed cotton fabric better light fastness qualities (less color fading).

Conclusion

The interest in using extracted natural colorants has grown in recent times for application on textile cotton fabric as an eco-friendly, non‐toxic and non‐carcinogenic. For this reason, this study focuses on the extraction of natural dye and natural mordant from plant sources. From the results obtained, it could be concluded that natural dyestuff extracted from spent coffee ground and bio-mordant from mango bark are of textile importance. After the extraction process, the maximum and minimum dye yields of 18.41% and 10.39% were obtained at 60 g/l, 70°C, 90 min and 20 g/l, 50°C$,$ 60 min, respectively. Also, the highest mordant yield of 19.03% was achieved at 45 g/l, 70°C and 90 min. These were due to the higher concentrations of effective components such as phenolic, flavonoid and tannin in the spent coffee ground and mango bark. And also, the results of dyed and mordanted cotton fabric of fastness properties value obtained from good to excellent results (wash and rubbing fastness from 3/4–5). Spent coffee ground and mango bark are potential renewable sources of natural colorants. It has been widely available in Ethiopia and hence gives the benefit of reducing foreign currency for factories. These findings in the future could replace synthetic dyes and solve environmental problems caused by synthetic dyes to a certain extent.

Highlights

• Natural dye stuff extracted from spent coffee ground and natural bio-mordant from mango bark are of textile importance.

• Dyeing experiments were optimized using Response Surface Methodology.

• The dyed and mordanted cotton samples exhibited good fastness characteristics.

• The maximum dye yield of 18.41% was obtained at 60 g/l, 70°C, 90 min.

• The highest mordant yield of 19.03% was achieved at 45 g/l, 70°C and 90 min.

Authors’ contributions

All authors have made substantive intellectual contribution to this study in data analysis, preparation and editing of the manuscript. All authors read and approved the final manuscript.

Acknowledgments

The authors would like to thank Wollo University for supporting this study.

Additional information

Funding

This study was funded by Wollo University.