Mango Seed Kernel Agronomical Bio-Waste for Ecofriendly Cotton Dyeing: Optimization of Dyeing Period and Temperature

Typical synthetic colorant and their application processes include various negative eco-toxicological effect and human health risk. Intend to depose the impediments of synthetic dyeing herein mango seed kernel agronomical bio-waste was employed for sustainable dyeing of cotton fabric. 100% cotton knitted single jersey commercially scoured-bleached fabric having areal density of 160 grams per square meter was used for this study. Natural dye was extracted by alkali extraction method from raw seed kernel of Mangifera indica. Optimum dyeing temperature and duration were quantified. Colorimetric appearance of the dyed samples for different dyeing condition were evaluate by using CIE L*a*b* color space in terms of color co-ordinates, color strength (K/S), brightness index (BI) and degree of color levelness values. Dye fiber bonding stability of the dyed fabric was evaluated in terms of colorfastness to wash, water, perspiration, rubbing and light. Overall the colorfastness values were recorded as 4-5 except light fastness. Excellent colorimetric appearance and serviceability indicates future green coloration of cotton fabric through mango seed kernel as well as decent agronomical bio-waste management.


Introduction
In recent decades, synthetic coloration of textiles is the alarming issue around the world because of ecological imbalance as well as a future threat for human being. It was noticed that approximately 250-350kg water consumed to process per kg cotton fabric. Additionally unexhausted synthetic dyes and hazard chemicals produces about 4-37% waste water with huge amount of pollutants [01, 02] more enough for environmental threat. Also exhausted and unexhausted synthetic dyes in fabric caused various human health toxicity as skin sensitization, respiratory problem, carcinogenesis, headaches, dark circle under the eyes, fatigue, lack of concentration etc. [03, 04, 05]. In special cases it may leads cancer [06].
To release from this problem, eco-friendly natural dyeing technologies are thriving worldwide as alternative of synthetic colorant. Inherently the natural dyes have variety of shades and tones. Besides, they are safe for human body and environment, abundant in availability, cheap, and have no disposal problems [07].
Plants, animals or insects, minerals are the typical sources of natural dyes. Now-a-days, different renewable bio-resources products were also using as sources of natural dye to gratify the ecological balance [08].
Among several plant sources, mango could an excellent option of dye source. In a complete mango fruit, the seed partake about 10 to 25%. And in a seed the kernel share is ranging between 45-75%. And roughly the seed presumes as 20% share of the whole fruit [09]. Moreover, mango is considered as the "King of Fruits" in Indian subcontinent and also popular in many tropical courtiers due to its unique delicious taste, captivating flavor with multifarious color, source of nutritive values. Moreover, mango possess different functional properties namely anti-oxidant, anti-viral, anti-diabetic, anti HIV, anti-bacterial, anti-fungal, anti-allergic, anti-microbial, pyro-lytic liquid [10,11]. So, these vast deployments of mango yields huge amount of agronomical waste which have no remarkable effective exploitation. Regarding mango byproduct utilization, several researchers had used mango waste for decolonization of textile effluent. [12,13,14,15].
But mango seed kernel possesses tannins and mangiferin which may have outstanding dyeing characteristics [11,16]. To our best concern so far no study had been carried out for cotton coloration with mango seed kernel. So for the first time here mango seed kernel extracted dye was used for cotton coloration.
In this study, dye was extracted from mango seed kernel according to alkali extraction method. Dying temperature and time was optimized in terms of several colorimetric properties and dye-fiber binding permanency and agronomical bio-waste of mango was effectively exploited as well. Mango (Mangifera indica) seed kernel agronomical waste used as a dye source for this investigation which was collected from Mawlana Bhashani Science and Technology University, Santosh, Tangail-1902. Caustic soda (NaOH) and water (laboratory grade) used for dye extraction. ISO Standard Soap, James heal, England had used for removing the unfixed dye from the surface of colored sample.

Dye Extraction:
At first the ripen mango (Mangifera Indica) seed raw kernel agronomical waste were separated by sharp knife and then crash it in a Hamam dasta. Around 40-50g mango raw kernel weighted in an electric balance and 2 g of Caustic soda dissolved in 200 ml water. Then boiled it at 100℃ about 60 minutes and cooled. A brownish jelly type phase was achieved. The mango kernel jelly strained through the nylon strainer carefully. The extracted dye liquor prepared for dyeing and stored in a glass container in cool place to protect the extracted dye solution from sun rays and avoid unwanted evaporation and possible chemical reaction [17].

Dyeing
Dyeing had carried out according to exhaust method by Infra-red lab sample dyeing machine (XIAMEN RAPID, China) at 40, 60, 80, 100 and 110℃ respectively for 60 minutes ( Figure 2) to find out the optimum dyeing temperature. In all cases 100℃ was noticed as the best dyeing temperature. Latter the samples were dyed about 110, 110, 90, 80, 70, 60, and 50 minutes to find out the best dyeing time (Figure2). After dyeing action, the bath was cooled at 40℃ and samples were washed at room temperature. Samples were squeezed and air dried in flat dryer machine (MESDAN, Italy).Then soaping was performed for removing unfixed dye form the fabric surface by 0.5 g/L ISO standard soap at 80 ℃ for 10 minutes. For both dyeing and soaping material to liquor ratio had kept as 1:20 [18].

Mango tree with fruits
Mango seed kernel (45-70% of seed)  Dual beam reflectance Data-color spectrophotometer, (Spectroflash SF 650X, USA) was used to determine the color co-ordinates value of dyed sample based on CIE Lab system. Following setting was used: Illuminant D65, Medium area view, Specular included and CIE 1964 supple-mental standard observer (10° observer). Each sample was folded twice to give an opaque view with four plies and the color coordinates values were measured automatically [19].

Determination of Degree of Color Levelness:
The degree of color levelness of each dyed sample was measured by using Data color spectrophotometer considering the reading-1 as standard and other nines as sample batches. Data for each batch are analyzed with respect to color difference, ΔE value. ΔE is a single value that takes into account the differences between the L*, a* and b* values of the sample and standard in the CIE L*a*b* color system. The Equation 1 was used to calculate the ΔE value [20] Where, ΔL* = L* sample − L* standard, Δa* = a* sample − a* standard, Δb* = b* sample − b* standard; standard refers to the reading-1 in dyed fabric, sample refers to other readings in the corresponding dyed fabric. The degree of levelness was described according to ΔE values [21] as shown in Table 2.

Determination of Color Strength
The color strength (K/S) value of the dyed samples was evaluated by data color spectrophotometer based on Kubelka Munk theory which gives the relationship (Equation 2) between K/S and R as mentioned below [22,23] Where, R is reflectance of an incident light from the dyed material, K & S is absorption and scattering coefficient of the dyed fabric respectively. Brightness index of dyed sample was measured according to (ISO-2470(ISO- -1977 [18] method using following relationship (Equation 3) after measuring the reflectance value of the corresponding sample by Data color spectrophotometer according to specified setting only specular excluded was set. Each sample was folded twice to give an opaque view with four plies and the reflectance value was measured automatically.
Brightness Index =

Color Co-ordinates value of dyed samples
The dynamic equilibrium state of dyeing process may be attained rapidly by raising the temperature and period for enhance the degree of fibre swelling and the rate of diffusion of dye molecules. But in case of 70, and 90℃ contradictory upshot looked probably due to chemical potential difference between dye-fiber molecule adsorption and desorption simultaneously taken place up to attain equilibrium [19].

Degree of Color Levelness
The table 04 represents the degree of color levelness of different dyed sample at various conditions. The dyeing temperature and time both has negative and positive effects on degree of color levelness [29]. The orders of sample for color levelness dyed at constant dyeing period about 60 minutes were noticed as 0.177>0.144>0.139>0.128>0.105 respectively for 110>40>80>60>100 ℃ . The lowest ∆E value was recorded for sample 100℃ i.e. the excellent levelness. The samples of 110, 80, 60 and 40 were 40.67%, 24.46%, 17.97% and 27.08% less level than the samples of 100℃. Similarly for color levelness for constant dyeing temperature the orders of samples were determined as 0.323>0.262>0.206>0.171>0.152>0.135>0.127 respectively for 90>50>100>70>110>80>60 minutes where the excellent levelness obtain for 60 minutes samples i.e. lowest ∆E value. Though there was color difference in ∆E, but all the samples exhibit excellent degree of color levelness. Though, there was difference in average color difference value but all samples showed excellent color levelness. The continuing upturn of dyeing time and temperature boosts the fiber swelling to promote easier penetration of dye into interior of the fiber homogeneously which conceivably leads positive impact on color levelness [19].

Color Strength (K/S) Value, Reflectance and
Brightness Index Figure 04 and 06 represents the color strength (K/S) value, reflectance and brightness index upshots different samples for dyeing time and temperature variation. For constant dyeing duration, at various temperature samples the order of K/S values were recorded as 3.97>3.67>3.48>3.80>2.69 for 100>110>80>60>40 ℃ respectively. Maximum K/S values were revealed for the sample of 100℃. The specimens of 110, 80 and 60℃ samples were 26.70%, 22.70% and 29.21% more strong respectively than the sample of 40℃. The maximum color strength at 100℃ was 32.24% higher than minimum.
Similarly for constant dyeing temperature at 100℃ for altered dyeing duration the samples order were noticed as 3.51>3.49>3.47>3.15>3.12>2.52>2.43 for 60>100>80>90>50>110>70 minutes respectively. The maximum color strength at was appeared at 60 minutes. The samples of 110, 90, 80, 60 and 50 minutes dyeing period were calculated as 3.57%, 22.85%, 29.97%, 30.76% and 22.11% more strength respectively than that of 70 minutes. The minimum color strength was 30.37% higher than the lower color strength value. For successive increase in dyeing time and temperature the rate of diffusion of dye molecules in the bulk of dye bath increase the gradient of dye adsorption rate on fibre surface i.e. pseudo-second order rate constant remarkably which bolster the fashion of yielded K/S values. Thermal degradation may be a probable reason of lower K/S value at 110℃ [19]. In case of reflectance%, the samples order was observed as 14.41>1273>11.93>11.68>11.45 respectively for 40>100>60>110>80℃ (figure 5 and 6) in case of the dyeing period 60 minutes. The minimum reflectance was obtained for the sample at 80℃; more dark shade and it was 0.23%, 1.28%, 0.48% and 2.96% more than the sample of 110, 100, 60 and 40 ℃ .  Table 05 indicates the colorfastness properties of different samples dyed in various conditions. All most overall result of colorfastness to wash was very good to excellent. The sample of 100℃ and 60 minutes showed the optimum result little bit staining in wool. The sample dyed for 60 minutes at 100℃ performed better against colorfastness to wash very good to excellent. It has a very good rating in cotton and polyester. Except samples at 40 and 110℃ about dyeing 60 minutes all samples were exhibited excellent results in color change.

Color Fastness to Rubbing and Light
The performance of different conditional (time and temperature) dyed samples in case of rubbing and light fastness have showed in the table 06. The overall results of colorfastness to rubbing were good to very good. The sample dyed at 100 and 80℃ about 60 minutes were achieved the rating very good. Sample dyed at 100℃ about 60 minutes showed very good rating in both dry and wet rubbing. The performance of the dyed samples against light fastness is fair to moderate but not satisfactory. The pigments of natural dye may be unstable in light because sunlight can damage the dye-fiber interaction.  Table 07 illustrates the color fastness to water properties of different dyed sample. All most all sample showed the excellent result in case of color change and color staining without sample dyed at 110 and 40℃ about 60 minutes due to low temperature or excess temperature in dyeing. At low temperature dye-fiber interaction causes less strength and may be in high temperature natural dyes are unstable.   Table 08 showed the result of colorfastness to perspiration of different dyed samples. Overall result of colorfastness to perspiration both acidic and alkaline was very good to excellent. Except 110℃ color change of dyed samples were very good to excellent but staining in color good to very good. It causes worst result at low dyeing temperature and low dyeing time 50 minutes 40℃.

Color Fastness to Perspiration
With increasing the dyeing temperature and time it improves the fastness properties may be due to their better fixation as example 80 and 100℃ dyed sample about 60 minutes also 60, 70, 80, 90 and 100 minutes samples at 100℃. Higher dyeing time and temperature may swell the fiber more as dye uptake and fixation more but excess time and temperature may cases the damage of natural dye due to their instability and also damaged by excessive alkaline or acidic condition.