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The purpose of this study is to extract and characterize a novel natural dye from the leaves of Lannea coromandelica and the extraction with finding ways of dyeing cotton fabric using three mordants.

The colouring agents were extracted from the leaves of Lannea coromandelica using an aqueous extraction method. The extract was characterized using analysis methods of pH, gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared (FTIR), ultraviolet-visible (UV-vis) and cyclic voltammetry measurement. The extract was applied to cotton fabric samples using a non-mordant and three mordants under the two mordanting methods. The dyeing performance of the extracted colouring agent was evaluated using colour fastness properties, colour strength (K/S) and colour space (CIE Lab).

The aqueous dye extract showed reddish-brown colour, and its pH was 5.94. The GC-MS analysis revealed that the dye extract from the leaves of Lannea coromandelica contained active chemical compounds. The UV-vis and FTIR analyses found that groups influenced the reddish-brown colour of the dye extraction. The cyclic voltammetry measurements discovered the electrochemical properties of the dye extraction. The mordanted fabric samples showed better colour fastness properties than the non-mordanted fabric sample. The K/S and CIE Lab results indicate that the cotton fabric samples dyed with mordants showed more significant dye affinities than non-mordanted fabric samples.

Researchers have never discovered that the Lannea coromandelica leaf extract is a natural dye for cotton fabric dyeing. The findings of this study showed that natural dyes extracted from Lannea coromandelica leaf could be an efficient colouring agent for use in cotton fabric.

Natural dyes are mostly used for dyeing of natural fibre textiles to improve their eco-friendly features. For successful commercial use of natural dyes, the appropriate and standardized dyeing techniques need to be adopted. Appropriate scientific techniques or procedures need to be derived from scientific studies on dyeing methods, dyeing process variables, dyeing kinetics and compatibility of selective natural dyes with minimal use of hazardous chemicals.

In the present study, different enzymes (protease, amylase, xylanase, pectinase, phytase) were used efficiently with Rubia dye by using simultaneous and two-step processes; both the processes were developed with an aim for conservation of time and energy, for the ease of industrial use. The highlights of the study are twofold: eco-friendly natural dyeing by using enzyme replacing metal mordant and room temperature dyeing, which is a completely new concept.

Experiments showed that enzymatic treatment can give good colour strength to silk fabric using Rubia as a dye source and has good potential for commercial dyeing. It is a non-toxic dye. Use of enzymes were a deliberate attempt to avoid metal mordanting in silk dyeing, as it would make textile dyeing eco-friendlier. The order of reactivity of enzymes in one-step process was found to be protease > phytase > xylanase > amylase > pectinase. Similarly, for two-step dyeing process, the order of reactivity of enzymes observed was protease > amylase > xylanase = pectinase > phytase. Protease enzyme was the best option in both the cases. Overall, it can be concluded that in the case of enzymatic treatment, the two-step process was better in terms of larger K/S values, colour coordinate values and dye adherence.

A new domain of room temperature dyeing technique has been introduced.

In the present study, different enzymes (protease, amylase, xylanase, pectinase, phytase) were used efficiently with Rubia dye by using simultaneous and two-step processes; both the processes were developed with an aim for conservation of time and energy, for the ease of industrial use. The highlights of the research are twofold: eco-friendly natural dyeing by using enzyme replacing metal mordant and room temperature dyeing, which is a completely new concept. Overall, the ease of use for industrial application. Rubia dye from Sri Lanka has been used in conjunction with different enzymes to show that metal mordanting can be easily replaced by the use of eco-friendly and biodegradable enzymes. The most attractive feature of this study is the low-temperature dyeing at 30-40°C. For any dyeing house, this process can be easily adapted on jigger, winch or even in continuous padding machine. Good fastness properties and dye adherence have been the other highlights of this study.

Artocarpus heterophyllus Lam (local name jackfruit) belongs to the family of Moraceae. It produces natural dye from the bark of the tree which has been shown as a prospective natural dye source for textiles. In the present study, innovative extraction of yellow colorants using ultrasound energy is shown. Dyeing with jackfruit bark extract has been shown to give good dyeing results. Pretreatment with 1 % metal mordant and 4 % of bark extract (owf) was found to be suitable and showed very good fastness properties for cotton, wool and silk dyed fabrics with hue colors ranging from light brown to greenish to brown. The dye uptake by cotton fabric ranged from 55-62%, 68-70% for silk and 59-73% for wool with different mordants. The effectiveness of metal mordant-artocarpus in better dye uptake appears to be an improved process resulting in good dye adherence and good fastness properties.

The purpose of this paper is to evaluate the efficiency of dyeing on cotton wool and silk fabrics with natural dye obtained from kitchen waste of dry skin extract of Allium cepa.

The dry skin of onion produces natural dye which has been used for dyeing textiles. In the present study, innovative dyeing with onion has been shown to give good dyeing results. Pretreatment with 2 per cent metal mordant and using 5 per cent of plant extract (owf) was found to be optimum and showed very good fastness properties for cotton, wool and silk dyed fabrics. For effective natural dyeing with dry skin extract of Allium cepa, conventional method of dyeing was carried out using metal mordants. The purpose of using this source was with an idea to produce value addition dyed product from kitchen waste as the dye has very good potential of uptake, adherence to the fabric and has good wash and light fastnesses. Results show very attractive hue colours.

The preference of using easily and cheaply available material for dyeing by conventional dyeing lowers the cost of natural dyeing and enhances resource productivity and as a result, reduces waste. This makes onion scale one of the easily available materials for natural dyeing industry.

Although metal mordanting with copper sulphate and potassium dichromate are not ecofriendly but we have used only 2 per cent of these metal salts to prepare different shades with dry scales of Allium cepa extract.

The method developed for natural dyeing of cotton, silk and wool fabrics using skin extract of allium in conjunction with metal mordanting has shown very deep coloration. The stepwise dyeing of cotton fabric with metal mordant by the natural dye Allium cepa showed that the stepwise dyeing process gave very good result. The dye uptake in case of stepwise dyeing was from 65‐68 per cent in the case of cotton, 70‐74 per cent in silk and 78‐82 per cent in wool with different mordants.

The method developed for natural dyeing of cotton, silk and wool fabrics using skin extract of allium in conjunction with metal mordanting has shown marked improvement in terms of dye adherence and fastness properties and can thus be recommended for industrial application.