Abstract
This study is a novel approach toward the development of a chemical-free and sustainable textile dyeing process with minimum environmental risks. Cotton fabrics were cationized with (3-chloro-2-hydroxypropyl) trimethylammonium chloride in four concentrations and subsequently dyed with the black tea extract. Eco-friendly colorant extraction from raw black tea leaves was carried out in aqueous media avoiding the use of hazardous organic solvents. The major coloring components in the black tea extract are polyphenols like theaflavins and thearubigin. Cationized cotton fabrics were dyed in four different shade depths without employing auxiliary chemicals in the dyeing process. For comparison, un-cationized cotton was dyed with the same extract in the same shades. It was observed that un-cationized cotton samples exhibited very low color strength (K/S) values and excellent colorfastness rating. However, the cationized samples showed remarkable enhancement in their color strength with an increase in the concentration of the cationizing agent. Furthermore, colorfastness to washing, rubbing, and perspiration was excellent, but lightfastness was poor. Deep shades (K/S = 8.996) were obtained for cotton sample cationized (20 g/l) and dyed (6%) shades. Thus, the extraction of natural colorants without toxic solvents, economically viable surface modification of cotton, and chemical-free dyeing render the dyeing process cleaner, sustainable, and practicable at an industrial scale. The textile units could easily adopt this approach to regulate a pollution-free dyeing process without modifying their existing infrastructure.
Highlights
The textile dyeing and finishing industry contributes more to water contamination and environmental pollution around the world (Hossain et al, 2018; Khan et al, 2018; Khan et al, 2020)
It was observed that cotton cationized in the concentration (5 g/l) revealed better color strength (K/S) values when dyed with black tea extract in various shade depths (Figure 2)
The un-cationized cotton fabrics showed no significant affinity to black tea extracts and revealed very low color strength (K/S) values
Summary
The textile dyeing and finishing industry contributes more to water contamination and environmental pollution around the world (Hossain et al, 2018; Khan et al, 2018; Khan et al, 2020). The increasing demand for eco-safety has forced textile industries to implement cleaner production technologies, rather than the adoption of effluent treatment strategies. It is better to adopt cleaner production approaches to minimize the waste generation in textile dyeing and processing units. To this end, several advancements including the production of synthetic dyes with better fixing properties and improvements in dyeing processes have helped to reduce the use of auxiliary chemicals. There has been an increasing demand to minimize the negative ecological impacts of synthetic dyes in textile dyeing and replace them with bio-based colorants (Vankar et al, 2007; Vankar and Shanker, 2008; Haji, 2017). Natural dyes have emerged as biocompatible, environment-friendly, and non-toxic substitutes, and their facile applications could validate the concept of pollution-free dyeing of textile materials (Ibrahim et al, 2010; Baaka et al, 2018)
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