Open Access

ARTICLE

Reduction Discoloration of Reactive Dyed Cotton Waste and Chemical Recycling via Ionic Liquid

by Aline Ferreira Knihs, Larissa Klen Aragão, Miguel Angelo Granato, Andrea Cristiane Krause Bierhalz^*, Rita de Cassia Siqueira Curto Valle

Department of Textile Engineering, Federal University of Santa Catarina, Blumenau, 89036-256, Brazil

* Corresponding Author: Andrea Cristiane Krause Bierhalz. Email:

Journal of Renewable Materials 2024, 12(9), 1557-1571. https://doi.org/10.32604/jrm.2024.052963

Received 20 April 2024; Accepted 08 July 2024; Issue published 25 September 2024

Abstract

The textile industry generates large volumes of waste throughout its production process. Most of this waste is colored, therefore, discoloration is an important step toward recycling and reusing this waste. This study focused on the chemical reductive discoloration of textile waste composed of cotton dyed with reactive dye. The experimental design demonstrated the significant influence of the concentration of reducing agent and time of reaction on the degree of whiteness of the cotton fibers. The concentration of the alkaline agent was not significant in the process. The optimization of the reaction conditions lead to Berger degree of 50.5 ± 3.5. The discolored cotton was chemically recycled through dissolution in ionic liquid 1-ethyl-3-methylimidazolium chloride and regeneration in film form in water. The microstructure of the regenerated cellulose films was evaluated by Scanning Electron Microscopy (SEM) indicating complete dissolution and uniform regeneration. The discoloration process reduced the polymerization degree and crystallinity index of the cotton fibers but retained the cellulose I structure. The dissolution and cellulose regeneration process results in transparent films with an amorphous structure. The thermal behavior, evaluated by thermogravimetric analysis, indicated that residues and regenerated film presented a main decomposition step. The maximum decomposition rate temperature of the regenerated films was approximately 40°C lower than the cotton fibers, which correlates well with the reduction in polymerization degree and amorphous structure. In general, the study demonstrated that textile cotton waste dyed with reactive dyes can be chemically discolored to form transparent and amorphous films, contributing to the development of sustainable strategies for the textile industry.

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