Citation: Slama, N.; Ben Ticha, M.; Smiri, B.; Dhaouadi, H. Exploration of the Fluorescence Property of Acrylic Fibers Dyed with the Residues Extract of Juglans regia Barks. Sustainability 2022, 14, 12275. https://doi.org/10.3390/su141912275 Academic Editor: Matthew Jones Received: 29 August 2022 Accepted: 21 September 2022 Published: 27 September 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Article Exploration of the Fluorescence Property of Acrylic Fibers Dyed with the Residues Extract of Juglans regia Barks Nourhene Slama 1 , Manel Ben Ticha 2, *, Badreddine Smiri 3,4 and Hatem Dhaouadi 1 1 Faculty of Sciences of Monastir, Research Laboratory—Environmental Chemistry and Clean Processes (LR21ES04), University of Monastir, Monastir 5000, Tunisia 2 Department of Early Childhood, University College of Turabah, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia 3 Laboratoire de Micro-Optoélectronique et Nanostructures (LR99ES29), Faculté des Sciences Monastir, Université de Monastir, Avenuede l’Environnement, Monastir 5019, Tunisia 4 LPCNO, INSA-CNRS-UPS, Université de Toulouse, 31077 Toulouse, France * Correspondence: mobenticha@tu.edu.sa Abstract: This study aims to check the fluorescence property of acrylic fabrics dyed with Juglans regia bark extract. Fluorescence measurements have been developed on the aqueous extract and acrylic samples. The extraction process was assisted by a microwave with the following conditions: a concentration of 5 g·L -1 , a power of 850, a pH of 5 and an extraction duration of 4 min. Afterwards, the dyeing quality was assessed by measuring the color strength (K/S) and the photoluminescence intensity (PL) of acrylic fibers dyed at 350 W for 3 min, with the extract already prepared. The effect of certain factors (pH, power, concentration and duration of dyeing) on the dyeing process was also investigated. Subsequently, this process was optimized thanks to the surface response method in order to maximize the photoluminescence intensity of dyed acrylic fibers. Best dyeing properties were achieved at 500 W, pH 2 for 4 min. The results showed good washing fastness and acceptable light fastness. Keywords: natural dye; microwave extraction; optimization; photoluminescence 1. Introduction Synthetic substances such as pesticides, dyes and plastics are non-bio-degradable because of their complicated and long structures. Their natural cycle takes a prolonged period to lead to an environmental contamination. For environmental regulation, natural dyes have been exanimated to replace the synthetic ones. They provided part of the pigments used in paint and were also of great importance in the cosmetic, pharmaceutical and food industry [1–5]. The use of natural organic dyes represents a strategic choice whose importance would be wrong to underestimate [6–11]. In fact, in the same way as leather, furs and animal and vegetable textile fibers, dye plants are renewable resources of coloring matter. In this research, particular importance should be attached to tinctorial species that are unknown but abundant in Tunisia and in all the Mediterranean countries. In this paper, a special focus is put on the residues of Juglans regia, Juglandaceae, widely known as Persian or English walnut. In traditional medicine, Juglans regia is a valued medicinal plant with a capability to act as an antidote against different diseases. Thanks to its anti-inflammatory and antioxidant activity [12], the bark of Juglans regia is used as tooth brush. In addition, many countries (Iran, Saudi Arabia, etc.) use this plant as a natural dye (lips coloring). Juglans regia bark extract has also been used to dye wool fabrics [12,13]. Acrylic is one of the fibers that are difficult to dye because of the electrostatic repulsions which can develop between the carboxylate groups COO- of the dyes and sulfonates SO 3 - of the acrylic. In the case of natural dyeing, this fiber generally Sustainability 2022, 14, 12275. https://doi.org/10.3390/su141912275 https://www.mdpi.com/journal/sustainability