Sustainable Extraction of Indigo from Natural Sources and Textile for Green Electronics

The textile and electronic industries have experienced escalating concerns regarding manufacturing practices and sustainable recycling. More specifically, the extensive use of indigo dye in the denim industry presents significant challenges. For instance, the improper management of denim waste leads to serious ecological issues, because of the release of the indigo. Similarly, improper disposal of e-waste leads to the release of toxic substances, like mercury or cadmium.<br/>Further, utilizing bio-sourced or recycled organic materials, such as indigo, for electronics could help to avoid the need for petroleum-based precursors for the synthesis of those materials. Unfortunately, the conventional extraction methods for these materials from bio-sources or waste are often harmful for the environment due to the use of toxic chemicals and energy extensive processes.<br/>Here, we propose to extract indigo from <i>Persicaria tinctoria</i> and textile waste, such as denim, using a low-energy, environmentally benign process. Because it is well-suited to the climates of Europe and North America, <i>Persicaria tinctoria</i> is preferred in this study over Indigofera tinctoria, a plant more commonly used because of its high yield. Collecting data on <i>Persicaria tinctoria</i> and recycled indigo from textiles, such as denim, could encourage the use of these sources over synthetic indigo or <i>Indigofera</i> imports.<br/>Initially, analytical chemistry and spectroscopic methods have been used to obtain indigo concentration and ion determination and concentration in the bio-source. Afterwards, after indigo extraction by adoption of an optimal extraction protocol following LCA considerations, we have proceeded to study optical absorption, conductivity and photoconductivity in indigo printed films. The results of the systematic comparison between the functional properties of synthetic, bio-sourced and recycled indigo will be also included in the present contribution.<br/><br/><b>References:</b><br/>John, P. (2009). Indigo – Extraction. <u>Handbook of Natural Colorants</u><b>: </b>105-133.<br/>Michels, L., et al. (2021). "Electronic and structural properties of the natural dyes curcumin, bixin and indigo." <u>RSC Adv</u> <b>11</b>(23): 14169-14177.<br/>Wan, Z., et al. (2024). "Electrocatalytic recycling of indigo dye from waste denim fabric: an engineering approach toward efficient denim dye reuse." <u>Textile Research Journal</u>.<br/>Saikhao, L., et al. (2017). "Comparison of sodium dithionite and glucose as a reducing agent for natural indigo dyeing on cotton fabrics." <u>MATEC Web of Conferences</u> <b>108</b>: 03001.<br/>Irimia-Vladu, M., et al. (2012). "Green and biodegradable electronics." <u>Materials Today </u><b>15</b>(7): 340-346.