Sustainability: Obtaining natural dyes from waste matrices using the prickly pear peels of opuntia ficus-indica (L.) miller

In this work, the effect of dyes extracted through the Naviglio method (an eco-innovative solid-liquid extraction technique) was tested, which proved interesting for such an extraction. The dyes extracted from Opuntia ficus-indica (L.) Miller waste were treated to maximize the extraction of the coloring molecules. The extraction method was compared with conventional methods under the same conditions. The results showed that the extracts obtained with the different techniques, in the same extraction conditions (solvent, pH, temperature, time), were richer in the pigments for the extract obtained with the Naviglio method. The stability of the dyes was tested before the staining. A plant-based fiber, cotton, as well as an animal-based fiber, wool, were chosen for the staining tests. For the two types of fiber, two etching methods were used: one with rock alum, a method widely used to fix a color and one with lemon juice, a method used for a long time by rural populations who practiced the coloring of hides and tissues. In addition, the qualitative content of the pigments was also verified with an HPLC profile of the Opuntia ficus-indica (L.) Miller extracts. Ultimately, the results suggest that the Opuntia ficus-indica (L.) Miller fruit can be of great interest as a natural source of dyes and be used for tinctures.