The release of aqueous residues generated by the extraction process of essential oils presents a real risk of environmental pollution. This work aims to reduce this risk and produce value-added materials. The aqueous residue of Dittrichia graveolens (D. graveolens) hydrodistillation has been reused in two valorization ways: 1/ in the ecological dyeing. 2/ in biological eld. First, a phytochemical study of the aqueous residue was carried out by determining the ployphenols and avonoids content and high performance liquid chromatography (HPLC) analysis. Second, the eco-dyeing process with the aqueous residue was performed on the polyamide fabric, the process was optimized by the surface response methodology using Minitab software and was evaluated by the fastness tests for the optimal conditions. Third, the aqueous residue was assessed for its biological activities. Promising coloring power and biological potential of the aqueous residue showed that this last could be an important source for developing environmentally friendly natural dyes and bioactive products.

The objective of this work was to determine the chemical composition, the antioxidant and antibacterial activities of the essential oils (EOs) extracted by hydrodistillation from different organs of the D. viscosa: flowers, leaves and aerial parts. The main compounds identified by GC/MS are oxygenated sesquiterpenes. Among these compounds, (E)-nerolidol (40.7%) is the most abundant constituent of flowers' essential oil while caryophyllene oxide (9.9%), isolongifolan-7-α-ol (10.3%) and α-eudesmol (9.1%) are the major constituents of the leaves' essential oil. The presence of these compounds in the aerial parts' essential oil is solely due to those of the flowers and leaves that constitute these aerial parts. The volatile extracts showed antioxidant effects with IC 50 values ranging between 9.25 and 9.75 mg.mL −1. On the other hand, EOs showed antibacterial effects on both Gram-positive and Gram-negative bacteria. The highest activity was obtained with flowers' essential oil against Enterococcus faecalis and Escherichia coli.

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The agro-sector generates organic waste of various kinds, which potentially could be used to prepare functional materials, lessen environmental problems, and enhance circularity. In this context, the hypothesis that was put forward in this work is that prickly pear seed waste from the Tunisian agro-food industry could be used to prepare activated carbons. The prickly pear seed waste was first hydrothermally carbonized and the resulting hydrochar was activated in CO2 at 800 °C. The yield of the hydrothermal carbonization process is of importance, and it was the highest at intermediate dwell times and temperatures, which was ascribed to the re-precipitation of hydrochar particles on the heat-treated biomass. The hydrochars and activated carbons were characterized with scanning electron microscopy, thermogravimetry, Raman spectroscopy, and N2 and CO2 adsorption/desorption analyses. The activated carbons had micro- (<2 nm) and mesopores (2–50 nm), and specific surface areas and total pore volumes of about 400 m2 −1 and 0.21 cm3 g−1. The study showed that the prickly pear seed waste could be effectively transformed into both hydrochars and activated carbons and that is advisable to optimize the hydrothermal process for the mass yield. A life cycle analysis was performed to assess the environmental impact of the production of typical activated carbons using the approach of this study. Further studies could be focused on enhancing the properties of the activated carbons by further optimization of the activation process.

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