Hydrochars from lavandin straw waste for energy and environmental applications ; Les hydrochars de déchets de paille de lavandin valorisés comme combustible solide et comme matériau adsorbant

The Provence-Alpes-Côte d'Azur region in the south-east of France has been one of the main production centres of the perfume and cosmetics industries for centuries. The extraction of Lavandin yields 100 kilograms/ha of essential oil, while a large amount of solid waste, known as lavandin distilled straw, is generated. The objective of this thesis work was to explore economic and environmental friendly valorisation routes of this waste in order to convert it into high value-added products.For that, Lavandin straws (L) waste was submitted to hydrothermal carbonization (HTC) in order to get a carbonaceous material called hydrochar. The valorisation of Lavandin straw (L) and its hydrochars as solid fuel and adsorbent was investigated in this thesis.For the production of fuel, the L was subjected to HTC at various temperatures (180 to 260ºC) and retention times (1 to 20 h). In order to evaluate the quality of hydrochars as solid fuel, fuel properties were evaluated according to the severity factor calculated based on HTC temperature and retention time. The obtained hydrochars presented fuel properties close to sub-bituminous coal and lignite.For the valorization of Lavandin as adsorbent, the most suitable hydrochar for adsorption was selected. Adsorption of Ni(II), Cd(II), Pb(II) on L, hydrochar, NaOH- and HNO3-modified hydrochar was studied as a function of contact time, pH, initial single concentration of metal, initial mixed concentrations of metals. Pb(II) was more efficiently adsorbed than Ni(II) and Cd(II), on all adsorbents. When metals were simultaneously present, surface competition occurred. Surface modifications using NaOH or HNO3 improved the adsorption capacity of hydrochar, but the production yield of modified hydrochar was low when high concentration of acid was used for the surface modification.Lavandin straw can be valorised as solid fuel and adsorbent in an environmental and economic approach. ; La région Provence-Alpes-Côte d'Azur, dans le sud-est de la France, est depuis des siècles l'un des ...