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Communication Dans Un Congrès Année : 2023

NMR kinetic monitoring of the cutting fluid organic waste’s hydrolysis all along the immobilization in alkali-activated materials

Résumé

Geopolymers (GP) are synthetic inorganic aluminosilicate cements that are formulated at room temperature by activating a precursor solid in alkaline conditions. Recently, the immobilization of organic liquids (OL) into GP has been successfully applied to nuclear waste, where the OL is permanently confined in the form of micrometric droplets. One type of OL that is commonly found in nuclear waste is cutting fluids, which currently have no direct treatment route. In this study, the immobilization of cutting fluids into GP is investigated. Cutting fluids are typically emulsions of OL in water – with various additive depending on the specifications of the cutting operation – and eco-friendly cutting fluids are often made of vegetable oils, which are triglycerides. When these oils are immobilized in GP under highly alkaline conditions, saponification reactions are thought to occur, transforming the triglycerides into carboxylates and glycerol. On one hand, the fatty acid soaps produced by this reaction act as surfactants, making it easier to immobilize the OL by dispersing it in small droplets within the GP matrix. On the other hand, the division of a molecule with a high molecular size into smaller molecules promotes the phenomenon of leaching and the diffusion of these molecules outside of the matrix. The saponification kinetics in a GP environment are studied in this research using Nuclear Magnetic Resonance (1H NMR) Spectroscopy. Sunflower oil is initially hydrolyzed in a typical GP porewater composition, and the resulting saponification products are quantified, with a focus on glycerol and fatty acid soaps [1]. The study finds that saponification is almost complete, with only small amounts of by-products present (Figure 1). During the geopolymerization, the silicate species present in the activating solution act as “hydroxide reservoirs”, and progressively release the hydroxide ions during the condensation of aluminosilicate species [2]. Therefore, 29Si NMR investigates the structures changes of silicate species during the geopolymerization, in order to evaluate the effect of the saponification reaction. The research also investigates the incorporation of a commercial cutting oil into GP, to determine how saponification reactions occur and whether they modify the cutting oil composition. The study seeks to identify mobile components of the cutting oil within the GP porewater and to explore means of retaining them within the GP. References 1. Bassetti, J., Pierlot, C., Davy, C., Lambertin, D., & Poulesquen, A. (2023). Characterization of hydrolysable organic nuclear waste prior to their immobilization in geopolymers by quantitative 1H NMR. Science Talks, 100205. 2. Aupoil, J., Champenois, J.-B., d’Espinose de Lacaillerie, J.-B., & Poulesquen, A. (2019). Interplay between silicate and hydroxide ions during geopolymerization. Cement and Concrete Research, 115, 426–432.
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Dates et versions

hal-04547906 , version 1 (16-04-2024)

Identifiants

  • HAL Id : hal-04547906 , version 1

Citer

Christel Pierlot, Jordan Bassetti, Catherine Davy, Arnaud Poulesquen, David Lambertin. NMR kinetic monitoring of the cutting fluid organic waste’s hydrolysis all along the immobilization in alkali-activated materials. Formula XI, Jul 2023, Lille, France. ⟨hal-04547906⟩
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