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In the past century, waste production has risen tenfold, and by 2025 it will double again to reach 6 million tonnes per day1. Solutions have then to be found to this waste problem. Organic waste (e.g. pig slurry, sewage sludge etc.) represent a significant part of the world waste production and can be valorized following two routes. The first one is agricultural recycling. Organic wastes (OW) have fertilizing properties and can be used as an alternative to chemical fertilizers2. The second one is an energetic valorization. OW can be digested to produce biogas used to generate electricity and heat. Besides, this digestion produces a byproduct than can also be recycled in agriculture3. However, OW can have high pollutant concentration among which heavy metal (HM) is particularly concerning. Indeed, soils that have been amended with OW can present HM accumulation at their surface layers4. This accumulation could induce phytotoxicity and groundwater quality degradation. Consequently, the fate of HM in the cultivated soil system after OW amendment is a key issue, and it can better be predict by determining their speciation in the OW. Studies that investigate heavy metal speciation in OW with X-ray absorption spectroscopy (XAS) are presented. In the first study, pig slurry spreading on a tropical soil is used as an example (agricultural recycling valorization). Pig slurry present high concentration of Cu and Zn. Field experiment showed Cu and Zn accumulation in soil at different layers4. XAS permitted to elucidate the Cu and Zn speciation in pig slurry5 and explain their behavior on the field. The second study deals with anaerobic digestion of OW (energetic valorization). The anaerobic digestion of the studied OW permitted the production of methane, but increased the Cu and Zn concentration in the by-product. XAS was used to compare the Cu and Zn speciation in the OW (before digestion) and in the by-product (after digestion). Results shows that the anaerobic digestion ten

In the past century, waste production has risen tenfold, and by 2025 it will double again to reach 6 million tonnes per day1. Solutions have then to be found to this waste problem. Organic waste (e.g. pig slurry, sewage sludge etc.) represent a significant part of the world waste production and can be valorized following two routes. The first one is agricultural recycling. Organic wastes (OW) have fertilizing properties and can be used as an alternative to chemical fertilizers2. The second one is an energetic valorization. OW can be digested to produce biogas used to generate electricity and heat. Besides, this digestion produces a byproduct than can also be recycled in agriculture3. However, OW can have high pollutant concentration among which heavy metal (HM) is particularly concerning. Indeed, soils that have been amended with OW can present HM accumulation at their surface layers4. This accumulation could induce phytotoxicity and groundwater quality degradation. Consequently, the fate of HM in the cultivated soil system after OW amendment is a key issue, and it can better be predict by determining their speciation in the OW. Studies that investigate heavy metal speciation in OW with X-ray absorption spectroscopy (XAS) are presented. In the first study, pig slurry spreading on a tropical soil is used as an example (agricultural recycling valorization). Pig slurry present high concentration of Cu and Zn. Field experiment showed Cu and Zn accumulation in soil at different layers4. XAS permitted to elucidate the Cu and Zn speciation in pig slurry5 and explain their behavior on the field. The second study deals with anaerobic digestion of OW (energetic valorization). The anaerobic digestion of the studied OW permitted the production of methane, but increased the Cu and Zn concentration in the by-product. XAS was used to compare the Cu and Zn speciation in the OW (before digestion) and in the by-product (after digestion). Results shows that the anaerobic digestion ten

Very high levels of C content characterize Andic horizons of volcanic soils. Stabilization of organic matter is due to the presence of short-range ordered aluminosilicates (imogolites, allophanes or proto-imogolites). These phases are often characterized through selective chemical extractions from which the "allophane" content is calculated. However, chemical dissolutions preclude the characterization of the structure of the short-range ordered aluminosilicates. Imogolite is easily distinguishable because of its tubular structure, whereas allophane compounds-usually described as spheres-are harder to identify, especially because of their variable structure and occurrence patterns. In addition, the local structure of allophanes can be very similar to that of proto-imogolite (imogolite precursor). Strangely, this similarity is seldom considered in most characterization studies. In this context, our study focuses on the structure of two short range-ordered aluminosilicates of two different origins, from: (i) an Andosol B horizon (Andosol sample); and (ii) a weathered pumice grain (pumice sample). These natural samples were compared to a synthetic proto-imogolite. The three samples were analyzed using experimental tools that are commonly used for the identification of these nanophases (chemical composition, X-ray diffraction, nuclear magnetic resonance, Fourier transform infrared spectroscopy and transmission electron microscopy). The three samples exhibited the same local structure, but significant differences were observed at a larger scale. The pumice sample clearly showed ring-shaped particles, while the Andosol sample and the synthetic proto-imogolite were amorphous. Our results suggest that poorly ordered proto-imogolite, rather than allophanes, is present in Andosol horizons.

Reactivity of nanopar8cles represents a central issue for many laboratories around the world. Among many supported efforts the control of the morphology of nanopar8cles is mo8vated by the fact that morphology strongly influence the proper8es of the final products. Among the vast family of available nanopar8cles, imogolite is a clay nanotube for which perfect control of the diameter is possible. Imogolites were first observed in volcanic soils[1]. They are natural aluminosilicate nanotubes having the general formula (OH)3Al2O3SiOH with a 2 nm external diameter and up to micrometers in length. The impressive monodispersity in imogolite nanotube diameter has mo8vated research on their forma8on mechanism. Synthesis protocols to produce imogolite were quickly developed. Farmer et al. were the first to obtain synthe8c imogolite using low concentra8ons of AlCl3 and SiO 2 monomers as star8ng materials (millimolar concentra8ons of the reagents) [2]. However, the produc8on of large amount of imogolite or imogolite type materials remained challenging for long 8me. We will present our most recent results concerning the possibility to produce imogolite type materials from highly concentrated stock solu8ons. We will also detail the possibility to form double wall Al- Ge nanotubes and the different stages of their forma8on [3-7]. We will then detail the surface reac8vity of these nanotubes toward metals at he lab scale as well as in natural soil.

Reactivity of nanopar8cles represents a central issue for many laboratories around the world. Among many supported efforts the control of the morphology of nanopar8cles is mo8vated by the fact that morphology strongly influence the proper8es of the final products. Among the vast family of available nanopar8cles, imogolite is a clay nanotube for which perfect control of the diameter is possible. Imogolites were first observed in volcanic soils[1]. They are natural aluminosilicate nanotubes having the general formula (OH)3Al2O3SiOH with a 2 nm external diameter and up to micrometers in length. The impressive monodispersity in imogolite nanotube diameter has mo8vated research on their forma8on mechanism. Synthesis protocols to produce imogolite were quickly developed. Farmer et al. were the first to obtain synthe8c imogolite using low concentra8ons of AlCl3 and SiO 2 monomers as star8ng materials (millimolar concentra8ons of the reagents) [2]. However, the produc8on of large amount of imogolite or imogolite type materials remained challenging for long 8me. We will present our most recent results concerning the possibility to produce imogolite type materials from highly concentrated stock solu8ons. We will also detail the possibility to form double wall Al- Ge nanotubes and the different stages of their forma8on [3-7]. We will then detail the surface reac8vity of these nanotubes toward metals at he lab scale as well as in natural soil.

Very high levels of C content characterize Andic horizons of volcanic soils. Stabilization of organic matter is due to the presence of short-range ordered aluminosilicates (imogolites, allophanes or proto-imogolites). These phases are often characterized through selective chemical extractions from which the "allophane" content is calculated. However, chemical dissolutions preclude the characterization of the structure of the short-range ordered aluminosilicates. Imogolite is easily distinguishable because of its tubular structure, whereas allophane compounds-usually described as spheres-are harder to identify, especially because of their variable structure and occurrence patterns. In addition, the local structure of allophanes can be very similar to that of proto-imogolite (imogolite precursor). Strangely, this similarity is seldom considered in most characterization studies. In this context, our study focuses on the structure of two short range-ordered aluminosilicates of two different origins, from: (i) an Andosol B horizon (Andosol sample); and (ii) a weathered pumice grain (pumice sample). These natural samples were compared to a synthetic proto-imogolite. The three samples were analyzed using experimental tools that are commonly used for the identification of these nanophases (chemical composition, X-ray diffraction, nuclear magnetic resonance, Fourier transform infrared spectroscopy and transmission electron microscopy). The three samples exhibited the same local structure, but significant differences were observed at a larger scale. The pumice sample clearly showed ring-shaped particles, while the Andosol sample and the synthetic proto-imogolite were amorphous. Our results suggest that poorly ordered proto-imogolite, rather than allophanes, is present in Andosol horizons.

Abundance within andosols of highly reactive aluminosilicate nanoparticles makes of these an important factor affecting soil dynamics (carbon sequestration1, trapping pollutants2 ...). Gaining knowledge of the structural characteristics of such nanoparticles is of fundamental importance to understand their interactions with the different soil compartments. Aluminosilicate nanoparticles can adopt two main structures. Imogolites (Al2SiO3(OH)4), natural aluminosilicate nanotubes that have been well characterized since their discovery in 19723; And allophanes, aluminosilicates with identical chemical composition but with a different structure. allophanes have been described as hollow nanospheres with a diameter ranging from 3 to 5 nm and their structure depends on the Al/Si ratio: (i) Al-rich allophanes (Al/Si=2, Imogolite type local structure); (ii) Si-rich allophanes (Al/Si<2). Nonetheless, the only evidence for allophanes spherical nature up to date has solely come from TEM observations. The actual morphological structure of allophanes still needs to be further investigated. In the present work, Aluminosilicate samples obtained from soils collected in La Reunion (a French volcanic island in the Indian Ocean region) are studied using an array of diverse characterization techniques. While XRD and FTIR results are consistent with the characteristic allophane fingerprint, NMR analysis reveals an imogolite-type local environment of silicon and aluminium, pointing to a type i Al-rich structure. However, no spherical objects could be observed using TEM. In view of such observations, we propose that the structure of these type i Allophane is not consistent with that of a hollow sphere geometry. To obtain further insight into this matter, we synthesised aluminosilicate nanoparticles (both allophane and imogolite), and thoroughly characterized them using a wide variety of high specificity techniques ranging from the macro crystalline structure (TEM, XRD) to the atomic scale

Abundance within andosols of highly reactive aluminosilicate nanoparticles makes of these an important factor affecting soil dynamics (carbon sequestration1, trapping pollutants2 ...). Gaining knowledge of the structural characteristics of such nanoparticles is of fundamental importance to understand their interactions with the different soil compartments. Aluminosilicate nanoparticles can adopt two main structures. Imogolites (Al2SiO3(OH)4), natural aluminosilicate nanotubes that have been well characterized since their discovery in 19723; And allophanes, aluminosilicates with identical chemical composition but with a different structure. allophanes have been described as hollow nanospheres with a diameter ranging from 3 to 5 nm and their structure depends on the Al/Si ratio: (i) Al-rich allophanes (Al/Si=2, Imogolite type local structure); (ii) Si-rich allophanes (Al/Si<2). Nonetheless, the only evidence for allophanes spherical nature up to date has solely come from TEM observations. The actual morphological structure of allophanes still needs to be further investigated. In the present work, Aluminosilicate samples obtained from soils collected in La Reunion (a French volcanic island in the Indian Ocean region) are studied using an array of diverse characterization techniques. While XRD and FTIR results are consistent with the characteristic allophane fingerprint, NMR analysis reveals an imogolite-type local environment of silicon and aluminium, pointing to a type i Al-rich structure. However, no spherical objects could be observed using TEM. In view of such observations, we propose that the structure of these type i Allophane is not consistent with that of a hollow sphere geometry. To obtain further insight into this matter, we synthesised aluminosilicate nanoparticles (both allophane and imogolite), and thoroughly characterized them using a wide variety of high specificity techniques ranging from the macro crystalline structure (TEM, XRD) to the atomic scale