Application of olive mill waste-based biochars in agriculture: Impact on soil properties, enzymatic activities and tomato growth.

The olive oil industry is an important economic sector in Mediterranean countries. However, oil production is unfortunately accompanied by the generation of huge amounts of olive mill solid wastes (OMSW) and olive mill wastewater (OMWW). In the present study, a strategy is proposed for converting these olive mill wastes into biochar through pyrolysis, for their later use as an organic amendment in agriculture. Specifically, two biochars were prepared from the pyrolysis of OMSW at 500 °C, either alone or impregnated with OMWW (OMSW-B and I-OMSW-B). The characterization of the OMSW and I-OMSW samples and their derived biochars showed that the fixed carbon and ash contents in the feedstocks increased by 38% and 11% respectively for OMSW-B, and by 37% and 12% respectively for I-OMSW-B. Interestingly, the impregnation process significantly increased Na, P, K, Ca and Fe contents in the produced biochars. The effect of OMSW-B and I-OMSW-B amendments at different application dose (1%, 2.5% and 5% wt/wt) on the enzymatic activity of an agricultural soil was performed at laboratory scale with a pot test. The experimental results showed that phosphatase and urease activity increased with biochar application rate; amendment with I-OMSW-B at 1%, 2.5% and 5% enhanced the phosphatase activity by 63%, 142% and 285% and urease activity by 50%, 116% and 149%, respectively. On the other hand, dehydrogenase and protease activities were higher for the application rate of 2.5% biochar. Biochar amendment promoted tomatoes seedling growth after 10 weeks, which was highest in the application rates of 2.5% and 5% for both OMSW-B and I-OSMW-B. Thus, the produced biochars had great potential to be used as biofertilizers in agriculture.

Thermal Reduction of Graphene Oxide Mitigates Its In Vivo Genotoxicity Toward Xenopus laevis Tadpoles.

The worldwide increase of graphene family materials raises the question of the potential consequences resulting from their release in the environment and future consequences on ecosystem health, especially in the aquatic environment in which they are likely to accumulate. Thus, there is a need to evaluate the biological and ecological risk but also to find innovative solutions leading to the production of safer materials. This work focuses on the evaluation of functional group-safety relationships regarding to graphene oxide (GO) in vivo genotoxic potential toward X. laevis tadpoles. For this purpose, thermal treatments in H2 atmosphere were applied to produce reduced graphene oxide (rGOs) with different surface group compositions. Analysis performed indicated that GO induced disturbances in erythrocyte cell cycle leading to accumulation of cells in G0/G1 phase. Significant genotoxicity due to oxidative stress was observed in larvae exposed to low GO concentration (0.1 mg.L-¹). Reduction of GO at 200 °C and 1000 °C produced a material that was no longer genotoxic at low concentrations. X-ray photoelectron spectroscopy (XPS) analysis indicated that epoxide groups may constitute a good candidate to explain the genotoxic potential of the most oxidized form of the material. Thermal reduction of GO may constitute an appropriate "safer-by-design" strategy for the development of a safer material for environment.

Activated Carbon/Transition Metal (Ni, In, Cu) Hexacyanoferrate Nanocomposites for Cesium Adsorption.

Transition metal hexacyanoferrate/microporous activated carbon composites were obtained using a simple successive impregnation approach. The effect of metal type (nickel, indium, or copper), and the carbon oxidation on the composite characteristics (porosity, metal structure, and particle size), as well as on the removal efficiency of cesium from aqueous solution was investigated. Successful formation of the desired metal hexacyanoferrate phase was achieved and the size of the metallic nanoparticles and their dispersion in the carbon network was found to depend on the metal type, with the indium and nickel-based materials exhibiting the smallest particle size distribution (< 10 nm). Adsorption tests performed under batch conditions demonstrate that the copper hexacyanoferrate/activated carbon composite present the highest cesium removal capacity from aqueous solution (74.7 mg·g-1) among the three studied metal-based nanocomposites. The carbon oxidation treatment leads to the increase in the number of functional groups to the detriment of the porosity but allows for an improvement in the Cs adsorption capacity. This indicates that the Cs adsorption process is governed by the carbon surface chemistry and not its porosity. Moreover, combining oxidized carbon support with copper hexacyanoferrate induces the highest cesium adsorption capacity (101.5 mg·g-1). This could be related to synergistic effects through two absorption mechanisms, i.e., a cation exchange mechanism of Cs with the metallic hexacyanoferrate phase and Cs adsorption via carbon oxygen surface groups, as demonstrated using X-ray photoelectron spectroscopy (XPS) analyses.

Carbonaceous adsorbents derived from textile cotton waste for the removal of Alizarin S dye from aqueous effluent: kinetic and equilibrium studies.

Recycling cotton waste derived from the textile industry was used as a low-cost precursor for the elaboration of an activated carbon (AC) through carbonization and zinc chloride chemical activation. The AC morphological, textural, and surface chemistry properties were determined using different analytical techniques including Fourier transform infrared, temperature programmed desorption-mass spectroscopy, nitrogen manometry and scanning electron microscopy. The results show that the AC was with a hollow fiber structure in an apparent diameter of about 6.5 µm. These analyses indicate that the AC is microporous and present a uniform pore size distributed centered around 1 nm. The surface area and micropore volume were 292 m2.g-1 and 0.11 cm3.g-1, respectively. Several types of acidic and basic oxygenated surface groups were highlighted. The point of zero charge (pHPZC) of theca was 6.8. The AC performance was evaluated for the removal of Alizarin Red S (ARS) from aqueous solution. The maximum adsorption capacity was 74 mg.g-1 obtained at 25 °C and pH = 3. Kinetics and equilibrium models were used to determine the interaction nature of the ARS with the AC. Statistical tools were used to select the suitable models. The pseudo-second order was found to be the most appropriate kinetic model. The application of two and three isotherm models shows that Langmuir-Freundlich (n = 0.84, K = 0.0014 L.mg-1, and q = 250 mg.g-1) and Sips (n = 0.84, K = 0.003 L.mg-1, and q = 232.6 mg.g-1) were the suitable models. The results demonstrated that cotton waste can be used in the textile industry as a low-cost precursor for the AC synthesis and the removal of anionic dye from textile wastewater.

Composition and size dependence of hydrogen interaction with carbon supported bulk-immiscible Pd-Rh nanoalloys.

In-depth clarification of hydrogen interaction with noble metal nanoparticles and nanoalloys is essential for further development and design of efficient catalysts and hydrogen storage nanomaterials. This issue becomes even more challenging for nanoalloys of bulk-immiscible metals. The hydrogen interaction with bulk-immiscible Pd-Rh nanoalloys (3-6 nm) supported on mesoporous carbon is studied by both laboratory and large scale facility techniques. X-ray diffraction (XRD) reveals a single phase fcc structure for all nanoparticles confirming the formation of nanoalloys in the whole composition range. In situ extended x-ray absorption fine structure (EXAFS) experiments suggest segregated local structures into Pd-rich surface and Rh-rich core coexisting within the nanoparticles. Hydrogen sorption can be tuned by chemical composition: Pd-rich nanoparticles form a hydride phase, whereas Rh-rich phases do not absorb hydrogen under ambient temperature and pressure conditions. The thermodynamics of hydride formation can be tailored by the composition without affecting hydrogen capacity at full hydrogenation. Furthermore, for hydrogen absorbing nanoalloys, in situ EXAFS reveals a preferential occupation of hydrogen for the interstitial sites around Pd atoms. To our knowledge, this is the first study providing insights into the hydrogen interaction mechanism with Pd-Rh nanoalloys that can guide the design of catalysts for hydrogenation reactions and the development of nanomaterials for hydrogen storage.

Realistic molecular model of kerogen's nanostructure.

Despite kerogen's importance as the organic backbone for hydrocarbon production from source rocks such as gas shale, the interplay between kerogen's chemistry, morphology and mechanics remains unexplored. As the environmental impact of shale gas rises, identifying functional relations between its geochemical, transport, elastic and fracture properties from realistic molecular models of kerogens becomes all the more important. Here, by using a hybrid experimental-simulation method, we propose a panel of realistic molecular models of mature and immature kerogens that provide a detailed picture of kerogen's nanostructure without considering the presence of clays and other minerals in shales. We probe the models' strengths and limitations, and show that they predict essential features amenable to experimental validation, including pore distribution, vibrational density of states and stiffness. We also show that kerogen's maturation, which manifests itself as an increase in the sp(2)/sp(3) hybridization ratio, entails a crossover from plastic-to-brittle rupture mechanisms.

Hydrogen sorption properties of Pd-Co nanoalloys embedded into mesoporous carbons.

Pd90Co10 and Pd75Co25 nanoalloys embedded into mesoporous carbon hosts have been prepared by two synthetic methods: direct and indirect. The average nanoparticles size can be tuned by both the temperature during thermal treatment and the chemical composition: the higher the treatment temperature and the richer the Pd composition, the larger the nanoparticle size. Twofold size- and composition-dependence of the hydrogen sorption properties at room temperature are evidenced. The Co substitution in Pd nanoalloys increases the equilibrium pressure at room temperature relative to nanosized Pd. The hydrogen sorption capacity decreases by Co substitution in Pd, as also demonstrated by SQS + DFT calculations.

One-pot laser-assisted synthesis of porous carbon with embedded magnetic cobalt nanoparticles.

A novel one-pot laser-assisted approach is reported herein for the synthesis of ordered carbons with embedded cobalt nanoparticles. The process is based on a UV pulsed laser exposure of an ethanolic solution consisting of green carbon precursors, a structure directing agent and a cobalt salt. Very short irradiation times (5 to 30 min) are only required to polymerize and cross-link carbon precursors (i.e. phloroglucinol and glyoxylic acid) independent of a catalyst presence. The influence of three metallic salts (acetate, nitrate and chloride) on the phenolic resin and carbon characteristics (structure, texture and particle size/distribution) was systematically studied. When exposed to UV laser, the metallic salt exhibited a strong influence on the particle size and distribution in the carbon matrix rather than on the textural carbon properties. Using cobalt acetate, very small (3.5 nm) and uniformly dispersed particles were obtained by this simple, fast and green one-pot synthesis approach. An original combined (13)C CP-MAS and DP-DEC solid state NMR spectroscopy analysis allowed to determine the structure of phenolic resins as well as the location of the cobalt salt in the resin. Complementarily, the (1)H solid-state and relaxation NMR provided unique insights into the rigidity (cross-linking) of the phenolic resin and dispersion of the cobalt salt. The magnetic properties of cobalt nanoparticles were found to be size-dependent: large Co nanoparticles (∼50 nm) behave as bulk Co whereas small Co nanoparticles are superparamagnetic.

Microporous carbon adsorbents with high CO2 capacities for industrial applications.

In this study we attempt to investigate the potential use of two zeolite template carbon (ZTC), EMT-ZTC and FAU-ZTC, to capture CO(2) at room temperature. We report their high pressure CO(2) adsorption isotherms (273 K) that show for FAU-ZTC the highest carbon capture capacity among published carbonaceous materials and competitive data with the best organic and inorganic adsorbing frameworks ever-known (zeolites and mesoporous silicas, COFs and MOFs). The importance of these results is discussed in light of mitigation of CO(2) emissions. In addition to these new experimental CO(2) adsorption data, we also present new insight into the adsorption process of the two structures by Monte Carlo simulations: we propose that two separate effects are responsible for the apparent similarity of the adsorption behaviour of the two structures: (i) pore blocking occurring on EMT-ZTC, and (ii) the change of the carbon polarizability due to the extreme curvature of FAU-ZTC.

Influence of surface chemistry on the adsorption of oxygenated hydrocarbons on activated carbons.

The objective of this work was to study the adsorption of different oxygenated hydrocarbons (methanol, ethanol, 1 and 2-butanol, methyl acetate) on activated carbons from organic mixtures with cyclohexane. Three activated carbons prepared by thermal and chemical treatments of a commercial carbon were employed for this purpose. Their textural properties were found to be similar, whereas their surface chemistries were modified, as shown by temperature-programmed desorption coupled to mass spectrometry (TPD-MS) and X-ray photoelectron spectroscopy (XPS). The adsorption isotherms were obtained by depletion method, and the analysis of adsorbed species was evaluated by TPD-MS to obtain new insight into the interactions between the different hydrocarbons and the carbon surface. Ethanol leads to a high-energy interaction between its hydroxyl function and the oxygenated surface groups and also to a lower energy interaction between the aliphatic part of the molecule and the carbon material. The desorption activation energy for this hydrophilic interaction is high (50 to 105 kJ/mol), and it is related to the nature of the carbon surface groups. The relative importance of these two interactions depend on the size of the alcohol/methanol is similar to ethanol, whereas butanols lead to more dispersive interactions. Methyl-acetate cannot undergo this kind of strong interaction and behaves like cyclohexane, having desorption activation energies ranging between 25 and 45 kJ/mol no matter the molecule and the carbon surface chemistry.

Electrosprayed metal oxide semiconductor films for sensitive and selective detection of hydrogen sulfide.

Semiconductor metal oxide films of copper-doped tin oxide (Cu-SnO(2)), tungsten oxide (WO(3)) and indium oxide (In(2)O(3)) were deposited on a platinum coated alumina substrate employing the electrostatic spray deposition technique (ESD). The morphology studied with scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows porous homogeneous films comprising uniformly distributed aggregates of nano particles. The X-ray diffraction technique (XRD) proves the formation of crystalline phases with no impurities. Besides, the Raman cartographies provided information about the structural homogeneity. Some of the films are highly sensitive to low concentrations of H(2)S (10 ppm) at low operating temperatures (100 and 200 °C) and the best response in terms of R(air)/R(gas) is given by Cu-SnO(2) films (2500) followed by WO(3) (1200) and In(2)O(3) (75). Moreover, all the films exhibit no cross-sensitivity to other reducing (SO(2)) or oxidizing (NO(2)) gases.