Propriétés adsorbantes des billes de lignine: application au traitement des eaux usées

This study investigated the adsorption of the heavy metal ions Cd (II) on a lignin isolated from sugar cane bagasse, by alkali treatment. This lignin is converted to beads using another polymer of marine origin, to test its ability to remove heavy metals from wastewater. Factors influencing Cd adsorption such as initial Cd ion concentration (5-50mg/l), pH (1-8), contact times (15min-4h) were investigated. The adsorption process was relatively fast and equilibrium was established about 2h. Maximum adsorption of cadmium ions occurred at around pH 5. The adsorption equilibrium data fitted best with the Freundlich and Dubinin-Radushkevich isotherms, and showed that the adsorption was physical in natureCette étude a eu pour but d’examiner l'adsorption des ions de métaux lourds Cd (II) sur une lignine isolé à partir de la bagasse de canne à sucre, après un traitement alcalin. Cette lignine est convertie en des perles en utilisant un autre polymère d'origine marine, pour tester son aptitude à éliminer les métaux lourds des eaux usées. Les facteurs influant sur l’adsorption du Cd tels que la concentration d'ions de Cd initiale (5-50mg / L), le pH (1-8), les temps de contact (15min-4h) ont été étudiés. Le processus d'adsorption est relativement rapide et l'équilibre a été établi après environ 2h. L’adsorption maximale des ions de cadmium est obtenue à un pH d'environ 5. Les équilibre d'adsorption suivent les isothermes de Freundlich et Dubinin-Radushkevich, et ont montré que l'adsorption était de nature physique

One-Pot dry chemo-mechanical deconstruction for bioethanol production from sugarcane bagasse

The aim of this study was the application of an innovative dry chemo-mechanical pretreatment using different mechanical stresses to produce bioethanol from sugarcane bagasse (SB). The effect of different milling methods on physicochemical composition, enzymatic hydrolysis, bioethanol production and energy efficiency was also evaluated. SB was pretreated with NaOH and H3PO4 at high materials concentration (5 kg/L). Results indicate that vibratory milling (VBM) was more effective in the reduction of particles size and cellulose crystallinity compared to centrifugal (CM) and ball (BM) milling. NaOH pretreatment coupling to BM and VBM was preferred to enhance glucose yields and bioethanol production, while CM consumed less energy compared to BM and VBM. Moreover, the highest energy efficiency (eta = 0.116 kg(glucose)/kWh) was obtained with NaOH-CM. Therefore, the combination of dry NaOH and CM appears the most suitable and interesting pretreatment for the production of bioethanol from SB

Synthesis of CoFeO mixed oxides via an alginate gelation process as efficient heterogeneous catalysts for lignin depolymerization in water

A catalytic oxidative fragmentation of a lignin dimer and polymer extracted from wheat straw was successfully performed under eco-friendly conditions: 10% O2/N2 as the oxidizing agent, water as the solvent (pH ≈ 7), and Co3O4, Fe2O3 and CoFeO mixed oxides as heterogeneous catalysts and at temperatures of T = 150 °C and 200 °C. These catalysts unexpectedly showed tunable selectivity that directly depends on the composition of the selected bimetallic nanoparticles. High selectivity for benzoic acid and alkylbenzene (above 50%) was observed over Co50–Fe50 at 200 °C. Under similar conditions, the conversion of wheat organosolv lignin over Co50–Fe50 at 150 °C for 4 h yielded up to 50 wt% of monomeric species (based on dry lignin) and up to 19% of aromatic molecules with high selectivity to aromatic aldehydes (syringaldehyde and vanillin), up to 60%. An important fraction of water-soluble oligomers, with low molecular weights, was also formed during the catalytic treatment. The oxide nanomaterials were readily separated from the residual lignin during the recyclability test. The yield and the product distribution can be tuned by choosing the oxidation parameters: temperature, reaction time, oxygen partial pressure, solvent and catalyst charges

Pyrochars from bioenergy residue as novel bio-adsorbents for lignocellulosic hydrolysate detoxification

The robust supramolecular structure of biomass often requires severe pretreatments conditions to produce soluble sugars. Nonetheless, these processes generate some inhibitory compounds (i.e. furans compounds and aliphatic acids) deriving mainly from sugars degradation. To avoid the inhibition of the biological process and to obtain satisfactory sugars conversion level into biofuels, a detoxification step is required. This study investigates the use of two pyrochars derived from solid anaerobic digestates for the detoxification of lignocellulosic hydrolysates. At a pyrochar concentration of 40 g L−1, more than 94% of 5-HMF and 99% of furfural were removed in the synthetic medium after 24 h of contact time, whereas sugars concentration remained unchanged. Furfural was adsorbed faster than 5-HMF by both pyrochars and totally removed after 3 h of contact. Finally, the two pyrochars were found efficient in the detoxification of corn stalks and Douglas fir wood chips hydrolysates without affecting the soluble sugars concentrations

Oxidative conversion of lignin over cobalt-iron mixed oxides prepared via the alginate gelation

The depolymerization of polymer lignin model to low molecular weight products was studied in water, at 200 °C under 100 MPa of 10% O2 using cobalt-iron mixed oxides as catalysts. These nanostructured oxides with different Co/Fe ratios were prepared via alginate gelation. X-ray diffraction, scanning electron microscope, and size exclusion chromatography were used to study the influence of the Fe/Co ratios on the structure and the proprieties of the oxides as well as the morphology, the structure, and the composition of the obtained degraded products. The results showed that the oxides used in this study were versatile catalysts with a high catalytic activity for lignin depolymerization. Furthermore, these oxides demonstrated high yield and high selectivity towards aromatic compounds

Thermochemical treatment of olive mill solid waste and olive mill wastewater Pyrolysis kinetics

In olive-oil-producing countries, large amounts of waste material are generated as by-product for which there is no ready use and in some cases may have a negative value because of the cost of disposal. Most of these countries depend on fossil fuels for their energy uses, and olive mill wastes can be used to supplement such energy sources using thermochemical conversion processes such as pyrolysis. However, efficient operation of thermochemical conversion systems requires a thorough understanding of the influence of the composition and thermal properties of these by-products on their behaviour during the conversion process. In this study, the thermal behaviour of two olive mill wastes samples (olive mill solid waste: OMSW, and concentrated olive mill wastewater: COMWW) was examined at different heating rates ranging from 5 to 50 A degrees C min(-1) in inert atmosphere using the technique of thermogravimetric analysis. As the increment of heating rates, the variations of characteristic parameters from the TG-DTG curves were determined. The initial temperature of degradation is higher in OMSW, which present a high amount of cellulose in comparison with COMWW. Three methods were used for the determination of kinetic reaction parameters: Friedman, Ozawa-Flynn-Wall and Vyazovkin methods. The results showed that apparent activation energy obtained for the decomposition of hemicelluloses and cellulose derived from OMSW was given as 150-176 and 210.5-235.7 kJ mol(-1), while for COMWW, the values were 133-145 and 255-275 kJ mol(-1), respectively

Characteristics of nanostructured Zn1-xVxO thin films with high vanadium content elaborated by rf-magnetron sputtering

Nanostructured Zn1−xVxO (0 ⩽ x ⩽ 0.50) thin films were synthesized by rf-magnetron sputtering at two different substrate temperatures (room temperature (RT) and 200 °C) and with variable sputtering powers (60, 80 and 100 W). In this method, single targets based on Zn1−xVxO nanopowders prepared by the sol–gel process were used. Characterization of the Zn1−xVxO nanoparticles showed that they crystallize in the hexagonal wurtzite structure. Their size ranged from 20 to 40 nm. The effect of process parameters on the physical and chemical properties of Zn1−xVxO thin films has been studied. For x ⩽ 0.30, the results obtained at 200 °C and 60 W indicate that the films have a high quality of crystallinity. Vegard’s law is respected, indicating that vanadium is incorporated in the ZnO matrix. The chemical compositions of these films were found to be close to the stoichiometry. The films exhibit a columnar structure and a smooth surface. Their average transmission, from the visible to the NIR, was in the range of 75–90%. The values of the band gap of the Zn1−xVxO thin films with x ⩽ 0.30 and elaborated at 200 °C and 60 W, vary from 3.29 to 3.74 eV. This is consistent with blue shifting of near-band edge cathodoluminescence emission. Under particular growth conditions, the investigation shows that the Zn0.80V0.20O sample presents the best properties for potential use in various optoelectronic applications, namely: a single wurtzite phase, low surface roughness (Ra ∼ 0.2 nm), a high transparency of 90% in the UV–Vis–NIR, a wide band gap of 3.74 eV and a resistivity of ∼5 × 10+3 Ω cm

Mechanical pretreatments of lignocellulosic biomass: towards facile and environmentally sound technologies for biofuels production

The transformation of lignocellulosic biomass into biofuels represents an interesting and sustainable alternative to fossil fuel for the near future. However, one still faces some major challenges for the technology to be fully realized including feedstock costs, novel pretreatment processes, production, transportation, and environmental impact of the full chain. The development of new technologies focused to increase the efficiency of cellulose conversion to biofuels determines successful implementation. Mechanical fractionation is an essential step in order to increase final carbohydrate output, appropriate particle sizes and densification, enzymatic accessibility, and bioconversion affectivity without the production of toxic side streams. In this review article, we surveyed a substantial amount of previous work in mechanical fractionation or pretreatments of a variety of lignocellulosic biomasses; these include numerous milling schemes and extrusions, and their impacts on the physical and physicochemical properties of the lignocellulosic matrix (crystallinity, surface area, particle size, etc). We have also compared results with other pure chemical and physicochemical pretreatments in order to show the new aspects and advantages/disadvantages of such an approach. Last, but not least, the effec

Toward a functional integration of anaerobic digestion and pyrolysis for a sustainable resource management. Comparison between solid-digestate and its derived pyrochar as soil amendment

The integration of different technologies acts as a leverage in boosting "circular economy" and improving resource use efficiency. In this respect, the coupling of anaerobic digestion with pyrolysis was the focus of this work. Solid-digestate obtained from anaerobic digestion was addressed to supply pyrolysis thus increasing the net energy gains and obtaining "biochar" (called "pyrochar" in our case) to be used as soil amendment alternatively to solid-digestate. The current interest on biochar is linked to its long-term soil carbon sequestration, thus contributing to global warming mitigation. A parallel detailed screening of the physical and chemical properties of both solid-digestate and pyrochar was performed, inferring their effects on soil quality. Results showed that while P and K are enriched in pyrochar, total N showed no significant differences. Heavy metals revealed higher concentrations in pyrochar, but always largely below the biochar quality thresholds. Pyrochar exhibited a higher surface area (49-88 m(2) g(-1)), a greater water holding capacity (352-366%), and a more recalcitrant carbon structure. Both solid-digestate and pyrochar showed good soil amendments properties but with complementary effects. Although starting from the same biomass, being the original feedstock processed differently, their ability to improve the physical and chemical soil properties has proved to be different. While several other soil improvers of organic origin can substitute digestate, the important role played by biochar appears not-replaceable considering its precious "carbon negative" action