Pyrolysis of ficus nitida wood: Determination of kinetic and thermodynamic parameters

International audienceIn the present work, the kinetic and thermodynamic analysis of ficus wood was carried out using the thermogravimetric analysis (TGA). Thermal degradation of ficus wood has been evaluated under dynamic conditions from 373 K to 1173 K at heating rates of 5, 10, 20, and 50 K.min−1. The kinetic analysis was performed using isoconversional methods (Friedman (FR), Flynn-Wall-Ozawa (FWO) and Vyazovkin (VYA)) and the integral master-plots method to estimate the kinetic triplets. The thermogravimetric and kinetic data were used to calculate the thermodynamic parameters (ΔG, ΔH and ΔS) and kinetic compensation effects. The conversion range of 0.05 ≤ x ≤ 0.9 shows clearly that the pyrolysis of ficus wood could represent a triple-step reaction, which corresponds to the pyrolysis of hemicellulose, cellulose, and lignin, respectively. From the isoconversional plots of ficus wood having average activation energy values of 171.4–180.3 kJ.mol−1, 206.48–214.42 kJ.mol−1 and 237.85–248.23 kJ.mol−1 for hemicellulose, hemicellulose, and lignin, respectively. The experimental data of focus wood had overlapped the D4, D2, and F3 in the conversion range of 5–35%, 35–75%, and 75–90%, respectively. All values of ΔH and ΔG maintain at a positive constant, whereas the value of ΔS is negative in the range of 5–35%. The difference between E-values and the ΔH value for the three pseudo-components of ficus wood is about ≈5 kJ.mol−1. The kinetic and thermodynamic parameters will be beneficial in assimilating the thermal decomposition of ficus wood for its use in bioenergy

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

New highly hydrated cellulose microfibrils with a tendril helical morphology extracted from agro-waste material: application to removal of dyes from waste water

Cocoa bean shells (CBS) are a by-product of the cocoa bean processing industry. They represent 12–20 wt% of dry cocoa beans, after having been separated from these by a roasting process. CBS often end up as a waste product which contains around 34 wt% of cellulose. The transformation of this waste into valuable and marketable products would help to improve waste disposal. Indeed, the large annual production of this waste makes it a sustainable and renewable bio-source for the production of chemicals and fibers for advanced applications. In this work, new cellulose microfibrils (CMFs) with a tendril helical morphology and highly hydrated gel-like behavior were successfully extracted from CBS waste using a controlled chemical extraction process. During this study, several physico-chemical characterizations were carried out in order to identify the properties of each of the products at different stages of treatment. Microscopic observations show that the extracted CMFs have a tendril helical shape like climbing plant tendrils. Due to this special morphology, the extracted CMFs show a highly hydrated state forming a gel network without additional modifications. The as-extracted CMFs were used as adsorbent material for the removal of methylene blue from concentrated aqueous solution, as an application to wastewater treatment for the removal of basic dyes. Swelling properties, adsorption kinetics and isotherms were carried out in batch experiments. The results indicated that the CMFs have a high swelling capacity (190%). The pseudo second order model can be effectively used to evaluate the adsorption kinetics and the adsorption isotherms can also be described well by the Langmuir isotherm model with a maximum adsorption capacity of 381.68 mg g−1. Thus, the as-extracted CMFs with unique characteristics have the potential to be used as efficient adsorbent material for the removal of different cationic dyes from industrial wastewater

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