A. Aboulkas

Pyrolysis of olive residue and sugar cane bagasse: Non-isothermal thermogravimetric kinetic analysis

Thermal degradation and kinetics for olive residue and sugar cane bagasse have been evaluated under dynamic conditions in the presence of nitrogen atmosphere, using a non-isothermal thermogravimetric method (TGA). The effect of heating rate was evaluated in the range of 2-50 K min(-1) providing significant parameters for the fingerprinting of the biomass. The DTG plot for the olive residue and sugar cane bagasse clearly shows that the bagasse begins to degrade at 473 K and exhibits two major peaks. The initial mass-loss was associated with hemicellulose pyrolysis and responsible for the first peak (538-543 K) whereas cellulose pyrolysis was initiated at higher temperatures and responsible for the second peak (600-607 K). The two biomass mainly devolatilized around 473-673 K, with total volatile yield of about 70-75%. The char in final residue was about 19-26%. Mass loss and mass loss rates were strongly affected by heating rate. It was found that an increase in heating rate resulted in a shift of thermograms to higher temperatures. Ozawa-Flynn-Wall and Vyazovkin methods were applied to determine apparent activation energy to the olive residue and sugar cane bagasse. Two different steps were detected with apparent activation energies in the 10-40% conversion range have a value of 153-162 kJ mol(-1) and 168-180 kJ mol(-1) for the hemicellulose degradation of olive residue and sugar cane bagasse, respectively. In the 50-80% conversion range, this value is 204-215 kJ mol(-1) and 231-240 kJ mol(-1) for the cellulose degradation of olive residue and sugar cane bagasse, respectively.

Pyrolysis of olive residue/low density polyethylene mixture:Part I Thermogravimetric kinetics

This paper demonstrates the thermal pyrolysis of olive residue, low density polyethylene (LDPE) and olive residue/LDPE mixture in an inert atmosphere of N2 using thermogravimetric analysis (TGA). Measurements were carried out in the temperature range 300 K~973 K at heating rates of 2 K/min, 10 K/min, 20 K/min and 50 K/min. Based on the results obtained, three temperature regimes were selected for studying the non-isothermal kinetics of olive residue/LDPE mixture. The first two were dominated by the olive residue pyrolysis, while the third was linked to the LDPE pyrolysis, which occurred at much higher temperatures. Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis. The maximum degradation temperatures of each component in the mixture were higher than those the individual components; thus an increase in thermal stability was expected. The kinetic parameters associated with thermal degradation were determined using Friedman isoconversional method.

Effects of acid treatments on Moroccan Tarfaya oil shale and pyrolysis of oil shale and their kerogen

Abstract In this study, the kerogen of oil shale from Moroccan Tarfaya deposits was isolated and the changes in the initial organic matter during the removal of the mineral matrix were examined. Chloroform extraction of the oil shale increases the intensity of the peaks in the X-ray diffractograms. Infrared spectra and X-ray diffractograms reveal the presence of mineral, calcite, quartz, kaolinite, and pyrite in the mineral matrix of the oil shale. Hydrochloric and hydrofluoric acids dissolution do not alter the organic matter. The nonisothermal weight loss measurements indicate that thermal decomposition of the isolated kerogen can be described by first-order reaction. A single kinetic expression is valid over the temperature range of kerogen pyrolysis between 433 and 873 K. Furthermore, the results indicate that the removal of mineral matter causes a decrease in the activation energies of the pyrolysis reactions of oil shale.

Processing and properties of eco-friendly bio-nanocomposite films filled with cellulose nanocrystals from sugarcane bagasse

Novel synthesis strategy of eco-friendly bio-nanocomposite films have been exploited using cellulose nanocrystals (CNC) and polyvinyl alcohol/carboxymethyl cellulose (PVA/CMC) blend matrix as a potential in food packaging application. The CNC were extracted from sugarcane bagasse using sulfuric acid hydrolysis, and they were successfully characterized regarding their morphology, size, crystallinity and thermal stability. Thereafter, PVA/CMC-CNC bio-nanocomposite films, at various CNC contents (0.5-10wt%), were fabricated by the solvent casting method, and their properties were investigated. It was found that the addition of 5wt% CNC within a PVA/CMC increased the tensile modulus and strength by 141% and 83% respectively, and the water vapor permeability was reduced by 87%. Additionally, the bio-nanocomposites maintained the same transparency level of the PVA/CMC blend film (transmittance of ∼90% in the visible region), suggesting that the CNC were dispersed at the nanoscale. In these bio-nanocomposites, the adhesion properties and the large number of functional groups that are present in the CNCs surface and the macromolecular chains of the PVA/CMC blend are exploited to improve the interfacial interactions between the CNC and the blend. Consequently, these eco-friendly structured bio-nanocomposites with superior properties are expected to be useful in food packaging applications.

Reuse of red algae waste for the production of cellulose nanocrystals and its application in polymer nanocomposites

Red algae is widely available around the world and its exploitation for the production of agar products has become an important industry in recent years. The industrial processing of red algae generates a large quantity of solid fibrous wastes, which constitutes a source of serious environmental problems. In the present work, the utilization of red algae waste as raw material to produce high-quality cellulose nanocrystals (CNC) has been investigated, and the ability of the as-isolated CNC to reinforce polymer has been studied. Red algae waste was chemically treated via alkali, bleaching and acid hydrolysis treatments, in order to obtain pure cellulose microfibers and CNC. The raw waste and the as-extracted cellulosic materials were successively characterized at different stages of treatments using serval analysis techniques. It was found that needle-like shaped CNC were successfully isolated at nanometric scale with diameters and lengths ranged from 5.2±2.9 to 9.1±3.1nm, and from 285.4±36.5 to 315.7±30.3nm, respectively, and the crystallinity index ranged from 81 to 87%, depending on the hydrolysis time (30, 40 and 80min). The as-extracted CNC were used as nanofillers for the production of polyvinyl alcohol (PVA)-based nanocomposite films with improved thermal and tensile properties, as well as optical transparency. It is shown that the addition of 8wt% CNC into the PVA matrix increased the Youngs modulus by 215%, the tensile strength by 150%, and the toughness by 45%. Additionally, the nanocomposite films maintained the same transparency level of the neat PVA film (transmittance of ∼90% in the visible region), suggesting that the CNC were dispersed at the nanoscale.

Valorization of algal waste via pyrolysis in a fixed-bed reactor: Production and characterization of bio-oil and bio-char

The aim of the present work is to develop processes for the production of bio-oil and bio-char from algae waste using the pyrolysis at controlled conditions. The pyrolysis was carried out at different temperatures 400-600°C and different heating rates 5-50°C/min. The algal waste, bio-oil and bio-char were successfully characterized using Elemental analysis, Chemical composition, TGA, FTIR, 1H NMR, GC-MS and SEM. At a temperature of 500°C and a heating rate of 10°C/min, the maximum yield of bio-oil and bio-char was found to be 24.10 and 44.01wt%, respectively, which was found to be strongly influenced by the temperature variation, and weakly affected by the heating rate variation. Results show that the bio-oil cannot be used as bio-fuel, but can be used as a source of value-added chemicals. On the other hand, the bio-char is a promising candidate for solid fuel applications and for the production of carbon materials.

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.

Non-isothermal Determination of the Pyrolysis Kinetics of a Mixture of Olive Residue and Polystyrene

Abstract Pyrolysis of olive residue, polystyrene and their mixture (1:1 weight ratio) were investigated by thermogravimetry. Experiments were conducted under N2 atmosphere at four heating rate of 2, 10, 20, and 50 K/min from room temperature to 900 K. The results showed that the thermal degradation temperature range of olive residue was 430–660 K, while that of polystyrene was 580–800 K. In general, we can note that the domains of degradation are well differentiated. Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis. The maximum degradation temperatures of polystyrene in the mixture were higher than the polystyrene pure. The calculated residue was found to be higher than experimental. These experimental results indicate a significant synergistic effect during pyrolysis of mixture of olive residue and polystyrene at the high temperature region. The kinetic studies were performed using the Friedman kinetic-modeling equation. The overall activation energies were: 165 and 219 kJ/mole for hemicellulose and cellulose, respectively; 180 kJ/mole for polystyrene; and 160, 215, and 166 kJ/mole for hemicellulose, cellulose, and polystyrene in the mixture, respectively. Thus, it has been found that there exists an overall synergy, when two materials were pyrolyzed together.

Production of cellulose nanocrystals from vine shoots and their use for the development of nanocomposite materials

In the present work, cellulose nanocrystals (CNC) were produced from vine shoots waste using chemical treatments followed by acid hydrolysis process. FTIR analysis confirmed that the non-cellulosic components were progressively removed during the chemical treatments, and the final obtained materials are composed of pure cellulose. AFM and TEM observations showed that the extracted CNC possess a needle-like shape with an average length of 456 nm and an average diameter of 14 nm, giving rise to an average aspect ratio of about 32. The as-extracted CNC exhibit a cellulose I structure with high crystallinity index (82%), as determined by XRD characterization. Importantly, the resulted CNC provide a higher thermal stability in comparison with CNC extracted from other resources, using the same extraction process. The isolated CNCs surface charge density was evaluated by XPS analysis and resulted in ~2.0 sulfate groups per 100 anhydroglucose units. In order to identify the reinforcing ability of the new extracted CNC, Carboxymethyl cellulose nanocomposite films were prepared with various CNC contents (1, 3, 5, 8 wt%) and their mechanical properties were investigated by uniaxial tensile test. The results showed that the as-extracted CNC displayed a higher reinforcing ability for nanocomposite materials.

Date stone based activated carbon/graphite electrode for catechol analysis: physico-chemical properties and application in beverage samples

The purpose of this paper is the modification of a carbon paste electrode (CPE) with activated carbon synthesized from date stones using a pyrolysis system followed by physical activation. This material has the advantage of very low cost and facilitates charge transfer. The modified electrode was used for electrocatalysis and determination of catechol. A series of analyses and tests were carried out to demonstrate the nature, the surface functional groups and even the porosity of the resulting product. The activated carbon exhibited remarkable electrocatalytic activity toward catechol oxidation. The electron transfer coefficient, surface coverage and number of electrons for catechol oxidation at the surface of the AC-CPE were determined using electrochemical approaches. Subsequently, a sensitive and convenient electrochemical method was proposed for catechol analysis. The linear range is between 1.0 × 10−6 and 1.0 × 10−3 mol L−1 with a correlation coefficient of 0.993. The limit of detection is as low as 4.8 × 10−8 mol L−1. Finally, this novel method was employed to determine the catechol in tap water, green, black and peach teas, and in coffee samples.