Recycling solid industrial wastes into valuable materials is always the priority solution in waste management. In this perspective, sugar scum and fly ash were used to produce an effective low-cost porous ceramic membrane. The impacts of the sintering temperature, amount of sugar scum, and sintering time on the properties of the prepared ceramic membrane were investigated and optimized using experimental design. A simultaneous rise in both the sintering temperature and the amount of sugar scum leads to a notable increase in porosity. Moreover, the simultaneous increase or decrease in the time and the amount of sugar scum causes a significant decrease in the compressive strength. The optimal conditions have been determined as a sintering temperature of 1197 °C, a sugar scum amount of 12.06 %, and a sintering time of 253 min. Under these conditions, the density, porosity, and compressive strength were found to be 2.16 g/cm³, 34.66 %, and 28.24 MPa, respectively. In addition, the obtained ceramic membrane has a water permeability of 2356.68 L/h m2 bar, a pore size in the range 0–4.5 μm, and excellent chemical resistance in both acidic and basic media. Finally, the performance of the prepared ceramic membrane was evaluated by the filtration of methylene blue. The results indicate that sugar scum and fly ash are suitable precursors to manufacture an effective ceramic membrane for the treatment of wastewater.
Pyrolysis kinetics of oil shale mixed with high-density polyethylene (HDPE) was investigated using a thermogravimetric analysis (TGA) system at various heating rates of 2, 10, 20 and 50 K/min in the temperature range of 300-1273 K in the nitrogen atmosphere.Kissinger-Akahira-Sunose, Friedman, Flynn-Wall-Ozawa and Coats-Redfern methods have been used to determine activation energies of materials degradation.The analysis of the process mechanism by Criado and Coats-Redfern methods showed the following: the mechanism of thermal degradation process of HDPE is describable by the "Contracting cylinder" model (R2 mechanism); and the most probable model for the pyrolysis process of oil shale kerogen is the diffusion model (D4 mechanism), while the mixture degrades following the kinetic model of D4.It has been found that during thermal decomposition of oil shale/HDPE mixture no significant interaction of solid-phase components had taken place under the experimental conditions investigated.
Microwave technology is currently very interesting because it offers, in many industrial processes, a new alternative energy for drying and treatment of various materials. In this context, the drying of the Gelidium sesquipedale (Rhodophyta), which is a red algae, is carried out under microwave irradiation in the aim to optimize the energy consumption in the drying process and the quality of the extracted products. The drying process of Gelidium sesquipedale under microwave irradiation is carried out by studying the thermal and kinetic aspects of drying under different irradiation conditions. The experiments were performed on samples of different initial masses ranging from 2 to 30 g. The samples are irradiated in an experimental device combining a gravimetric balance and microwave assembly that may impose different power microwave ranging from 50 to 200 W. The analysis of the experimental curves of the drying process shows that the initial mass of the sample has little influence and the applied microwave power has a significant effect on the drying kinetics. The comparative study of the drying of Gelidium sesquipedale by conventional heating and under electromagnetic field shows that the controlling kinetic mechanism depends on the way in which the sample is dried. The action of the electromagnetic field allows faster heat transfer leading to the rapid evacuation of water molecules from the seaweed.
Microwave heating and conventional heating were used in the drying process of white phosphates and the pyrolysis of black phosphate. Microwave drying has been found to present faster kinetics, and the reaction mechanism is controlled by interfacial progression with a cylindrical symmetry for low powers and by diffusion for high microwave powers. Infrared thermography analysis shows that the heating mode is a function of the incident microwave power, the diameter of the reactor and the initial mass of the sample. The results of this study allowed us to understand the phenomena occurring during the microwave pyrolysis of black phosphate. Three temperature domains were revealed. Heating is attributed to the relaxation of polar molecules (water, polar organic molecules...) and to conduction losses of the different components of the phosphates and the products resulting from the decomposition of the mineral matrix as well as the carbon in the residues. Dielectric measurements at microwave frequencies showed that the dielectric constants (epsilon' and epsilon") decrease with time and reach values that are independent of the humidity of the phosphates, which correspond to the complete desorption of water. Cracks were observed in the microwave pyrolysis residues which also showed better cristallinity as revealed by SEM observation and XRD analysis. XPS analysis revealed for the fist time that the microwave pyrolysis residues contain less carbon than the residues of conventional heating, i.e. more oil is produced by microwave pyrolysis.
In this paper, the use of microwave energy in a drying problem is examined. The purpose of this work is the investigation of the effect of incident microwave power to a material during drying and in particular the research of the experimental conditions which can be used to accelerate the drying phenomenon in order to save energy in the industrial processes. We describe, in the first instance, the experimental apparatus used and the results of kinetic and thermal aspects of drying induced by microwave heating. These results lead to the role of different parameters (microwave power, initial sample mass and diameter of the reactor) on the kinetic and the thermal aspects of the drying. In the second instance, the experimental results are presented and discussed taking into account the dielectric proprieties of the material, the literature and the use of the heterogeneous kinetic models. These studies point out important kinetic and thermal aspects allowing a better understanding of drying under microwave irradiation.
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