Showing papers by "University of Monastir published in 2022"

Agricultural waste materials for adsorptive removal of phenols, chromium (VI) and cadmium (II) from wastewater: A review

Abstract: Management of basic natural resources and the spent industrial and domestic streams to provide a sustainable safe environment for healthy living is a magnum challenge to scientists and environmentalists. The present remedial approach to the wastewater focuses on recovering pure water for reuse and converting the contaminants into a solid matrix for permanent land disposal. However, the ground water aquifers, over a long period slowly leach the contaminants consequently polluting the ground water. Synthetic adsorbents, mainly consisting of polymeric resins, chelating agents, etc. are efficient and have high specificity, but ultimate disposal is a challenge as most of these materials are non-biodegradable. In this context, it is felt appropriate to review the utility of adsorbents based on natural green materials such as agricultural waste and restricted to few model contaminants: phenols, and heavy metals chromium(VI), and cadmium(II) in view of the vast amount of literature available. The article discusses the features of the agricultural waste material-based adsorbents including the mechanism. It is inferred that agricultural waste materials are some of the common renewable sources available across the globe and can be used as sustainable adsorbents. A discussion on challenges for industrial scale implementation and integration with advanced technologies like magnetic-based approaches and nanotechnology to improve the removal efficiency is included for future prospects.

Experimental investigations on thermophysical properties of nano-enhanced phase change materials for thermal energy storage applications

Abstract: Thermophysical properties such as latent heat, viscosity and melting temperature could be changed for different physical properties of dispersed nanoparticle such as size, shape, and concentration. In this study, Nanocomposites-Enhanced Phase Change Materials NePCM are formed by dispersing Aluminium (Al) and Copper (Cu) nanoparticles into paraffin wax in various mass fractions (0.1, 0.3, 0.6, 1, 2.5 and 5%). The impact on the thermophysical properties of paraffin wax by the nanoparticles is also investigated. Heat conduction and differential scanning calorimeter experiments are used to investigate the effects of different nanoparticle concentrations on the melting point, solidification point, and latent capacity of nanocomposites. Experimental results show that the dispersion of nanoparticles of Al and Cu can decrease the melting temperature and increase the solidification temperature of PCM. this dispersion could also be limited due to increase in dynamic viscosity of the NePCM. Furthermore, Al and Cu nanocomposites with mass fractions of 2% and 1%, respectively, show better enhancements in the thermal storage characteristics of the paraffin compared to the next higher mass fraction.

Structural, optical, and dielectric properties for Mg0·6Cu0·2Ni0·2Cr2O4 chromite spinel

Abstract: In this work, the structural, optical, and dielectric properties for Mg0·6Cu0·2Ni0·2Cr2O4 chromite sample prepared by sol-gel process were investigated. The XRD characterization for this sample confirmed the development of the face-centered cubic spinel structure with F d 3 ‾ m space group. From the UV–Vis optical absorbance, the synthesized chromite shows significantly lower direct band gap energy and has an appropriate absorption rate in the visible light region. The variations of penetration depth, extinction coefficient, refractive coefficient, dispersion energy parameters, and dielectric permittivity constants were also interpreted. The Non-Overlapping Small Polaron Tunneling (NSPT) and the Correlated Barrier Hopping (CBH) are the suitable models to describe the conduction process for the prepared sample. The behavior of dielectric constants has been interpreted based on the Maxwell-Wagner's theory of interfacial polarization. The behavior of imaginary part of impedance (Z″) shows a dielectric-relaxation phenomenon in the sample with activation energies near to those determined from the conductivity study.

Extraction of lyophilized olive mill wastewater using supercritical CO2 processes

Abstract: The olive growing in Tunisia has an economic dominance and agricultural importance. However, the huge extraction of olive oil generates a large quantity of olive mill wastewater (OMW), which is discharged to the surroundings. The highly polluting potential (organic load) of OMW threatens the environment and requires an urgent solution. Supercritical fluid extraction (SFE) is a green extraction method that can be applied to purify OMW and, at the same time, to isolate a high quality oil from this wastewater. In order to explore and to valorize the compositions of Olive mill wastewater (OMW), extraction in different solvents (supercritical CO2, hexane) was carried out and chemical composition of the extracted oils were established by GC-FID. The Tunisia OMW were collected from two different zones namely Sousse and Sfax. In this work, we have investigated the effects pressure (P) and temperature (T) on the yield and the quality of oil. The suitable conditions for the extraction of oil from lyophilized OMW by Supercritical carbon dioxide (SC-CO2) were found to be the pressure of 30 MPa and the temperature of 60 °C. In order to simulate the process, the model of broken and intact cells (Sovova’s model) was applied. The model well represented the experimental data. Oil yields ranged from 21.3 % to 33.87 % depending on the extraction solvent used. Monounsaturated fatty acids (MUFA) were the major compounds of the oils, based on the fatty acid analysis. Chromatographic analysis revealed that the chemical compositions vary from one region to another, extraction solvent as well as the conditions of pressure and temperature.

An efficient QCA-based full adder design with power dissipation analysis

Abstract: Quantum Dot-Cellular automata (QCA) is a developing technology that is considered as the best viable alternate solution for CMOS technology which has short-channel effects. QCA is a transistor-free technology, and the information is distributed formulated on the charge of the electron and by Columbic repulsion theory. In this paper, an optimal adder circuit is proposed using QCA technology which consist only 14 cells. The proposed adder circuit is further utilised for designing of 4-bit adder design efficiently. Simulations results, are obtained precisely using QCADesigner software version 2.0.3., confirm that the proposed circuits work well. Moreover, the energy dissipations of the proposed adder circuit design is estimated using QCAPro tool. The performance of the proposed design was compared with the existing ones which shows better performance in terms of cell count, area, and latency. Suggested 1-bit and 4-bit QCA adders exhibit a delay of 0.5 and 1.25 clock cycle, occupy an active area of 0.01 and 0.1 and μm2, and use 14 and 84 QCA cells, respectively.