Centre International des Technologies de l'Environnement de Tunis

Abstract To degrade the tryptophan molecule through photocatalysis, the exploitation of solar energy in the present study necessitated the use of visible light active photocatalysts. Iron-transition metal nanoparticles were deposited on the surface of TiO2 powders through an impregnation method to obtain X%Fe-TiO2 for the purpose of improving the optical absorption of TiO2 in the visible light region. The effects of iron percentage (X%: 2,4 and 5), iron oxidation state and pH on the photocatalytic performance of TiO2 modified under solar irradiation were thoroughly studied. The characterization results by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS) and scanning electron microscopy/energy dispersive X-ray spectrometry (SEM-EDS) indicate that iron nanoparticles were successfully fixed on the TiO2 surface. The absorption wavelengths of all X%Fe-TiO2 photocatalysts shifted towards the visible, confirming successful modification of the TiO2 surface with iron. Based on the empirical results, X%Fe-TiO2 nanomaterials demonstrate a higher activity compared with the unmodified TiO2 under solar irradiation. The 4%Fe(III)-TiO2 photocatalyst, in particular, displayed the highest photocatalytic activity at natural pH. The degradation was complete in 60 min. Therefore, it is interesting to note that iron had more functions and benefits than noble metals. The mechanism of the Fe-TiO2 system has been proposed in detail.

This paper aims to evaluate the performance of steel slag in improving the properties of concrete by using different homogenization models and finite element simulations. The free vibration of functionally graded (FG) concrete beams reinforced with steel slag is investigated by using the Euler–Bernoulli and Timoshenko beam theories. It has been assumed that the modulus of elasticity and the density change in the thickness direction according to the power law. The equations governing the free vibration are resolved in an exact way for Euler–Bernoulli theory and by using ANSYS software for Timoshenko theory. Then, a parametric study is carried out in order to analyze the influence of volume fraction and distribution of steel slag, beam slenderness ratio and shear on the dynamic behavior of FG beams. The results demonstrate the significant effect of the studied parameters on the vibration of concrete beams reinforced with steel slag.

In Tunisia, olive mill wastewater (OMWW) locally named ‘margine’ constitutes a serious problem due to its huge amount, of about one million ton per year, and the high pollutant load resulting in the excessive chemical oxygen demand (COD) values and the presence of phytotoxic and antibacterial polyphenols. The most common treatment of OMWW was storage in evaporation ponds which are authorized but uncontrolled. Thus, it represents a potential contamination source of natural resources (air, soil and water) via infiltration. This study aims at a critically analysing the OMWW storage management on the site of Agareb in Sfax, Tunisia. The data relating to the OMWW production highlights that it exceeds its storage capacity due to the uncomplete OMWW evaporation. The geotechnical investigations confirmed the spread of OMWW through and below the storage basins. Furthermore, multiple slope sliding has been observed within embankments separating the OMWW storage basins. Faced with this alarming situation, the assessment of the incorporation of geomembrane is analysed in order to ensure the sustainability of OMWW landfilling. The slope stability analysis based on limit-equilibrium method (LEM) using Midas-Soil works software was investigated. The use of geomembrane can secure the slope stability and limit OMWW infiltrations in the landfill body and sub-soils in the studied site.