Browsing by Author "Nasrallah, N."

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Effect of impeller type on the mixing in torus reactors
(2008) Nasrallah, N.; Legrand, J.; Bensmaili, A.; Nouri, L.
Torus reactors are characterized by a homogeneous fluid circulation without dead zones. Torus reactors were used for applications in biotechnology, food processing, polymerization and liquid waste treatments. The relatively simple extrapolation of performances, due to the absence of dead volume, is one of the main advantages of this reactor, with low shear stresses and an effective radial mixing allowing efficient heat dissipation. This study is based on the mixing in order to analyse the fluid circulation, mainly in turbulent flow regime, and to characterize the torus reactor with the axial dispersion plug flow model. The objective of this study is to characterize the flow and the mixing in the torus reactors in batch and continuous modes. The mixing analysis was made according to the flow parameters and to the geometrical characteristics of the reactor and impeller. The mixing in the torus reactor can be characterized by the P´eclet number, PeD, defined with torus diameter. A representative model based on plug flow with axial dispersion and partial recirculation was proposed
Enhancement of photocatalytic reduction of Cr(VI) using hetero-system NiAl2O4/ZnO under visible light
(Aljest, 2019) Bouallouche Née Saadi, Rachida; Kebir, M.; Nasrallah, N.; Hachemi, M.; Amrane, A.; Trari, M.
Hexavalent chromium Cr(VI) is well known to be a toxic and non-biodegradable contaminant and can cause significant environmental damage if it is not eliminate from wastewater. However, it can be reduced to Cr(III), which is less toxic by photocatalysis process using the heterosystem NiAl2O4/ZnO. NiAl2O4 prepared by nitrate method crystalize in a spinel structure and was characterized, by XRD, FTIR, and SEM techniques. NiAl2O4 acts as electrons pump and the electron transfer to chromate is mediated via ZnO. Under the optimized conditions, the percentage of Cr(VI) reduction was 62 % for 20 mg/L, NiAl2O4/ZnO ratio (1/1) at pH~3.7 and under visible light. An improvement up to 72% was obtained when the reaction occurs in a Rishton reactor with six bleds after 6 h illumination. It is therefore concluded that the Cr(VI) photocatalytic reduction followed a pseudo first order kinetic model, in agreement with the Langmuir–Hinshelwood mechanism. This work revealed that the NiAl2O4/ZnO heterosystem exhibits a better photocatalytic efficiency for the photoreduction of Cr(VI) mainly due to the good separation of electron-hole pairs (e-/h+) in this combination.
Liquid–liquid extraction and quantitative determination of tungsten (VI) using macrocyclic reagent (DB-18-C-6) as a thiocyanate complex [WO (SCN)5]2
(Taylor & Francis, 2014) Nabiev, M.; Hamada, B.; Nabieva, A. M.; Amrane, A.; Nasrallah, N.; Saoud, A.
In recent years, the extraction using crown ethers has reached a resounding success in different scientific and technical fields. In this work, the authors report the results of the main steps of extraction and determination (proportioning) of the tungsten ion (VI) using a chloroformed solution of crown ether. The dibenzo–18–C-6(2,3,11,12-dibenzo-1,4,7,10,13,16-hexaoxacyclooctadeca- 2,11-diene according to the IUPAC systematic nomenclature). The identification and quantification of W(VI) using the absorption spectrum, the influence of the necessary reagents, the needed acidity level for complete extraction and complexation of W (VI) using a crown ether, and the influence of multivalent metal ions were examined, considering that the sensitivity, selectivity, and detection limits have been determined. This system obeys Beer’s law in the range of 0.18–18.3 lgcm 3of tungsten with a molar absorption of 1.6 104 mol 1 cm 1 at 415nm and the detection, quantification limits were, respectively, equal to 0.7–1.8 lgcm 3. The developed method was applied for the extraction of W(VI) in the high speed steel (HSS): HS2–9-1–8 containing 2% W, 9% Mo, 1% V, and 8% C