Mostefa Abbessi

Cyclic voltammetric evidence of facilitation of the reduction of nitrite by the presence of molybdenum in Fe- or Cu-substituted heteropolytungstates

Fe- or Cu-containing Dawson-type tungtodiphosphates substituted by two, four or five Mo atoms are studied by cyclic voltammetry at pH 3 and 5. Their catalytic activities towards the reduction of nitrite are established and compared with those of the corresponding Fe- or Cu-substituted fully tungstic Dawson heteropolyanions. Whatever the pH, the presence of Mo atoms in the catalysts is found to be beneficial as concerns the current intensity or the potential location of the catalytic wave. Specifically, it is found that the first step with Fe derivatives is the formation of a nitrosyl complex which is further reduced at the potential of a subsequent wave of the heteropolyanion. In the case of Cu- and Mo-substituted compounds, the two heteroatoms are found to exert their beneficial influence in concert.

Stability of the emulsion (W/O): application to the extraction of a Dawson type heteropolyanion complex in aqueous solution.

Dawson type heteropolyanions form complexes with transition metals. These mixed complexes possess some remarkable electrocatalytic properties. Being soluble in aqueous and organic phases, they are used in homogeneous catalysis. In the setting of the recuperation and the regeneration of these complexes, the extraction of a mixed heteropolyanion (alpha 2P2W12Mo5O61Fe)(7-) is the subject of this work. This extraction was carried out by emulsified liquid membrane using (SPAN80) as surfactant and (TIBA) as extractant. Sulfuric acid was used as the internal phase. The stability of the emulsion was studied according to different parameters and the extracting efficiency in optimal conditions was found to be 70%.

Pillared clays as catalysts for methyl parathion removal by advanced oxidation processes

A natural bentonite from Mostaganem in Algeria was modified by intercalation with polyoxocationic solutions (Al·Fe, Al·Co, Al·Cu, Al·Fe·Cu or Al·Fe·La). The modification of the bentonite occurred via pillaring by ionic exchange with these solutions. The addition of these solutions led to the formation of pillared clays with important catalytic properties in environmental impact reactions. The structural and textural properties of materials calcined at 500 °C were determined by several techniques: X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and N2 adsorption–desorption analysis. The pillared clays were then used as a Fenton-type heterogeneous catalyst for the heterogeneous sono-Fenton process for the oxidation of methyl parathion in water. The catalytic tests revealed the activity of the introduced iron species and the promoter effect of lanthanide or copper on the catalytic activity of these species. The sono-Fenton method showed promising results for the degradation of methyl parathion when compared with the Fenton method. Therefore, the sono-Fenton method can be a viable alternative technology to the existing methods for treating methyl parathion in wastewater.

Decolorization of organic dye (NBB) using Fe(III)P2W12Mo5/H2O2 system

ABSTRACT This study evaluates the potential of Fe(III)P2W12Mo5/H2O2 system in the decolorization of one common industrial azo dye, naphthol blue black (NBB). The effects of different parameter’s dye decolorization were investigated. The studied parameters were: the initial pH, the initial H2O2 concentration, the catalyst mass, and the initial dye concentration. The optimal conditions for a maximum discoloration efficiency (100%) are: pH: 3, [NBB]0 = 10 mg/L, Catalyst mass : 0.3 g, [H2O2]0 = : 2 m M. The spectrophotometric analysis indicated that the decolorization of the azo dye with Fe(III)P2W12Mo5/H2O2 was due to the reduction of the azo bonds. This study verifies the viability of the use of Fe(III)P2W12Mo5/H2O2 in the decolorization of NBB.

Study of simultaneous complexation of heavy metals by a mixed heteropolyanion of dawson type

In this work, the simultaneous complexation of the bivalent elements (Ni 2+ ,P b 2+ ,C d 2+ )b y a lacunar mixed heteropolyanion of Dawson type (α2P2W15Mo2O61·nH2O) 10� was studied. These elements are in couple (Ni 2+ ,P b 2+ ), (Ni 2+ ,C d 2+ ), and (Pb 2+ ,C d 2+ ) in aqueous solutions. From the characterization of UV visible spectroscopy, the stability of the formed complexes [NiPbP2W15 Mo2] 6� , and [CdNiP2W15 Mo2] 6� , [CdPbP2W15 Mo2] 6� according to the pH, the time, and the temperature of the reactional medium was studied. The stoechiometry and the constant of stability of these formed complexes were also given. From where it was noted that new mixed compounds having rather high constants of stability were ended, thus they could be steady to the elimination of heavy metals existing in water of industrial wastes.