Ridha Abdelhedi

Detection of Chemlali Extra-Virgin Olive Oil Adulteration Mixed with Soybean Oil, Corn Oil, and Sunflower Oil by Using GC and HPLC

Fatty acid composition as an indicator of purity suggests that linolenic acid content could be used as a parameter for the detection of extra/virgin olive oil fraud with 5% of soybean oil. The adulteration could also be detected by the increase of the trans-fatty acid contents with 3% of soybean oil, 2% of corn oil, and 4% of sunflower oil. The use of the ΔECN42 proved to be effective in Chemlali extra-virgin olive oil adulteration even at low levels: 1% of sunflower oil, 3% of soybean oil, and 3% of corn oil. The sterol profile is almost decisive in clarifying the adulteration of olive oils with other cheaper ones: 1% of sunflower oil could be detected by the increase of Δ7-stigmastenol and 4% of corn oil by the increase of campesterol. Linear discriminant analysis could represent a powerful tool for faster and cheaper evaluation of extra-virgin olive oil adulteration.

Electrochemical degradation of waters containing O-Toluidine on PbO2 and BDD anodes

Electrochemical oxidation of O-toluidine (OT) was studied by galvanostatic electrolysis using lead dioxide (PbO2) and boron-doped diamond (BDD) as anodes. The influence of operating parameters, such as current density, initial concentration of OT and temperature was investigated. Measurements of chemical oxygen demand were used to follow the oxidation. The experimental data indicated that on PbO2 and BDD anodes, OT oxidation takes place by reaction with electrogenerated hydroxyl radicals and is favoured by low current density and high temperature. Furthermore, BDD anodes offer significant advantages over PbO2 in terms of current efficiency and oxidation rate.

Phenolic profile characterization of Chemlali olive stones by liquid chromatography-ion trap mass spectrometry.

Aqueous methanol extracts of Chemlali olive stones were analyzed by reverse phase high-performance liquid chromatography (HPLC) with diode array detection and mass spectrometry [LC-MS/MS]. Oleoside, oleoside 11-methyl ester, nuezhenide, oleoside 11-methyloleoside, nuezhenide 11-methyloleoside, oleuropein, and glycosides of tryosol and hydroxytyrosol glycosides were identified in stones of Chemali olives. The antioxidant activity observed for the extract of the olive stones (IC50 = 13.84 μg/mL, TEAC = 0.436 mM) may be due to the high content of phenolic compounds, of which the main compounds are nuezhenide (325.78 mg/100g), methoxy derivative of nuezhenide (132.46 mg/100g), and nuezhenide-11-methyloleoside (82.91 mg/100g). These results suggest the use of olive stones as sources of natural antioxidants.

Degradation of 4-chloroguaiacol by dark Fenton and solar photo-Fenton advanced oxidation processes.

This paper evaluates the dark Fenton and the solar photo-Fenton advanced oxidation processes for the treatment of solutions containing 4-chloroguaiacol (4-CG). The 4-CG was chosen as a model compound found in pulp and paper wastewater formed in the bleaching process in the pulp industry. The effects of operating parameters, including reaction time, hydrogen peroxide-to-ferrous iron molar ratio (H2O2/Fe2+), initial chemical oxygen demand (COD), pH value, and temperature, on 4-CG degradation efficiency using the solar photo-Fenton process were investigated. It was demonstrated that both processes could effectively degrade 4-CG in water and followed first-order kinetics. The degradation rate in solar photo-Fenton oxidation was much faster than that of the dark reaction. The 4-CG degradation depends on its concentration in the solution. The degradation efficiency decreases when the concentration of the 4-CG increases. Under the conditions of pH 3, H2O2/Fe2+ molar ratio 2, H2O2 16 mmol x L(-1), Fe2+ 8 mmol x L(-1), initial COD 640 mg x L(-1), reaction time approximately 24 minutes, and temperature 25 degrees C, the 4-CG and COD percent removal were greater than 80 and 89%, respectively.

Treatment of dilute methylene blue-containing wastewater by coupling sawdust adsorption and electrochemical regeneration.

In the present work, the coupling of adsorption and electrochemical oxidation on a boron-doped diamond (BDD) electrode to treat solutions containing dyes is studied. This coupling may be convenient for the treatment of diluted pollutant that is limited by the low rate of electrooxidation due to mass-transfer limitation. A pre-concentration step by adsorption could minimize the design of the electrochemical reactor. The adsorbent chosen was mixed with softwood sawdust, and methylene blue was chosen as the model dye molecule. Isotherms of adsorption and kinetics were investigated as well as the effects of current density and regeneration time. The BDD electrochemical oxidation of methylene blue adsorbed onto sawdust led simultaneously to its degradation and sawdust regeneration for the next adsorption. It was observed that multiple adsorption and electrochemical regeneration cycles led to an enhancement of adsorption capacity of the sawdust. This study demonstrated that adsorption–electrochemical degradation coupling offers a promising approach for the efficient elimination of organic dyes from wastewater.

Oxidation of the insecticide dimethoate by Fenton and solar photo-Fenton processes using a lab-scale continuous flow reactor

AbstractIn this study, advanced oxidation processes utilizing Fenton’s and solar photo-Fenton’s reactions were investigated for the degradation of dimethoate, an organophosphorus insecticide extensively applied in agriculture. Effect of Fe2+, H2O2, pH, and temperature on the degradation of this insecticide was studied. The kinetic rate constants (kapp) for COD removal were determined. The test results show that the degradation of dimethoate proceeded rapidly at pH value of 3.0. kapp enhanced with the increase of initial Fe2+ concentration and H2O2 dosing rate. However, higher levels of Fe2+ and H2O2 also inhibited the reaction kinetics. kapp decreased with the increase of initial dimethoate concentration, but increased with the increase of temperature. The activation energy for COD removal by Fenton oxidation, derived from the empirical Arrhenius expression, is 21.38 kJ mol−1. A noticeable kapp increase (∼50%) was obtained when using the solar photo-Fenton process, which means about 50% gain of H2O2.

Crystal structure, phase transitions and dielectric properties of the mixed compound [Cs0.92(NH4)0.08]2HgBr4

Abstract The crystal structure of [Cs 0.92 (NH 4 ) 0.08 ] 2 HgBr 4 was determined by three-dimensional X-ray diffraction analysis. The space group is Pnma with a = 10.210(2), b = 7.928(1), c = 13.883(1)A and Z = 4 at 293K. The structure was refined to R = 0.067. The distribution of atoms can be described as isolated HgBr 4 2− tetrahedra , Cs + and NH 4 + cations. The main feature of this structure is the coexistence of two types of bonds: Cs +  Br − ionic bonds and NH…Br hydrogen bonds ensuring the cohesion of the crystal. Dicaesium-ammonium tetrabromomercurate exhibits three phase transitions at T 1 = 237K, T 2 = 244K and T 3 = 513K. These transitions were detected by differential scanning calorimetry and analysed by dielectric measurements using the impedance and modulus spectroscopy techniques. The phase change at high temperature is related with the orientational disorder of NH 4 + cations. Transport properties in this material appear to be due to a H + ion hopping mechanism.