Ridha Abdelhédi

Effect of olive storage conditions on Chemlali olive oil quality and the effective role of fatty acids alkyl esters in checking olive oils authenticity

The present paper accounts for the study of the storage of Chemlali olive fruits at two conditions of limited aerobiosis: in closed plastic bags and in open perforated plastic boxes for different periods before oil extraction. The ultimate objective is to investigate the effect of the container type of the postharvest fruit storage on the deterioration of the olive oil quality. The results have shown that the oil quality of Chemlali olives deteriorated more rapidly during fruit storage in closed plastic bags than in perforated plastic boxes. Therefore, the use of perforated plastic boxes is recommended for keeping the olives for longer periods of storage. The repeated measures analysis of variance of all parameters analyzed indicated that the olive oil quality is mainly affected by the olives storage conditions (containers type and storage periods). Finally, blends of extra-virgin olive oil and mildly deodorized low-quality olive oils can be detected by their alkyl esters concentrations.

Application of electrochemical technology for removing petroleum hydrocarbons from produced water using lead dioxide and boron-doped diamond electrodes

Although diverse methods exist for treating polluted water, the most promising and innovating technology is the electrochemical remediation process. This paper presents the anodic oxidation of real produced water (PW), generated by the petroleum exploration of the Petrobras plant-Tunisia. Experiments were conducted at different current densities (30, 50 and 100 mA cm(-2)) using the lead dioxide supported on tantalum (Ta/PbO2) and boron-doped diamond (BDD) anodes in an electrolytic batch cell. The electrolytic process was monitored by the chemical oxygen demand (COD) and the residual total petroleum hydrocarbon [TPH] in order to know the feasibility of electrochemical treatment. The characterization and quantification of petroleum wastewater components were performed by gas chromatography mass spectrometry. The COD removal was approximately 85% and 96% using PbO2 and BDD reached after 11 and 7h, respectively. Compared with PbO2, the BDD anode showed a better performance to remove petroleum hydrocarbons compounds from produced water. It provided a higher oxidation rate and it consumed lower energy. However, the energy consumption and process time make useless anodic oxidation for the complete elimination of pollutants from PW. Cytotoxicity has shown that electrochemical oxidation using BDD could be efficiently used to reduce more than 90% of hydrocarbons compounds. All results suggest that electrochemical oxidation could be an effective approach to treat highly concentrated organic pollutants present in the industrial petrochemical wastewater and significantly reduce the cost and time of treatment.

Boron doped diamond sensor for sensitive determination of metronidazole: Mechanistic and analytical study by cyclic voltammetry and square wave voltammetry.

The performance of boron-doped diamond (BDD) electrode for the detection of metronidazole (MTZ) as the most important drug of the group of 5-nitroimidazole was proven using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. A comparison study between BDD, glassy carbon and silver electrodes on the electrochemical response was carried out. The process is pH-dependent. In neutral and alkaline media, one irreversible reduction peak related to the hydroxylamine derivative formation was registered, involving a total of four electrons. In acidic medium, a prepeak appears probably related to the adsorption affinity of hydroxylamine at the electrode surface. The BDD electrode showed higher sensitivity and reproducibility analytical response, compared with the other electrodes. The higher reduction peak current was registered at pH11. Under optimal conditions, a linear analytical curve was obtained for the MTZ concentration in the range of 0.2-4.2μmolL(-1), with a detection limit of 0.065μmolL(-1).

Infrared characterization and electrochemical study of γ-methacryloxypropyltrimethoxysilane grafted in to surface of copper

The formation of a protective layer of γ-methacryloxypropyltrimethoxysilane (γ-MPS) on copper is studied by diffuse reflectance infrared spectroscopy (DRIFT), gravimetric chemical (weight loss) and electrochemical (cyclic voltammetry and potentiodynamic polarization) measurements. By simple immersion in the silanic bath (90/5/5 v/v ethanol/water/silane), this agent immediately physisorbed on copper, but the protective effects are poor. Thiolate and siloxane band formation improve the performances of the silanic layer on the surface of copper especially after heat treatment process. Chemical and electrochemical measurements show that the protective action of heat treatment (HT/Cu-MPS) process is higher than that of aged process (aged/Cu-MPS).

Electrochemical removal of the insecticide imidacloprid from water on a boron-doped diamond and Ta/PbO2 anodes using anodic oxidation process

The removal of pesticides from water is a major environmental concern. This study investigates the electrochemical removal of the insecticide imidacloprid (IMD) from aqueous solutions on a boron-doped diamond (BDD) and Ta/PbO2 anodes under galvanostatic electrolysis. The influence of operating parameters, such as applied current density (50–100 mA cm−2), initial chemical oxygen demand COD (0) (281–953 mg L−1), temperature (25–65 °C) and pH (3.0–10.0) on COD and instantaneous current efficiency (ICE), was studied using the BDD electrode. The degradation efficiency of IMD increased by increasing current density and temperature, but noticeably decreased by the increase of initial pH value and initial concentration of IMD. The COD decay follows a pseudo-first-order kinetic, and the process was under mass transport control. COD removal reaches 90% when using an apparent current density of 100 mA cm−2, initial COD of 953 mg L−1, pH of 3.0 and at 25 °C after 4.5 h electrolysis time. Compared with Ta/PbO2, BDD anode has shown better performance and rapidity in the COD removal using the same electrolysis device.

Inhibitive action of stored olive mill wastewater (OMW) on the corrosion of copper in a NaCl solution

HPLC analysis shows that stored OMW is greatly enriched in phenolic compounds, mainly hydroxytyrosol (HT) (2.54 g L−1) and tyrosol (0.775 g L−1). But, after 4 years these compounds decrease in concentration. Potentiodynamic polarization measurements show that OMW acts as a mixed-type corrosion inhibitor for copper in 3 wt% NaCl solution. The exceptional effect of this inhibitor is above Ecorr. The full passivation range greatly increases upon the addition of inhibitor and increases further with increasing OMW concentration. For sufficiently-high OMW concentrations, a notable absence of trans-passivation phenomenon until 2500 mV is detected and no pits are observed on the samples’ surface.

Depollution of syringic acid aqueous solutions by electrochemical oxidation using high oxidation power anodes

The anodic oxidation of syringic acid aqueous solutions has been comparatively studied using lead dioxide (PbO2) and boron-doped diamond (BDD) anodes in an electrolytic cell. The influence of several operating parameters such as current density and SA concentration on the performance of both systems has been investigated and the energy consumption has been also evaluated. Galvanostatic electrolyses always cause concomitant generation of hydroxyl radicals that lead to the SA destruction. The efficiency of the electrochemical process increases at lower current density and higher SA initial concentration while it decreases with the COD removal progress. The performance of the BDD anode is always better than that of PbO2, requiring shorter electrolysis time to reach overall mineralization, due to the high amounts of effective hydroxyl radicals generated from water oxidation at each anode, which lead to a higher current efficiency and a lower specific energy consumption when BDD anode was used. A possible reaction mechanism for SA oxidation with ˙OH was proposed. The kinetics decay for the SA degradation on the PbO2 anode follows a pseudo-first order reaction with a rate constant of 8.3 10−3 min−1 for a japp value of 15 mA cm−2.

Depollution of 1,3,5-trimethoxybenzene through its electrochemical conversion into a high added value product 2,6-dimethoxy-1,4-benzoquinone

The first part of this work relates to the analytical study of the electrochemical behavior of 1,3,5-trimethoxybenzene (TMB) by cyclic voltammetry at treated gold electrode. The second part is relative to the results of its conversion into a high added value product 2,6-dimethoxy-1,4-benzoquinone (DMBQ) by electrolysis at lead dioxide anode. The used electrolyte which is a simulated solution of TMB in water–acetone mixture should be prepared using a preconcentrated TMB wastewater. The partial substitution of water by acetone permit to control the TMB solubility to avoid the electrochemical efficiency reduction by TMB transfer limitation. Moreover, the DMBQ desorption from the electrode surface by the effects of acetone and its displacement by TMB provides the slowdown of its degradation. The electrochemical DMBQ recovery increases with the enhancement of acetone volumic percentage and decreases by increasing the current density.