Elimame Elaloui

Treatment of heavy metal polluted industrial wastewater by a new water treatment process: ballasted electroflocculation

This laboratory study investigated the parameters efficiency of the new technology: ballasted electro-flocculation (BEF) using aluminum (Al) electrodes to remove cadmium and zinc from industrial mining wastewater (MWW). The principle of the BEF process is based on the use of micro-sand and polymer together to increase the weight of the flocs and the rate at which they settle is radically changing the electrocoagulation-electroflocculation settling methodology. Based on the examination of the operation parameters one by one, the best removal percentage was obtained at a current intensity of 2A, a the flow rate of 20L/h, a micro-sand dose of 6g/L, a polyéthylèneimine (PEI) polymer dose of 100mg, the contact times of 30min, a stirring speed of 50 RPM, a monopolar configuration of the electrodes, and an electrodes number of 10. The results showed that the flow rate and the current density have a preponderant effect on the variability of the quality of the settled water. In comparison, filterability was found to be more sensitive to number of electrodes, micro sand dosages and current density. It was dependent on the ratio of microsand to PEI polymer dosage, and improved when this ratio increased. Response surface methodology was applied to evaluate the main effects and interactions among stirring speed, polymer dose, current intensity, and electrodes number. The removal of Cd and Zn from industrial MWW was done for very low cost of 0.1TND/m3 equivalent to 0.04€/m3. The investigation of BEF process proposes a highly cost-effective wastewater treatment method if compared to Actiflo TM and electrocoagulation.

Detoxification of 4-chlorophenol in TiO2 sunlight system: effect of raw and treated solution on seed germination and plants growth of various sensitive vegetables

The mineralization and detoxification of 4-chlorophenol (4-CP) were studied using a TiO2-paper/sunlight system. The possibility of reusing the photocatalyst was examined to determine the cost effectiveness of the method. Experiments were performed to establish optimum conditions for 4-CP removal. Phytotoxicity of photo-treated and raw 4-CP (100 mg L−1) solutions on seed germination and plant growth were carried out with the aim of water reuse and environment protection. The seeds irrigated with raw 4-CP solution showed lower sprout length while increase in sprout length was observed with the photo-treated solution for tomato (Lycopersicon esculentum), lettuce (Lactuca sativa), onion (Allium cepa), and turnip (Brassica rapa). Plant growth tests with the photo-treated 4-CP solution did not affect the leaf numbers compared to those irrigated with tap water. Photo-treated 4-CP solution can be used for irrigation in agriculture.

Novel and facile synthesis of transparent-monolithic TiO2 gels by sol-gel method based on an esterification reaction

Abstract Transparent TiO2 monoliths were obtained through a modified sol-gel route from titanium isopropoxide as a precursor. By controlling the hydrolysis of this precursor through the intermediate of esterification reaction between acetic acid and isopropanol at 40 °C, transparent TiO2 xerogel monoliths were obtained. The monoliths prepared by this method were transparent in the wavelengths between 400 nm and 700 nm. Fourier transform infrared (FT-IR) spectroscopy suggested that the acetic acid played also an active role as a chelating agent, forming Ti[(OH)y(OOCCH3)x] less reactive species. Powder X-ray diffraction confirmed the amorphous-to-anatase phase transformation with the formation of unknown Ti-containing complex at 90 °C. Only anatase TiO2 could be observed in the samples calcined at 250 °C and 450 °C. Optical aspects of the gel (transparent-transluscent transformation of monolithic gel) and gelation time were controlled by changing the amount of external water.

Anodic Oxidation of Chlorinated Pesticides on BDD and PbO 2 Electrodes: Kinetics, Influential Factors and Mechanism Determination

In this work, the removal of two pesticides 1, 2- dichlorobenzene and 1, 4- dichlorobenzene by electrolysis using BDD and Pb/PbO2 as anodes is studied. Different operating conditions and factors affecting the treatment process including anode material, applied current density, supporting electrolyte and initial pH value were studied and optimized. Results demonstrate, as expected, that the influence of the anode material used on the degradation of pesticides was very significant in all cases. Infact electrolysis with diamond electrodes can attain the complete depletion of the pesticide and its mineralization faster than with PbO2 anode. Electrolysis experiments strongly improves that the complete degradation of pesticides occurred in the presence of Na2SO4 as conductive electrolyte at current density equals 20 mA cm-2. Acidic pH would accelerate dichlorobenzene degradation, whereas alkaline condition showed negative effects. The disappearance of the pesticides followed a pseudo-first-order kinetics. Reversed-phase chromatography allows detecting Catechol, 2-chlorophenol and Pyrogallol as primary aromatic intermediates of 1,2-DCB and Hydroquinone, Benzoquinone and 4-chlorophenol for 1,4-DCB. Dechlorination of these products gives chloride ions Cl-. Ion-exclusion chromatography reveals the presence of maleic, formic, fumaric, malonic, glyoxylic, acetic and oxalic acid. An oxidation mechanism is proposed in agreement with other works shown in the literature.

Sol–gel synthesis of microporous carbon using resorcinol and formaldehyde

Microporous carbon materials were prepared by thermal decomposition of a xerogel. The xerogel was synthesised through polycondensation of resorcinol and formaldehyde using an acid-catalysed sol–gel method. Acetic acid (1 M) was used as a catalyst. The effect of the molar ratio of resorcinol/catalyst (10/3, 5, 10, 20) on the obtained hydrogel was studied. The temperature range 25–110 °C was used to convert the hydrogel into a solid resorcinol/formaldehyde xerogel. The optimum molar ratio of resorcinol/catalyst was found to be 10/3. The dried xerogels were pyrolysed under an argon atmosphere at 800 °C to obtain microporous carbon materials with a uniform structure consisting of hollow particles and a specific surface area of 650 m2 g−1.