Chemistry

Two smectitic Tunisian clays were organically modified by exchange reaction with dioctadecyl dimethylammonium chloride (DODMA) and hexadecyl benzyl dimethylammonium chloride (HBDMA). The resulting organoclays were used in the formulation of lubricating greases. The results of the performance tests applied to the obtained greases showed that their physicochemical and mechanical characteristics are in conformity with the extreme-pressure (EP) greases specifications. The

Nous avons etudie de la modification organique de deux argiles tunisiennes du type smectite en vue de leurs utilisations dans la preparation d'agents epaississants. Ces deux argiles ont ete selectionnees grâce a leur importante capacite d'echange cationique (CEC). Elles ont ete ensuite organiquement modifiees par deux sels d'ammonium quaternaires: le chlorure de benzyl dimethyl hexadecyl ammonium et le chlorure de dioctadecyl dimethyl ammonium. Les agents epaississants prepares a partir de ces argiles presentent des proprietes physico-chimiques et rheologiques comparables a celles d'une bentonite modifiee industriellement (Bentone 34).

Calcium greases were manufactured from oliveresidue oil in a closed reactor by substituting olive-residue oil for animal tallow. The results of the performance tests applied to the obtained greases showed that their physicochemical and mechanical characteristics are comparable to those of calcium grease manufactured industrially by using animal tallow. The substitution of part of the animal tallow with olive-residue oil increased the thermal and mechanical stability of the grease. Olive-residue oil could constitute, alone or in combination with animal tallow, a raw material in the formulation of lubricating calcium grease.

This paper presents an improved synthesis of trans-chalcones and a,a 0-bis(arylmethylidene) cycloalkanones under ultrasound irradi ation in the presence of commercial acid-resins as catalysts in solvent free condit ions. Several trans-chalcones and a,a 0-bis(arylmethylidene) cycloalka nones were synthesized in good yields and excellent selectivity in a short reaction time.

This study elucidate the modification on oxidative and thermal stability of acid olive oils during the neutralization step. The neutralization of an acidified olive oil, chosen as model, was carried out by substituting lime (calcium hydroxide) for soda (sodium hydroxide) as the neutralizing agent. Resulting olive oil preserved almost 95% of their a-tocopherol content and had higher temperatures of thermal decomposition than oils neutralized with soda. Oils neutralized with lime had better oxidative stability since the losses of their natural antioxidants, particularly tocopherols, were very limited. The neutralization with soda was accompanied by a passage of epoxides and hydroperoxides (products of first stage of oxidation) to a, b-unsaturated aldehydes and ketones (products of second stage of oxidation). These purposes were confirmed by thermal spectrophotometric analyses and the increase of the carbonyl value after neutralization.

An efficient and reusable catalyst, alkaline-modified Montmorillonite K10, has been developed and used in the Knoevenagel condensation. A series of condensation reactions based on ultrasound irradiation of different types of active methylene compounds and a variety of aromatic aldehydes showed the high efficiency of the prepared catalyst. This protocol has notable advantages, such as being eco-friendly, the ease of the work-up and reuse of the catalyst. The isolated compounds were synthesized in high yields (83-100%) in a short reaction time and were obtained, after crystallization, in pure form (IR, NMR and GC) without further purification. When ethyl cyanoacetate was used as active methylene compound, the reaction is highly stereoselective with only E geometry.

: This research paper presents a green, safe and easy synthesis of trans-chalcones under ultrasound irradiation in the presence of anionic resins. Several trans-Chalcones have been obtained following an environmentally friendly methodology using Amberlyte IRA-410 and Amberlyte IRA-400 resins as heterogeneous and efficient catalysts. The products of the condensation reaction were generally synthesized in good yields and the analysis confirmed their structures well.

Three different graphite powders with different particles sizes were tested to synthesize tubular monochannel carbon supports for micro and ultrafiltration membranes using a new process. Carbon graphite powders and organic additives were mixed with an ethanolic solution of Resol s type phenolic resin. The extruded tubes were firstly consolidated by curing the resin at 150 1C then carbonized under nitrogen stream (1 mL min −1 ) for graphitization and pores opening.

The potential of hybrid organic-inorganic membranes for separating organic molecules from air, based on solubility selective mechanism, was evaluated. Alumina and titana membranes with average pore size near 4 nm were surface modified using trimethoxysilane fluorinated coupling reagent. The permeabilities to helium, nitrogen, methane, ethane, propane, butane and carbon dioxide were evaluated at feed pressures lying between (1.5 × 10 5 and 3.5 × 10 5 Pa) 1.5 and 3.5 bar and permeate outlet near 1 × 10 5 Pa (1 bar). The permeabilities of the grafted membranes generally decreased by about two to three orders of magnitude compared with the untreated membranes. The CO 2 /N 2 permselectivity increased significantly in the case of the TiO 2 grafted membrane. The membranes performances were compared and the TiO 2 grafted membrane exhibits higher permselectivity and permeability, so that, it is a good candidate for CO 2 to N 2 separation and CO 2 to hydrocarbon separation.

Low-density polyethylene (LDPE) films with different copper contents were prepared from solu-tion. The TGA (thermogravimetric analysis) results show that the presence of copper particles can im-prove the thermal stability of the composite since a maximum increment of 14°C is obtained compared with the pure LDPE in this experiment. The results of DSC (differential scanning calorimetry) in stan-dard conditions show that the Cu content has little influence on the crystallinity, X c , of LDPE. But a trace of DSC under non-standard conditions suggests that the presence of the copper microparticles has a greater effect on the network phase than on the crystalline long-range-order phase. FTIR spectroscopy was used to study the phase content of LDPE in LDPE/Cu non-oriented composite films prepared from solution with different copper contents by analysis of CH2 rocking vibrations. A spectral simulation of transmission spectra performed using a two-phase model does not show any variation into the phase composition of the LDPE matrix for all copper contents. When a three-phase model was taken into account, the amount of the orthorhombic phase was found to be constant. However, the fraction of the amorphous and that of the network phase were found to increase and decrease respectively with increase in the copper particle load in the film.

The development and the characterisation of a new support for microfiltration and ultrafiltration membranes from fly ash applied to filtration are presented. The choice of this material is based primarily on its low cost (as fly ash is produced abundantly as a solid waste by coal fired power plants in many parts of the world).

New microfiltration membranes from mineral coal fly-ash material are obtained using ceramic method. Paste from mineral coal fly ash (obtained by calcinations at 800°C of non-grinded mineral coal) is extruded to elaborate a porous tubular configuration used as supports. The support heated at 1125°C, shows an average pore diameter and porosity of about 4.5 μm and 51%, respectively. The properties in terms of mechanical and corrosion resistances are very interesting. The elaboration of the layer based on fly-ash powder (obtained by sintering at 700°C of a finely grinded mineral coal) is performed by slip-casting method. The heating treatment at 800°C leads to an average pore size of 0.25 μm. The water permeability determined of this membrane is 475 L/h m 2 bar. This membrane can be used for crossflow microfiltration. The application to the treatment of the dying effluents generated by the washing baths in the textile industry shows an important decrease of turbidity (inferior to 1 NTU), of chemical oxygen demand (COD) values (retention rate of about 75%) and a total color removal. The performances in term of permeate flux and efficiency were determined and compared to those obtained using a commercial alumina microfiltration membrane. Almost the same stabilised permeate flux was obtained (about 100 L h −1 m −2 ). So, it seems that the prepared membrane is suitable for such wastewater treatment.

This work aims to develop a new mineral porous tubular membrane based on mineral coal fly ash. Finely ground mineral coal powder was calcinated at 700 • C for about 3 h. The elaboration of the mesoporous layer was performed by the slip-casting method using a suspension made of the mixture of fly-ash powder, water and polyvinyl alcohol (PVA). The obtained membrane was submitted to a thermal treatment which consists in drying at room temperature for 24 h then a sintering at 800 • C. SEM photographs indicated that the membrane surface was homogeneous and did not present any macrodefects (cracks, etc. . .). The average pore diameter of the active layer was 0.25 m and the thickness was around 20 m. The membrane permeability was 475 l/h m 2 bar.

Fasciolosis is a widespread parasitosis of farm live-stock in many developing countries. For this reason, it is necessary to search for new substances against parasitic diseases caused by flukes. Indeed, a wide variety of terrestrial plants have been subjected to chemical and pharmacological screening in order to discover their potential for human medicinal use. The molluscicidal and larvicidal activities of Atriplex inflata were tested on Galba truncatula and Fasciola hepatica larval stages infecting this snail in Tunisia. Phytochemical tests were conducted on extracts in order to establish a meaningful relationship with molluscicidal and larvicidal activities. The molluscicidal activity was evaluated by subjecting snails to sample aqueous solutions. Accordingly, hexane, ethyl acetate, methanol and methanol-water (8:2, v-v) were used as extraction solvents. As a result, hexane and ethyl acetate extracts showed potent activity, according to the World Health Organization, giving LC50...