Distribution of free amino acids,polyphenols and sugars of Ziziphus jujuba pulps harvested from plants grown in Tunisia

Ziziphus jujuba pulps are very much appreciated by the inhabitants and have been recently exported. This article reports on the chemical composition (amino acids, polyphenols and sugars) of the pulps of four Z. jujuba ecotypes (Choutrana, Mahdia, Mahres and Sfax). The major amino acids identified were proline, aspartic acid and glutamic acid. Among these, proline was the most abundant amino acid (17.4 mol). Considerable differences in total phenolic contents (15.85 mg/L) were found. Predominant phenols identified by using HPLC were rutin (1.09 mg/L) and chlorogenic acid (2.57 mg/100 g). Sugars isolated from Ziziphus pulps were found at a rate of 43.52%. Using HPLC method, three sugars from the pulp extract were identified: glucose, galactose and sucrose. The Mahdia ecotype was the richest in these sugars with 0.45, 136.51 and 113.28 mg/L, respectively.     

Investigation of electrocoagulation reactor design parameters effect on the removal of cadmium from synthetic and phosphate industrial wastewater

This study investigates the effect of reactor design parameters on cadmium removal from industrial wastewater discharged by the Tunisian Chemical Group (TCG) to improve as much as possible efficiency and cost of electrocoagulation (EC) process. Based on an examination of the design parameters one by one, the best cadmium removal was achieved for an inter-electrode distance (d_ie) of 0.5 cm, monopolar connection mode, stirring speed of 300 rev min^?1, surface-area-to-volume ratio (S/V) of 13.6 m^?1, and an initial temperature of 50 °C. These operating conditions are allowed to achieve efficient removal in a relatively short operating time with the lowest energy consumption and cost possible. The present study proved that the parameters that have an effect on the operating cost are the electrode configuration, inter-electrode distance and S/V ratio. The energy consumption, the pH evolution, and the treatment cost were studied. The investigation of the effect of all the selected optimum EC design parameters together on the removal of cadmium from the TCG wastewater proved that the treatment was highly efficient; 100% of cadmium removal was reached in 5 min, with a very low power consumption (1.6 kW h m^?3) and very low cost (0.116 TND m^?3). Moreover, EC was found to be capable of removing cadmium as well as other pollutants at the same time from the case-study industrial wastewater. The investigation carried out in this work explores and proposes a very cost-effective treatment method to remove heavy metals from industrial wastewater if compared to results reported about cost of this treatment process through other widely used technologies such as coagulation (4.36 Tunisian National Dinar (TND) m^?3) and precipitation (9.96 TND m^?3) employed in previous studies.     

Diagnosis of deactivation sources for vanadium catalysts used in SO2 oxidation reaction and optimization of vanadium extraction from deactivated catalysts

Physico-chemical analysis (X-ray, FTIR) and/or methanol oxidation reaction test were performed on fresh and deactivated vanadium catalysts used in H₂SO₄ manufacturing. It allowed the diagnosis of catalyst deactivation sources, as well as the processes of regenerating and recycling the worn out catalyst in converter. One of these processes is hydrometallurgical method. It consists in treating the deactivated catalyst with alkaline or acidic reagents and forming vanadate solution. A simple and non-costly operation of chemical attack permits the extraction of vanadium from silica in deactivated catalyst. The extracted vanadium can be used for the confection of regenerated catalysts or metallic tools. After optimization, this method can be used for industrial application.     

Coating of anatase titania on clinoptilolite by metal organic chemical vapor deposition method: enhanced mesoporosity and photocatalytic activity

Clinoptilolite-supported TiO₂ (TiO₂/CP_MOCVD) has been synthesized by metal organic chemical vapor deposition method (MOCVD). Titanium precursor was evaporated at 110 °C under nitrogen flow rate to promote the surface interaction between titanium species and clinoptilolite. The effect of titanium precursor on the crystalline structure and the surface area of clinoptilolite were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), transformed infrared spectroscopy (FT-IR), Raman spectroscopy, and Brunauer–Emmett–Teller measurement. XRD and SEM results indicate that TiO₂ precursor interacted with the support, decreasing the crystallinity of the clinoptilolite. The analysis by FT-IR spectroscopy further confirms that the titanium species were bound to clinoptilolite through Ti–O–Si bonds. The TiO₂/CP_MOCVD catalyst showed a mesoporous structure with the distribution of pores in several dimensions 3.7–7.1 nm, with high specific surface area (~ 471 m²/g). MOCVD improved the adsorption capacity of the catalyst surface towards the pollutants. TiO₂/CP_MOCVD particles turn yellow after adsorption of salicylic acid. The development of the yellow color is a clear indication of the formation of charge transfer titanium (IV) salicylate surface complex. Photocatalytic decomposition of SA in aqueous solution was carried out using TiO₂/CP_MOCVD. Experimental results revealed that TiO₂/CP_MOCVD required shorter irradiation time (120 min) for complete decomposition of SA than commercial P25 Degussa and TiO₂/CP_imp (clinoptilolite-supported TiO₂ using impregnation method). The TiO₂/CP_MOCVD can be recycled at least four times without loss in activity, indicating their magnificent stability.     

Tuning particle morphology of mesoporous silica nanoparticles for adsorption of dyes from aqueous solution

Spherical and rod mesoporous silica nanoparticles with hexagonal mesostructure were prepared using the modified Stöber method. The morphology, size and internal pore structure can be controlled by simple changing of surfactant concentration and water:ethanol molar ratio. Monodispersed spheroid MCM-41 was obtained at 40 °C under basic conditions using cetyltrimethylammonium bromide (C₁₆TAB) as template. Obtained materials were characterized by X-ray diffraction (XRD), nitrogen physisorption (BET), transmission electron microscopy (TEM) and scanning electronic microscopy (SEM). The results reveal that the pore volume and surface area increase when the amount of C₁₆TAB increases whereas the pore diameter and particle size decrease. However, the use of ethanol as cosolvent led to an increase in the particles’ size. Moreover, the addition of a 3-aminopropyltriethoxysilane greatly influenced the final particle shape. The material was effectively used for the removal of two fluorescent dyes (Hoechst 33342 and rhodamine 6g) from aqueous solution. Adsorption isotherm models, Langmuir, Freundlich and Temkin were used to simulate the equilibrium data. The Langmuir model was found to fit the experimental data better than others models.     

Étude mécanistique et structurale des résines R/F

The follow-up of the advance of the reaction of polymerization of resorcinol with formaldehyde in acid or basic medium by NMR shows that the structure of the obtained xerogel in both cases is the same one. Indeed, the junction between the aromatic nuclei is of type OCH₂OCH₂. While basing itself on the structure of the xerogel, we propose the mechanism for the polymerization reaction between resorcinol and formaldehyde.     

Synthesis,characterization of SiO2 supported-industrial phosphoric acid catalyst for hydrolysis of NaBH4 solution

Abstract

Tunisian industrial phosphoric acid H₃PO₄ was supported on silica gel SiO₂ (SIPA) to catalyze the hydrolysis reaction of aqueous alkaline sodium borohydride (NaBH₄). The SiO₂ was produced from purified quartz sand using alkali fusion-acidification chemical process. The BET surface area results indicate that the prepared silica gel could reach a specific surface area up to 585 m²/g. The addition of PO₃H₂ functional groups resulted in an increase of surface acidity of SiO₂ catalyst as shown by FT-IR and DTA-DTG spectra. The total acidity of SIPA catalyst was determined by titration to be 2.8?mmol H⁺/g. SEM/EDS maps reveal the distribution of heavy metals on the silica surface. The effect of supported PO₃H₂ functional groups and heavy metals on the NaBH₄ hydrolysis reaction was studied for different ratios of SIPA catalyst to NaBH₄. The sample 12SIPA/NaBH₄ leads to a very high hydrogen generation rate (up to 90%). The activation energy of hydrogen generation by NaBH₄ hydrolysis was 25.7?kJ mol^?1.