An efficient synthesis of new thioether compounds through the thia-Michael protocol under mild condition is described. The reaction of thiols and dithiols with β-carbonylethoxyallylic sulfones and sulfides, leads to the formation of di- and tetra-thioethers respectively. The methodology could be extended to the synthesis of new cyclic thioethers in high yields.
A. Hafedh, A. Abdelli, M.L. Efrit, H. Mrabet
Michael acceptor, thiols, allylicsulfure, thioethers
Pages 250-255
Solid-liquid extraction is one of the most used methods for the environment protection and especially for removal of heavy metals. The solid phase used in this work was a Tunisian smectite clay saturated by Na+ , and intercalated by functionalized crown ethers: Dibenzo-14-Crown-4 (NO2)2 (1), Dibenzo-14-Crown-4(NO2)2(Br)2 (2), Dibenzo-14-Crown-4(Br)4 (3) and Dibenzo-14-Crown-4(COOH)2 (4). These new obtained hybrid materials were firstly characterized by X-ray diffraction (XRD), IR spectroscopy and thermal analysis (DSC and DTA-TGA). After that they were used to extract heavy metals (Fe, Cu, Cd, Zn, Pb ,Mn and Co). Extraction percentages by modified clays varied in the following decreasing order Fe3+ ≥ Cu2+ ≥ Pb2+ > Co2+ ≥ Mn2+ > Cd2+ ≈ Zn2+.
B. Chrayet, F. Ammari, A. Ouerghui, F. Meganem
Functionalized crown ethers, Intercalation, Removal of heavy metals, Tunisian Smectite
Pages: 256-263
The activation effect generated by the dry grinding of a commercial quartz-free kaolin and a natural Tunisian quartz-rich kaolin was studied. The Tunisian kaolin has a similar chemical composition to that of pyrophyllite. The grinding operation was conducted using a laboratory planetary ball mill, while adding triethanolamine as a grinding aid. The textural analyses show that the grinding does not seem to follow the three steps conventionally observed when minerals are ground without the use of a grinding aid. The latter seems to prevent the particles agglomeration when minerals are milled for a long time. Regardless of the presence of quartz, a rapid and significant alteration of the kaolinite structure during the first 30 min of grinding was observed. Beyond those 30 min, alteration attenuates clearly. The distortion of the quartz structure follows a different evolution. Thermal events show classical evolution of the kaolinite dehydroxylation peak. However, the presence of quartz seems to affect the mullite crystallization peak: for the quartz-free sample, this peak widens but for the quartz-rich sample, it refines and its intensity increases when prolonging grinding. It is likely that Si-O-Al bonds are formed during grinding, where Si is derived from quartz and Al from kaolinite.
N. Ben Messaoud, Z. Ksibi, L. Bergaoui
Kaolinite, quartz, grinding, grinding aid, mullite
Pages: 264-275
The objective of the present study is to investigate the elimination of boron from brine (saline water), by adsorption using Mg(OH)2 precipitate in-situ as adsorbent. To optimize the experimental condition of boron removal and to evaluate statistically the important significant factors, an experimental methodology design was implemented using 23 full factorial design. The selected parameters were temperature (25°C and 70°C), molar ratio (10 and 30), stirring speed (200 and 600 rpm) and reaction time (15 min and 60 min), while Y1 (the % of boron removal) and Y2(the % of magnesium precipitate) are chosen as the responses variables. The results were analyzed statistically using the analysis of variance, F-test and the student’s t-test to check the significance of the variables effects. The model function equation for boron removal and magnesium precipitate was obtained. The obtained results showed that temperature, molar ratio, stirring speed and time affected boron removal. The optimum operating conditions were found as temperature: 25 °C, molar ratio Mg/B: 30, stirring speed: 600 rpm and time: 15 min. These optimum experimental conditions were used to eliminate 92% of boron initially present in brine in the form of Mg2B2O5.
A. Boughalmi, H. Hammi, A. M’nif
Adsorption; Boron removal, Experimental Design, Full Factorial Design, Hydroxide magnesium
Pages: 276-287
A simple chemical route, based on a modified polyol process, is used to synthesize mono-disperse triangular gold nanoprisms (Tr-AuNPs) in triethylene glycol (TREG) with polyvinyl-pyrrolidone (PVP) as capping agent. Both the solvent and the surfactant in the solution play important roles in the formation of the Tr-Au NPs. Shape, size and optical properties of the particles were tuned by changing the molar ratio of PVP to metal salts. The formation of such large, single-crystal Tr-Au NPs is explained by the preferential adsorption of some species of molecules from the solution onto the {111} planes of Au nuclei. The anisotropy in the nanoparticles’ shape shows strong localized surface plasmon resonance (SPR) in the near infrared region of the electromagnetic spectrum. These nanostructures may be used in areas that include photonics, optoelectronics, optical sensing and also for inducing hyperthermia in tumors. For this reason, the ecotoxicological effects of the Tr-Au NPs and their interactions with marine organisms were also studied in this work. It was found that Tr-Au NPs don’t seem to have a large effect on the non-target marine organism R. decussatus. Indeed, no significant modification (p > 0.05) was observed after 2 days on the glutathione-S-transferase activity of the clams exposed to Tr-Au NPs when compared to the control, both in the gill and the digestive glands.
A. Fkiri, A. Mezni, N. Ben Saber, B. Sellami, L.S. Smiri
Gold nanoparticles, Polyol; Triethylene glycol, Surface Plasmon resonance, Aquatic ecotoxicity
Pages: 288-293
Rss feed of the category