SOLVENT EXTRACTION ENHANCED MICROFILTRATION OF STRONTIUM AND TECHNETIUM WITH DI-2-ETHYLHEXYLPHOSPHORIC ACID AND QUATERNARY AMMONIUM SALTS

ABSTRACT

Application of extractants in form of microphase (micelles or microdrops) separated from aqueous matrix by microfiltration, “solvent extraction enhanced microfiltration (SEEMF)” is closely related to micellar enhanced ultrafiltration (MEUF) technique.

Uptake of strontium from aqueous solutions with microphase di-2-ethylhexylphosphoric acid (DEHPA) and pertechnetate with quaternary ammoniumsalts (QAS): trioctylmethylammonium chloride, benzyldodecyl-dimethylammonium bromide, and n-(α-carbethoxypenthadecyl)trimetyl-ammonium chloride was investigated as a function of microphase concentration and composition, pH and salinity of aqueous phase. Recovery of microfiltration on cellulose acetate 200 nm filters reached 95% for strontium with 4×10^?3 M DEHPA and 99% for technetium with 10^?4 M trioctyl-methylammonium chloride. A substantial part of 88-99% retention of technetium with investigated quaternary ammonium salts on microfilter may be caused by the filter wetting or sorption phenomena.     

Measurement of Helium Micro Flows for Gas Chromatography by the Dilution Method

More and more chemical analysis laboratories using gas chromatography need to measure the different flows involved during the analysis process (split ratio, column flow). The measurement of the column flow is certainly the most difficult because the flow of carrier gas is generally very small. For example, the flow of helium (the most often used carrier gas) is typically <15???g/s (5?cm³/min). To calibrate helium flowmeters, the ??traced gas method?? developed at LNE for nitrogen has been optimized for helium microflow measurements in the range of 0.75?C30???g/s (0.25?C10?cm³/min) with an expanded uncertainty of 0.6?% or less at the 95% confidence level. The traced gas method, the uncertainty estimation of the calibration bench and the calibration results of a laminar flow element type Molbloc and an industrial mass flowmeter are presented in this paper.     

Utilization of by-products of Hibiscus sabdariffa L. as alternative sources for the extraction of high-quality pectin

Food Science and Biotechnology - The by-products of Hibiscus sabdariffa L. (HsL), obtained after soaking or decoction of the calyces of Colima and Sudan cultivars, were used for pectin extraction....     

Acyl Derivatives of Eudesmanolides To Boost their Bioactivity: An Explanation of Behavior in the Cell Membrane Using a Molecular Dynamics Approach

Semisynthetic analogs of natural products provide an important approach to obtain safer and more active drugs and they can also have enhanced physicochemical properties such as persistence, cross-membrane processes and bioactivity. Acyl derivatives of different natural product families, from sesquiterpene lactones to benzoxazinoids, have been synthesized and tested in our laboratories. These compounds were evaluated against tumoral and nontumoral cell lines to identify selective derivatives with a reduced negative impact upon application. The mode of action of these compounds was analyzed by anti-caspase-3 assays and molecular dynamics simulations with cell membrane re-creation were also carried out. Aryl derivatives of eudesmanolide stand out from the other compounds and are better than current anticancer drugs such as etoposide in terms of selectivity and activity. Computational studies provide evidence that lipophilicity plays a key role and the 4-fluorobenzoyl derivative can pass easily through the cell membrane.     

Fertilizer dynamics in different tillage and crop rotation systems in a Vertisol in Central Mexico

N-fertilization dynamics and agronomic practices on a Vertisol in central Mexico were evaluated under irrigated conditions: (1) wheat-maize rotation with conventional tillage (CT) and burning of residues (W-M/CT/B, regional control); (2) wheat-beans rotation with CT and incorporation of residues into the soil (W-P/CT/I); (3) wheat-maize rotation with CT and incorporation of residues into the soil (W-M/CT/I); (4) maize-beans rotation bi-annual with CT and incorporation of residues into the soil (M-P/CT/Bi); and (5) wheat-maize, no tillage (NT) and residues left on the soil surface as mulch (W-M/NT/S). ¹⁵N and acetylene inhibition techniques were used to estimate N fertilizer efficiency and losses (N₂ + N₂O). Treatments received 240, 60, and 300 kg N ha⁻¹ for spring maize, beans and winter wheat, as ammonium sulphate enriched with 5.468% atoms ¹⁵N excess. In the spring summer cycle, the fertilizer N recovery ranged from 27% for W-M/NT/S to 68% for M-P/CT/Bi. From the total N-fertilizer applied, only 3 to 9% remained in soil after harvest (W-M/NT/S and W-M/CT/I being the respective extremes). Unaccounted N-fertilizer ranged between 27 and 69%, the highest losses corresponding to W-M/NT/S treatment. Fertilizer N recovery in wheat varied from 19 to 37% (W-M/NT/S–W-M/CT/B). N-fertilizer remaining in soil was 14 to 24% (W-M/NT/S – W-M/CT/I). N₂ and N₂O emissions were higher in the no tillage system. Emissions ranged from 3 to 28 kg N ha⁻¹ for W-P/CT/I and W-M/NT/S, respectively. The best treatments were those in which residues were incorporated resulting in N immobilization in top soil (0–15 cm), small N gas losses, and higher soil organic matter, these treatments were W-P/CT/I, W-M/CT/I.     

Improved extraction of carrageenan from red seaweed (Chondracantus canaliculatus) using ultrasound-assisted methods and evaluation of the yield,physicochemical properties and functional groups

Food Science and Biotechnology - Red seaweed Chondracanthus canaliculatus, an underexploited algae species, was used as a potential source for the obtaining of carrageenan. Seaweed was treated...     

Room-Temperature Ferromagnetism in Chemically Synthesized Ce0.97Cr0.03O2−δ Nanopowders

In this paper, we study structural and magnetic properties of undoped (CeO_2?δ ) and Cr-doped (Ce_0.97Cr_0.03O_2?δ ) cerium oxide nanopowders synthesized by a sol-gel-based method. We estimate the crystallite sizes calculated from X-ray diffraction measurements to be around 9.4±0.3 nm for both CeO_2?δ and Ce_0.97Cr_0.03O_2?δ samples. Raman measurements indicate that microstructural defects are generated when Cr substitutes the Ce in the CeO₂ crystal lattice. Magnetic measurements of the Ce_0.97Cr_0.03O_2?δ sample at 300 K indicate ferromagnetic behavior, with a coercive field of 34.27 Oe and a saturation magnetization of 5.8×10^?4 emu/g. We interpret the nature of room-temperature ferromagnetism by taking into account the exchange interaction between Cr³⁺ ions and oxygen vacancies in CeO₂.