Search results for "Precipitation"
showing 10 items of 826 documents
Water sorption isotherms of molecularly imprinted polymers. Relation between water binding and iprodione binding capacity
2017
International audience; Molecularly imprinted polymers are often used in aqueous medium in order to recognize specifically a target molecule. The molecular recognition is usually based on hydrogen bonding. In this case, water molecule presents a serious competition towards the target molecule. In this study, the water sorption by molecularly imprinted polymers was studied in aqueous medium. The molecularly imprinted polymers were specific for iprodione fungicide and were prepared using a 24 full factorial experimental design. They were synthesized using EGDMA or TRIM as crosslinker, methacrylamide or styrene as functional monomer and using bulk or precipitation polymerization. The water sor…
L -lysine and EDTA polymer mimics as resins for the quantitative and reversible removal of heavy metal ion water pollutants
2012
Traditional precipitation methods for inorganic micropollutant removal from waters are increasingly being replaced by sorption methods based on both natural and synthetic materials. In this context, two novel effective heavy metal ions absorbers are presented. These resins, LYMA and LMT85, were crosslinked poly(amidoamine)s carrying amine and carboxyl groups in their repeating units. In particular, the LYMA-repeating unit contains one carboxyl and two amine groups and is a mimic of L-lysine, whereas LMT85 contains two amine and five carboxyl groups and is a mimic of EDTA. Both resins were prepared at moderate cost by simple eco-friendly procedures. The heavy metal ion set adopted as benchma…
Peculiar behavior of degenerative chain transfer polymerization of a phosphonated methacrylate
2009
Living/controlled radical polymerization of dimethyl(methacryloyloxy)methyl phosphonate (MAPC) has been attempted using degenerative transfer to produce block copolymers. RAFT polymerization of this monomer is sensitive to very low level of oxygen and in any case limited to low monomer conversion. Reverse iodine transfer polymerization (RITP) leads to higher monomer conversion with a limited amount of living polymer (55% by H NMR), precluding an efficient synthesis of block copolymers. A PMMA-b-PMAPC diblock copolymer was therefore synthesized by iodine transfer polymerization (ITP) of MAPC from a PMMA-Imacro-chain transfer agent prepared by RITP. The diblock copolymer, purified by selectiv…
The application of the supported liquid membrane and molecularly imprinted polymers as solid acceptor phase for selective extraction of biochanin A f…
2018
An efficient sample clean-up and preconcentration procedure for phytoestrogens analysis in urine has been developed. It was based on a combination of solid phase extraction with hollow-fiber supported liquid membrane and molecularly imprinted beads (MIPs-HF-SLM-SPE). The molecularly imprinted polymers (MIPs) were synthesized by precipitation polymerization technique with biochanin A (BCA) as a template, giving narrowly dispersed microspheres with a regular shape. As the functional monomer, (dimethylamino)ethyl methacrylate (-DEM) turned out to be better than methacrylic acid (MAA) to get the best-imprinted effects. The MIPs used as sorbents in the MIPs-HF-SLM-SPE extraction process exhibite…
Management of tannery wastewaters: treatment of spent chrome tanning bath and vegetable tanning effluents
2013
Abstract In this work, a chain of treatment processes was proposed and described in order to reach better management of mineral and vegetable tannery wastewaters. First, chromium was precipitated from the spent chrome tanning bath by sodium hydroxide (NaOH) and then reformulated to form a complex of basic chromium sulfate which was tested successfully in mineral tanning process. On the other hand, the supernatant recovered after precipitation of chromium with NaOH was used to dilute vegetable tanning wastewaters characterized by a high concentration of polyphenols (about 2,574 mg/L). Diluted effluent was then treated by liming and tangential microfiltration using a ceramic membrane based on…
Size dependent light absorption modulation and enhanced carrier transport in germanium quantum dots devices
2015
Quantum confinement in closely packed arrays of Ge quantum dots (QDs) was studied for energy applications. In this work, we report an efficient tuning mechanism of the light harvesting and detection of Ge QDs. Thin films of SiGeO alloys, produced by rf-magnetron sputtering, were annealed at 600 degrees C in N-2 to induce precipitation of small amorphous Ge QDs into the oxide matrix. Varying the Ge content, the QD size was tailored between 2 and 4 nm, as measured by high resolution transmission electron microscopy. X-ray photoelectron spectroscopy (XPS) measurements indicate the formation of pure SiO2, as well as the presence of a sub-stoichiometric Ge oxide shell at the QD interface. Light …
Modelling biological and chemically induced precipitation of calcium phosphate in enhanced biological phosphorus removal systems
2011
The biologically induced precipitation processes can be important in wastewater treatment, in particular treating raw wastewater with high calcium concentration combined with Enhanced Biological Phosphorus Removal. Currently, there is little information and experience in modelling jointly biological and chemical processes. This paper presents a calcium phosphate precipitation model and its inclusion in the Activated Sludge Model No 2d (ASM2d). The proposed precipitation model considers that aqueous phase reactions quickly achieve the chemical equilibrium and that aqueous-solid change is kinetically governed. The model was calibrated using data from four experiments in a Sequencing Batch Rea…
Microwave flash-synthesis of iron oxides nanoparticles
1999
Hematite particles have been synthesized by a one step thermohydrolysis of nitrate iron (III) solutions. The microwave system (RAMO system) designed by the authors is able to induce very fast heating rates within an autoclave. These operating conditions induce precipitation reactions in the entire volume of the reactor. These precipitation conditions lead to instantaneous nucleation of monodisperse particles (separation of the nucleation and growth events). These results indicate that it should be possible to produce very well-crystallized hematite particles which can be used as precursors for production of magnetite or maghemite.
Struvite precipitation assessment in anaerobic digestion processes
2008
Struvite precipitation causes important operational problems during the sludge treatment process, especially when EBPR sludge is treated. Predicting struvite formation is critical to be able to design process alternative that best minimises struvite precipitation. With this aim, phosphorus precipitation in an anaerobic digestion pilot plant was studied using experimental data and mass balance analysis. The results obtained showed significant phosphorus precipitation as struvite (58% of the fixed phosphorus) and a low precipitation of calcium phosphates (15%), forming mainly hydroxyapatite (HAP). The rest of the phosphorus fixed in the digester (27%) was attributed to adsorption processes on…
Elucidation of reaction process between solid tricalcium silicate and a lanthanum salt solution in connection with the precipitation pH. Extension to…
1993
Abstract Dissolution of tricalcium silicate is strongly accelerated in a La salt solution and releases the amounts of OH, Ca and silicate ions just required to precipitate all of lanthanum at pH 8. It remained to be proved that (1) La silicate hydrate could form at pH 8, and (2) Ca silicate hydrate could not precipitate simultaneously. The plot of silicate hydrate and hydroxide precipitation pH of La, Ca and other elements (Th, Zr) against the dropped volume of K2SiO3 and KOH solution and some physico-chemical characterization methods bring affirmative answers to these questions and allow the immobilization process of La and other elements in the presence of tricalcium silicate to be better…