Search results for "Aqueous solution"
showing 10 items of 1610 documents
A new biodegradable and biocompatible hydrogel with polyaminoacid structure
2007
The preparation and physicochemical and biological characterization of a novel polyaminoacid hydrogel have been reported. The ,-poly(N-2- hydroxyethyl)-dl-aspartamide (PHEA) has been used as a starting polymer for a derivatization reaction with methacrylic anhydride (MA) to give rise to the methacrylate derivative named PHM. Photocrosslinking of PHM has been performed in aqueous solution at 313 nm and in the absence of toxic initiators. PHM-based hydrogel has been characterized by scanning electron microscopy, X-ray diffractometry, swelling measurements in aqueous media; the degradation of PHM-based hydrogel has been evaluated as a function of time in the absence or in the presence of ester…
Photo-Cross-Linked Hydrogels with Polysaccharide−Poly(amino acid) Structure: New Biomaterials for Pharmaceutical Applications
2006
The aim of this work has been the preparation and characterization of novel hydrogels with polysaccharide-poly(amino acid) structure having suitable physicochemical properties for pharmaceutical applications. In the first step, hyaluronic acid (HA) and alpha,beta-poly(N-2-hydroxyethyl)-DL-aspartamide (PHEA) have been derivatized with methacrylic anhydride (AMA), thus obtaining HA-AMA and PHM derivatives, respectively. In the second step, aqueous solutions of both these derivatives have been irradiated at 313 nm to obtain chemical hydrogels. The hydrogel obtained by irradiating for 15 min an aqueous solution containing 4% w/v of HA-AMA and 4% w/v of PHM resulted in the highest yield. Its swe…
Synthesis and characterization of modified sulfonated chitosan for beryllium recovery
2019
Abstract A new adsorbent, sulfated crosslinked chitosan (SGCH), has been synthesized for the effective extraction of beryllium ions from their aqueous solutions. In recent times, beryllium extraction has been of great importance because beryllium can be used in many applications such as in nuclear reactor, heat shields, high-technology ceramics, alloys and electronic heat sinks. SGCH has been synthesized by two successive phases. The first is the conversion of chitosan (CH) into non-soluble cross-linked chitosan (GCH) through the interaction between chitosan and glutaraldehyde. The second step is the formation of functional sulfonate groups onto the adsorbent material through the interactio…
Complexes of organometallic compounds
1966
Abstract The compounds (C2H5)2PbCl2, (C2H5)3PbCl and PbCl2 were studied by paper electrophoresis in aqueous LiCl solutions of various molarities. Determination was made of the formation of chloride complexes in which the electric charge was a function of ligand concentration in the solution. From the results of these experiments, and from a comparative examination of anion exchange data obtained in previous researches, useful information is obtained for determining the ligand concentrations relative to the preponderance of cationic, neutral and anionic complexes in the aqueous solutions. From this information it is possible to assume (C2H5)2PbCl42− and (C2H5)3PbCl32− as the fully coordinate…
Efficient H2 production by photocatalytic water splitting under UV or solar light over variously modified TiO2-based catalysts
2019
Abstract This paper focused for the first time on the comparison between three different approach to modify the chemico-physical properties of TiO2-based photocatalysts and their effect in the H2 production by photocatalytic water splitting both under UV and solar light irradiation, under the same experimental conditions. The application of pulsed laser irradiation to aqueous TiO2 suspensions (first approach) induced structural transformations both on the bulk and on the surface of TiO2, boosting the H2 production, under UV light irradiation, of almost three times (20.9 mmol/gcat·h) compared to bare TiO2 (7.7 mmol/gcat·h). The second strategy was based on a templating method to obtain TiO2 …
Preparation and characterization of sodium iron titanate ion exchanger and its application in heavy metal removal from waste waters.
2006
Abstract The ion exchange properties of sodium iron titanates, namely, NaFeTiO4, Na2Fe2Ti6O16 and iron-doped sodium nonatitanate were investigated. Conventional solid state and sol–gel methods were used in the synthesis of the sodium iron titanates. Structural characterization of the materials was performed with powder X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS) and with inductively coupled plasma optical emission spectrometry (ICP-OES). Based on TG analyses, the novel iron-doped sodium nonatitanate was proven to be a member of the layered titanate family. The different sodium iron titanates were compa…
Photocatalytic degradation of acid blue 80 in aqueous solutions containing TiO2 suspensions.
2001
The photocatalytic degradation of the anthraquinonic dye Acid Blue 80 in aqueous solutions containing TiO2 dispersions has been investigated. The process has been monitored by following either the disappearance of the dye (via HPLC) and the formation of its end-products (via IC, GC, and TOC analysis). Although a relatively fast decolorization of the solutions has been observed, the mineralization is slower, and the presence of residual organic compounds was evidenced even after long term irradiation, confirming the relevant stability of anthraquinone derivatives. The identification of various unstable intermedi ates formed after low irradiation times was performed by HPLC-MS, allowing us to…
New coordination polymers based on a novel polynitrile ligand: Synthesis, structure and magnetic properties of the series [M(tcnoetOH)2(4,4′-bpy)(H2O…
2008
International audience; A novel polynitrile anionic ligand, tcnoetOH−(=[(NC)2CC(OCH2CH2OH)C(CN)2]−), has been synthesized by a one-pot reaction from a cyclic acetal and malononitrile. This ligand has been successfully used to prepare, with 4,4′-bpy as co-ligand, a novel series of coordination polymers formulated as [M(tcnoetOH)2(4,4′-bpy)(H2O)2] with M(II) = Fe (1), Co (2) and Ni (3). These isostructural compounds present a linear chain structure consisting of octahedrally coordinated metal ions bridged by trans 4,4′-bpy ligands. The coordination sphere of the metal ions is completed with two terminal tcnoetOH− ligand and two water molecules. The magnetic properties indicate that the three …
Translational diffusion coefficients of volatile compounds in various aqueous solutions at low and subzero temperatures.
2005
International audience; Translational diffusion coefficients (D(12)) of volatile compounds were measured in model media with the profile concentration method. The influence of sample temperature (from 25 to -10 degrees C) was studied on translational diffusion in sucrose or maltodextrin solutions at various concentrations. Results show that diffusivity of volatile compounds in sucrose solutions is controlled by temperature, molecule size, and the viscosity of the liquid phase as expected with the Stokes-Einstein equation; moreover, physicochemical interactions between volatile compounds and the medium are determinant for diffusion estimation. At negative temperature, the winding path induce…
Interaction of the Alternating Double Stranded Copolymer poly(dA-dT)·poly(dA-dT) with NiCl2and CdCl22: Solution Behavior
2007
The thermal denaturation of the synthetic high molecular weight double stranded polynucleotide poly(dA-dT) x poly(dA-dT) has been studied in aqueous buffered solution (Tris 1.0 mM; pH 7.8+/-0.2) in the presence of increasing concentrations of either Ni(2+) (borderline cation) or Cd(2+) (soft cation) at four different constant ionic strength values (NaCl), making use of UV and circular dichroism (CD) spectroscopies. The experimental results show that the B-type double helix of the polymer is stabilized against thermal denaturation in the presence of both cations at low concentrations, relative to the systems where only NaCl is present, in the same conditions of ionic strength and pH. The eff…