Vojtěch Enev

Facile synthesis and rheological characterization of nanocomposite hyaluronan-organoclay hydrogels

We report a facile methodology for the synthesis of inorganic-organic hydrogels based on integrative assembly of aminopropyl magnesium phyllosilicate (aminoclay) and sodium salt of hyaluronic acid. The viscoelastic materials produced by electrostatic interactions and crosslinking of hyaluronan in the presence of exfoliated synthetic organoclay results in the formation of gel-like behavior retaining a high amount of water. This was confirmed by a rheological study revealing significant dominance of the elastic response over the entire deformation frequency range used. The mechanical strength of the aminoclay-hyaluronan hydrogels was found to be higher than that for related materials based on poly(vinylpyrrolidone)-aminoclay hydrogels.

Possibilities of Using Plasticizers in Alkali-Activated Systems

The study deals with the preparation process and properties of alkali-activated blast furnace slag with different addition of lignosulphonate plasticizer. The goal of this study is to evaluate the suitability of plasticizer and find the convenient dose of this admixture, which improve the workability and mechanical properties of alkali-activated slag. The stability of plasticizing admixture in alkali environment was studied by infrared spectroscopy (FTIR).

Fluorescence Analysis of Cu(II), Pb(II) and Hg(II) Ion Binding to Humic and Fulvic Acids

Abstract. The aim of this work was to study molecular and quantitative aspects of metal ion binding to humic substances (HS). The object of our study was characterization of two standards of humic substances (Elliott Soil standard HA 1S102H and Elliott Soil standard FA 2S102F). All samples of IHSS standards HS were characterized by elemental analysis (EA), ultraviolet-visible spectroscopy (UV/Vis), Fourier transform infrared spectroscopy (FTIR) and steady-state fluorescence spectroscopy. Chemical parameters on the complexation of Cu (II), Pb(II) and Hg(II), including the conditional stability constants and the percentage of fluorophores participating in the complexation, were estimated by the modified Stern–Volmer equation. The stability constants (log Ka) of Me(II)–ESHS complexes range from 3.70 to 5.15 in the order: Hg–ESHA>Cu–ESHA>Pb–ESHA>Cu–ESFA>Pb–ESFA. With respect to the ESHA, ESFA, which showed the smallest contents of O-containing functional groups (e.g. hydroxyl, carbonyl, ester, especially carboxyl groups on the aromatic ring) and the lowest humification degree, the ESFA was characterized by much smaller stability constants. Our findings suggest that soil HS belongs to class of important organic ligands for complexation with heavy metal ions and may significantly affect the chemical forms, mobility, bioavailability and ecotoxicity of heavy metals in the soil environment.