Ionela Carazeanu

Spectrometric studies about some dyes — anionic surfactant interactions in aqueous solutions

This work presents some alternative analytical methods for anionic surfactant quantitative determination in aqueous solutions. Interactions of aqueous solutions of three dyes (Rhodamin B, Methyl violet and Fuchsin basic), concentrations 0.3x10(-6) M, with two anionic surfactants in the concentration range of 10(-5) M (sodium salt of naphthalene sulphonate formaldehyde condensates and melamine sulphonate formaldehyde condensates) have been investigated. Spectrometric measurements were performed on an UV-Vis spectrometer Hewlett Packard 8452A with diode array detection. From the UV-Vis spectra of individual and mixed dye-anionic surfactant aqueous solutions in various concentration ranges, specific changes in the chromophore microenvironment and in the intensity of absorbance is observed. These changes can be attributed to the chemical and structural characteristics of dyes and anionic surfactants, and could be exploited for analytical purposes.

Investigation of the hydration process in 3CaO·Al2O3–CaSO4 · 2H2O–plasticizer–H2O systems by X-ray diffraction

The development of the hydration process in 3CaO.Al(2)O(3)-CaSO(4) . 2H(2)O-H(2)O system is studied by X-ray diffraction in the presence of varying contents of new plasticizer admixtures belonging to the lignosulphonates class (calcium lignosuphonate-LSC) and condensates melamine formaldehyde sulfonated class-MSF (VIMC-11). The plasticizer admixtures were added in proportion of 0.1-1% solid substance. The influence of the plasticizer admixtures on the hydration process with increasing time is observed and it is shown to depend on the nature and content of the admixtures and the reaction time. The strong adsorption of admixtures on the surfaces on the anhydrous or partially hydrated particles of the system can explain the influence of the admixtures upon the kinetics of the hydration process retardation or acceleration. These plasticizer admixtures influence also the evolution of the hydrated compounds and forming of the hardening structure in the 3CaO.Al(2)O(3)-CaSO(4) . 2H(2)O-H(2)O system; their proportion in the system and the considered length of hardening are correlated. In the 3CaO.Al(2)O(3)-CaSO(4) . 2H(2)O-H(2)O system there are two different influences of the plasticizer admixtures upon the hydration process. One is a delaying action, as a result of plasticizer adsorption on the surface of the anhydrous and hydrated compound particles and another one is the intensifying action due to the stronger dispersion of the particles in aqueous medium.

TEM study of CaTiO3 synthesized by sol-gel method

Nanometer-sized calcium titanate (CaTiO3) particles were synthesized by the modified sol-gel method, from Ca(CH3COO)2 and Ti(C4H90) an ideal cation stoichiometry for CaTiO4 perovskite. EDTA was used like chelating agent. XRD analysis for their crystal structure and TEM for their texture characterized the materials obtained after heating in the range 600 - 10000C. The TEM photographs reveal nanoparticles in the size range 50 - 45 nm with a mean diameter found at 120 nm.