Physical Chemistry of Colloids, Interfaces and Electrolytes
Main researcher
: KALLAY, NIKOLA (19896) Assistants
HRUST, VESNA (16680)
TOMIĆ, MELANIJA (114901)
PAVKOVIĆ, NEVENKA (35464)
SIMEON, VLADIMIR (43171)
TOMIŠIĆ, VLADISLAV (187592)
ŽALAC, SUZANA (171772)
KOVAČEVIĆ, DAVOR (900566)
Type of research: basic Duration from: 01/01/91. to 12/31/96. Papers on project (total): 65
Papers on project quoted in Current Contents: 30
Institution name: Prirodoslovno-matematički fakultet, Prirodoslovni odjeli, Zagreb (119) Department/Institute: Laboratory of Physical Chemistry Address: Marulićev trg 19/II City: 10000 - Zagreb, Croatia
Communication
Phone: 385 (0)1 446 528
Fax: 385 (0)1 446 528
Phone: 385 (0)1 446 001
Summary: The project deals mainly with the development of
theoretical models, mathematical interpretation and measurement methods.
The comparison of theoretical predictions with experimental results
enables development and testing of theoretical and experimental
approaches. The aims of the project belong to the field of fundamental
physical chemistry, but in some aspects (ecology, technology, corrosion)
the applied aspects are also considered. The results were published, and
the list of publications is enclosed. In addition, several publications
are in press or submitted. The project consists of several topics.
CHEMOMETRICS Two new statistical tests were designed and successfully
applied for the assessment of the effective rank of spectral data
matrices, enabling reliable determination of the number of spectrally
active species. Total least squeres method was applied as a step in target
factor analysis. An original program package for factor analysis of
chemical data was conceptualised and partly developed, including some
original concepts in the data weighting, principal component analysis and
target factor analysis. IONIC EQUILIBRIA By analysing UV/VIS and Raman
spectra of aqueous solutions of several inorganic salts (lithium nitrate,
lithium sulphate, magnesium nitrate, magnesium sulphate, cobalt(II)
nitrate, cobalt(II) sulphate) in a wide concentration range the presence
of associates (ionic pairs and/or complexes) was detected. This was made
possible owing to own chemometric methods (see above). SOLUBILITY It was
established that surfactant solubility is determined by the equilibria
involving micelles characterized cmc dependence on the electrolyte
concentration and ion exchange equilibrium constant. The precipitation in
surfactant mixture may be successfully interpreted on the basis of the
regular solution theory. The dissolution of surfactants is followed by
water cluster (iceberg) formation and consequently by temperature
dependence of enthalpy and entropy, due to significant change of the heat
capacity. Accordingly, the logarithm of the solubility is not a linear
function of the reciprocal thermodynamic temperature. The dissolution of
gel phase is accompanied with the negative heat capacity change which is
explained on the basis of synergistic effect of the chains in the nett
structure of the gel. MICELLES AND MICROEMULSIONS The theoretical
interpretation of the conductivity of micellar systems and microemulsions
were developed and experimentally verified. In the case of micelles, the
"true" cmc, equilibrium constant of counterion association and micellar
size could be obtained. In the case of water-in-oil microemulsions, for
viscous oils the insight into surfactant hydration and the water content
in droplets may be achieved, while for nonviscous oils the interpretation
on the basis of the charge fluctuation theory provides information on the
droplet structure, size and the surfactant shell thickness. ADSORPTION
The application of the surface complexation model to the adsorption
experiment design, yields the ionization state of the adsorbed organic
molecules, binding equilibrium constant and provides the insight in to the
interfacial layer structure. These results are relevant to ecology
(migration of pesticides in soil). ELECTRICAL INETRFACIAL LAYER The
interpretation of the adsorption data in the systems of different
permittivities resulted in the value of the electrokinetic slipping plane
separation. The mass titration method for the point of zero charge
determination was refined so that it can be used for unpurified samples.
The accuracy of the method enabled the determination of the enthalpy of
surface deprotonation and protonation. Previous calorimetric measurements
were not able to distinguish between the contributions of different
reactions taking place at the interface and the electrostatic effects. The
theoretical consideration resulted in a special experimental design
whereby these problems can be solved. The electrostatic effect on the
enthalpy of charging the metal oxide interface was examined. COAGULATION
AND ADHESION The adhesion method for point of zero charge (pzc)
determination of conductive surfaces was developed. This method enabled,
for the first time, the determination of pzc values of numerous metals.
The effect of thin (hydro)oxide layer was established. The method was
successfully applied in corrosion studies. The calorimetry method for
examination of kinetics of dissolution of CaCO3 in EDTA was developed.
Keywords: Surfactants, solubility, calorimetry, electrical interfacial layer, metal oxides, microemulsions, micelles, adsorption, adhesion, isoelectric point, electrokinetics, factor analysis, ionic association, ionic pair, orthogonal regression, principal components analysis, Raman spectroscopy, total least squares
Research goals: CHEMOMETRICS Development of numerical and
statistical methods of data processing and analysis (mainly for
spectrometric data): bi- and trimodal factor analysis (principal
components), statistical weighting, orthogonal multilinear regression
(known also as Total Least Squares, TLS), nonlinear models. IONIC
EQUILIBRIA Detection, identification and characterization of chemical
species (ion pairs and/or complexes) formed in concentrated electrolyte
solutions. STRUCTURE OF ELECTROLYTE SOLUTIONS Inferring the molecular
structure of chemical species present in concentrated aqueous solutions of
electrolytes, as well as supramolecular structures (associates, possibly
quasi-phase). SOLUBILITY To investigate the complex solubility of inorganic
salts and ionic surfactants with respect to the complex nature of the
solution i.e. the existence of the soluble species such as ion pairs,
complexes, micelles and mixed micelles. To find the relationships which
describe the equilibria and kinetics in such systems. To determine the
temperature dependence of these equilibria and to compare the results
(enthalpy, entropy, heat capacity change) to the calorimetric data.
MICELLES AND MICROEMULSIONS To investigate micelles and microemulsion
formation equilibria, by taking into account association of chains and
counterions, and to develop the experimental methods for characterization
of such systems (conductometry, potentiometry, light scattering).
ADSORPTION Development of the adequate model of interpretation of
adsorption equilibria in the systems with metal oxides dispersed in the
solutions of organic substances and surfactants. The examination of the
electrostatic effects by considering the data at isoelectric point.
ELECTRICAL INTERFACIAL LAYER To develop an adeqate model for describing the
equilibria in the interfacial layer and to distinguish between the
different contributions to the enthalpy of the surfaces processes. To
compare potentiometry and calorimetric data. COAGULATION AND ADHESION To
relate the kinetics of these processes to the equilibrium state of the
solid/liquid interface. To develop the adhesion method for isoelectric
point determination of conductive surfaces and to apply this method for
studying the corrosion processes.
COOPERATION - PROJECTS
Name of project
: Interaction of Pesticides and other Organic
Substances with Soil Colloids Name of institution: Institut fuer Angewandte Physikalische Chemie,
Forschungszentrum Juelich City: Juelich, Njemačka
Name of project
: Electrokinetic Phenomena in Ceramic Materials Name of institution: US National Bureau of Standards City: Washington DC, USA
COOPERATION - INSTITUTIONS
Name of institution
: Institut fuer Angewandte Physikalische
Chemie, Forschungszentrum Juelich Type of institution: State institute Type of cooperation: Joint project City: Juelich, Njemačka
Name of institution
: US National Bureau of Standards Type of institution: State institute Type of cooperation: Joint project City: Washington DC, USA
Name of institution
: Universitat Maria Curie Sklodowska Type of institution: University/Faculty Type of cooperation: Systematic exchange of information City: Lublin, Poljska
Name of institution
: Institut Jožef Štefan Type of institution: State institute Type of cooperation: Systematic exchange of information City: Ljubljana, Slovenija Other information about the project.