SVIBOR - Project code: 1-07-314

MINISTRY OF SCIENCE AND TECHNOLOGY

Strossmayerov trg 4, HR - 10000 ZAGREB
tel.: +385 1 459 44 44, fax: +385 1 459 44 69
E-mail: ured@znanost.hr

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Project code: 1-07-314


A Study of Solid Metastable Phase Formation in Precipitation Processes from Solution


Main researcher: BREČEVIĆ, LJERKA (5334)


Assistants
Type of research: basic
Duration from: 06/01/92. to 12/31/95.
Papers on project (total): 19
Papers on project quoted in Current Contents: 5
Institution name: Institut "Ruđer Bošković", Zagreb (98)
Department/Institute: Department of Chemistry Division for Technology, Nuclear Energy and Protection Laboratory for Precipitation Processes
Address: Bijenička cesta 54, 10001 Zagreb, p.p. 1016
City: 10000 - Zagreb, Croatia
Communication
Phone: 385 (0)1 4561-004
E-mail: brecevic@olimp.irb.hr
Fax: 385 (0)1 425-497
Summary: In the proposed project the study was directed toward gaining fundamental knowledge about the factors influencing thermodynamically metastable and stable phase formation in precipitation processes. An expertise arising from a physical chemical approach was used with a view to collect data about changes in the solid and liquid phases during these processes. Specific objectives were: (i) to define conditions under which the formation of metastable and stable phases is possible and can be studied; (ii) to investigate kinetics and mechanisms of nucleation, growth, dissolution and phase transformation of these solid phases using different experimental techniques; (iii) to study the interactions between solid phase and solution, the solid phase modifications and foreign ions and/or molecules, as well as the properties of the solid phase(s) formed and the foreign molecules added; (iv) to introduce the liquid membrane technique into the investigation of precipitate properties and the selective separation of sparingly soluble salts of similar properties from a suspension. Initial work was done using calcium carbonate as a model system since it is known that this forms several anhydrous polymorphs and hydrated forms, all of them except calcite being metastable. The study was also extended to some other inorganic (oxalates, silica) and organic (hydrocarbons) model systems. The objective of the study was to develop generic solutions to a wide range of problems that involve precipitation processes, as well as interactions between the solid phase and foreign ions and molecules, such processes being common in many sectors of industry, in biological and medical processes and in natural phenomena.

Keywords: Precipitation, nucleation, crystal growth, dissolution, phase transformation, kinetics, mechanisms, solubility, interphase, liquid membrane, separation, calcium carbonate, alkanes, surface-active agents, surface tension, foam density, foam stability

Research goals: The aim of the proposed study was to investigate metastable and stable solid phase formation and their behaviour in precipitation processes using the expertise arising from a physical chemistry background. Specific objectives were: (i) to determine the equilibria conditions in solid/liquid systems; (ii) to investigate formation, growth, dissolution, and transformation kinetics and mechanisms of different metastable and stable phases using different experimental techniques; (iii) to develop mathematical models of the interactions between these processes; (iv) to define thermodynamic and kinetic parameters of precipitation processes at equilibrium and dynamic conditions; (v) to characterize some metastable forms; (vi) to study the influence of additives and efficiency of their action on the precipitates and processes involved; (vii) to introduce the liquid membrane (LM) technique and apply it in the study of heterogeneous systems. Calcium carbonate was used as a first model system and some other inorganic (oxalates, silica) and organic (alkanes) systems were also investigated. By introducing the LM technique, a selective dissolution and separation of sparingly soluble salts of similar properties were investigated. Results define conditions at which a certain solid phase(s) forms and is stable as well as properties of the solid phase. Kinetics and mechanisms of the examined processes and the interactions between solid phase and additives are also given.

COOPERATION - PROJECTS



COOPERATION - INSTITUTIONS


  1. Name of institution: Tehnološki fakultet Sveučilišta u Splitu
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: 21000 - Split, Croatia

OTHER ACHIEVEMENTS


  1. Name: Nagrada Hrvatskog kemijskog društva za koloidnu i površinsku kemiju u 1994. godini
    Type of achievement: Other
    Authors: Dobitnik dr. Damir Kralj
Other information about the project.
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