V. Rudelis “Innovative reprocessing technologies of silica gel with incorporated aluminum and fluorine ions” doctoral dissertation defence

Author, Institution: Valdas Rudelis, Kaunas University of Technology

Science area, field of science: Technological Sciences, Chemical Engineering, T005

Scientific Supervisor:  Prof. Dr. Kęstutis Baltakys (Kaunas University of Technology, Technological Sciences, Chemical Engineering, T005).

Dissertation Defence Board of Chemical Engineering Science Field:
Prof. Dr. Rimvydas Kaminskas (Kaunas University of Technology, Technological Sciences, Chemical Engineering, T005) – chairman;
Doc. Dr. Joana Bendoraitienė (Kaunas University of Technology, Technological Sciences, Chemical Engineering, T005);
Assoc. Prof. Dr. Anatolijus Eisinas (Kaunas University of Technology, Technological Sciences, Chemical Engineering, T005);
Prof. Dr. Habil. Gundars Mezinskis (Riga Technical University, Technological Sciences, Materials Engineering, T008);
Dr. Rimvydas Stonys (Vilnius Gediminas Technical University, Technological Sciences, Materials Engineering, T008).

The doctoral dissertation is available at the library of Kaunas University of Technology (K. Donelaičio g. 20, Kaunas).

Annotation:

The aim of this work is to determine the influence of the peculiarities of AlF₃ production process on the chemical and mineral composition of silica gel waste and its properties. It was determined that it is possible to reduce the concentration of fluorine ions to 1.5% by changing the treatment conditions (leaching under static and dynamic conditions or mechanical activation), and by adding alkaline compounds (NH₄OH, Ca(OH)₂, NaOH, Al₂O₃). For the first time, it was determined that the compounds containing aluminum and fluorine ions, such as aluminum fluoride, calcium fluoride and/or katoite, are crystallized in the liquid medium which was separated from silica gel by using mechanical treatment or by leaching with alkaline solutions. In this work, fluorine ions removal technology was proposed; it not only allowed reducing the concentration of fluoride ions in silica gel to 1.5%, but also increased the yield of aluminum fluoride. Based on the results of the work, additional equipment was installed, and industrial tests were carried out in the AlF3 production line of Lifosa, JSC.