Neutralization of AlF3 production waste and its application for the hydrothermal synthesis of C-S-H

Friday, June 2, 2017 - 14:00
Dissertation Defence Hall (K. Donelaičio St. 73- 403 room)

Author, Institution: Aliona Iljina, Kaunas University of Technology

Science Area, Field of Science: Technological Sciences, Chemical Engineering – 05T

Summary of the Doctoral Thesis: Summary

Scientific Supervisor:  prof. dr. Kestutis Baltakys (Kaunas University of Technology, Technological Sciences, Chemical Engineering - 05T).

Dissertation Defence Board of Chemical Engineering Science Field:

Prof. Dr. Rimvydas Kaminskas (Kaunas University of Technology, Technological Sciences, Chemical Engineering - 05T) – chairman,
Prof. Dr. Jonas Baltrušaitis (Lehigh University, USA, Technological Sciences, Chemical Engineering – 05T),  
Prof. Dr. Jadvyga Regina Kerienė (Vilnius Gediminas Technical University, Technological Sciences, Materials Engineering – 08T),
Assoc. Prof. Dr. Rima Klimavičiūtė (Kaunas University of Technology, Technological Sciences, Chemical Engineering - 05T), 
Dr. Rimvydas Stonys (Vilnius Gediminas Technical University, Technological Sciences, Materials Engineering – 08T).

The Doctoral Dissertation is available on the internet and at the library of Kaunas University of Technology (K. Donelaičio St. 20, Kaunas)

Annotation:

In PhD thesis the influence of AlF3 production waste on the crystallization of low base calcium silicate hydrates and their adsorption capacity for heavy metal ions as well were examined and the expedient areas for the application of the above mentioned waste were proposed. It was determined that dry waste from AlF3 production consists of 77.67% silicon dioxide, 8.82% F, and 4.08% Al2O3. It was found that in the mixtures with AlF3 production waste, the compound formation mechanism during low base C-S-H hydrothermal treatment occurs differently than in pure mixtures: when the molar ratio of C/S is equal to 0.55 and 0.66, the main synthesis compound – gyrolite – formed faster than in pure mixtures. Besides the main compound in the AlF3 production waste containing F ions, AlF3·3H2O, decomposes, and new compounds are formed: CaF2 and hydrogarnet. It was found that in higher basicity mixtures (C/S = 0.83 and 1.0) C-S-H compounds with a smaller C/S ratio were formed. Moreover, CaF2 and hydrogarnet formed together with synthesis products. It was determined that the thermal stability of synthetic calcium silicate hydrates and the formed CaF2 depends on the mineralogical composition of the synthesized compounds. It was found that the adsorption reactions of gyrolite in the alkaline solution were specific to the chemisorption process, which was confirmed by the pseudo second-order model.