Inorganic Chemicals Industry >
Study on thermal decomposition kinetics of sodium fluosilicate
Received date: 2024-08-20
Online published: 2024-09-09
In view of the difficulty in dealing with defluorinated acid residue produced by Dicalcium Phosphate production enterprises，the thermal decomposition behavior of sodium fluorosilicate（Na2SiF6） was studied，which was the main form of fluorine.A systematic thermodynamic analysis of the thermal decomposition process of Na2SiF6 was carried out by using HSC Chemistry 6.0 thermodynamic software.The changes of ΔG and ΔH of the decomposition reaction of Na2SiF6 with the temperature and its equilibrium composition changes during the thermal decomposition process were calculated.Based on the thermal decomposition data of Na2SiF6 at different heating rates by thermogravimetric analyzer，the temperature at the fastest reaction rate of its thermal decomposition equilibrium，Tp=579 ℃，was calculated.The kinetics of thermal decomposition of Na2SiF6 was fitted using the NETZSCH Kinetics Neo kinetics software，and the results of three commonly used multiple heating rate methods were compared with the fits of sixteen common mechanism functions.It was determined that the thermal decomposition of Na2SiF6 was a three-dimensional phase-interface reaction，which was consistent with a shrinking globular function，with an activation energy E=231.32 kJ/mol.The product of Na2SiF6 was analyzed by SEM-EDS and XRD，and the thermal decomposition process of Na2SiF6 was revealed.Na2SiF6 could be completely decomposed into NaF and SiF4 after roasting at 650 ℃ for 120 min.This study provided theoretical support for the fluorine recovery process by thermal decomposition of defluorinated acid residue.
SHOU Zhixin , XU Dehua , LIU Yujia , YANG Wengong , WANG Xinlong . Study on thermal decomposition kinetics of sodium fluosilicate[J]. Inorganic Chemicals Industry, 2025 , 57(8) : 28 -34 . DOI: 10.19964/j.issn.1006-4990.2024-0462
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