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Synthesis of Tobermorite by Dynamical Decomposing Potassium Feldspar: An Experimental Study

Author: QiuMeiZuo
Tutor: MaHongWen
School: Chinese Geology University (Beijing)
Course: Materials Science
Keywords: potassium feldspar tobermorite hydrothermal synthesis potassium carbonate
CLC: TB321
Type: Master's thesis
Year: 2005
Downloads: 216
Quote: 2
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Abstract


The K2O content of the potassium feldspar in linxian, shanxi province is as high as 16.21%. We can get refined potassium feldspar powder which was crashed to -200 mesh . The potassium feldspar is hydrothermally decomposed at low temperature and low pressure with CaO as additive, and then to synthesize tobermorite, meanwhile a dilute KOH liquor is produced, which would be concentrated and carbonized to prepare highly pure potassium carbonate. The experiments demonstrate that the optimal technical parameters are: temperature is 200～250 ℃; n（Ca）/n（Al+Si） mol ratio is 0.8～1.0; reaction time is 5～8 hours; liquid/solid weight ratios is 20～25; and the rate of the stirring is 400 r/min, the dissociation proportion of the potassium feldspar can be up to 98%. The reactive products are globle –like reunites which are formed by intercrossing of the tobermorite, and the frame-structure of the globle –like reunites shows high compressive strength, intensity, and heat insulation performance. In the thesis, I also explored how the K+、Al3+ and Fe3+ affect the crystallization of tobermorite. The experiments indicate that the K+、Al3+ can enter the crystal lattice of tobermorite, and make it stable, so it’s hard for tobermorite to convert to xonotlite. The Fe3+ wouldn’t affect the crystallization of the tobermorite but tend to increase the density of the products . During the hydrothermal reaction of potassium feldspar and calcium oxide, firstly, the calcium oxide is to hydrate and the calcium hydroxide is ionized to Ca2+ and OH-, then the structure of the potassium feldspar is destroyed , with the K+ entering the solution , while Ca2+、Al3+、Si4+ integrate to be hydrogarnet . The potassium feldspar continue to be decomposed, then the C-S-H（II） and C-S-H（I） comes into being and then changes to needle-like tobermorite with increasing temperature, which form the “chestnut shell”globe by stirring. LCA technique was used to evaluate the influence of the procedure developed in this research to the environment in the process of the decomposition of the potassium feldspar and the preparation of the tobermorite. This technique, which used the aluminosilicate sol after distilled potassium from the potassium feldspar to prepared tobermorite, is 100% in availability of the insoluble potassium resource, and has no waste water, exhaust gas and solid residue. The energy cost of the technique is low. Therefore this technique accords kindly with the requestment of the environment protection and cleaning processing.

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