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I am a student of tropical agriculture. I am taking the class of agronomic chemistry and plant nutrition. I want to make use of silicate source I have at home for e.g. zeolite, wood ashes, diatomaceous earth, silica sand. I have hydroxide of calcium, potassium and sodium. Can I use any of these to make silicate for use on plant nutrition ?

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You can make the silicates by fusing the hydroxides with silica. Potassium silicate fertilizer grade are successfully produced by direct fusion of silica ($\ce{SiO2}$) and potasium compounds($\ce{KOH}$ and $\ce{K2CO3}$) in furnaces at temperatures up to melting point of mixture. The fusion temperature reaches around 1350 °C.

$$\ce{SiO2 + 2 KOH ->[\Delta] K2SiO3 + H2O}$$ $$\ce{SiO2 + K2CO3 ->[\Delta] K2SiO3 + CO2}$$

Calcium silicate is prepared by reacting calcium hydroxide and silica. This paper1 discussed the reaction at 30-85 °C.

References

  1. https://www.matec-conferences.org/articles/matecconf/pdf/2016/21/matecconf_bisstech2016_01021.pdf
  2. REACTION BETWEEN SILICA AND CALCIUM HYDROXIDE SOLUTIONS. I. KINETICS IN THE TEMPERATURE RANGE 30 TO 85°, S. A. Greenberg, The Journal of Physical Chemistry 1961 65 (1), 12-16, DOI: 10.1021/j100819a005
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    $\begingroup$ You should add that the potassium silicate obtained by fusion of $\ce{KOH + SiO2}$ is extremely difficult to dissolve into water. This can only be done with hot water and under pressure. $\endgroup$
    – Maurice
    Apr 17 at 6:58

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