Processes > Dissolution and precipitation

Comparison of simulation data and laboratory experiments

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Aksenova:
Hello!
I have a task to develop a chemical composition that can dissolve amorphous silica.
I decided to compare the modeling data and the data obtained in the laboratory

I have deposits from a natural object, which consist mostly of amorphous silica.
For the basis of the composition, I decided to take a solution of sodium hydroxide.
Dissolution time is 4 hours, temperature 95C.

For dissolution, I took a 5% mass concentration of sodium hydroxide (10 ml) and 1 g of a sample of mineral (from amorphous silica).
It turned out that from approximately 1 gram of rock, 0.444 grams remained.
It turned out that from about 1 gram of rock, 0.444 grams remained.
Please tell me, is my logic and code correct?
And is it possible to somehow take into account the reaction time?
--- Code: ---SOLUTION 1
   ph 7 charge
    temp      95
    pe        4
    redox     pe
    units     mg/kgs
    density   1
            Na      30302.5
    water    0.010013 # kg
EQUILIBRIUM_PHASES 1
    SiO2(a)   0 0.017
END

--- End code ---

dlparkhurst:
You have calculated the solubility of one silica phase. However, there are a whole range of silica phases ranging in stability from quartz, chalcedony, amorphous silica, to silica gel. Your experimental work may give you a clue as to the stability (log K) that is appropriate for your material.

You can add the time evolution with KINETICS and RATES, but again, you will probably need to use your experimental data to find parameters appropriate for your material. The databases kinec_v3.dat and phreeqc_rates.dat have rate definitions that you can use as templates for your experiments.

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