Probably, the presence of silica rich minerals (crystalline and as well as amorphous forms) in the host rocks are the sources of dissolved silica in groundwater. The solubility of silica in water may have also control on the concentration of SiO2 in groundwater. What are the solubility limits of different silica rich minerals?
Yes you are correct that (acid) weathering of silica rocks/minerals can produce dissolved silica. There are data on mineral solubility in PHREEQC model databases and you can assess solubility by looking at Si mineral saturation indices from model outputs after entering your water chemistry, here are some of Si minerals in PHREEQC:
SiO2(a)
SiO2 + 2 H2O = H4SiO4
-log_k -2.71
-delta_h 3.340 kcal
Chalcedony
SiO2 + 2 H2O = H4SiO4
-log_k -3.55
-delta_h 4.720 kcal
Quartz
SiO2 + 2 H2O = H4SiO4
-log_k -3.98
-delta_h 5.990 kcal
We have had to deal with high silica in our project exploring water treatment at Ft. Irwin
https://www.researchgate.net/publication/270582101_Development_of_a_Treatment_Process_for_Electrodialysis_Reversal_Concentrate_with_Intermediate_Softening_and_Secondary_Reverse_Osmosis_to_Approach_98-Percent_Water_Recovery
Article Development of a Treatment Process for Electrodialysis Rever...
Thanks to Dr. Luke Mosley for reply.
See from literature it is seen that the solubility limit for SiO2 in water is estimated at approximately 120 mg/L at 25°C. In general,what are the solubility limits of quartz and silica rich amorphous minerals?
Dr. Victor F. Medina,
Sir, Thanks for reply. I will read your paper.
Silica is insoluble in water in normal temperature and pressure condition. There are various varieties of Silica such as quartz, amourphous, However chalcedony ( amarphous ) has little solubility. As to select the parameter responsible for silica solubility, it is require to study chemical kinetic / phase study of silica. Because silica solubility depend upon number of factors which one has to study based on their conditions.
Dr. Virendra Kumar Saxena - Yes Sir, You are right. Chemical kinetic / phase study is very important to understand the same. Thanks for your reply.
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