Calculate CO2 consumption to neutralize water pH

[londonfog2012]

Hi,

I need help on how to calculate the CO2 consumption to be able to neutralize the pH of water to 7 from its current pH of 11.2.

The CO2 is to be bubbled into a 2m pipe with 1-in. diameter, the water is pumped into the pipe at a rate of 3gpm.

The aim is to have the water be in a neutral pH by the time it leaves the 2m pipe.

There is a 55lb compressed tank that will supply the CO2 to the pipe, how long till I need to change tank?

Thanks

 

[bimr]

You need a little more carbon dioxide than that necessary to convert the carbonate alkalinity to bicarbonate alkalinity.

CO2(aq) + CO3 + H2O ↔ 2HCO3

To calculate the amount of carbon dioxide, you need a water analysis showing the amount of alkalinity that is present.

http://www.phadjustment.com/pH.html

http://www.phadjustment.com/TArticles/Carbon_Dioxide.html

The residence time that you have allowed is probably not adequate. First, you have to dissolve the carbon dioxide into solution. If not, it will be wasted into the atmosphere.

 

[moltenmetal]

If you have no idea what is in that water to give it a pH of 11.2, you have no idea how much acid of any kind it will take to bring it back to 7.

A titration will tell you. A water chemistry analysis will allow someone to estimate it for you, but a titration is cheaper and more accurate.

 

[shahyar]

If your temperature is around 25degC, use deffeyes diagrams to find how much co2 you need for neutralization. To be able to do that, you need to know the alkalinity of your water. If the temperature is very different than 25degC, you need to do calculation. you find these diagram with some example by googling.
Hope this help