Pool Water Chemistry (Warning: Can Get Technical)

[chem geek]

I didnt think this post deserved its own thread, but it is some useful info regarding ozone and chlorine. waterbear (Evan) and I worked out how ozone could oxidize chlorine since there were some reports of people using ozonators finding greater chlorine usage (loss). The following is apparently what happens:

O3 + H2O + 2e --> O2 + 2OH- ............ Eo = +1.24V
OCl- + 2OH- ... --> ClO2- + H2O + 2e .. Eo = -0.66V
-------------------------------------------------------------
O3 + OCl- ...... --> O2(g) + ClO2- ........ Eo = +0.58V
Ozone + Hypochlorite ion --> Oxygen + Chlorite ion

O3 + H2O + 2e --> O2 + 2OH- ............ Eo = +1.24V
ClO2- + 2OH- .. --> ClO3- + H2O + 2e .. Eo = -0.33V
-------------------------------------------------------------
O3 + ClO2- .... --> O2(g) + ClO3- ......... Eo = +0.91V
Ozone + Chlorite ion --> Oxygen + Chlorate ion

With the net result being the following:

2O3 + OCl- ... --> 2O2(g) + ClO3- ......... Eo = +1.49V
Ozone + Hypochlorite ion --> Oxygen + Chlorate ion

So ozone will oxidize chlorine to form chlorate. This is a very strong (likely) reaction, but the above info does not determine the rate of the reaction.

Richard