Example 15, Kinetic Biodegradation, Cell Growth

[hagar.haithm@gmail.com]

Hello everyone,

below reaction is in example 15:

HNta2- + 1.62O2 + 1.272H2O + 2.424H+ = 0.576C5H7O2N + 3.12H2CO3 + 0.424NH4+.

"Furthermore, the reactants should be charge balanced (no net charge should enter or leave the solution)"

this statement mentioned in example 15. why only reactants should be charge balanced what about the products?

Thank you for your help

[dlparkhurst]

The statement is meant to refer to both reactants and products. If a charge is defined in the -formula, it is ignored by PHREEQC. So, if you define

-formula Na+ 1

in actuality simply Na, that is, sodium metal, will be added to solution.

Note also, it is the net reaction that is added. If you define

-formula H2O 1 OH- -1 H+ -1

again the charge is ignored, but H2O - OH - H will net to zero net change in concentrations.

Another common mistake is to attempt to force a redox reaction, such as

-formula SO4-2 -1 H2 -4  S-2 1 H2O 4

Again, the net reaction is zero change in element concentrations. The most common way to introduce reduction reactions is to add organic matter, often

-formula CH2O 1

The electron acceptor--O2, NO3-, SO4-2, etc--will be determined by thermodynamics.