Ion Balance in Wastewater
Ion Balance in Wastewater
(OP)
Hi
I have been struggling to balance ions in a solution with multiple cations and anions and a pH of 2. I have heard that at low pH values that this is expected, i.e. that the ion balance will not necessarily work at very low pH. Is there anyone with water chemistry experience that could confirm this?
I have been struggling to balance ions in a solution with multiple cations and anions and a pH of 2. I have heard that at low pH values that this is expected, i.e. that the ion balance will not necessarily work at very low pH. Is there anyone with water chemistry experience that could confirm this?





RE: Ion Balance in Wastewater
For instance, suppose a solution of BaCl2 0.1 M (0.208 mg/l), having received few drops of aq HCl to result in pH=2.1, that is (H+)=10^-2.1=0.007943 grion/l. Since (H+)*(OH-)=10^-14 (25 oC), (OH-)=10^-11.9=1.259*10^-12 grion/lt. Above balance is expressed as 2*(Ba++)+(H+)=(Cl-)+(OH-), that is 2*0.1+0.007943 = (Cl-)+1.259*10^-12. So (Cl-)=0.207943 grion/l, of which 0.20 grion/l from solved baCl2 and rest 0.007943 from aq HCl.
It is noted that (Ba++)*(OH)^2=0.1*(1.259*10^-12)^2=1.6*10^-25, much less than Ba(OH)2 solubility product = 5*10^-3 (~25oC). In similar calculations check for cation precipitation had better be made, especially when pH increases (gets more alkaline). Preliminary indications at <http://www.chem.sc.edu/analytical/chem111/backup_0...; and <http://bilbo.chm.uri.edu/CHM112/tables/KspTable.ht...;.
RE: Ion Balance in Wastewater
"http://www.chem.sc.edu/analytical/chem111/backup_0..."
"http://bilbo.chm.uri.edu/CHM112/tables/KspTable.ht..."
Hopefully they will work now, it seems better to include then in quotation marks than in < >
RE: Ion Balance in Wastewater
PS. I was unable to access either of the links you posted.
RE: Ion Balance in Wastewater
The ion balance is used to check analytical results. The ion balance should be very close to equal but may have slight discrepancies due to errors in analytical testing.
Total anions must be in balance with total cations. Therefore the sum of the concentrations of anions should equal the total concentration of cations and the ratio of total anions to total cations should be 1.
When you have carefully converted all the elements of your water analysis in meq/L units, the sum of anions should be the same as the sum of cations. The only exceptions to that rule are:
•A small difference due to imprecision in the analytical procedures is acceptable as long as the difference between total cations and total anions is less than 3 %.
•At high pH (> 8.2), e.g. in the presence of ammonia or after lime decarbonation, there will be hydroxide or carbonate ions. Hydroxide ions are usually not reported separately. Carbonate ions are not always reported. In such a case, you would have more cations than anions.
•At low pH (say < 6.8), the water may contain either free mineral acidity (very rare for natural water) or free carbon dioxide, both producing H ions wich are usually not reported separately.
http://dardel.info/IX/water_analysis.html
RE: Ion Balance in Wastewater
I can access links in post no 3. They mentioned solubility rules and solubility products, not of primary importance to the subject.
RE: Ion Balance in Wastewater
RE: Ion Balance in Wastewater
http://www.ecs.umass.edu/cee/reckhow/courses/572/5...
http://www.google.com/url?sa=t&rct=j&q=sta...
Why is this important?
RE: Ion Balance in Wastewater
Thanks anyway. I appreciate your effort.
RE: Ion Balance in Wastewater
We have always used the ion balance as a rough check on the quality of the water analysis. And if a parameter in the water analysis was missing, the value was determined by the subtracting the known values from the total.
In certain wastewaters, you may have parameters such as dissolved metals that may be present. Ferric chloride for example.
If your solution consists basically of acid, HCl for example, the cations would consist of H.
RE: Ion Balance in Wastewater
RE: Ion Balance in Wastewater