Table: Molar Henry's Law Constants for Aqueous Solutions at 25oC
Gas
He
O2
N2
H2
CO2
NH3
http://dwb.unl.edu/Teacher/NSF/C09/C09Links/www.chem.ualberta.ca/courses/plambeck/p101/p01182.htm
Here we can see that nitrogen is the most soluble gas
Take 1 L of water and pressurize it to 2 atmospheres in equilibrium with atmospheric gases. Determine the concentration of each of the gases
Enter the data from the table into MathCAD equations.
Molecular weights of relevant gases
Dry air contains roughly (by volume) 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide,
http://en.wikipedia.org/wiki/Earth%27s_atmosphere
The are the fractional compositions of the atmopheric gases
These three gases account of 99.1% of the atmosphere
We will reduce the pressure to 1 atmosphere and allow a gas bubble to form. We conserve mass and determine the resulting concentrations and volumes.
The sum of the partial pressures must add to 1 atmosphere.
Henry's law must be obeyed for each gas.
Mass must be conserved for each gas.
Let volume of water be 1 L (to make it easier to think about what is happening)
number of moles of dissolved gas per volume of water
volume of dissolved gas per volume of water
Now we calculate the mole fractions in the bubble that forms.
The problem is we don't know the total moles of gas. I will use an iterative solution to get the total moles of gas.
guess at the total moles of gas
Pi.g is the mole fraction of gas i
The total number of moles of gas i is the sum of the dissolved gas and the gas in the bubble
The gas composition of the bubble can now be calculated
The bubbles are enriched in oxygen.
Check to make sure that the mole fractions of gas in the bubble add up to 1.
Calculate the bubble volume per volume of water
Calulate moles of each gas that went to the bubble
Now calculate how much of each species remains in solution
Although significant concentration of oxygen remains in solution and although this concentration is higher than the equilibrium concentration, we don't have to worry about anymore of the oxygen coming out of solution because this solution is in equilibrium with the bubbles that it can form.
This means 18 mL/L per atm of excess pressure
How much clay could be made buoyant?
Set the density of the bubble plus the clay to equal the density of water
BubbleVolume is volume of air per volume of water
The target bubble volume has to be very tiny to not lift any flocs. Thus the goal has to be to reduce the dissolved gas concentration under conditions of lower hydrostatic pressure than are present in the sed tank at the top of the lamella. This means that we want the top of the sand in the gas bubble stripper to be closer to the water surface than the top of the lamella in the sed tank.
It is possible that surface tension will help us here. Maybe there is a minimum excess pressure required to get a bubble to start forming and thus that could make it possible to have non zero potential bubble volumes without actually creating any bubbles.