System and method to measure cation exchange capacity
A system for determining cation exchange capacity includes: a container containing a solution having a solute and a solvent; a sample; a pressure sensor configured to measure an osmotic pressure of the sample generated by a flow of the solution through the sample; and a control unit configured to determine the cation exchange capacity of the sample based on the osmotic pressure measured by the pressure sensor.
1 . A system for determining cation exchange capacity, comprising:
a container containing a solution, the solution includes a solute and a solvent;
a sample;
a pressure sensor configured to measure an osmotic pressure of the sample generated by a flow of the solution through the sample; and
a control unit configured to determine the cation exchange capacity of the sample based on the osmotic pressure measured by the pressure sensor,
wherein the control unit is configured to determine the cation exchange capacity of the sample based on equation:
CEC
=
ϕ
10
(
1
-
ϕ
)
ρ
s
V
0
f
(
V
0
f
RT
p
osmotic
+
2
m
sol
s
)
2
-
4
(
m
sol
s
)
2
where
m
sol
s
is a concentration of the solute in the solution, ρ s is a grain density of the sample, φ is a porosity of the sample,
V
0
f
is a partial molar volume of the solvent, R is universal gas constant which equals 8.314 J/K/mol, T is a temperature of the solution in Kelvin.
2 . The system of claim 1 , wherein the sample comprises at least one of soil and rock, and at least one of clay and an organic matter.
3 . The system of claim 1 , wherein the solute comprises one or more of NaCl, MgCl 2 , and CaCl 2 ).
4 . The system of claim 1 , further comprises a support fixed to the container and configured to hold the sample.
5 . The system of claim 1 , further comprises a tubing having two ends that connects the sample and the pressure sensor, wherein a first end of the tubing is arranged inside a cavity of the sample and a second end of the tubing is connected to the pressure sensor.
6 . The system of claim 1 , wherein the container has an inlet configured to introduce the solution to the container and an outlet configured to guide the solution out of the container.
7 . The system of claim 6 , wherein the outlet is exposed to an atmosphere.
8 . The system of claim 6 , wherein a flow rate at the inlet and a flow rate at the outlet range from 10 −4 m 3 /s to 10 −3 m 3 /s.
9 . The system of claim 6 , wherein a pressure change caused by the flow of the solution around the sample is negligible compared to atmosphere pressure.
10 . A method for determining cation exchange capacity, comprising:
disposing a sample in a container;
immersing the sample in a solution that includes a solute and a solvent;
flowing the solution through the sample;
measuring, using a pressure sensor, an osmotic pressure in the sample; and
determining the cation exchange capacity of the sample based on the osmotic pressure measured by the pressure sensor,
wherein the determining the cation exchange capacity of the sample is based on equation:
CEC
=
ϕ
10
(
1
-
ϕ
)
ρ
s
V
0
f
(
V
0
f
RT
p
osmotic
+
2
m
sol
s
)
2
-
4
(
m
sol
s
)
2
where
m
sol
s
is a concentration of the solute in the solution, ρ s is a grain density of the sample, φ is a porosity of the sample,
V
0
f
is a partial molar volume of the solvent, R is universal gas constant which equals 8.314 J/K/mol, T is a temperature of the solution in Kelvin.
11 . The method of claim 10 , wherein the sample comprises at least one of soil and rock, and at least one of clay and an organic matter.
12 . The method of claim 10 , wherein the solute comprises one or more of NaCl, MgCl 2 , and CaCl 2 ).
13 . The method of claim 10 , further comprises connecting the sample and the pressure sensor by a tubing having two ends, wherein a first end of the tubing is arranged inside a cavity of the sample.
14 . The method of claim 10 , further comprising introducing the solution to the container through an inlet of the container and guiding the solution out of the container through an outlet of the container.
15 . The method of claim 14 , wherein the outlet is exposed to an atmosphere.
16 . The method of claim 14 , further comprising controlling a flow rate at the inlet and a flow rate at the outlet, such that a pressure change caused by the flowing of the solution around the sample is negligible compared to atmosphere pressure.