IS SOLUBILITY THE ONLY CONTROL ON SOLUTE CONCENTRATIONS?. The answer is NO! Solubility often controls the concentrations of major solutes such as Si, Ca, and Mg, and some minor or trace solutes such as Al and Fe.
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+ 2 H+
≡S-OSorption to ≡S-OH sites
Where Dz is the stoichiometric net change in surface charge due to the sorption reaction (+1 here), F is Faraday’s constant (96485 Coulombs per mole), is the electrical potential at the surface, R is the gas constant, and T is temperature in Kelvins, the whole right term is called the coulombic term
Cs+ > Rb+ > K+ > Na+ > Li+
Ba2+ > Sr2+ > Ca2+ > Mg2+
Hg2+ > Cd2+ > Zn2+
Cu2+ > Ni2+ > Co2+ > Fe2+ > Mn2+
where S m is the mass of the solid.
The Freundlich isotherm is described by
where K is the partition coefficient and n 1.
When n < 1, the plot is concave with respect to the C axis. When n = 1, the plot is linear. In this case, K is called the distribution coefficient (Kd ).
The Langmuir isotherm describes the situation where the number of sorption sites is limited, so a maximum sorptive capacity (S max) is reached.
The governing equation for Langmuir isotherms is:
nAm+ + mBX mBn+ + nAX
log Koc = 1.377 + 0.544 log Kow