Freundlich Non-Linear Sorption

Freundlich Non-Linear Sorption is represented by the relationship:

S = K_f c^E

where,

	S = mass of solute sorbed per unit mass of soil,

	Kf = empirically determined parameter,

	E = empirically determined exponent.

The parameters K_f and E are best determined by performing batch tests on samples. When non-linear sorption is used, the program splits the deposit into sublayers and uses an iterative technique to determine an equivalent linear distribution coefficient (K) value of each layer. Since this is an emprical equation, particular care is required ensuring correct usage, especially when E is not unity. Large errors can results from the use of mixed units or errors in converting form one set of units to another.

This is done by:

(a) calculating the concentration at the top and bottom of each sublayer based on an estimated linear K value for each sublayer.

(b) determining a new secant K for each sublayer.

K = K_f c’^E-1

where,

c’ = the average of the previous estimates of the concentration at the top and bottom of the sublayer.

(c) repeating steps (a) and (b) using the new estimate of K for each sublayer until the process converges.

The number of sublayers should be experimented with to ensure that the results obtained are sufficiently accurate.