P concentrations, and the Langmuir equation is applied to high P concentrations (Zhou et al.
1997).
Linear isotherm: S = KC So
S = the amount ofP sorbed in the solid phase, [tg g-1
K = P-sorption coefficient
C = P concentration in solution after 24-h equilibration [agL-1
So = constant, amount of originally adsorbed P
In addition, the equilibrium phosphorus concentration (EPC), which is defined as the
concentration of P in a solution when neither sorption or desorption is occurring, is equal to
C when S = 0 (Pant et al. 2002). Therefore the EPC was calculated from regression statistics
data as the intercept (point at which a line intersects the y-x-axis) divided by the x-variable.
Freundlich isotherm: S = KCn
Kf= constant
n