The fact that k2 declines with increasing initial concentration, indicates that it is faster
for the biosorption system to reach a specific temporal equilibrium at lower initial
concentration. The most commonly used technique for identifying the mechanism
involved in the sorption process is by fitting the experimental data in an intraparticle
diffusion plot. The plot of qt versus t1/2 represents multi linearity, which characterizes
the two or more steps involved in the sorption process. Plots were not linear over the
whole time range and did not pass through the origin, implying that the biosorption
process proceeds by film diffusion and intraparticle diffusion.