occurring on porous adsorbent [40,41]:
qt = kit1/2 + xi
where qt is the adsorption amount at time t (mg g−1 ), ki is rate con- stant for the intraparticle diffusion (mgg−1 min−1/2) and xi is the intercept of the line (mg g−1 ) which is proportional to the boundary layer thickness.
Fig. 7 presents the plots of qt versus t1/2 for adsorption of MTBE onto the postcrosslinked polymer at different initial concentrations and the parameters are listed in Table 6. The results showed that the intraparticle diffusion model well described MTBE adsorption processes, and the values of ki increased with increasing initial concentrations of MTBE. In addition, three consecutive steps were observed on each plot, with the first steep linear step corresponding