The amount of RhB adsorbed by PK-AC

The amount of RhB adsorbed by PK-AC increased along with the increase of contact time. When the contact time exceeded 5 h, the changes of the uptake were very small (Fig. 2), which indicated that the equilibration time was around 5 h. The adsorption capacity of RhB was described by the amount of RhB adsorbed by activated carbon at equilibration time. At the beginning of the adsorption,a large number of active sites (including pore) on the surface of activated carbon were not occupied. Consequently, a rapid adsorp-tion presented at 0–0.5 h. And then, the adsorption slowed down(0.5–6 h) with the decrease of the available adsorption sites, during this process, the RhB molecules had to traverse deeper pores inside the activated carbon and overcome a lager resistance.