The uptake of MB onto RPR and APR as a function
of dye concentration is shown in Figs. 2a and 2b.
It can be seen that the amount of MB adsorbed per unit
mass of adsorbent increased with increasing dye concentration
(25-200 ppm), although percentage removal
decreased with increase in initial dye concentration.
This may be attributed to an increase in the driving
force of the concentration gradient with the increase in
the initial dye concentration