Effect of solution pH
The influence of pH on the adsorption characteristics of MB and
EY by PC were studied over a broad range of pH (pH 3–11) using
1 g/L adsorbent dose with dye concentration of 200 mg L1 at
303 K. The solution pH was controlled by addition of 0.1 N HCl and
0.1 N NaOH. The results are presented in Fig. 8.
In case of MB adsorption, the percentage removal was found to
increase up to pH 7 with increasing solution pH and further
increase in pH show a decreasing trend. Lower value of removal
percentage at acidic pH may be either due to a force of repulsion
between MB dye cations and adsorbent surface or due to the
presence of excess H+ ions competing with the charged MB dye
cations for vacant adsorption sites. With increase in pH, the
number of negatively charged sites increases which favor the
adsorption of MB due to electrostatic forces of attraction. Although
the trend for EYadsorption is similar to that for MB,