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358 Industrial Wastewater Treatment, Recycling, and Reuse

presence of 4-NP produces greater hindrance for the adsorption of 4-CP. The
overall net effect is the presence of competition, which lowers the adsorption
capacity of both the individual components in the binary mixture. The repul-
sion between the individual binary components resulted in specific heteroge-
neous sites being less available for adsorption.
Figure 8.17 shows the adsorption of 4-CP under varying concentrations
1
of 4-NP (100–1000 mg L ). The inverse of that was investigated to deter-
mine the optimum mixture concentration under which ANL could effec-
tively remove the mixture. The adsorption of 4-CP was found to be higher
at low initial 4-NP concentrations. 4-CP showed a binary adsorption yield
1
of 98.76% at 100 mg L of 4-NP. Hence, a binary solution consisting of
4-NP:4-CP in 1:10 ratio was found to be the critical combination for max-
imum adsorption of the less favorable adsorbate, 4-CP. Similarly, in the case
of 4-NP in the binary mixture consisting of various ratios, the uptake of the
more favorable adsorbate was higher at a lower 4-CP initial concentration,
and a maximum q e of 99.69 mg g 1 was achieved at a 1:10 mixing ratio. This
is because of less competition for adsorption sites at lower initial concentra-
tion of the less favorable adsorbate and a higher concentration gradient of
4-NP, which becomes freely available to the active sites of ANL.
The binary adsorption of 4-NP and phenol over ANL was similarly
investigated to observe the changes in the adsorption behavior when phenol

Figure 8.17 Effect of varying mixing ratios in binary adsorption using ANL.