Langmuir Model

Freundlich  Model

PH

   GAC   Biofilm GAC/Biofilm   GAC      Biofilm    GAC/Biofilm

5.5
7.0
8.0

0.92 
0.89
0.91

0.86
0.85
0.88

0.66   
0.68   
0.65

0.85
0.87 
0.84

0.83 
0.82  
0.81  

0.83
0.81
0.85
Table 1: Freundlich and Langmuir isotherm correlation coefficients (R2) for adsorption of Ni (II) on GAC, Biofilm and GAC/Biofilm at different pH.