Figure 4: Lagergren plots for the adsorption of Ni(II) by Biofilm /GAC at pH=7 ,adsorbent dose 100 mg/L uptake ( e.g. 0.23 mg Ni /gr GAC at pH 6.9 to 0.26 mg Ni / gr GAC at pH 8 ), whereas Ni(II) uptake in acidic condition (pH=5) was the same as natural condition ( pH=7.0).