Once the pre-set contact time (3 h) reached, the
samples were withdrawn and centrifuged at 4000 rpm for 5 min
and the supernatant solutions were analyzed for the residual metal
ion concentration by using Agilent model 3510 atomic absorption
spectrophotometer. The amount of biosorption (q) was calculated
by the following equation
Biosorption isotherms describe how adsorbate interacts with
biosorbents and equilibrium is established between adsorbed
metal ions on the biosorbent and the residual metal ions in the
solution during the surface biosorption.