The Langmuir model can describe the equilibrium data
for biosorption of zinc ions onto the dried activated sludge
better than the Freundlich model, and the maximum adsorption
capacity was 17.86 mg/g. The kinetic data forthe biosorption followed well the pseudo second-order
kinetic model. The FT-IR spectral analysis indicated that
amide group was mainly responsible for zinc(II) removal
and that hydroxide group was also involved in zinc(II)
binding to some degree. Based on these results, it can be
concluded that as a low-cost biosorbent, the dried activated
sludge, can be used for zinc(II) ions removal from aqueous
solutions.