used to correlate the experimental data and to determine the kinetic parameters. Four well-known
adsorption isotherms were chosen to describe the biosorption equilibrium. The experimental data were
analyzed using two two-parameter models (Langmuir and Freundlich) and two three-parameter models
(Redlich–Peterson and Sips). The equilibrium biosorption isotherms showed that peanut shells possess high
affinity and sorption capacity for Cu(II) and Cr(III) ions, with monolayer sorption capacities of 25.39 mg Cu2+
and 27.86 mg Cr3+ per 1 g biomass, respectively. All results showed that peanut shells biomass is an
attractive, alternative low-cost biosorbent for removal of heavy metal ions from aqueous media.