Characteristics of thermodynamic, isotherm, kinetic, mechanism and design equations for the analysis of adsorption in Cd(II) ions-surface modified Eucalyptus seeds system

The adsorption of Cd(II) ions from synthetic wastewater was performed using two types of newly prepared adsorbent: (i). Surface modified Eucalyptus seeds by sulphuric acid (SMES-S) and (ii). Surface modified Eucalyptus seeds by hydrochloric acid (SMES-H). SMES-S showed better performance for the Cd(II) ions removal than the SMES-H. The thermodynamics of the Cd(II) ions-SMES system was feasible, spontaneous and exothermic in nature. The maximum monolayer adsorption capacities of the adsorbents were found to be 71.15 mg/g (SMES-S) and 64.16 mg/g (SMES-H). The kinetics of the system followed the pseudo-second order kinetic model. The effective diffusivity values were calculated for the SMES-S: 2.0578 × 10−11, 2.2641 × 10−11, 2.3382 × 10−11, 2.5022 × 10−11 and 2.5445 × 10−11 m2/s for the initial Cd(II) ions concentration from 20 to 100 mg/L, respectively. The SMES-S can be used as an effective adsorbent for the removal of Cd(II) ions.