Study of adsorption kinetic, mechanism, isotherm, thermodynamic, and design models for Cu(II) ions on sulfuric acid-modified Eucalyptus seeds: temperature effect

Abstract

The present research was investigated to remove the Cu(II) ions from aqueous solution by adsorption technology using surface-modified Eucalyptus seeds (SMES). Adsorption kinetics, mechanism, isotherms, and thermodynamic parameters were estimated. It was found that the adsorption of Cu(II) ions onto SMES follows pseudo-second-order kinetics. Adsorption mechanism was well explained with intraparticle diffusion and Boyd kinetic models. Diffusivity values of the Cu(II) ions to the SMES were estimated at different temperatures. Effective diffusivity values were estimated at 30°C: 1.9297 × 10−11, 2.1446 × 10−11, 2.0165 × 10−11, 2.2440 × 10−11, and 2.7434 × 10−11 m2 s−1 for an initial Cu(II) ions concentration of 20–100 mg L−1, respectively. Freundlich adsorption isotherm model agreed with the experimental data to a greater extent, showing the multilayer adsorption of Cu(II) ions onto SMES. The maximum monolayer adsorption capacity of SMES for Cu(II) ions was found to be 76.94 mg of Cu(II) ions g−1 of SMES at 30°C. The determinations from the thermodynamic study show that the process was feasible, spontaneous, and exothermic in nature. A single-stage batch adsorber was designed using Freundlich isotherm model, to estimate the amount of adsorbent that was needed to treat the known volume of the effluent.