Kinetics, Thermodynamics, and Competitive Adsorption of Heavy Metals from Water Using Orange Biomass.

Adsorption of heavy metals on modified orange biomass has been studied. This biomass was treated with NaOH and CaCl₂ to improve its adsorption properties. Kinetic and thermodynamic studies of the adsorption of Cd, Ni, Cu, and Zn were performed at different operating conditions, including competitive adsorption studies with binary metallic mixtures. Results show that this adsorption process was endothermic where an ion exchange mechanism played a relevant role. Adsorbent effectiveness decreased in binary solutions, indicating a strong antagonistic adsorption behavior caused by counter-ions. This antagonistic adsorption was highly dependent on the counter-ion type and its concentration. Multicomponent adsorption of Cu ions was not significantly affected by the presence of other metallic counter-ions, whereas the adsorption of Ni could be totally suppressed by the other ions. The modeling of binary adsorption isotherms was successful using the modified Langmuir equation, which outperformed the Ideal Absorbed Solution Theory-Sips and modified Redlich-Peterson models.