Enthalpic Contribution of Ni(II) in the Interaction between Carbonaceous Material and Aqueous Solution

Solid adsorbents were prepared from corn cob that was modified with a solution of HNO3 6 M at different contact times. The solids are characterized by physical N2 adsorption at 77 K to know their surface area by applying the BET model and surface chemistry is determined using the Bohem method. Once we have prepared the adsorbents we determine the immersion enthalpy, Δ, of the solids in Ni(II) aqueous solutions of different concentrations between 20 and 800 mg·L−1, with values for Δ between 10.0 and 35.3 J·g−1. From the results obtained for the immersion enthalpy in function of the ion Ni(II) concentration we calculate the contribution to the immersion enthalpy that corresponds to the ion when it is treated with the system adsorbent-solution as a mixture in which the solid, the solvent, and the adsorbate are involved. The solution thermodynamics allows for establishing the enthalpic changes that bring the ion in function of the concentration and the intensity of the interaction of solid-metal ion that is favored by the presence of acid groups in the solid.

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