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

Abstract

Solid adsorbents were prepared from corn cob that was modified with a solution of HNO 3 6 M at different contact times. The solids are characterized by physical N 2 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 im , of the solids in Ni(II) aqueous solutions of different concentrations between 20 and 800 mg⋅L −1 , with values for Δ im 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.

Data of the immersion enthalpy of activated carbon in benzene and cyclohexane. Influence of the content of surface oxygenated groups

“…Next, the capture of the output electric potential started and the stabilization of the calorimeter until base line was achieved; later, the immersion of the sample into the liquid was performed and the resulting thermal changes were recorded until the baseline was attained again. Finally, a post-period was recorded, and the electric calibration was executed [1] , [2] , [3] , [4] .…”

Enthalpic and Liquid-Phase Adsorption Study of Toluene–Cyclohexane and Toluene–Hexane Binary Systems on Modified Activated Carbons

“…This parameter is interesting because it is useful to see the changes in the mixture and its properties when the quantities of the components are modified, since each of them contributes to the enthalpy of the mixture. This differential enthalpy and its variations could be expressed per mole; but if the changes in this parameter are calculated for a solution that interacts with an activated carbon, it is better to determine grams instead of moles of the component [ 38 , 39 , 40 ].…”

“…It allows us to determine the change of the partial quantities (related to the differential enthalpy) in regard to the composition of the system; this depends on T and P, but they are considered constant during the process. Through this mathematical relationship, the differential enthalpy variations for solvent and solid in the solid could be evaluated according to the solute fraction [ 38 , 39 ].…”

“…This, in order to: (i) determine how the solid–liquid interactions change when the binary mixtures are put in contact with the adsorbent and (ii) analyze the contribution of the components of the solution and the activated carbon through the differential enthalpy change. Thus, the work of this manuscript is relevant since little has been studied in this aspect, because it has been evaluated for other materials such as graphite, zeolites [ 41 , 42 , 43 ] and some carbonaceous materials, but only for aqueous solutions [ 38 , 39 ].…”