Thermodynamics Lab Report

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3.2.2. Adsorption thermodynamics
The deduction of the thermodynamic Gibbs free energy (ΔG◦), enthalpy (ΔH◦) in addition to entropy change (ΔS◦) was carried out by examining the adsorption batches under different temperatures ranged between 20 and 400C.
After performing the adsorption under any definite temperature, the equilibrium constant (KC) were anticipated using the following equation.
KC = Cad / Ce (6) where Cad is the concentration of Hg(II) ions adsorbed on the resin at equilibrium (mg/g) and Ce is the equilibrium concentration of Hg(II) ions in the aqueous medium (mg/L).
Eq. (7) can be then employed to estimate ΔG◦ (kJ mol-1)
ΔGoads = −RT ln KC (7) where R = 8.314 J/mol K
Both ΔH◦ and ΔS◦ were finally anticipated by plotting the reciprocal of temperature (Kelvin) versus lnKC (Fig. 5).in accordance with Eq. 8. lnKC = ΔSoads/R − ΔHoads/RT
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These interfering metal ions were chosen on the bases of similar charge and mode of coordination with our target template Hg2+ ions. The estimated selectivity parameters including distribution and selectivity coefficients were collected in Table 7. As can be seen, NI-PMTF resin exhibited a high distribution coefficient with respect to Cd2+, Hg2+ and Pd2+, which indicate a considerable potential of the resin in separation of these heavy metals pollutants from aqueous media. Moreover, the distribution coefficient in case of Hg-PMTF showed an obvious increase with Hg2+ ions, with relative selectivity coefficient greater than 1 for each interfering ion, revealing the great improvement of Hg(II) selectivity after the ion-imprinting process due to the creation of specific recognition active sites based on the charge, ionic radius and coordination geometry of Hg2+

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