Some thermodynamic data of the energetics of the interaction cation-piperazine immobilized on silica gel

The interactions involving piperazine-functionalized silica with Cu(II), Fe(III), Cr(III), and Mo(III) chlorides in ethanolic solution were investigated by adsorption using batchwise process and determined by a calorimetric titration technique. The net thermal effects were calculated after subtracting the respective thermal effect of dilution for all systems. The sequence of the maximum retention capacity was 0.56, 0.54, 0.26, and 0.24 mmol g−1 for Cr(III), Cu(II), Mo(III), and Fe(III), respectively. The amount of piperazine anchored on surface of silica was 0.54 mmol g−1. The enthalpy of these processes gave the following values: −12.90±0.08, −67.83±0.09, −199.08±0.09, and 67±1.5 kJ mol−1 following the same sequence of these mentioned metals, at 25.003±0.003 °C. The Gibbs free energy values are in agreement with favorable processes.