From speciation study to removal of Pb2+ from natural waters by a carnosine-based polyacrylamide/azlactone copolymer

Thermodynamic and voltammetric study on carnosine and ferrocenyl-carnosine

“…As mentioned earlier, CAR is able to coordinate to a number of bivalent metal cations. 1,2,11 To evaluate the interactions with Hg 2+ and Cd 2+ , speciation studies were experimentally performed by potentiometric titrations under different conditions of ionic strength, temperature and metal-ligand concentration ratio. In the calculation of the complex formation constants, literature values of protonation constants of CAR, hydrolysis constants of the metal cations and formation of chloride species were taken into account.…”

“…The thermodynamic parameters reported in Table 2 are very useful for predictive purposes allowing the calculation of the formation constants at any value of ionic strength and temperature in the range 0 ≤ I /mol L −1 ≤ 1 and 278.15 ≤ T /K ≤ 318.15. In Table 2, thermodynamic parameters concerning the formation of the Pb 2+ -CAR system, previously determined, are also reported, 11 useful for later considerations.…”

“…aRefers to reaction (1).bIn kJ mol −1 .cAt I = 0.15 mol L −1 (NaCl).d≥95% of confidence interval.e Ref. 11.…”

“…3. In the diagram, along with Hg 2+ and Cd 2+ , Pb 2+ is also reported, whose interactions with CAR were recently studied 11 and are provided in Table 2. As can be observed, the highest sequestering ability of CAR is towards Hg 2+ , following the trend: Hg 2+ ≫ Pb 2+ > Cd 2+ …”

“…1 In this regard, the thermodynamic behavior of Ca 2+ , Mg 2+ , Cu 2+ , Mn 2+ , Zn 2+ , and Pb 2+ -CAR systems was recently elucidated. 2,5,11 Therefore, the present study focused on the determination of the thermodynamic interaction parameters of CAR with Hg 2+ and Cd 2+ by means of potentiometry in NaCl aqueous solutions with different ionic strengths (0.15 ≤ I/mol L −1 ≤ 0.96) and temperatures (288.15 ≤ T/K ≤ 310. 15).…”