Binary and ternary interactions of Gantrez™ AN-169 with epinephrine and copper(II) in NaCl aqueous solution: Thermodynamic approach and simulations in real conditions

In this investigation, Gantrez™ AN-169 (anhydride of the monoalkyl esters of poly(methyl vinyl ether/maleic acid); GTZ4−, L″) copolymer, widely employed in different industrial and application fields, was tested as sequestering agent towards epinephrine (Eph-, L') and copper(II). This speciation study was perfomed at the temperature of T = 298.15 K, and at the ionic strength value of I = 0.15 mol dm−3 in NaCl(aq). The formation of binary and ternary complexes was investigated, and the possible Eph−/GTZ4− interaction was analyzed by ISE-[H+] potentiometry and DOSY NMR. The dependence of the equilibrium constants on I/mol dm−3 and T/K was studied using an extended Debye-Hückel and a Van't Hoff equation, allowing the modelling of the thermodynamic parameters (i.e., equilibrium constants and enthalpy change values of formation). The entropic contribution was found to be the driving force behind the complex formation. The sequestering ability of Eph− and GTZ4− on Cu2+, evaluated by the pL0.5 calculation, increases with pH and ionic strength. Since freshwater and seawater are generally the final destination of wastewaters, simulations were carried out in aqueous solutions simulating these two natural media, with the aim of highlighting which are the main species of the components under those conditions.