antidepressants, ZnO nanoparticles, adsorption, zeta potential

Interactions between trycyclic antidepressants and zinc oxide nanoparticles have been studied. Amitriptyline and nortryptyline, which were immobilized from buffer medium at 37 °C, were selected as models. The key factor influencing the adsorption of these substances on zinc oxide is pH. During the adsorption, an acid-base equilibrium was established between the buffer, zinc oxide and the antidepressant. These pH changes were also reflected in the surface charge of the adsorbent and the values of the zeta potential, which was also monitored. Both substances have a similar structure, yet they differ in their acid-base properties and also in their ability to form micelles. These different properties caused different values of the amount adsorbed on the surface of the zinc oxide. Adsorption isotherms show an sigmoidal course. The highest adsorbed amount of amitriptyline on ZnO is 6.38 mmol g-1, in the case of nortryptyline it is 3.68 mmol g-1. The adsorption is directed in accordance with the pseudo-second-order kinetic equation. The values from the kinetic equations, as well as the changes in the zeta potential, indicate different mechanisms of immobilization of amitriptyline and nortryptyline on the surface of zinc oxide nanoparticles. In the case of both substances, due to the interaction with zinc oxide, they were significantly removed from the liquid medium; in the case of amitryptyline, the residual concentration was less than 10% at an initial concentration of 5 mmol L-1.