Modular Photocatalytic Reactor for the Removal of Estrogens from Aqueous Solutions

Estrogens, widely used for therapeutic or contraceptive purposes, act as endocrine disruptors in aquatic systems and have adverse effects on a wide range of living organisms. Wastewater insufficiently treated by conventional methods is the main way for estrogens to enter aquatic systems. Therefore, the purpose of this paper is to develop a novel photocatalytic system for the removal of the estrogenic mixture estradiol valerate/norgestrel from wastewater. The photocatalytic modules are operated in a plug flow reactor system under a UV-A radiation field, and the photocatalyst (TiO2, ZnO or TiO2/ZnO) is immobilized on an inert support of glass balls that are strung on stainless-steel wire and arranged in rows along the photocatalytic modules. The photocatalysts were synthesized by the sol–gel method and then deposited on the inert glass support by the hot method, after which it was calcined for two hours at a temperature of 500 °C. The experimental results showed that the efficiency of photocatalytic degradation largely depends on the dose of photocatalyst. The dose of photocatalyst can be adjusted by adding or removing photocatalytic modules, each of which have an approximately equal amount of photocatalyst. The best result was obtained for the TiO2/ZnO photocatalyst, the organic substrate being practically mineralized in 120 min, for which only two photocatalytic modules are needed.