PROGRAMME

The occurrence of trace amounts of antibiotics in various bodies of water was directly linked to the development of antibiotic resistant pathogens. Recently, Amoxicillin (AMX) was added on the second EU “watch list” based on the proposed European Decision 2018/840/EU. Its presence in drinking water samples and wastewater effluents is related to limited removal by common municipal wastewater treatment plants. As such, new remediation techniques must be applied to remove these substances. One of the promising solutions is the application of advanced oxidation technologies, e.g. sustainable solar-assisted photocatalysis. In this study, composites made of TiO2 and α-Fe2O3 (hematite) were developed, prepared and immobilized in a form of thin films. The sandwich-type composite includes commercial TiO2 (P25 Aeroxide) and α-Fe2O3 with different layer configurations immobilized to the substrate via spin coating technique forming: (i) TiO2 layers covering α-Fe2O3, (ii) α-Fe2O3 layer over TiO2 and (iii) physically mixed 50% (w/w) of TiO2/Fe2O3. Since the composites were obtained using commercial nano-powders, they were inspected for optical properties only using DRS analysis. Photocatalytic activity under solar irradiation was assessed by treating targeted pharmaceutical pollutant AMX in the presence and absence of additional oxidants; hydrogen peroxide (H2O2) and persulfate (S2O82-). In the absence of any oxidant, TiO2 (top) – α-Fe2O3 (bottom) achieved the fastest degradation of AMX among all as-prepared composites, possessing first order rate constant of 4.6 x 10-3 min-1, higher comparing to benchmark TiO2 P25 as well (3.5 x 10-3 min-1). The same arrangement of composite was found to be of highly beneficial toward AMX removal in the presence of persulfate salts, while H2O2 did not show significant influence. The influence of pH and persulfate salt on AMX degradation rate was establish by the means of statistical planning and response surface modeling. The AMX degradation pathway was established and formed intermediates evolution/degradation were correlated with the changes in biodegradability and toxicity toward two bioassays; Daphnia magna and Vibrio fischeri. Influence of water matrix constituents (Cl-, CO32- , NO3- , PO43- and natural organic matter) on AMX removal was established, while Reactive Oxygen Species (ROS) scavenging was also employed for further understanding of AMX degradation mechanism.