Degradation of β-blockers in hospital wastewater by means of ozonation and Fe2+/ozonation

- The β-blockers were completely degraded by ozonation and Fe2+/ozonation.
- Fe2+/Ozonation was the most efficient means of removing the organic load.
- The effect of the variables pH and [Fe2+] was evaluated by multivariate experimental design.
- Pseudo and biphasic first-order kinetics are proposed as a function of pH.
- Degradation products and degradation pathways were identified.

This study investigates the degradation of the β-blockers in hospital wastewater by direct ozonation and Fe2+/ozonation with a focus on measurements at different initial pHs and Fe2+ concentrations, and the determination of kinetic constants. The results showed that these 'emerging contaminants' were completely degraded, when the removal rate of organic matter reached 30.6% and 49.1% for ozonation and Fe2+/ozonation, respectively. Likewise, the aromaticity removal rates were 63.4% and 77.9% for ozonation and Fe2+/ozonation, respectively. The experimental design showed that pH was the variable which had the greatest effect on the Fe2+/ozonation. The kinetic constants of atenolol, metoprolol and propranolol degradation by direct ozonation complied with pseudo-first-order conditions, while Fe2+/ozonation was suited to a biphasic degradation model. The kobs tended to rise when the pH increases; propranolol showed high kobs, which can be attributed to the naphthalene group (an electron-rich moiety). The identification of degradation products was carried out in aqueous solution using HPLC-MS2, followed by a suggestion of degradation pathways by means of ozonation. The degradation products proved to be dependent on the initial pH, and followed pathways that are based on direct ozonolysis and free radicals.

Statement of novelty. This study focused on the degradation of β-blockers in hospital wastewater. Ozonation was evaluated as a function of pH, while Fe2+/ozonation was optimized by means of multivariate experimental design. The kinetic constants followed both of the pseudo and biphasic first-order reactions. The degradation products were identified by HPLC-MS/MS. 284