Ozonation of Propranolol: Transformation, Biodegradability, and Toxicity Assessment

This work studies the ozonation of the pharmaceutical propranolol (PRO) in aqueous solution. Experimental results demonstrated that ozonation was an efficient method to remove PRO, achieving its complete abatement after 8 min of treatment (ozone dose of 0.47 mmol L―1), starting from a PRO initial concentration of 0.38 mmol L―1. The total organic carbon (TOC) analysis indicated that 1 h of ozonation (ozone dose of 3.54 mmol L―1) was able to achieve only about 5% of the total organic carbon removal. The ozonation of PRO aqueous solutions has not promoted a prompt increase of the ratio of biological oxygen demand to chemical oxygen demand, thus indicating the need for higher ozone doses to initiate the biodegradability enhancement. The acute toxicity increased in the first minutes of reaction with a posterior reduction to values slightly higher than the toxicity of the PRO raw solution. Some early intermediate structures were proposed, and finally, kinetic constants for the direct attack of ozone on PRO structure were calculated. These values are in the order of magnitude of 105 L mol―1 s―1.