The Treatment Of Pharmaceutical Wastewater With Fenton Reaction

The Fenton degradation of sulfasalazine solution is studied in this work. The effects of reaction parameters such as Fe3+ concentration, initial H2O2 dosage, pH and the reaction temperature are evaluated. For sulfasalazine of 100 mg/L, the removal of sulfasalazine, chemical oxygen demand (COD) and total organic carbon (TOC) reached 99.5%,84.2% and 41% in 60 min with 0.20 mM Fe3+ and 16 mM H2O2 at 35℃, respectively. The complexation of the sulfasalazine with the Fe3+ greatly affects the reaction kinetics of the Fenton degradation. The complexed Fe3+ presents a reaction constant of 0.062 min-1·mM-1 while that of free Fe3+ is 2.526 min-1·mM-1. The Fenton degradation of salicylic acid and industrial sulfasalazine wastewater were also investigated.LC-MS technology was used to analyze the possible degradation intermediates in the Fenton degradation of sulfasalazine, by which 20 kinds of degradation intermediates were identified. A degradation pathway of sulfasalazine with the Fenton reaction is thus proposed. The Fenton degradation of sulfasalazine principally begins with the attack of hydroxyl radical on the azo-group as well as the sulfanilamido group. Both intramolecular rearrangement and bimolecular reaction occur simultaneously in sulfasalazine degradation after the hydroxyl radical attack.The Fenton degradation of nalidixic acid is studied in the fourth part. The effects of reaction parameters such as Fe3+ concentration and initial H2O2 dosage are evaluated. For nalidixic acid of 50 mg/L, the removal of nalidixic acid and TOC reached 99.1% and 33% in 60 min with 0.25 mM Fe3+ and 10 mM H2O2 at 35℃, respectively. LC-MS technology was also used to analyze the degradation intermediates, by which 16 kinds of degradation intermediates were identified. The degradation pathway of nalidixic acid with Fenton reaction is proposed, in which the ring-opening reaction and the oxidation of alkyl chain by the hydroxyl radical attacking is concluded.