Evaluation of Process Influencing Factors, Degradation Products, Toxicity Evolution and Matrix-Related Effects during Electro-Fenton Removal of Piroxicam from Waters

Abstract

The degradation kinetics, the operational influencing factors, the determination of short-chain organic by-pro-ducts, the mineralization degree, the evolution of residual toxicity, as well as the treatment of complex matriceswere systematically investigated on removal of piroxicam by Electro-Fenton process (EF), due to its persistenceand low removal in water matrices. The second order reaction rate constant between piroxicam and hydroxylradical (•OH) was determined as (2.19 ± 0.01) × 109M−1s−1. It was found that the process was able to almostcompletely mineralize 0.08 mM piroxicam solution (92% TOC removal) at 6 h treatment. Based on identificationof short-chain carboxylic acids, released inorganic ions and the removal of total organic carbon, a schematicproposal of piroxicam degradation by EF treatment was done. The evolution of the acute toxicity of treatedpiroxicam solution was monitored by Microtox method, showing a significant toxicity reduction at 180 mintreatment. Remarkably, piroxicam in simulated urine and hospital wastewater was completely degraded after120 min of EF treatment. Therefore, the results indicate that the tested EF process constitutes an efficient optionfor the elimination of piroxicam in aqueous media.