TiO2 nanoparticles removal by electrocoagulation using iron electrodes: Catalytic activity of electrochemical sludge for the degradation of emerging pollutant

Abstract

Increase in use of TiO2-based nanoparticles induced the presence of TiO2 nanoparticles (TNPs) in water resources. TNPs have adverse impacts of human health and the ecosystems. Although, several studies demonstrated toxicity and health effects of TNPs, TNPs removal from water resources are limited. In this work, TNPs were removed from the aqueous solution by electrocoagulation (EC) process using iron electrodes. The effect of pH, applied current, and initial concentration of TNPs was investigated on TNPs removal. More than 95% of TNPs were eliminated under neutral pH, 100 mA applied current and 50 mg/L TNPs. Electrochemical sludge (ES) produced was considered as catalyst for peroxymonosulfate (PMS) activation to degrade ciprofloxacin (CIP) as an emerging pollutant. Iron species in ES was in the form of Fe3O4, which is confirmed by several methods. ES could activate PMS effectively to degrade 88% of CIP under optimum condition of 2 mM PMS, 0.1 g/L ES, and 60 min reaction time. The pseudo-first-order model was fitted for the PMS/ES process with a rate constant of 0.047 min−1. The catalytic activity of ES was kept for three-time use. However, iron leaching was considerable for the first use. Sulfate radical was the main agent of CIP degradation. ES was compared with commercial Fe3O4 nanoparticles for PMS activation in terms of CIP degradation and TOC removal. Finally, the use of electrochemical sludge can be a suitable strategy for minimizing waste and preparation of the catalyst.