Optimization of pulsed DBD plasmas for the degradation of Valsartan in water − application to pharmaceutical pollutants of other molecular classes
Konstantia Papalexopoulou, I.E. Triantaphyllidou, Spyros S. Skandalis, Gerasimos Rassias, C.A. Aggelopoulos
Abstract
A multiparameter optimization of Pulsed dielectric barrier discharge (DBD) plasma induced degradation of Valsartan was undertaken to investigate the viability of this technology in remediating aqueous solutions of metabolically resistant pharmaceuticals. To gain insight into background effects on plasma species and changes in the characteristics of the solution, two DBD reactor configurations (gas–liquid DBD and underwater plasma bubbles), three carrier gases (air, oxygen and argon) and two water matrices (ultra-pure and tap water) were examined first in the absence of pollutant. The degradation of Valsartan was then optimized with respect to carrier gas, reactor configuration, treatment time, pollutant concentration and water matrix which resulted in a process with high degradation and energy efficiencies (>99 % and 0.56 g kWh −1 , respectively) under plasma bubble configuration in tap water with air as the carrier gas. The active plasma bubble species and their relative contributions in the degradation process were determined using diagnostic techniques and scavenging experiments and a consistent degradation mechanism was formulated based on UPLC/MS analysis of samples from various timepoints of the treatment. More importantly, the remediated solution under optimized conditions showed no toxicity in biochemical testing against two cell lines. The optimized plasma conditions were also applied successfully in the degradation of representative members of the sulfanilamide and fluoroquinolone classes of antibiotics. Overall, the optimized plasma bubble process constitutes a competitive remediation technology not only for water contaminated by sartans but also by diverse structural types of pharmaceutical pollutants.