On the performance of distinct electrochemical and solar-based advanced oxidation processes to mineralize the insecticide imidacloprid

Abstract

Water contamination by contaminants of emerging concern is one of the main challenges to be solved by our desired sustainable society. In the same time, different technologies for water treatment are becoming enough mature to be implemented. In this work, two different advanced oxidation processes (AOP) were investigated: i) electrochemical processes (electrochemical, photoassisted electrochemical, electro Fered-Fenton, and photo-electro Fered-Fenton – PEF-Fered) using a BDD and DSA® electrodes under UVA and UVC irradiation (9 W) and ii) solar-based AOP using four distinct oxidants (HOCl, H2O2, S2O82−, HSO5−) in the presence or absence of Fe2+ ions to oxidize and mineralize imidacloprid (IMD: 50 mg L−1) containing solutions. The PEF-Fered (1.0 mM Fe2+ and 50 mg L−1 h−1 H2O2) under UVA or UVC irradiation and HOCl/UVC (NaCl 17 mM) processes using a BDD and DSA® electrodes (10 mA cm −2), respectively, performed equally well to completely oxidize and mineralize (∼90%) IMD at the expense of only ∼0.3 kWh g−1. Low amounts and highly oxidized byproducts identified through liquid chromatography tandem mass spectrometry were observed for the HOCl/UVC process using a DSA® electrode. Concerning the solar-based AOP, all assessed oxidants (4 mM h−1) successfully oxidized IMD within 3 h of treatment, whereas only H2O2 and HOCl led to significant (∼60%) TOC abatement after 6 h treatment. The use of Fe2+ (0.5 or 1.0 mM) had no significant improvement in the oxidation and mineralization of IMD.