The Effect of Fe2+ Ions Addition on Reactive Oxygen and Nitrogen Species (RONSs) with Controlled Initial pH of Nitrate Synthesis using Plasma Electrolysis Reactor

Abstract

Plasma electrolysis offers an environmentally friendly approach to nitrate synthesis. This study aimed to investigate the effect of Fe²⁺ ion addition on the formation of reactive oxygen and nitrogen species (RONSs) and nitrate production under controlled initial pH conditions (pH = 6). The experiment utilized a plasma electrolysis reactor with a 0.02 M K₂SO₄ electrolyte, an air flow rate of 0.8 L/min, Fe²⁺ ions at a concentration of 30 ppm, and a temperature of 60°C. Nitrate production was measured using a UV-VIS spectrophotometer, while RONSs emission intensity was analyzed using an electron spin resonance (ESR). The results showed that with and without the addition of Fe²⁺ ions accelerated the pH drop from 6 to 3 in just 60 minutes. Nitrate production increased significantly with Fe²⁺, reaching 2432 ppm compared to 2046 ppm without Fe²⁺. RONSs emissions without Fe²⁺ included •OH (306 nm), •H (654 nm), •O (844 nm), N₂ (317 nm), N₂⁺ (416 nm), and N (777 nm). With Fe²⁺ addition, the emission intensities of these species remained consistent, indicating the role of Fe²⁺ in enhancing nitrate production without significantly altering RONSs profiles.