Harianingsih Harianingsih, Nur Qudus, Catur Rini Widyastuti, Nuni Widiarti, Nabila Khoirunisa, Kristian Saputra, Tonni Agustiono Kurniawan
The objective of this study was to identify the reactive species and intermediate compounds formed during the degradation of Remazol Red RB-133 using plasma electrolysis. Remazol Red RB-133 is an azo dye that is highly resistant to biological degradation, necessitating the use of alternative treatment technologies, such as plasma electrolysis. Plasma electrolysis, as an advanced oxidation process, generates reactive species capable of accelerating the cleavage of the azo bond, the primary chromophore responsible for the red color, leading to decolorization. The process was carried out in the glow discharge zone at 600 W, an air injection flow rate of 0.8 L min-1, 60 min of operation, 50°C, and an initial pH of 8. To identify the functional group transformations, FTIR spectroscopy (4000–500 cm-1) was used, while degradation of Remazol Red RB-133 was monitored using UV–Vis spectrophotometry at 518 nm. Reactive species formation was examined using OES at 200–800 nm, and intermediate products were analyzed by LC–MS. The results showed that decolorization reached 90% at 60 min. FTIR confirmed the cleavage of the azo band at 3400 cm-1, the reduction of aromatic bands at 1500 cm-1, the decrease of sulfonate groups at 1170 cm-1, and the appearance of a C=O peak at 1710 cm-1. OES successfully identified the formation of •OH radicals (309 nm), N2* (357 nm), H• (656 nm), and O• (777 nm). The LC-MS spectrum shows that Remazol Red RB-133 degrades through azo bond cleavage and oxidation. The ion peaks at m/z 279.15 and m/z 428.27 indicate fragmentation and the formation of oxidation products. © 2026 Institute of Electrostatics. All rights reserved.
Department of Chemical Engineering, Faculty of Engineering, Universitas Negeri Semarang, Sekaran Gunungpati, Semarang, 50229, Indonesia; Department of Civil Engineering, Faculty of engineering, Universitas Negeri Semarang, Sekaran Gunungpati, Semarang, 50229, Indonesia; Department Chemistry, Faculty of Mathematics and Natural Science, Universitas Negeri Semarang, Sekaran Gunungpati, Semarang, 50029, Indonesia; College of Ecology and The Environment, Xiamen University, Fujian, Xiamen, 361102, China
