Mechanistic investigation of ciprofloxacin degradation using NiFe2O4/CA-cellulose acetate composite films in a novel dielectric barrier discharge plasma system
Husseini Sulemana, Rongjie Yi, Chengwu Yi, Bo Zhang, Muhammad Imran Nawaz, Emmanuel Nkudede, Charles Obinwanne Okoye, Jiangwei Zeng, Jianan Zhang, Zaina Omary Mochiwa
Abstract
Conventional wastewater treatments often exhibit limited efficiency in removing antimicrobial residues, thus requiring innovative methods to tackle antimicrobial contamination in the environment. This study employed a dielectric barrier discharge (DBD) plasma reactor with NiFe 2 O 4 -cellulose acetate (CA) composite films for ciprofloxacin (CIP) degradation in water. The catalytic efficiency of NiFe 2 O 4 /CA films was tested across the degradation rate of CIP in synthesized wastewater, reaction kinetics, energy utilization, and reductions in total organic carbon (TOC) and chemical oxygen demand (COD), both with and without the films in the DBD system. Optimal degradation conditions of 10 mg/L CIP concentration, 195 V, 6.5 Hz, 9% catalyst loading, and 4.32 L/min flow rate achieved 89.63% CIP removal within 60 min, with alkaline pH further enhancing degradation. UV–Vis analysis confirmed that extending DBD treatment time improved degradation rates. Variations in solution conductivity, pH, and concentrations of H 2 O 2 and O 3 were tracked to verify the catalytic role of NiFe 2 O 4 /CA films. Moreover, radical scavengers such as tert-butanol (TBA), benzoquinone (BQ), and triethylenediamine (TEDA) were introduced to the system which identified that •OH, · O 2 − , and 1 O 2 were the key reactive oxygen species responsible for CIP degradation. Liquid chromatography-mass spectrometry (LC-MS) was used to determine the intermediate and by-products of the CIP degradation and four potential degradation pathways were proposed. Pathway III was considered the prominent route involving hydroxylation and piperazine ring cleavage, producing fewer toxic intermediates supported by density functional theory (DFT) calculations. Toxicity assessment showed most intermediates had reduced developmental toxicity and bioaccumulation potential compared to CIP. This highlights the environmental safety of the DBD plasma and NiFe 2 O 4 /CA system, as a promising, eco-friendly alternative to traditional methods, with reduced toxicity, minimal bioaccumulation, and potential for sustainable, large-scale application.