Magnetic Carbon Material Treatment of Tetracycline-Containing Wastewater in a Membrane Capacitive Deionization-Coupled Peroxymonosulfate Oxidation System

Abstract

A membrane capacitive deionization (MCDI) system coupled with peroxymonosulfate (PMS) oxidation was developed for the synchronous removal of salts and tetracycline (TC) from saline wastewater. A magnetic carbon electrode (MAC-ns) was synthesized via pyrolysis of ammonium iron oxalate and activated carbon. The carbon matrix facilitated ion adsorption, while iron compounds enabled PMS activation for oxidative TC degradation. Under optimal conditions (Fe:C = 1:1, PMS = 15 mg, TC = 30 mg/L, NaCl = 0.5 g/L), the system achieved a salt adsorption capacity of 26.7 mg/g and a 75.9% TC removal rate. Quenching and electron paramagnetic resonance experiments confirmed that both free radicals (•SO₄^–, •OH, •O₂^–) and nonradical ¹O₂ contributed to TC degradation. Liquid chromatography–mass spectrometry and toxicity evaluation indicated reduced developmental toxicity and mutagenicity of degradation byproducts. The MAC-ns electrode also exhibited good electrochemical performance and superparamagnetism. This study demonstrates a low-cost, efficient, and magnetically responsive system for treating complex saline organic wastewater.