Magnetic EDTA functionalized CoFe 2 O 4 nanoparticles (EDTA-CoFe 2 O 4 ) as a novel catalyst for peroxymonosulfate activation and degradation of Orange G

Abstract

EDTA functionalized CoFe₂O₄ nanoparticles (EDTA-CoFe₂O₄) synthesized using a facile one-pot solvothermal method were employed as catalysts to activate peroxymonosulfate (PMS) with Orange G (OG) as the target pollutant. Effects of operating parameters including initial solution pH, catalyst dosage, PMS dosage, and water matrix components such as Cl⁻, NO₃⁻, CO₃²⁻, and humic acid were evaluated. A degradation efficiency of 93% was achieved in 15 min with 1 mM PMS and 0.2 g/L EDTA-CoFe₂O₄ catalyst, while only 57% of OG was degraded within 15 min in CoFe₂O₄/PMS system. The degradation of OG followed pseudo-first-order kinetics, and the apparent first-order date constant (k _obs) for OG in EDTA-CoFe₂O₄/PMS and CoFe₂O₄/PMS system was determined to be 0.152 and 0.077 min⁻¹, respectively. OG degradation by EDTA-CoFe₂O₄/PMS was enhanced with the increase of catalyst and PMS doses at respective range of 0.1–2.0 g/L and 0.5–10.0 mM. Higher efficiency of OG oxidation was observed within a wide pH range (3.0–9.0), implying the possibility of applying EDTA-CoFe₂O₄/PMS process under environmental realistic conditions. Humic acid (HA) at low concentration accelerated the removal of OG; however, a less apparent inhibitive effect was observed at HA addition of 10 mg/L. The k _obs value was found to decrease slightly from 0.1601 to 0.1274, 0.1248, and 0.1152 min⁻¹ with the addition of NO₃⁻, CO₃²⁻, and Cl⁻, respectively, but near-complete removal of OG could still be obtained after 15 min. Both of the sulfate radicals and hydroxyl radicals were produced in the reaction, and sulfate radicals were the dominant according to the scavenging tests and electron paramagnetic resonance (EPR) tests. Finally, a degradation mechanism was proposed, and the stability and reusability of the EDTA-CoFe₂O₄ were evaluated.

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