Ozone-assisted regeneration of magnetic carbon nanotubes for removing organic water pollutants

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 335; pp. 384 - 391
• Main Authors: Ateia, Mohamed, Ceccato, Marcel, Budi, Akin, Ataman, Evren, Yoshimura, Chihiro, Johnson, Matthew S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2018
• Subjects: Atrazine; Degradation byproducts; DFT; Ethanol; Magnetic carbon nanotubes; Ozone; Regeneration; XPS; Regeneration; DFT; Ethanol; Degradation byproducts; Ozone; XPS; Magnetic carbon nanotubes; Atrazine
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2017.10.166

[Display omitted] •Ozonation followed by washing with ethanol can regenerate CNTs for atrazine removal.•Ethanol removes degradation byproducts from CNT surface to recover adsorption sites.•XPS analysis show minimal changes in CNT oxidation level and the π−π interactions. There is a significant interest in sustainable and eco-friendly methods of regenerating spent nanomaterials in order to use resources more efficiently and minimize the cost of materials and techniques. This paper investigates the feasibility of using ozone to regenerate magnetic carbon nanotubes (MCNTs) after they have been used to remove organic pollutants from water. We ran MCNT through multiple regeneration cycles (i.e. magnetic collection → ozone regeneration → washing with ethanol then water) to adsorb atrazine. The results of our adsorption experiments show that the atrazine removal capacity of the MCNTs decreased from 57.8 to 27.6 mg/g in three cycles if only ozone treatment is used as a regeneration method. However, this capacity increased when MNCTs are washed with ethanol following ozone treatment. MCNTs were seen to retain 85–93% of its original adsorption affinity even after ten consecutive regeneration cycles. Additionally, we used a three layer graphite slab as a model system for CNTs and performed density functional theory (DFT) calculations to determine the free energy of adsorption and the free energy of solvation of atrazine and its byproducts in water and ethanol. The results of X-ray photoelectron spectroscopy (XPS) measurements and DFT calculations showed that π−π interactions of MCNTs were not affected by ozonation and/or washing with ethanol and this procedure could remove the degradation byproducts attached on the surface. Overall, this is the first report that demonstrates the feasibility of regenerating spent MCNTs using ozone assisted by ethanol washing as an efficient and facile treatment.