Degradation of anti-inflammatory drugs in municipal wastewater by heterogeneous photocatalysis and electro-Fenton process

ABSTRACT

Non-steroidal anti-inflammatory drugs (NSAID) are compounds frequently found in municipal wastewater and their degradation by conventional wastewater treatment plants (WWTP) is generally incomplete. This study compared the efficiency of two advanced oxidation processes (AOP), namely heterogeneous photocatalysis (HP) and electro-Fenton (EF), in the degradation of a mixture of common NSAID (diclofenac, ibuprofen and naproxen) dissolved in either deionized water or effluent from a WWTP. Both processes were effective in degrading the NSAID mixture and the trend of degradation was as follows, diclofenac > naproxen > ibuprofen. EF with a current density of 40 mA cm⁻² and 0.3 mmol Fe²⁺ L⁻¹ was the most efficient process to mineralize the organic compounds, achieving up to 92% TOC removal in deionized water and 90% in the WWTP effluent after 3 h of reaction. HP with 1.4 g TiO₂ L⁻¹ at pH 7 under sunlight, produced 85% TOC removal in deionized water and 39% in WWTP effluent also after 3 h treatment. The lower TOC removal efficiency shown by HP with the WWTP effluent was attributed mainly to the scavenging of reactive species by background organic matter in the wastewater. On the contrary, inorganic ions in the wastewater may produce oxidazing species during the EF process, which contributes to a higher degradation efficiency. EF is a promising option for the treatment of anti-inflammatory pharmaceuticals in municipal WWTP at competitive electrical energy efficiencies.

KEYWORDS:

• Diclofenac
• drug mixture
• ibuprofen
• naproxen
• wastewater

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Minerva Villanueva-Rodríguez http://orcid.org/0000-0001-7481-2499

Ricardo Bello-Mendoza http://orcid.org/0000-0002-4596-9363

Aracely Hernández-Ramírez http://orcid.org/0000-0002-4267-157X

Edgar J. Ruiz-Ruiz http://orcid.org/0000-0001-9524-7927

Additional information

Funding

A postdoctoral fellowship granted by El Colegio de la Frontera Sur (ECOSUR) to M.V.R. and financial support from Programa de Apoyo a la Investigación Científica y Tecnológica, Universidad Autónoma de Nuevo León (PAICYT-[IT 476-15]UANL) are gratefully acknowledged.