Temperature and nitrogen-induced modification of activated carbons for efficient catalytic ozonation of salicylic acid as a model emerging pollutant

C A L Graça; R Zema; C A Orge; J Restivo; J Sousa; M F R Pereira; O S G P Soares

doi:10.1016/j.jenvman.2023.118639

Temperature and nitrogen-induced modification of activated carbons for efficient catalytic ozonation of salicylic acid as a model emerging pollutant

J Environ Manage. 2023 Oct 15:344:118639. doi: 10.1016/j.jenvman.2023.118639. Epub 2023 Jul 20.

Authors

C A L Graça¹, R Zema², C A Orge³, J Restivo³, J Sousa², M F R Pereira³, O S G P Soares³

Affiliations

¹ LSRE-LCM - Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal; ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal. Electronic address: catiaalgraca@fe.up.pt.
² INL, International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga s/n, 4715-330, Braga, Portugal.
³ LSRE-LCM - Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal; ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.

PMID: 37480639
DOI: 10.1016/j.jenvman.2023.118639

Abstract

The occurrence of emerging pollutants on effluents of wastewater treatment plants makes unfeasible their reutilization and consequently to comply with the sixth goal of 2030 Agenda for sustainable development. Thus, it is extremely important to find ways to remove these pollutants without compromising the quality of reclaimed water. Ozonation has been successfully explored for this purpose, but it still presents limitations towards some oxidant-resistant pollutants. To surpass this, the conversion of ozone (O₃) into more reactive species is required, which can be accomplished by using catalysts. Carbon catalysts, such as activated carbons (ACs), represent a more environmentally attractive option than traditional metal-based catalysts, with the advantage of being easily modified to tune their textural and surface properties to the reaction chemistry. In this study, two different sources of ACs were tested in the catalytic ozonation of a frequently detected emerging pollutant: salicylic acid (SalAc). These ACs were submitted to thermal treatment under H₂ and functionalization with N precursors, such as melamine and poly(ethyleneimine), to induce changes in the surface properties, especially in the nitrogen content. Although no correlation was found between the N-content and catalytic activity, the thermal treatment under H₂ increased the mesopores surface area (S_meso), which reflected in greater catalytic activity. As that, the best-performing AC was the one with the highest S_meso, which revealed also to be resistant to O₃ and able to convert O₃ into more reactive species, evidenced by the capacity of oxalic acid, a well-known ozone-resistant by-product. The same AC was then submitted to three consecutive reutilization cycles and a more significant activity loss was observed in terms of SalAc degradation rate (⁓ 40%) then total organic carbon removal (⁓ 25%), from the first to the third cycle. This decline in efficiency was ascribed to the presence of by-products adhered to the catalyst surface, which impede its ability to react effectively with O₃.

Keywords: Activated carbon; Catalytic ozonation; Pollutant abatement; Salicylic acid; Thermal treatment.

MeSH terms

Charcoal
Environmental Pollutants*
Nitrogen
Oxalic Acid
Ozone*
Salicylic Acid
Temperature

Substances

Salicylic Acid
Charcoal
Environmental Pollutants
Nitrogen
Oxalic Acid
Ozone