Valorisation of polyolefins into magnetic carbon nanotubes: application as catalysts in wet peroxide oxidation of paracetamol

Abstract

This work deals with the application of magnetic carbon nanotubes (MCNTs) in the catalytic wet peroxide oxidation (CWPO) of paracetamol (PCM), a pharmaceutical compound selected as model contaminant of emerging concern (CEC). MCNTs were synthetized by catalytic chemical vapor deposition (CCVD) at 850 ºC, considering low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) as carbon precursors representative of urban plastic solid waste. Magnetite supported in alumina (Fe3O4@Al2O3) nanoparticles previously synthesized by sol-gel were used as catalysts in the CCVD process. The synthesized MCNTs were tested in the CWPO of PCM at 80 ºC, monitoring during 24 h the concentration of H2O2, PCM, Total Organic Carbon (TOC) and aromatic compounds. All MCNT catalysts show activity allowing to decompose completely the pharmaceutical in aqueous solutions after 360 min. In particular, the MCNTs synthesized from HDPE lead to complete removal of the pollutant after 30 min of reaction. By TOC analysis, it was observed that the CNTs led to obtain mineralization degrees higher than 38% of the pollutant after 24 h. Aromaticity test indicated that the catalyst prepared from HDPE promotes more degradation of the intermediates than the catalyst prepared from LDPE and PP.