Carbon nanotubes synthesized from LDPE for application in wet peroxide oxidation of paracetamol

Carbon nanotubes (CNTs) were produced by chemical vapor deposition (CVD) considering low-density polyethylene (LDPE) as a carbon source and as an alternative to upcycle plastic solid waste. The CNTs were synthesized over bimetallic catalysts (Ni and Fe) supported on Al2O3 and purified with H2SO4 to dissolve the metal particles from the material. Both original (CNT-O) and purified materials (CNT-P) were tested as catalysts in catalytic wet peroxide oxidation (CWPO) of paracetamol (PCM). Both catalysts promoted the complete conversion of PCM within 8 h of reaction and were able to mineralize 60% of the organic content of the effluent (measured as TOC) in 24 h. Catalyst CNT-O was able to completely decompose hydrogen peroxide (H2O2) within 24 h, whereas CNT-P was only able to decompose ~80%. Therefore, the efficiency of H2O2 consumption, measured as XTOC/XH2O2, was higher for catalyst CNT-P (0.75) than for CNT-O (0.61). Metal leaching, especially Ni, was observed during the CWPO run with CNT-O, while it is avoided when using CNT-P. Thus, purified CNTs have proved to be active in CWPO of PCM, allowing a more controlled decomposition of H2O2 and avoiding leaching of metal species.