Author(s): Martin-Martinez, Maria ; Machado, Bruno ; Serp, Philippe ; Morales-Torres, Sergio ; Silva, Adrián ; Figueiredo, José ; Faria, Joaquim ; Gomes, Helder
Date: 2018
Persistent ID: http://hdl.handle.net/10198/20375
Origin: Biblioteca Digital do IPB
Catalytic wet peroxide oxidation (CWPO) uses H2O2 as a source of hydroxyl radicals (HO) for the oxidation of organic species. This process is regarded as a potential solution for the treatment of aqueous effluents containing recalcitrant and toxic organic pollutants, difficult to remove by conventional biological processes, mainly if present at high concentrations (1- 10 g L-1) [1]. In a recent study, three magnetic carbon nanotube (CNT) samples, named A30 (N-doped), E30 (undoped) and E10A20 (partially N-doped), were synthesized by chemical vapor deposition and tested in the CWPO process [2]. It was revealed that N-doped hydrophilic surfaces promoted a fast decomposition of H2O2 into non-reactive species (H2O and O2), limiting the CWPO performance. In the present study, the surface of the CNTs was modified by introducing oxygenated surface groups (oxidation with HNO3, samples CNT-N), and by heat treatment at 800 °C for the removal of surface functionalities (samples CNT-HT). The effect of these modifications was analysed during 24-hours- CWPO-experiments of highly concentrated 4-nitrophenol solutions (4-NP, 5 g L-1), at atmospheric pressure and 50 °C, adjusting the initial pH to 3, using a catalyst load of 2.5 g L-1 and the stoichiometric amount of H2O2 needed for the complete mineralization of 4-NP. Given the magnetic properties of the Fe nanoparticles encapsulated inside the CNTs (formed during the CVD synthesis), catalyst separation
