Comparison of the activation efficiency of peroxymonosulfate on carbon nanotubes modified by carbon nitride vs nitrogen-doping for nonradical degradation of p-hydroxybenzoic acid

Abstract

The carbon nanotubes (CNT) were modified with graphitic carbon nitride (g-C3N4) for the first time to prepare new metal-free composites for peroxymonosulfate activation. The results showed that the modification of CNT with g-C3N4 significantly enhanced the catalytic performance in activating PMS for the degradation of p-hydroxybenzoic acid (HBA)than the traditional N doping. Moreover, the oxidation system was not affected by the water quality factors (e.g., Cl−, NO3−, HCO3−, and humic acid) as it had a high pollutant mineralization rate with the removal of total organic carbon (TOC) was ≈72%, and could effectively remove other pollutants (e.g., ferulic acid, methylparaben, phenol, and paracetamol). The singlet oxygen was the main active species involved in the reaction, indicating that HBA degradation mainly depended on non-free radical oxidation mechanisms.

Keywords

• Metal-free catalysts
• Graphitic carbon nitride-modified carbon nanotubes
• Peroxymonosulfate
• Non-radical activation
• Singlet oxygen