N-doped carbon as a highly active and sustainable metal-free catalyst for the enhanced degradation of non-steroidal anti-inflammatory drugs in single and binary systems

Abstract

This work synthesized an N-doped Carbon (NdC) using acetonitrile as a carbon and nitrogen source and zeolite Y as a structure-directing agent. The synthesis was carried out without organic solvents, resulting in carbonization inside and outside the zeolite pores, as confirmed by several characterization techniques. The NdC catalyst presented a remarkable band gap of 0.78 eV, leading to its test as a catalyst in the photodegradation of two widely used pharmaceuticals: ketoprofen (KTP) and ibuprofen (IBP). The optimal reaction conditions were obtained under rather mild conditions, using the natural pH of the solution, a catalyst dosage of 0.1 g L−1, and an initial drug concentration of 40 mg L−1. The degradation kinetics were better represented by the pseudo-first-order model, with high kinetic rate constant (k) values, which were found to be 0.077 min−1 for KTP and 0.091 min−1 for IBP. The NdC catalyst remained stable for reuse in up to 4 cycles, exhibiting excellent removal results for both drugs. Moreover, near-complete mineralization was achieved in 30 min in binary systems. Thus, despite its low surface area, which has shown to be an attractive characteristic for catalysis, NdC was able to present excellent optical properties and remarkable photocatalytic performance, pointing to its high efficiency for the degradation of recalcitrant pollutants, such as KTP and IBP.