Preparation of nitrogen doped silica photocatalyst for enhanced photodegradation of polychlorinated biphenyls (PCB-209)

Abstract

The development of chemically stable and efficient photocatalyst for persistent organic pollutants (POPs) disposal is highly significant and remains a major challenge. In this work, the nitrogen-doped silica was successfully synthesized and applied for the photocatalytic degradation of PCB-209. The nitrogen-doped silica calcined at 300 °C had the nanometer size with many surface defects, lager BET surface area, pore size, and pore volume than undoped silica calcined at 300 °C, and owned highest photocurrent response and minimum charge transfer resistance among as-prepared materials calcined at different temperature. In addition, the N-doped SiO2-300 catalyst had a smaller band gap (3.45 eV) than undoped-SiO2-300 material. Solution pH, sample dosage, and dissolved organic matter have certain effects on PCB-209 photocatalytic degradation. Additionally, PCB-209 can also be effectively photocatalytic degraded in the three investigated real water matrices. The production of •OH and 1O2 through photocatalysis contributed to PCB-209 degradation, which was demonstrated by the results of electron paramagnetic resonance detection and scavenging experiments. Successive dechlorination and hydroxylation were main reaction mechanisms of PCB-209. The dechlorination efficiency of PCB-209 by the photocatalysis process over N-doped-SiO2-300 reached 82.5%, and the toxicity of photocatalytic degradation products was much less than that of parent compound. In summary, this study can enhance the present understanding on the photocatalytic performance of silica materials, which has great application potential for removal of organic pollutants.