Efficient photocatalytic degradation of gaseous N,N-dimethylformamide in tannery waste gas using doubly open-ended Ag/TiO2 nanotube array membranes

• Published in: Applied surface science 2018-06, Vol.444, p.610-620
• Main Authors: Zhao, Yang, Ma, Lin, Chang, Wenkai, Huang, Zhiding, Feng, Xugen, Qi, Xiaoxia, Li, Zenghe
• Format: Article
• Language: English
• Subjects: Doubly open-ended Ag/TiO2nanotube arrays; HS-GC-MS (headspace gas chromatography mass spectrometry); N,N-Dimethylformamide; Photocatalysis; Tannery waste gas
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2018.03.038

•Doubly open-ended Ag/TiNT array membranes are prepared for removal of gaseous DMF.•HS-GC-MS is developed to analyze the degradation process and the organic products.•Photocatalysis of TiNT array is improved with the bottom opening and Ag decorating.•Possible photocatalytic mechanisms and degradation pathways of DMF are proposed.•Actual polluted tannery waste gas can be treated effectively by this photocatalysis. Gaseous N,N-dimethylformamide (DMF), typical volatile organic compound exhausted from manufacturing factories, may damage the health of workers under long-term exposure even at low levels. The defined geometry, porous surface and highly ordered channels make the free-standing anodic TiO2 nanotube (TiNT) arrays particularly suitable for applications of practical air purification by flow-through photocatalysis. In the present work, crystallized doubly open-ended Ag/TiNT array membranes were designed and prepared by employing a lift-off process based on an anodization-annealing-anodization-etching sequence, followed by uniform Ag nanoparticles decoration. For the photocatalytic degradation of gaseous DMF at low concentration levels close to that found in realistic pollutant air, an analytical methodology for the monitoring and determination of degradation process was developed based on the coupling of headspace sampling with gas chromatography mass spectrometry (HS-GC-MS). The doubly open-ended Ag/TiNT arrays exhibited higher removal efficiency of gaseous DMF from air compared with conventional bottom-closed Ag/TiNT arrays and pure bottomless TiNT arrays. These results indicated that the photocatalytic properties of TiNT arrays were improved with the open-bottom morphology and the Ag nanoparticles decoration. Based on the analysis with GC-MS and high performance ion chromatography (HPIC), it was found that demethylation is the main pathway of DMF degradation in photocatalytic reactions. Furthermore, decontamination of actual polluted tannery waste gas collected in leather factory proved that the photocatalysis on doubly open-ended Ag/TiNT array membrane is an efficient way and a promising application to treat air contaminated by DMF despite the complexity of various volatile organic compounds.