Treatment of Polyaniline Wastewater by Coupling of Photoelectro-Fenton and Heterogeneous Photocatalysis with Black TiO₂ Nanotubes

Abstract

In this study, mineralization of organic pollutants in polyaniline (PANI) wastewater was achieved by a combination of photoelectro-Fenton (PEF) and heterogeneous photocatalysis with black TiO 2 nanotubes. Organics were decomposed by the • OH radicals and SO 4 −• radicals formed on the black TiO 2 nanotube photocatalyst and at the IrO 2 /Ti anode during water oxidation and from the Fenton's reaction between Fe 2+ and generated H 2 O 2 . Poor chemical oxygen demand (COD) removal was obtained utilizing visible light/TiO 2 , anodic oxidation with generated H 2 O 2 (AO-H 2 O 2 ), visible light/ black TiO 2 /AO-H 2 O 2 , and electro-Fenton. The mineralization was strongly increased by the PEF/black TiO 2 process because of the photolysis of products under visible light irradiation; it was improved by coupled heterogeneous photocatalysis due to the additional • OH radicals at the black TiO 2 nanotube surface. The results demonstrated that about 96.4% COD and 85% total organic carbon of PANI wastewater were removed after 360 min by the PEF/black TiO 2 process under the optimal conditions. The black TiO 2 nanotubes exhibited good stability as the mineralization ratio in 360 min which was still above 80% after 10 cycles' degradation, showing that the black TiO 2 nanotubes are powerful and promising photocatalysts for improving the removal efficiency of PANI wastewater.

Deactivation and Stabilization Mechanism of Photothermal CO2 Hydrogenation over Black TiO2

“…Figure 1d suggests that the Raman spectrum of TiO 2−x H x included E g , B 1g , and B 1g + A 1g vibration modes, which were manifested in the Ni/TiO 2−x H x and TiO 2 samples. 28 However, for Ni/ TiO 2−x H x and TiO 2−x H x , the peak widths of several Raman peaks are different, indicating that the defect structure will cause a certain shift in the peak position of its Raman vibration. 29 Figures S1 and S2 indicate that Ti, Ni, and O elements were distributed evenly on the surface.…”

Performance Evaluation of Fenton Based Processes in Reducing COD of the Petroleum Effluents Using the Waste of Steel Slag

“…Considering previous researches, little information is available on the performance of the heterogeneous PEF process. On the other hand, in these studies, most experiments have been performed on acidic pH (where catalysts can be partially dissolved) (Khataee, Zarei and Asl, 2010;Khataee and Zarei, 2011;Mousset et al, 2017;Flores et al, 2018;Oriol et al, 2019;Ou et al, 2019;Ye et al, 2019). Thus, the efficiency of this process in neutral pH was also investigated.…”

“…Performance of Fenton-based processes are differen; Comparison between Fenton, EF, Sono-Electro-Fenton (SEF) and PEF processes for phenol removal showed that the degradation efficiency of the processes is as follows: PEF ˂ SEF ˂ EF ˂ Fenton (Babuponnusami and Muthukumar, 2012a). In the Photo Catalysis / PEF hybrid system 85% of TOC and 96% of COD were removed from effluent containing Polyaniline (Ou et al, 2019).…”

Photocatalytic Degradation of Organic Dyes with Magnetically Separable PANI/Fe3O4 Composite under Both UV and Visible‐light Irradiation

“…[16] Polyaniline (PANI) as a p-type semiconductor has been applied as a possible photocatalyst thanks to its high hole transportability, large absorption coefficient in the visible-light region, outstanding redox properties, easy protonation reversibility, fast charge carrier separation, and low-cost production process. [17] Thus, successful utilization of PANI as a visible-lightdriven photocatalyst has been reported for the degradation of organic dyes including MG, [18] Congo red (CR) [19] methylene blue (MB), [20] rhodamine (RhB), [21] and others [16,[21][22] However, the difficulties in separation of PANI-based photocatalysts from solutions as well as the rapid charge recombination and hole weedy photocatalytic process are the main challenges for the practical applications. [16,23] To overcome those issues, it is necessary to design more efficient both UV and visible-lightdriven composite materials that could be simply separated from aqueous solution have been required.…”