Investigation the effect of anodization voltage on the geometrical properties and photocatalytic activity of TiO2 nanotube arrays for degradation of p-nitrophenol

Abstract

p-nitrophenol (PNP) is a nitroaromatic compound that poses a potential environmental hazard because of its acute toxicity, high carcinogenicity, low biodegradability and cumulative effect. Titanium dioxide (TiO2) nanotubes have shown great potential as ideal and powerful photocatalysts in purification of polluted water due to their high photo oxidation, anti-fogging, nontoxicity, good chemical stability and low cost. Therefore, TiO2 nanotube arrays were fabricated by two-step anodization process at 30,40 and 50V; and were used in photocatalytic degradation of organic pollution p-nitrophenol. In order to have the crystal structure, nanotubes were annealed at 450 °C for 2 hours. Characterizing of TiO2 nanotubes were evaluated by FESEM, XRD and Spectrophotometry analyses. Effect of anodization voltage on nanotube’s length and diameter were investigated. The result showed that as anodization voltage increases from 30V to 50V, nanotube’s length, diameter and wall thickness increase linearly from 1.4 μm to 4.8 μm, 45 nm to 100nm and 15nm to 25 nm, respectively. Increasing in anodization voltage lead to enhancement in porosity (0.4-0.5) and roughness factor (109-194) of TiO2 nanotubes, respectively. By investigating kinetic of degradation of p-nitrophenol, it was observed that mechanism of photocatalytic degradation for all samples are followed first order kinetic. The results indicate that amongst all synthesized samples, 50 V sample with 38%, shows the most efficiency in degradation of p-nitrophenol under UV irradiation.