Simultaneous Removal of Phenol and Cr(VI) by TiO_2 Nanotube Array Photoelectrocatalysis

TiO2 nanotube arrays were prepared by electrochemical anodization on pure Ti surfaces.The products were characterized by X-ray diffraction,scanning electron microscopy and electrochemical workstation.The results showed that the prepared sample was anatase with a diameter of about 100 nm and a tube length of about 2μm.The maximum photocurrent could be achieved when the bias potential of 0.5 V was applied on the TiO2 nanotube array electrode.The photoelectrocatalytic properties of the TiO2 nanotube array electrode were evaluated by the simultaneous removal of phenol and Cr(VI).The effects of catalytic processes,pH values,and various initial concentrations of Cr(VI) and phenol on the removal efficiency of phenol and Cr(VI) were investigated.The results indicated that in the photoelectrocatalytic mode,phenol and Cr(VI) removal ratios were 86.7% and 96.9%,respectively,while in the photocatalytic mode they were 48.2% and 65.2%,respectively.The removal efficiency by photoelectrocatalysis was higher than that by photocatalysis.The acidic solutions were favorable for the photoelectrocatalytic simultaneous removal of Cr (VI) and phenol,and the optimum pH was 2.In the phenol-Cr(VI) co-existed system,phenol and Cr(VI) were more efficiently eliminated than in the single phenol or Cr(VI) system.The reduction of Cr(VI) and the oxidation of phenol produced a synergistic effect,which promoted the simultaneous removal of Cr(VI) and phenol.