An Effective, Point-of-Use Water Disinfection Device Using Immobilized Black TiO₂Nanotubes as an Electrocatalyst

Abstract

The following study characterized titanium dioxide nanotube arrays (TNAs) annealed in air (air-TNA), nitrogen (N2-TNA) or hydrogen with a nitrogen balance (H2-TNA) for the rapid disinfection of waterborne bacteria. The H2-TNA became black after annealing due to a large concentration of oxygen vacancies, leading to a higher absorbance in the visible light region compared to the air-TNA and N2-TNA. Photoelectrochemical testing showed that the N2-TNA had the highest photocurrent response in the absence of an applied bias; however, under the application of a 6 V anodic bias, the photocurrent response of all the samples was dampened and the dark current of the H2-TNA was ≥50% higher than N2-TNA and air-TNA. The higher defect density in the H2-TNA compared to the other anodes led to the formation of more oxidizing radical species using only an applied bias. Complete inactivation of total coliform and E. Coli from natural creek water was obtained using a 50 ml/min flow reactor containing the H2-TNA after 25 s and under a +6 V potential in the absence of solar illumination.

Development of titanium dioxide nanotube-based arrays for the electrocatalytic degradation and electrochemical detection of emerging pharmaceuticals in water

“…The anodic formation of the TiO 2 -NT arrays are described in detail in our earlier work (Carlson et al [5]); however, the following is an overview of the process. A titanium wire coil (ESPI metals, 99% purity) was used for the degradation array (DA) and titanium foil (ESPI metals, 99% purity) was used for the sensor array (SA).…”

“…Carlson et al [5] demonstrated that annealing TiO 2 -NTs in a reducing atmosphere creates such a high concentration of defects that oxidizing species can be generated in the absence of UV irradiation using only an applied bias. This technique was utilized for the inactivation of bacteria in a multi-channel flow reactor where +6 V was applied to the DA to produce the maximum radical generation without causing physical damage to the NTs.…”

“…0.20 after 1.5 min, corresponding to current densities of ca. 0.30 mA/cm 2 (Carlson et al [5]). Gas bubbles swept from the surface allowed for the DPD dye to interact directly with the highly oxidizing DA surface.…”

“…We have recently demonstrated that defect-laden titanium dioxide nanotube (TiO 2 -NT) arrays are capable of generating hydroxyl radicals under an applied bias in the absence of illumination (Carlson et al [5]). The following report describes the use of TiO 2 -NT in a batch reactor for the degradation of Ibuprofen.…”

Electrochemical Detection of E. coli O157:H7 in Water after Electrocatalytic and Ultraviolet Treatments Using a Polyguanine-Labeled Secondary Bead Sensor

“…The novel focus of this paper is to demonstrate that the electrochemical sensor could be paired with ER sterilization. The disinfection system consists of a defect laden titania nanotube-based reactor that physically destroys waterborne pathogens via the electrocatalytic generation of oxidizing radicals [ 14 , 15 , 16 ]. Cell death occurs in this electrocatalytic reactor (ER) via interaction with oxidizing radical species formed on the surface of the titania anode.…”