Stability of ZnO nanorods coated on the channel wall under continuous flow conditions

The damage given to the ZnO nanorod coating immobilized at the bottom of a rectangular channel by water flow is assessed in this work. The experiments were conducted in complete darkness to determine the inherent stability of the nanorod coating without the interfering effect of UV radiation. The quality and morphology of the nanorod arrays before and after use were determined by x-ray diffraction, scanning electron microscopy; rod breakage, by dynamic light scattering; and the extent of erosion, by concentration and weight measurements. The effect of pH of the flowing water in the range 4pH10, and the effect of the volumetric flow rate in the range, 3.333 cm 3 /s are investigated in this work as parameters. ZnO erosion reaches a low- level plateau in the pH range of 6pH10. Within this range, water velocity and alignment of the nanorods control the extent of dissolution. Dissolution of ZnO nanorods essentially takes place on the polar (0001)-Zn plane of ZnO, resulting in the formation of serrated surfaces. Furthermore, inclined rods joining at the top surface is subjected to further dissolution through pit formation originating at the junction interface, and extending outwards. ZnO nanorod arrays could be used as a photocatalyst in the photocatalytic water treatment processes, where the dissolution from nanorods is in the range of 2.0−2.5 wt% after 24 h of operation under a flow rate of 3.30 cm 3 /s (≈12 L/h), well under the requirements of World Health Organization. Copyright © 2014 VBRI press.