Facile fabrication of crescentic ZnO nanorod-based photo-catalytic micro-fluidic reactors

Abstract

With a ZnO nanorod (ZnONR)-coated glass rod in diameter 8 mm inserted into a glass tube in diameter 9 mm and the bare glass rod into the ZnONR-coated inner surface of the glass tube, two types of crescentic ZnONR-based micro-fluidic reactors were readily constructed at a low cost. In presence of ultraviolet (UV) light and at different volume flow rate Q aqueous methylene blue (MB) solution was degraded with the ZnONR-based micro-fluidic reactors hydrothermally synthesized at varied Zn2+ concentration of the growth solution. It is found that the crescent-shaped micro-channel facilitates adequate MB mass-transport and plentiful UV irradiation. The optimal Q exists at which sufficient MB species transport towards and are fully adsorbed on the ZnONRs. The Zn2+ concentration of the growth solution remarkably influences the contact angle (CA) of the ZnONRs and the solid-liquid contact surface area of the ZnONRs with aqueous MB solution, and further the reaction constant K of the micro-fluidic reactors. The largest K values of two kinds of the micro-fluidic reactors were determined to be 1.30 and 1.23 min−1 at both Q value 50 μl/min of aqueous MB solution and Zn2+ concentration 50 mM of the growth solution. The cost-effective crescentic micro-fluidic reactor has potential to be used to photo-degrade other organic pollutants in waste water with high photo-degradation efficiency.