This paper reports fast and efficient chemical decontamination of water within a tree-branched centimeter-scale microfluidic reactor. The microreactor integrates Zinc oxide nanowires (ZnO NWs) in situ grown acting as an efficient photocatalytic nanomaterial layer. Direct growth of ZnO NWs within the microfluidic chamber brings this photocatalytic medium at the very close vicinity of the water flow path, hence minimizing the required interaction time to produce efficient purification performance. We demonstrate a degradation efficiency of 95% in o 5 s of residence time in one-pass only. According to our estimates, it becomes attainable using microfluidic reactors to produce decontamination of merely 1 l of water per day, typical of the human daily drinking water needs. To conduct our experiments, we have chosen a laboratory-scale case study as a seed for addressing the health concern of water contamination by volatile organic compounds (VOCs), which remain difficult to remove using alternative decontamination techniques, especially those involving water evaporation. The contaminated water sample contains mixture of five pollutants: Benzene; Toluene; Ethylbenzene; m-p Xylenes; and o-Xylene (BTEX) diluted in water at 10 p.p.m. concentration of each. Degradation was analytically monitored in a selective manner until it falls below 1 p.p.m. for each of the five pollutants, corresponding to the maximum contaminant level (MCL) established by the US Environmental Protection Agency (EPA). We also report on a preliminary study, investigating the nature of the chemical by-products after the photocatalytic VOCs degradation process.

Phone: þ331 6095 7276, Fax: þ331 6095 7297A study of the ZnO nanowire array photocatalysis performance has been carried out under UV radiation for the degradation of the toxic organic compounds such as methylene blue (MB), methyl orange (MO), and acid red 14 (AR14) dyes, which are commonly used in textile and pharmaceutics industries. UV-Vis spectrometry has been used to follow the dye degradation characterization. The degradation mechanism has been proposed for each dye, which will give a reasonable explanation about different degradation degree under same experimental conditions. MB and AR14 showed a better degradation performance than MO.

Abstract:In order to improve the photocatalytic efficiency of ZnO nanowires, iron-doped ZnO nanowires (ZnO:Fe NWs) were successfully synthesized. The morphology, optical properties and photocatalytic performance of ZnO:Fe NWs were studied by scanning electron microscopy (SEM), UV-Visible spectrophotometry and photoluminescence spectroscopy (PL), respectively. The SEM observations showed that the morphology of the ZnO NWs was not modified by iron doping, but the band gap was reduced from 3.29 eV for ZnO NWs to 3.25 eV for ZnO:Fe NWs. This band gap reduction allows the semiconductor to harvest more photons to excite more electrons in the valence band; subsequently, resulting in an improvement of the degradability of the understudied organic dyes: methylene blue (MB), methyl orange (MO), and acid red 14 (AR14). The photocatalytic study showed that the photo-degradation rate of the MB, MO, and AR14 was improved 9%, 20%, and 5% respectively by 1% iron doping in the ZnO NWs.

Two types of ZnO nanostructure have been fabricated to make a comparative study on their gas sensing performance: the conventional ZnO nanowire arrays were synthesized by hydrothermal method and the hierarchical ZnO nanowires/nanofibers nanostructures were prepared through a combination of the hydrothermal and electrospinning methods. Field emission scanning electron microscopy study showed a quiet homogeneous morphology both for both nanostructures. Three kinds of commonly used gases, such as ethanol, acetone and ammonia were chosen for ZnO nanostructure gas sensing property study. The UV‐Visible spectroscopy measurements showed a higher detection sensitivity of ZnO NWs for ammonia compared to ethanol and acetone, and an enhanced sensing performance for the hierarchical nano‐ structure, which has a higher surface to volume ratio. On the other hand, the enhancement was more obviously in the case of ethanol sensing. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)