Zinc oxide nano-enabled microfluidic reactor for water purification and its applicability to volatile organic compounds

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 o5 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.

Direct growth of ZnO nanowires on civil engineering materials:smart materials for supported photodegradation

Photocatalysis is one of the most promising processes for treating air and water pollution.Innovative civil engineering materials for environmental depollution by photocatalysis have already been synthesized by incorporating TiO_(2) or ZnO nanoparticles in cement.This method suffers from two flaws:first,most of the NPs are incorporated into the cement and useless for photocatalysis;second,rain and wind could spread the potentially carcinogenic nanoparticles from the cement surface into nature.Thus,we propose the efficient synthesis of nontoxic and biocompatible ZnO nanostructures solely onto the surface of commercially available concrete and tiling pavements by a low-cost and lowtemperature hydrothermal method.Our samples exhibited enhanced photocatalytic activity for degrading organic dyes in aqueous media,and dye molecules are commonly used in the pharmaceutical,food,and textile industries.Durability studies showed no loss of efficiency after four photocatalysis experiments.Such supported structures,which are easy to implement onto the varying surfaces of commercially available materials,are promising for integration into civil engineering surfaces for environmental depollution in our daily life.