Crystalline ZnO Photocatalysts Prepared at Ambient Temperature: Influence of Morphology on p-Nitrophenol Degradation in Water

Julien G Mahy,Sophie Hermans,Tommy Haynes,Raphael Henrique Marques Marcilli,Nathalie Body,Benjamin Elias,Charles-André Fustin,Simon De Kreijger,Louise Lejeune

doi:10.3390/catal11101182

Abstract

Since the Industrial Revolution, technological advances have generated enormous emissions of various pollutants affecting all ecosystems. The detection and degradation of pollutants has therefore become a critical issue. More than 59 different remediation technologies have already been developed, such as biological remediation, and physicochemical and electrochemical methods. Among these techniques, advanced oxidation processes (AOPs) have been popularized in the treatment of wastewater. The use of ZnO as a photocatalyst for water remediation has been developing fast in recent years. In this work, the goals are to produce ZnO photocatalysts with different morphologies, by using a green sol-gel process, and to study both the influence of the synthesis parameters on the resulting morphology, and the influence of these different morphologies on the photocatalytic activity, for the degradation of an organic pollutant in water. Multiple morphologies were produced (nanotubes, nanorods, nanospheres), with the same crystalline phase (wurtzite). The most important parameter controlling the shape and size was found to be pH. The photoactivity study on a model of pollutant degradation shows that the resulting activity is mainly governed by the specific surface area of the material. A comparison with a commercial TiO2 photocatalyst (Evonik P25) showed that the best ZnO produced with this green process can reach similar photoactivity without a calcination step.

Highlights

Too often poorly appreciated and considered as an almost inexhaustible resource, water is becoming a scarce commodity [1]
The Z14 sample, composed of hexagon, presents a high normalized photoefficiency that is ten times higher than P25. These results suggest that if the surface area of the Zinc oxide (ZnO) samples could be increased, an activity much higher than the one of Evonik would be obtained
ZnO nanoparticles were synthesized by a sol-gel process, in order to obtain different morphologies in green conditions

Summary

Introduction

Too often poorly appreciated and considered as an almost inexhaustible resource, water is becoming a scarce commodity [1]. Its excessive and disproportionate use in some regions of the world, combined with the overall increase in the population, adds increasing pressure on water reserves and increases the general level of aqueous pollution. To face these problems, treating and decontaminating wastewater for reuse appears to be a promising solution [2,3,4]. Depending on the type and quantity of pollutants present, as well as the volume of water to be treated, various treatment methods can be used [5]. This work will focus on organic pollutants and the associated degradation processes

Methods

Results

Conclusion