Abstract
In this paper we examined the photocatalytic efficiency of a laser-synthesized colloidal solution of ZnO nanoparticles synthesized by laser ablation in water. The average size of the obtained colloidal ZnO nanoparticles is about 47 nm. As revealed by electron microscopy, other nanostructures were also present in the colloidal solution, especially nanosheets. A photocatalytic degradation of UV-irradiated Methylene Blue and Rhodamine B solutions of different concentration in the presence of different ZnO catalyst mass concentrations was studied in order to examine their influence on photodegradation rates. ZnO nanoparticles have shown high photocatalytic efficiency, which is limited due to different effects related to UV light transmittivity through the colloidal solution. Therefore, increasing catalyst concentration is effective way to increase photocatalytic efficiency up to some value where photodegradation rate saturation occurs. The photodegradation rate increases as the dye concentration decreases. These findings are important for water purification applications of laser-synthesized ZnO nanoparticles.
Highlights
Water pollution is one of the greatest ecological problems which is expected to become even larger in the future and occurs due to large amount of industrial waste material released into natural waters
The mass concentration of Zinc oxide (ZnO) inofas-synthesized colloidal calculated according volume of ablated material) was determined from crater semi-profile shown in Figure 1. with a a procedure described in [30].Volume of a crater VZnO remaining on the ZnO target after ablation procedure described in [35]
Colloidal solution synthesized by pulsed laser ablation of ZnO target, which contains mostly ZnO
Summary
Water pollution is one of the greatest ecological problems which is expected to become even larger in the future and occurs due to large amount of industrial waste material released into natural waters. Photodegradation of pollutants (organic or inorganic) into simpler and non-toxic components using photocatalytic materials is a very promising and widely researched technique for wastewater treatment [1]. Zinc oxide (ZnO) is one of the most examined and promising photocatalytic semiconductor materials after TiO2 due to its low cost, high photocatalytic efficiency and non-toxicity [2]. One of the advantages of ZnO over TiO2 is much larger electron mobility ZnO compared to 0.1–4 cm V−1 s−1 in TiO2 ) which contributes to larger photocatalytic efficiency in photodegradation of surrounding pollutants due to rapid electron transfer. The recombination rate of photogenerated electron-hole (e− /h+ ) pairs is large, decreasing their availability for redox reactions with surrounding material and increasing energy dissipation as heat. The main disadvantage of ZnO is the occurrence of Materials 2020, 13, 4357; doi:10.3390/ma13194357 www.mdpi.com/journal/materials
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