Green fluid—process in the synthesis of nanomaterials from supercritical water and their environmental applications

Abstract

Nanomaterials are emerging as important contributors in various applications and can be used especially in environmental catalysis. Herein, a brief summary on the basic knowledge of supercritical hydrothermal synthesis (SCWHS) is presented, including the synthesized functional nanomaterials, the effects of different experimental conditions on the properties of nanoparticles, and examples of their applications in environmental catalysis, highlighting the environmental and economic advantages of SCWHS. This review focuses on supercritical water as an environmentally friendly particle engineering tool for the production of high-quality, high-yield nanoparticles and the possibility of achieving their continuous production in industry. Nanoparticles are nucleated within a short time and their particle size can be controlled by SCWHS. Therefore, attention is given to the relationship between the formation and experimental conditions, as well as the properties of the obtained material in terms of particle size, surface area, crystallinity, morphology and surface properties. In addition, SCWHS can combine organic wastewater treatment, waste resource utilization and nanoparticle synthesis, and the in situ-generated nanoparticles can promote the oxidation of organic wastewater and the resourceful conversion of solid wastes as well as have production value as a by-product. The work may provide guidance for the further development of SCWHS, preparation of functional nanomaterials, and exploration of multiple applications.