Nanoscale and submicron powder of zinc oxide (ZnO) is known as a highly efficient photocatalyst that is promising for solving the problem of wastewater treatment from toxic organic pollutants including phenol and its derivatives. The results of laboratory studies of ZnO preparation by a simple, energy-saving, and highly productive method of solution–combustion synthesis from a mixture of solutions of zinc nitrate and glycine, as well as the use of the ZnO powder synthesized by combustion for the photocatalytic decomposition of phenol, are presented. The modes and characteristics of combustion, phase composition, chemical composition, and structure of the combustion product at different ratios of glycine with zinc nitrate were determined. It is shown that calcination at 650 °C reduces the content of carbon impurity in the combustion product to ~1 wt.% and leads to obtaining ZnO powder in the form of porous agglomerates up to 100 μm in size sintered from crystalline nanoscale and submicron ZnO particles with an average crystallite size of 44 nm. The ZnO powder exhibits high photocatalytic activity, leading to the almost complete degradation of phenol in an aqueous solution under the action of ultraviolet irradiation in less than 4 h.

The paper presents the results of a detailed study of the process and products of combustion during self-propagating high-temperature synthesis (SHS) of ZnO zinc oxide powder from mixtures of such common reagents as oxidizer zinc nitrate and reducing agent (fuel) glycine, as well as the application of synthesized highly dispersed submicron and nanosized ZnO powder for the phenol photocatalytic decomposition under the action of ultraviolet irradiation. An aqueous solution of a mixture of reagents (the SHS-S process or Solution Combustion Synthesis – SCS) and the gel from a mixture of initial dry reagents formed when they were moistened due to hygroscopicity (the SHS-G process or Gel Combustion Synthesis – GCS) were combusted. The authors studied the phase and chemical compositions, the structure of the combustion product, and the effect of calcination in an oxidizing air medium and grinding in drum ball and planetary-centrifugal mills, as well as in mortar, on them and their photocatalythic activity. The study showed that calcination considerably increases the photocatalytic activity of combustion products due to a significant decrease in carbon impurity in the unburned fuel remains, and grinding in mills reduces the photocatalytic activity due to iron contamination and coarsening of ZnO particle agglomerates. The difference between the photocatalytic activity of the SHS-G and SHS-S products in the phenol decomposition is evident only at the initial stage of ultraviolet irradiation, after which this difference disappears. The authors discuss the direction of further research to increase significantly the photocatalytic activity of zinc oxide synthesized during combustion to use it effectively for the phenol decomposition under the action of visible light.