Известия Томского политехнического университета: Инжиниринг георесурсов (May 2019)
Destruction of organic compounds in gaseous and liquid media in microwave discharge plasma
Abstract
The paper introduces the results of experimental studies of organic compounds molecular destruction in gaseous and liquid media using a microwave discharge plasma at atmospheric pressure. A microwave plasma generator has been developed and used as a source of plasma discharge. The plasma generator was of guided-wave type with the frequency of 2,45 GHz and power of up to 3 kW. Hydrocarbon gas was used as the gas medium; the water solutions of methylene blue and more complex organic compound in the form of humic substances served as liquid medium. The research was carried out for promoting the plasma generator technology in waste management, cleaning liquid environments from harmful substances, new materials, surface modification of materials, etc. The aim of the research is to study molecular compounds destruction in microwave discharge plasma at atmospheric pressure in such media as petroleum gas, water solutions of methylene blue, and humic substances. Methods: optical spectroscopy, photocolorimetric analysis, analytical chemistry, pH measurement. Results. New materials such as hydrogen, acetylene, ethylene, carbon nanostructured material were generated as the result of destruction of natural gas molecules in microwave discharge plasma. It is shown that nitrogen addition into natural gas increases the destruction level of the natural gas molecules. It also provides a stable operation of the plasma generator. In the experiments the 70 % destruction degree was reached. Air, nitrogen, argon were used as the plasma gases in experiments on destructing water solutions of organic substances molecular compounds. It is shown that destruction of molecular compounds in water solutions of organic substances in plasma is based on redox reactions. It was ascertained that the highest efficiency of the molecular destruction of compounds in the solution takes place when air plasma gas is used. Methylene blue solution reduces the intensity of the color in the visible spectrum at 590 nm and becomes colorless. The mechanism of destruction of organic compounds in water solutions under microwave discharge plasma was offered.
