märkäoksidointi

Märkäoksidointi, known in English as wet oxidation, is a chemical process used for the treatment of industrial wastewater, particularly those containing recalcitrant organic pollutants. It involves the oxidation of organic matter in an aqueous medium at elevated temperatures and pressures, typically between 150-350 degrees Celsius and 10-20 MPa. The process utilizes oxygen or air as the oxidizing agent.

The primary goal of wet oxidation is to convert harmful organic compounds into less toxic substances, such as carbon dioxide, water, and inorganic salts. This is achieved through a series of complex free-radical reactions. The high temperatures and pressures are crucial for increasing the solubility of oxygen in water and accelerating the reaction rates.

While wet oxidation can be effective for a wide range of pollutants, its main advantages lie in its ability to treat concentrated and difficult-to-biodegrade wastewaters, such as those from the pulp and paper industry, chemical manufacturing, and pharmaceutical production. It can also be used for sludge treatment.

The process can be carried out under subcritical or supercritical conditions. Subcritical wet oxidation occurs below the critical point of water (374 °C and 22.1 MPa), while supercritical wet oxidation occurs above these parameters. Supercritical conditions offer enhanced oxidation efficiency due to the unique properties of water as a solvent. However, these higher temperatures and pressures require more robust and expensive equipment.

Challenges associated with wet oxidation include the potential for scaling and corrosion of equipment, as well as the formation of inhibitory intermediates if not optimized correctly. Despite these challenges, wet oxidation remains a valuable technology for specific wastewater treatment applications where conventional methods are insufficient.