Wet chemical oxidation (HCO3) is one of the most important and effective methods for cleaning and removing organic and inorganic pollutants from the environment and various industrial plants. This process is based on a chemical oxidation reaction in the presence of an oxidizing agent, usually in the liquid phase. Under specific temperature and pressure conditions, and with the action of a strong oxidizing agent, organic compounds and pollutants are converted into simpler and safer substances such as carbon dioxide, water, and inorganic salts.
Since wet chemical oxidation can effectively remove stubborn pollutants, it is considered an effective alternative to some traditional methods such as waste incineration or purely physical methods such as filtration.
History and development
The concept of wet oxidation originated at the beginning of the 20th century. Scientists discovered that many organic compounds readily decompose in aqueous solutions at high temperatures and pressures. Industrial application of this process began in the 1950s. Advances in materials science and reactor design significantly improved its efficiency and safety.
Today, this technology is widely used in industries such as petrochemicals, pharmaceuticals and food processing, as well as in industrial wastewater treatment.
Principle and mechanism of interaction
Wet chemical oxidation is based on the oxidation of organic compounds by oxidizing agents (for example):
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Oxygen (O₂)
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Air
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Hydrogen peroxide (H₂O₂)
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Ozone (O₃)
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Potassium permanganate (KMnO₄)
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Hypochlorite
The properties of these materials depend on the process conditions. Temperature and pressure are typically set between 150 and 370 degrees Celsius and between 0.5 and 22 MPa , respectively , to achieve optimal reaction rates and product yields.
General mechanism:
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Dissolution of pollutants in the aquatic environment
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Activation of oxidizing agents (under the influence of temperature or catalysts)
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It acts on organic compounds and breaks down carbon bonds .
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Formation of intermediate products such as short-chain organic acids
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It eventually transforms into carbon dioxide, water, and stable mineral compounds.
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Design of equipment and systems
The reactors used in this process are typically made of stainless steel or corrosion-resistant alloys and are designed to withstand high pressure and high temperatures.
Main components:
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High-pressure reactor : This is where the reaction takes place.
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Oxidant supply system : air compressor or hydrogen peroxide injection pump
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Heat exchangers : are used for energy recovery and temperature control.
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Safety systems : Safety valves and pressure regulating units
Types of wet chemical oxidation processes
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Non-catalytic wet oxidation:
In this method, only high temperatures and high pressures are used to activate the oxidizing agent. -
In catalytic wet oxidation (CWAO),
catalysts such as metal oxides (e.g., MnO₂, CuO, Fe₂O₃) are used to significantly improve the speed and efficiency of the process. -
Supercritical wet oxidation:
In this process, water temperatures exceed 374 °C and pressures exceed 22.1 MPa. Under these conditions, the physical and chemical properties of the water change, making it a highly reactive solvent and reaction medium.
To use
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It completely removes stubborn pollutants such as phenolic compounds, dyes and pharmaceuticals.
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No dangerous secondary pollutants are produced in this process ( unlike combustion, which releases toxic gases).
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Heat recovery in some structures
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Suitable for various types of wastewater.
Limitations and problems
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High-voltage systems require a high initial investment.
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Due to the high temperature and high pressure, energy consumption is very high.
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If the conditions are not properly controlled, byproducts (e.g., organic acids) can form.
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Equipment corrosion problems in the presence of strong chemicals
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Industrial and environmental applications
Wet chemical oxidation technology is used in many areas, including:
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industrial wastewater treatment
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Wastewater from the petrochemical, textile, pharmaceutical and food industries
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Removal of aromatic compounds, phenols and dyes.
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Hazardous waste management
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Decomposition of toxic and persistent chemicals
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Destruction of chlorine and nitrogen compounds
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Through biological pretreatment,
many complex compounds are converted into simpler, biodegradable substances via wet oxidation. -
Specific applications
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Oxidation of municipal sewage sludge
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Recycling of some valuable materials
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Future prospects
Given global concerns about environmental pollution and the need for sustainable technologies, wet chemical oxidation will play an increasingly important role in the future. Recent research focuses on improving catalysts, reducing energy consumption, and integrating this technology with other processes such as membrane separation or bioreactors.
On the other hand, using renewable energy sources such as solar energy or biomass to generate heat for the process can improve its sustainability.
In conclusion
Wet chemical oxidation is an effective method for removing organic compounds and persistent pollutants from water bodies. In this process, toxic substances are converted into simpler, safer compounds using oxidizing agents under specific pressure and temperature conditions . Despite high initial costs and energy requirements, wet chemical oxidation remains a key technology for pollutant treatment due to its high efficiency and broad range of applications.