Efficient Degradation of High-COD Wastewater: Ozone Catalytic Oxidation Technology Explained
Mechanism of COD reduction in wastewater by ozone treatment
Ozone has extremely strong oxidizing power, with an oxidation-reduction potential of up to 2.07 eV. The oxidation proceeds mainly through two pathways: direct reaction of ozone molecules with pollutants, and reaction of hydroxyl radicals produced by ozone decomposition with pollutant molecules. Although ozone alone can remove organics to a certain extent, its utilization rate is limited and pollutant removal is often insufficient.
Ozone catalytic oxidation technology adds a catalyst to the ozone system to greatly increase ozone decomposition efficiency and thus generate large amounts of hydroxyl radicals (-OH), which decompose organics in water non-selectively. It is an innovative method developed to overcome the insufficient oxidation efficiency of ozone alone.
The catalyst's function in ozone oxidation is mainly to promote the conversion of ozone into hydroxyl radicals with stronger oxidizing power, thereby significantly improving overall oxidation performance.
The core principle is to use catalytic materials to convert the strong oxidant ozone into hydroxyl radicals (-OH) with non-selective oxidation characteristics. Hydroxyl radicals are more oxidizing than ozone molecules and react non-selectively, effectively decomposing various organic pollutants in wastewater. In the catalytic system, ozone and wastewater enter the catalytic oxidation tower together and flow upward through the catalytic packing layer, where large amounts of hydroxyl radicals are generated. These radicals transform refractory macromolecular organics into small molecules through chain scission and ring opening, and further mineralize them into carbon dioxide and water. Ozone finally decomposes into oxygen with no secondary pollution, ensuring effluent quality meets discharge standards.
By form, ozone catalysts can be divided into homogeneous and heterogeneous types. Homogeneous catalysts mainly rely on the catalytic function of metal ions in solution, while heterogeneous catalysts usually use solid metals, metal oxides, or metals and metal oxides supported on carriers as active components. These catalysts enable ozone to directly oxidize organics into CO2 and H2O, or decompose macromolecular organics into more easily treatable small molecules.
With the introduction of the catalyst, both ozone utilization efficiency and organic mineralization capacity are significantly improved. Using a composite porous high-strength silicon-aluminum-titanium material as the carrier, plus catalytic components that do not easily dissolve out, enhances catalyst stability and mechanical strength, extends service life, and eliminates the hassle of periodic dosing. The catalyst also has a large specific surface area and large treatment capacity, extends the contact time between wastewater and catalyst, saves floor space, and can be flexibly adjusted according to fluctuations in water quality and quantity, with outstanding adaptability and shock-load resistance.
Common ozone catalysts on the market fall into the following categories by carrier:
Ceramsite/clay type: physical bonding, poor physical strength, catalyst easily lost, short service life;
Activated carbon type: physical bonding, catalyst easily lost, short service life; columnar shapes increase head loss during backwashing;
Silicon-aluminum composite type: formed by introducing partial alumina onto the traditional ceramsite carrier, it is an upgraded version of the ceramsite-support catalyst, with low production cost, relatively high strength and hardness, and lower abrasion than ceramsite; however, it still wears and sheds powder easily, and powder shed from some packing can color the effluent.
Activated alumina type: the matrix and catalytic components are bonded chemically, so catalytic components are not easily lost; long service life, strong anti-pollution capability under neutral conditions, stable performance.
Shenzhen SINOKLE uses various transition metal oxides and precious metals as catalytic components, showing excellent adaptability and high catalytic activity for different wastewaters. It catalyzes efficient ozone conversion to produce -OH, with oxidation efficiency 2-5 times higher than conventional ozone catalytic oxidation; this technology can effectively reduce wastewater COD.
Key technical innovations of the high-efficiency heterogeneous catalyst:
(1) Uses various transition metal oxides as catalytic components; through extensive experiments and engineering verification, the material ratios are adjusted so that the catalyst has excellent
adaptability to different wastewaters while providing high catalytic activity;
(2) Adopts medium-low temperature sintering technology, which, while preserving the active components, effectively reduces production energy consumption and the loss rate of the catalyst during use, preventing secondary pollution;
(3) Uses high-activity component materials as the catalyst carrier with a porous structure providing a high specific surface area, and dopes in catalytic components that do not easily leach out, improving catalyst stability. The carrier has high mechanical strength and long service life.
(4) The catalyst effectively lowers the reaction activation energy, achieving deep oxidation and maximizing removal of organic pollutants.
(5) It can accelerate the self-decomposition of ozone in water and increase the concentration of -OH produced in water, thereby improving ozone oxidation performance, with oxidation efficiency 2-5 times higher than ozone oxidation alone.
(6) Adopts atomic deposition technology to modify the catalyst; the catalyst carrier has super hydrophilicity, so the catalyst is not easily contaminated, scaled or clogged and can operate over long cycles.
