Application and Practice of Ozone Oxidation Technology in Wastewater Treatment
With its strong oxidizing property (standard electrode potential E₀ = 2.07 V), ozone can effectively degrade organic and inorganic pollutants in water. Early applications focused mainly on sterilization and removal of microbial communities from drinking water or secondary effluent. As ozone generation equipment continued to improve, producing ozone from air became possible, significantly reducing operating costs and driving widespread attention to this technology in wastewater treatment research in recent years. It is generally accepted that ozone oxidizes organics in water mainly through two pathways.
1. Direct oxidation
The ozone molecule has two structural forms and can participate in reactions both as an electrophile and as a nucleophile. Direct oxidation is generally considered to involve electrophilic substitution, nucleophilic addition and cycloaddition, with reactivity in the order: chain hydrocarbons > amines > phenols > polycyclic aromatic hydrocarbons > alcohols > aldehydes > alkanes.
Two structures of the ozone molecule
2. Indirect oxidation
Ozone is less stable in aqueous environments and tends to decompose. The process involves three stages — chain initiation, chain propagation and chain termination — and generates more strongly oxidizing reactive free radicals during decomposition, especially hydroxyl radicals (·OH). This process is affected by multiple factors such as pH, temperature, and inorganic and organic concentrations. Certain substances in water can promote or inhibit free radical generation, and are classified into initiators (e.g., H₂O₂, OH⁻, UV radiation), promoters (e.g., humic acid, ferrous ions, methanol) and inhibitors (e.g., HCO₃⁻, PO₄³⁻, tert-butanol).
Although ozone oxidation has achieved results in many fields, the inherent limitations of the ozone-only process constrain large-scale adoption, mainly including: selectivity of the oxidation process, difficulty achieving complete mineralization of organics, limited utilization due to low water solubility, and the ease of forming small-molecule acidic by-products during the reaction.
To overcome these technical bottlenecks, researchers have made improvements in two directions: one is to couple auxiliary technologies such as UV radiation and electrochemistry to enhance ozone decomposition efficiency; the other is to introduce catalysts to accelerate ozone decomposition, such as adding Fe²⁺ and Mn²⁺ metal ions. However, homogeneous catalysts require subsequent disposal of the metal ions, increasing treatment costs. Heterogeneous catalytic ozone oxidation technology has therefore emerged.
In heterogeneous catalysis research, solution pH, reaction temperature, ozone dosage, catalyst dosage and the concentrations of natural organics and inorganic ions in the water are the main influencing factors. Based on an in-depth analysis of heterogeneous ozone catalytic mechanisms, SINOKLE has integrated multiple active metal oxides, high-porosity microporous molding processes, hydrophilic anti-fouling and anti-clogging and other key technologies to successfully develop a series of high-efficiency heterogeneous ozone catalysts tailored to the characteristics of organic wastewater in different industries.
High-efficiency heterogeneous ozone catalyst
Combining the ozone catalytic oxidation-cyclonic integration technology, SINOKLE has developed the CDOF (Cyclonic Dissolved Ozone Flotation) integrated cyclonic dissolved-air flotation unit, which creatively combines ozone advanced oxidation, cyclonic flow and dissolved-air flotation technologies to achieve efficient, comprehensive removal of various difficult-to-treat wastewaters.
The unit comprehensively integrates ozone multi-catalytic oxidation (homogeneous and heterogeneous catalysis), cyclonic flow technology, dissolved-air flotation, fully enclosed fully automatic pressurized catalytic oxidation, supercritical catalytic oxidation, high-efficiency heterogeneous catalysts, cavitation supercritical catalysis and high-efficiency flocculation, achieving good comprehensive treatment of various pollutants.
CDOF unit and application cases
This wastewater treatment unit offers high ozone utilization, fast reaction rates and short reaction times, a small footprint, few supporting facilities, a high degree of automation, safety and environmental protection, and low overall investment. It can be widely used for wastewater treatment in petroleum refining, the new energy industry, municipal landfill leachate and other sectors, providing professional solutions for wastewater treatment in different fields.
