Advanced oxidation technology mainly achieves degradation and mineralization of refractory organic matter by generating hydroxyl radicals (OH: E0 = 2.8 V). Common AOPs include Fenton oxidation, ozone oxidation, photocatalytic oxidation, and electrochemical oxidation. Compared with other AOPs, ozone has strong oxidizing capability and can react directly (O3: E0 = 2.07 V) or indirectly generate OH to react with compounds in wastewater. Ozone oxidation features high reaction efficiency and no secondary pollution, and can effectively disinfect and decolorize in wastewater treatment; hence it is widely used for high-concentration and refractory organic wastewater such as municipal, industrial, papermaking, and dye-industry wastewaters.

Traditional ozone oxidation processes have drawbacks such as low gaseous ozone utilization, poor process selectivity, and incomplete organic oxidation. Therefore, it is necessary to develop improved ozonation processes that both enhance ozone mass transfer and promote OH generation. Studies show that adding a catalyst during ozonation promotes generation of the active species OH and improves ozone's direct oxidation capability, achieving advanced treatment of organic pollutants. As shown in Figure 1, based on the different forms of the catalyst in solution, ozone catalytic oxidation can be divided into homogeneous and heterogeneous ozone catalytic oxidation.

Figure 1. Classification of ozone catalytic oxidation technology

Homogeneous catalysts can be added to synergize with ozone oxidation; their catalytic mechanisms can be divided into two types:

1 Transition-metal ions catalyze ozone to generate more OH;

2 Complexes form between the catalyst and organic matter or ozone, increasing the contact time and reaction efficiency between ozone and pollutants.

However, in practice the catalyst metal ions are difficult to recover, sludge generation is large causing secondary pollution, and water treatment costs are high, all of which limit homogeneous ozone catalysis.

Figure 2. Pathways by which catalyst and ozone act on organic matter in a heterogeneous catalytic oxidation system

To solve the above problems, SINOKLE independently developed a heterogeneous Fenton catalyst and obtained a patent grant, fixing catalytic transition-metal ions onto a solid catalyst carrier through doping, adsorption, and grafting modification. The transition-metal ions used include one or several of Cu, Fe, Mn, Co, Zn, Ce, Ni, and Cr.

The main mechanisms by which such catalysts catalyze ozone oxidation are:

1 The solid catalyst catalyzes ozone to generate more OH to oxidize pollutants;

2 Organic pollutants adsorb onto the solid catalyst, facilitating reaction between ozone and pollutants;

3 The catalyst's adsorption and catalysis jointly degrade organic pollutants;

As shown in Figure 2, ozone decomposes at the Lewis centers of metal oxides (such as Al2O3, TiO2, etc.); ozone decomposition occurs on the hydroxyl groups on the metal-oxide surface, and these active sites are regarded as potential catalytic centers promoting ozone decomposition. Therefore, the performance of supported catalysts mainly depends on the synergy between catalyst and carrier.

Figure 3. SINOKLE's proprietary patented heterogeneous ozone oxidation catalyst

Through extensive experiments and engineering validation, SINOKLE's heterogeneous catalyst optimizes the proportioning of components to develop a catalyst with high adaptability and catalytic activity. Using multi-stage precisely temperature-controlled sintering, it maintains activity while improving stability, effectively reducing loss during use and preventing secondary pollution. A special pore-forming technique yields a specific surface area above 250 m2/g; oxidation efficiency is 2-5x that of ozone oxidation alone, and it is resistant to contamination, scaling, and clogging with a service life exceeding five years, enabling long-cycle operation.