On the big stage of sewage treatment, ozone catalytic oxidants are a "star player". Today, let's talk about what kind of divinity it is, what its strengths are, and what direction it will develop in the future.
1, Classification of Ozone Catalytic Oxidants
Simply put, ozone catalytic oxidants can be divided into two categories: homogeneous catalysts and heterogeneous catalysts.
Let's talk about homogeneous catalysts first. They mainly utilize the catalytic effect of metal ions in solution, such as manganese ions, iron ions, cobalt ions, etc. These metal ions can accelerate ozone decomposition and produce hydroxyl radicals with strong oxidizing properties. But it has a big problem, which is the difficulty in recovering metal ions, which limits its large-scale promotion and use.
Heterogeneous catalysts are mainly composed of solid metals, metal oxides, or metals or metal oxides supported on a carrier. Common metal oxides include aluminum oxide, titanium dioxide, manganese dioxide, etc; Load type materials such as copper and titanium are loaded onto carriers such as alumina and titanium dioxide. Heterogeneous catalysts can be easily separated from water, with less secondary pollution and a simple treatment process, so they are widely used in engineering nowadays.
2, Components of ozone catalytic oxidants
The composition of different types of ozone catalytic oxidants also varies. In heterogeneous catalysts, commonly used carriers include activated carbon, alumina, titanium dioxide, etc. Activated carbon not only has strong adsorption capacity, but also has certain catalytic ability; Aluminum oxide has good stability and high mechanical strength; Titanium dioxide has shown good performance in both photocatalytic and ozone catalytic oxidation. The active ingredients are generally transition metals and their oxides, such as copper, manganese, cobalt, iron, etc. These metals and their oxides can effectively catalyze ozone decomposition and improve oxidation efficiency.
3, Reaction principle of ozone catalytic oxidation
Ozone itself has strong oxidizing properties, with a redox potential of 2.07 eV. Its oxidation process is divided into direct oxidation and indirect oxidation. Direct oxidation refers to the reaction between ozone molecules and pollutants directly; Indirect oxidation is the decomposition of ozone to produce hydroxyl radicals, which then react with pollutants.
In the ozone catalytic oxidation system, the addition of catalyst greatly enhances this process. The heterogeneous catalytic oxidation process generally consists of three steps: the first step is that ozone dissolves into the liquid phase, is adsorbed and activated by the catalyst, and generates hydroxyl radicals; The second step is for the catalyst to adsorb organic pollutants onto the surface, forming surface chelates; The third step is the oxidation reaction between hydroxyl radicals and surface chelates, which degrades organic pollutants.
For example, when treating wastewater containing organic compounds, ozone generates a large number of hydroxyl radicals under the action of catalysts. These radicals act like "little bombs", attacking organic molecules and oxidizing and decomposing large organic compounds into small molecules, even directly oxidizing them into carbon dioxide and water.
4, The effectiveness of using ozone catalytic oxidants
1. Improve the biodegradability of wastewater: For difficult to degrade organic compounds, ozone catalytic oxidants can break some of their cyclic or long-chain molecules into small molecules, making subsequent biochemical treatment more convenient. For example, in the treatment of printing and dyeing wastewater, dye macromolecules that were originally difficult to degrade become easily decomposed by microorganisms after ozone catalytic oxidation, greatly improving their biodegradability.
2. Reduce pollutant concentration: It can directly oxidize easily degradable organic matter into carbon dioxide and water, effectively reducing indicators such as chemical oxygen demand (COD) and total organic carbon (TOC) in wastewater. Data shows that when treating some industrial wastewater, the use of ozone catalytic oxidants can achieve COD removal rates of over 60%.
3. decolorization and deodorization: It is also effective for wastewater with color and odor. Like leachate from garbage, it is black and odorous. After ozone catalytic oxidation treatment, its color and odor are significantly improved.
5, The future development direction of ozone catalytic oxidants
1. Developing high-performance catalysts: In the future, efforts will be made towards improving catalyst activity, stability, and selectivity. For example, by using nanotechnology to prepare nanoscale catalysts, increasing the specific surface area and improving catalytic activity; Or develop composite catalysts that combine multiple active ingredients together to achieve synergistic effects.
2. Expand application areas: In addition to sewage treatment, there will also be more exploration in areas such as drinking water purification and air purification. For example, removing trace organic pollutants from drinking water and purifying air contaminated with ozone.
3. Combined with other technologies: Combined with biological treatment technology, membrane separation technology, etc., to further improve treatment efficiency and reduce costs. For example, the combination of ozone catalytic oxidation and biological aerated filter (BAF) can first use ozone catalytic oxidation to decompose recalcitrant organic matter, and then use BAF for biological treatment, which can achieve better water purification effect.
