Physical and Chemical Properties, Uses, Advantages and Disadvantages of Ozone
During the oil extraction process, considerable amounts of wastewater are generated from activities such as drilling, fracturing, and crude oil dehydration. This wastewater typically contains organic matter, is black or yellow in color, has odor, and is toxic. If this water is discharged directly, it will cause serious pollution. Therefore, selecting an appropriate treatment process to remove inorganic salts and organic matter, as well as to remove the color from the wastewater, making it clear and meeting relevant standards, is a worthwhile topic for research and experimentation.
Currently, ozone oxidation is a common choice for oilfield wastewater treatment. This article aims to introduce the physical and chemical properties, uses, and advantages and disadvantages of ozone.
1. Physical Properties of Ozone
Ozone is a colorless gas with a fishy odor at normal temperature and pressure. It has a molecular weight of 47.9982, and its solubility in water is more than 10 times that of oxygen. Generally, 1×10-6 of ozone in water corresponds to 1 mg/L. Long-term exposure to ozone concentrations greater than 0.1×10-6 can be harmful to human health.
2. Chemical Structure and Production of Ozone
Ozone (O3) is an allotrope of oxygen, with a V-shaped molecular structure. It is the only element with an asymmetric, paramagnetic, and polar molecular configuration. Ozone can be produced through chemical, ionization, or ultraviolet methods.
3. Oxidizing Properties of Ozone
Ozone is a strong oxidant with a high oxidation potential. In water, its redox potential is second only to fluorine. Fluorine reacts with water to form HF acid, which cannot exist in the environment. Therefore, ozone is the strongest elemental oxidizing agent in water among commonly used oxidants. After oxidizing substances, ozone is converted into oxygen and escapes into the atmosphere without causing pollution, making it an environmentally friendly oxidant.
4. Ozone Related Chemical Reactions
4.1 Ozone Reacting with Inorganic Substances
Except for platinum, gold, iridium, and fluorine, ozone can react with almost all elements in the periodic table. Ozone can oxidize transition metals to higher or the highest oxidation states, forming less soluble oxides. This property is often used to remove heavy metal ions such as Fe2+, Mn2+, Pb, Ag, Cd, Hg, and Ni from wastewater.
4.2 Ozone Reacting with Organic Substances
① Reaction with Cyanides: 2CN- + 3O3 + H2O = 2CO2 + N2 + 2OH- + 2O2
Ozone reacts with cyanides (e.g., polyacrylonitrile) to reduce or eliminate their toxicity by producing carbon dioxide, nitrogen, and oxygen.
② Reaction with Olefin Compounds: R1C=CR2 + O3 → HOO–(R1C)–G + R2C=O
G can be OH, OCH3, OCCH3, etc. The olefin double bond breaks, decomposing into aldehydes and acids.
③ Reaction with Aromatic Compounds:
Ozone reacts with xylene to produce CO2 and H2O. It also reacts with phenol, benzene, naphthalene, and anthracene to form butyraldehyde, oxalic acid, and other organic acids.
④ Reaction with Amino Acids, DNA, and RNA:
Ozone reacts with amino acids to form amino alcohols and damages the molecular chains of DNA and RNA.
⑤ Reaction with Organic Amines:
Ozone reacts with hydroxylamine to form nitro compounds and with amino alcohols to form amino aldehydes and organic acids.
5. Uses, Advantages, and Disadvantages of Ozone's Oxidizing Properties
Ozone is used for sterilization, wastewater treatment, bleaching, decolorization, odor removal, and disease treatment. In water treatment, it is the strongest oxidant. It can disinfect, break down humic substances in water, reduce TOC or toxicity, and improve water quality.
5.1 Advantages:
- Ozone's sterilizing ability is unaffected by pH changes or ammonia.
- Its disinfection and sterilization effects occur almost instantaneously (ozone concentrations of 0.3-2 mg/L in water can kill bacteria within 0.5-1 minute).
- It requires smaller amounts compared to other disinfectants, such as chlorine. To achieve a 99% reduction in E. coli, the required ozone dosage is only 0.0048% of that needed for chlorine.
- Ozone’s strong oxidizing power not only kills bacteria but also reacts with organic substances to remove color, odor, and other organic pollutants.
- A significant advantage is its rapid decomposition and the absence of residual substances, making it an eco-friendly disinfectant for purifying both water and air.
5.2 Disadvantages:
- Ozone is unstable and must be produced on-demand, making it unsuitable for storage and transport.
- It has some toxicity hazards.
- It is corrosive to metals and rubber (it should be stored in corrosion-resistant rubber or stainless steel containers).
