Ozone removal of iron and manganese

Brief description of iron and manganese removal technology <br> China has abundant groundwater resources, and many towns and industrial and mining enterprises use groundwater as a water source. However, according to incomplete statistics, there are 18 provinces and municipalities that contain excessive amounts of iron and manganese in groundwater, which is not in line with the needs of industrial production and people's lives. Therefore, groundwater iron and manganese removal occupies an important position in the water treatment technology.
Over the past decades, through the efforts of the majority of domestic scientific and technological workers, great progress has been made in the research of groundwater removal of iron and manganese, and the degree of practicality is also quite high. However, it should be pointed out that all kinds of process equipment based on the contact oxidation method still have shortcomings such as large equipment and large process space for many years.
Applying ozone technology to the iron and manganese removal process, aiming at the deficiencies of the original traditional process, trying to solve the problem of large volume of process equipment and large infrastructure - low process efficiency, in order to develop a new technology for groundwater removal of iron and manganese. Program.
Second, the reaction of ozone and inorganic substances <br> In addition to platinum, gold, antimony, fluorine, ozone can almost react with all elements of the periodic table. Ozone can oxidize transition metal elements to higher or high oxidation states, forming more insoluble oxides. Therefore, we can often use this property to treat heavy metals such as Fe2+, Mn2+ and Pb, Ag, Cd, Hg and Ni in sewage. Ion removal.
The abundance of Fe and Mn in the earth's crust is large, and their main oxidation states exist in the form of Fe3+ and Mn4 +, but their reduced states (such as MnCO3 and FeCO3) can exist in water. The removal of iron and manganese is mainly carried out by filtering the soluble ions into precipitates (Fe(OH)3 and MnO2).
According to the equilibrium distribution of the pH of Fe in water, it is known that at neutral pH, the conversion of reduced Fe to oxidized Fe is thermodynamically allowed; therefore, Fe2+ can be easily oxidized by O3.

The reaction formula indicates that 0.43 mg of O3 is required for oxidation of 1 mg of Fe2+. Since the former is the initiator of the latter decomposition, the reaction should be carried out by electron transfer.
In 1983, Harr et al. proposed the proposed reaction mechanism (omitted).
According to the equilibrium distribution map of Mn in water, Mn is more difficult to oxidize than Fe, and the dosage should be at least 0.8-1.2 mg (O3) / 1 mg (Mn). The reaction system should consider a combination of complex processes such as O3-UV technology.
Converted into the habit of tons of water treatment: calculated as 2mg per liter of iron and manganese, you can calculate the amount of 3 - 3.5g / t; to simplify the calculation and win the design, the amount can be reduced to 4g / t. The value of water treatment for different iron and manganese content can be deduced by analogy.
III. Feasibility analysis of ozone process application 1. At present, almost all iron and manganese removal processes are based on contact oxidation method – whether it is air pressure method, jet method or natural water drop method, by using as high efficiency as possible. The oxygen component in the air is used to oxidize iron and manganese in the water to form insoluble oxides and then filter out.
2. Ozone is an isomer of oxygen, which has strong oxidizing properties. The redox potential of 2.07 is second only to fluorine, and the redox potential of oxygen is only 1.23. It can be seen that ozone is a practical industrial oxidant.
3. Under normal temperature and normal pressure, the solubility of ozone in water is 13 times that of oxygen - only a huge difference in process efficiency can be seen.
4. Ozone has the functions of disinfection, sterilization, decomposition of organic matter and micro-flocculation in water treatment, which embodies multiple process effects and is multi-purpose for one machine. This is irreplaceable in any traditional process.
5. Compared with the traditional process, the oxidation rate is greatly improved, the requirements on the filter material composition are reduced, and the bulky air device and space are not required, and the operation can be almost performed without noise.
6, according to its chemical characteristics, can adapt to more complex water quality.