Water purification from heavy metals is undoubtedly an important factor for obtaining a ready-to-use, clean and harmless to human fluid. For heavy metals include chemical elements that have metallic properties and at the same time have a significant atomic mass.
They have a destructive effect on the functions of animal and human organisms, and also tend to accumulate in organs and tissues and cause irreparable harm to health. That is why it is important to install water filters from iron, copper, lead, nickel, zinc, cobalt, mercury, cadmium and silver in water treatment plants.
The need for such filtering is due to the fact that due to the active use of water for various industries, the concentration of these metals in the stock is very high. Contaminants have a different structure and properties, which means that for each of their types it is necessary to resort to different methods and devices.
Water purification from heavy metals in the form of ions is made by chemical means and is reduced to a change in the level of acidity of the medium to the required. When the PH value is reached
The choice of chemicals by which industrial water treatment is performed depends on the following factors:
– required degree of purification;
– pollutant concentrations;
– the presence or absence of impurities.
After the substances have been converted to an insoluble form, a stage of their separation follows, most often with the help of gravitational metal deposition. The operation is performed using special precipitating tanks, from which the settled particles are pumped out for dehydration and drying. The advantage of this method is its simplicity, and the minus is highly sensitive to the presence of extraneous compounds that can interfere with the precipitation process. These can be soap, hydrogen peroxide or detergents.
Water purification from heavy metals is also done in another way. It is called “membrane” and is carried out using a special installation with partitions. As a rule, in water purified by membranes, the concentration of metals does not exceed 1 mg per liter, and on the other side of the filter they themselves are concentrated in the form of a gel-like mass.
It is this kind of water purification from heavy metals that is considered to be the most effective and promising. Its high quality is due to the special properties of the membranes, such as:
1. High selectivity, or, in other words, the ability to separate substances with different properties. The partition is semi-permeable and passes only water completely free from impurities. The latter accumulate on the other side of the membranes.
2. The alloy from which the partitions are cast is distinguished by special strength and resistance to chemical attack.
3. The membrane is equally effective and fully performs its functions throughout the entire period of use. The advantage of the method is that metal impurities do not settle on the filtering surface and do not clog its pores, but are removed from the membrane in various ways.
The kind of cleaning is reverse osmosis. This method differs in that a pressure is applied to the solution (polluted water) that exceeds its own. The disadvantages of the method include high requirements to the quality of the materials from which purification plants are created and the difficulty in removing the concentration layer.
A large volume of liquid with a low concentration of heavy metals is advisable to be purified by ion exchange. As is known, its technology is based on the use of ion exchange resins, on the surface of which metal ions accumulate. Installations for these works allow operating resin for several years, excluding caking.
The most thorough purification method is the most complex in technical design cyclic treatment with ultrafiltration. However, this method is used only in electrolysis and electroplating industries, the wastewater of which contains a huge percentage of waste solutions and is saturated with chelanites. For such work use special reactors.