Purification of water from heavy metals: methods and devices

Purification of water from heavy metals, undoubtedly,is an important factor for obtaining a liquid ready for use, clean and harmless for humans. Heavy metals include chemical elements that have metallic properties and have a significant atomic mass.

They exert a destructive effect on the functionsorganisms of animals and humans, and also have the property of accumulating in organs and tissues and causing irreparable harm to the health. That is why it is important to install water filters on water treatment plants from iron, copper, lead, nickel, zinc, cobalt, mercury, cadmium and silver.

The need for such filtering is due tothe fact that because of the active use of water for various industries, the concentration of these metals in the runoff is very high. Pollutants have different structure and properties, which means that for each of their species one has to resort to different methods and adaptations.

Purification of water from heavy metals in the form of ionsis produced chemically and is reduced to a change in the acidity level of the medium to the required level. When PH reaches 9.0-10.5, any metals become insoluble and precipitate, which is eliminated quite simply.

The choice of chemical reagents through which industrial water purification is produced depends on the following factors:

- the required degree of purification;

- Concentration of pollutant;

- presence or absence of impurities.

Once the substances are transferred to theinsoluble form, follows the stage of their separation, most often by gravitational deposition of the metal. The operation is performed with the help of special sedimentation tanks, from which the settled particles are pumped out for dehydration and drying. Plus this method in its simplicity, and the minus - in high sensitivity to the presence of foreign compounds, which can interfere with the deposition process. It can be soap, hydrogen peroxide or detergents.

Purification of water from heavy metals is madealso in a different way. It is called "membrane" and is implemented 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 concentrate in the form of a gel-like mass.

It is such a purification of water from heavy metals is rightfully 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 different substances. The septum is semipermeable and lets through it only water, completely freed from foreign impurities. The latter accumulate on the other side of the membranes.

2. The alloy from which the septa is cast is distinguished by its special strength and resistance to chemical influences.

3. The membrane is equally effective and fully performs the assigned functions throughout the period of use. The advantage of the method is that the metal impurities do not settle on the filter surface and do not clog its pores, but in different ways they are removed from the membrane.

The type of such purification is reverse osmosis. This method is distinguished by the fact that a solution is applied to the solution (contaminated water), which exceeds its own. The shortcomings of the method include high requirements to the quality of materials, from which purification plants and complexity are created with the removal of the concentration layer.

Large volume of liquid with negligibleit is expedient to purify the concentration of heavy metals by ion exchange. As is known, its technology is based on the use of ion-exchange resins, on the surface of which metal ions are accumulated. Installations for these works allow the resin to be used for several years, excluding their caking.

The most thorough cleaning method isthe most complicated on the technical execution is cyclic processing with ultrafiltration. True, this method is used only in electrolysis and galvanic plants, whose wastewater contains a huge percentage of waste solutions and is saturated with chelates. For this work, special reactors are used.