SU1033669A1 - Method of removing salts from capillary-porous stone material - Google Patents

Abstract

A METHOD FOR REMOVING SALTS FROM A CONSTRUCTION FROM A CAPILLARY-POROUS STONE MATERIAL, including laying a wick on a surface to be treated, installing a plate anode on it, installing a cathode and supplying a constant electric current, different from the fact that in order to prevent a reduction in the strength of the strength of the unit, it is designed to prevent a reduction in the strength of the strength of the device. the removal of the entire amount of water-soluble salts in the thickness of the structure and the reduction of energy consumption, simultaneously with the application of direct electric current to the electrodes, does not produce intermittent rinsing of the near-anode zone with a fabric wick, the upper end of which is placed in the water tank and the lower end in the reservoir for collecting the filtrate, with the current density applied to the electrodes being 0.01-0.1 mA / cm. WITH QO about: O5 X)

Description

The invention relates to construction and can be used until the durability of the walls of architectural monuments is increased by extracting the most dangerous easily soluble salts.

Methods are known for removing salts that have crystallized on the surface by mechanical cleaning, followed by flushing with a water jet and applying a suction patch made from a material like pyemashe.

There is a known method of extracting salts from a masonry, which consists of covering the treated surface with a layer of liquid clay slurry, after drying it is dry, and the crust with the deposited layers is removed by a metallic brush. However, these methods make it possible to clear only surface layers from salts. Layers that remain in the thickness continue their permissive action and make costly restorations ineffective. There is a known method of electroosmotic drying of walls, foundations of buildings and structures, including monolithing the walls of electrodes, which are placed in two rows in pairs parallel to each other, with the electrodes of each pair being connected to the same ground element. Under the action of the potential difference created by the galvanic cells in this way, the water is squeezed into the ground. A known method of active electro-osmosis is characterized by the use of a source of a constant electric field, the positive terminal of which is connected to the wall electrode and the negative terminal to the ground electrode. This method allows for improved drainage efficiency. However, the use of the foregoing methods of drainage for the purpose of despound-. It is impossible to saltivate the walls of ancient buildings with a content of more than 3-6% by weight (depending on the porosity of the material) in the masonry of water-soluble salts, as with such a salt content, some of them crystallize on the surface of pores and do not lend out. In addition, it is unacceptable for architectural monuments to drill holes for rod electrodes. The closest solution to the technical essence is the known method of removing salts from a building from capillary-porous stone materials by the method of electrodialysis, which is used in the practice of restoration of relatively small and limited in size museum exhibits. The method includes laying the wet cloth wicks on the surface of the pre-moistened object on both sides, installing the following plaster: tin lead electrodes (anode and cathode) and supplying a constant electric current of 2-3 mA / cm density Under the action of the applied potential difference The oppositely charged ions, which rush to the respective electrodes and are retained in the fabric wicks. The wicks are changed every half hour, and the anode wick is wetted with a 1% ammonia solution to neutralize the acid formed at the anode before laying. Thus, a fresco with an area of 1 m and a thickness of 1 cm for 7 hours of treatment according to this method, previously removed from the wall, reduced salinity from 1.5% to hundredths of a percent. However, it is not possible to use the known method for processing large objects (for example, walls of buildings and structures), since under the action of a current density of:,., 2-3 mA / cm in the near-electrode zones, acid and base are formed, respectively, under the action of which the destruction of the surface layer of stone. Even with frequent replacement of wicks and neutralization of the acid with ammonia solution, the pH value at the anode decreases to 3-. Under building conditions, this indicator will have an even lower value, since it is necessary to use electrodes that are commensurate with the size of the wall to maintain a high current density, and replacing the wicks becomes a technically difficult task. In addition, with a high content of water-soluble salts in the masonry, complete desalination cannot be achieved, since there is no source of additional moistening necessary for the dissolution of its salt reserves. The use of a current density of 2-3 mA / cm for the treatment of buildings also entails large energy costs. The purpose of the invention is to prevent a decrease in the strength characteristics of the stone being processed, to remove the amount of water-soluble salts in the thickness of the structure and to reduce energy consumption. The goal is achieved by the method of removing salts from a structure from a capillary-porous stone material, including laying a fabric wick on the surface to be treated, installing a plate anode on it, installing a cathode and applying a constant electric current mankind

the current is produced by continuous washing of the near-anode zone with a fabric wick, the upper end of which is immersed in a tank of water, in the lower one - in a tank for collecting the filtrate, and the density of electric current supplied to the electrodes is 0.01-0.1 mA / cm.

The essence of the method is as follows.

Under the action of a constant electric current of a density of 0.010, 1 mA / cm in the capillary-porous masonry system, electroosmotic squeezing of a solution of salts from small pores into larger ones predominates - draining followed by discharge from the ground by gravitational forces. The work includes the entire thickness of the wall. The criterion for the end of the desalting process is the salt content in the basement of the wall at a depth of 5-10 cm from the surface, determined by chemical analysis of samples,

In the proposed method, in known hm, the normal environment at the anode is maintained not by changing the wick, but by washing, carried out continuously throughout the entire processing time, which ensures that the strength characteristics of the surface layers of the stone are preserved. In addition, rinsing provides additional wall moistening, which is necessary to dissolve the entire supply of salts.

The drawing shows a diagram, explaining the method, which is carried out as follows.

A plate anode 2 is installed along the upper face of the processed area of the wall 1, which can be made of sheet metal, lead or aluminum or another metal, as well as: conductive plastic. The cathode 3 in the form of metal pipes 25 25 cm is placed in the soil adjacent to the foundation at a distance of 2-3 m. A wick A of cotton fabric with high capillary properties is passed between the anode 2 and wall 1. The upper end of the wick 4 is lowered into the water reservoir 5, the lower end is dipped into the reservoir to collect the filtrate 6, which are located respectively and. below the anode. The anode 2 is connected to the positive terminal of the regulated source 7 of direct current, the cathode 3 to the negative. During the entire treatment period, a constant electric current with a density of 0.01-0.1 mA / cm is applied to the electrodes around the clock.

The choice of the optimal current density is carried out in laboratory conditions on artificially salted limestone samples of cm. (Cuioct 3.5% by mass). Electrodes

5 of lead (cm, 5 4 mm) - was pressed through a fabric wick made of cotton knitwear to the ends of the sample using a bandage. The upper end of the wick was lowered into the tank.

0 with water, lower - into the tank for collecting the filtrate. After 15 hours of treatment with a current of different density, the samples were divided into three parts: anodic, medium, and cathodic to determine the average salinity, B

Table 1 shows the results of processing-g. ky

Chemical analysis of filtrate at current densities of 3.0 and 1.0 mA / cm2

0 indicates the presence of a certain amount of electrolysis products, “which is undesirable. In addition, when using the current with a density of 3.0 mA / cm

5 compared with i 0.1 mA / cm, the same result is achieved by a large expenditure of electricity (30 times). Therefore, it is most expedient to conduct a treatment with a current i 0.1 mA / cm, the use of a current i 0.01 mA / cm. Admissible, but the process is much slower.

Example 1, Artificially salted brickwork (From 3.7%)

5 with a size of 0.5x1.0x2.0 (h) m. Was processed for 8 weeks with a current of 0.1 mA / cm density with constant washing of the anode zone with a cloth wick and cotton fabric. The lead anode (0,2d1,0m, $ 2, mm) was fixed with the help of wooden traffic jams and twists along the top of the wall. The cathode in the form of three steel pipes P 3 cm was installed in the ground at a distance of 2 metrog. from the wall. After disassembling the wall in order to determine the salinity in thickness, it turned out that the salt was practically removed from the upper rows (by 95%),

the bottom rows are about 10 less, which can be compensated for by an increase in processing time.

The use of the method allows desalting throughout the thickness of the wall and at the same time maintaining the strength characteristics of stones, which is confirmed by example 2,

Example 2. Artificially salted limestone samples (3x3x5 cm) were treated for 10 hours with a current density of .0.1 and 3.0 mA / cm without changing the wick during the entire treatment period, replacing the wick every half hour and wetting the anode wick 1 % ammonia solution, with continuous prion 3on.

anode cathode anodna middle cathode

After processing, the crushing strength of the surface layer of the samples was compared by the Protod Konova method (see Table 2).

The use of the proposed method will remove from the walls of ancient buildings the destructive water-soluble stone salts and thereby create

conditions for the normalization of their temperature-humidity regime. This will make it possible, with greater technical and economic efficiency, to carry out the restoration and preservation of historical objects, increase the inter-restoration period and ultimately increase the durability of architectural monuments.

Table 1

Desalting 100% by zones

vuw.,

without changing wick 6

with washing 7

Control sample

Table 2

62 64

7.5 4.5

67

67

67

/

X

Claims (1)

METHOD FOR REMOVING SALTS FROM ~ STRUCTURE FROM CAPILLARY-POROUS STONE MATERIAL, including laying on the surface of the fabric wick, installing a plate anode on it, installing the cathode and supplying direct electric current, which is in order to prevent a decrease in strength characteristics processed stone, removing the entire amount of water soluble salts. the thickness of the structure and the reduction of energy consumption, at the same time as applying constant electric current to the electrodes, the anode zone is continuously washed with a fabric wick, the upper end of which is lowered into the reservoir with water and the lower end into the reservoir to collect the filtrate, and the density of the electric current supplied to the electrodes is 0.01-0.1 mA / cm ² . § | a 00 00 about *