SU1125295A1 - Method for preparing iron hydroxide - Google Patents

Abstract

A METHOD FOR PREPARING IRON NECKPROXIDE by passing an electric current through iron electrodes placed in an electrolyte, characterized in that, in order to increase the purity of the product and to obtain particles with a size of 0.5-1.0 µm, distilled water with electrical conductivity is used as electrolyte 210-610 cm-cm; and the process is conducted in a galvanostatic mode with a current density of 0.010, 1 mA / cm with a change in the polarity of the electrodes.

Description

This invention relates to electrochemistry, in particular, to fine suspended suspensions of metal hydroxides under laboratory conditions.

A known method for producing metal hydroxides, in particular iron, from an aqueous solution of salts by alkalizing lj,

However, the duration of the process is noted. This method requires a large number of washes until the final removal of the anion salt, which is taken to produce hydroxide. At the same time, it is impossible to obtain a fine suspension with a particle size of from 0.5 to 1 micron. In addition to this, the method does not provide the possibility of continuous dosing of a fine suspension of a given concentration. In order to separate the fine suspension, an additional step of filtering through filters with a certain pore size is required.

There is also known a method for producing iron hydroxide by electrolysis of aqueous solutions of chlorides using iron electrodes. In this case, electrolysis is carried out with alternating current. The process is as follows. If, for example, electrolytes with iron electrodes are exposed to saline solution, then in the first fraction of a second at the anode cool reacts with the metal of the electrode and forms first FeCl2, and then FeCl ", which hydrolyzes with water to form a precipitate acids. At the same time, caustic sodium is obtained at the cathode. In the next split second, the current changes in direction, the anode becomes the cathode and NaOH begins to expand around it, the cathode becomes the anode and hydrochloric acid and iron oxide hydrate form around it, which is poorly soluble in water and therefore precipitates as flakes and When the current direction is changed, NaOH reacts with hydrochloric acid formed near the anode. After this, the cycle of electrolysis of salt begins again 2.

The iron oxide hydrate obtained in this way does not possess the necessary purity, since chloride cannot be excluded in the resulting product. In addition, the known method does not allow obtaining a fine suspension with a particle size of 0.5-1.0 µm due to the fact that the resulting product precipitates in the form of flakes.

The purpose of the invention is to increase the purity of the product and obtain particles with a size of 0.5-1.0 µm.

The goal is achieved by the fact that according to the method of obtaining iron hydroxide by passing an electric current through electrodes made of iron and placed in an electrolyte, distilled water with an electrical conductivity of 2 10 cm-cm is used as an electrolyte and the process is conducted in galvanostatic mode with a current density of 0, 01-0, 1 ÅCHA / cm when changing the polarity of the electrodes.

When voltage is applied at the cathode, hydrogen is 2 + 2 2 OH. At the anode Fe - + 3 OH- Fe (OH). The use of distilled water eliminates the possibility of ingress of foreign ions into the product and thereby ensures a decrease in the purity of iron hydroxide.

The proposed method can be carried out as follows. Distilled water with electrical conductivity 2 is poured into the electrolyzer supplied with bipolar iron electrodes. 6. 10 See cmPh. A constant current with a density of 0.01-0.1 mA / cm is supplied to the electrodes. To evenly operate the electrodes, their polarity periodically changes. Laboratory tests of the proposed method are carried out for 100 hours on the duct. Samples of fine suspension are taken every hour of operation and the particle size and Fe concentration are determined depending on the current density and electrical conductivity of distilled water. The dependences of particle size on current density are presented in Table. 1. Dependencies of particle size on electrical conductivity are shown in Table 2.

Table 1.

Current density |

Particle size, microns mA / cm

{

Process practically

not going

0.5 Continuation of table T; a-b l and c a not sample 0.5 0.5-1.0 10-40 In the practice of conducting research on the formation of iron deposits on heat transfer surfaces, iron oxide powder of various sizes is added to increase the iron content of water. dry powder of iron oxide which is very difficult to dissolve in water, and the need to separate particles of the required size from it considerably complicates the work, as well as large distortions in the process of iron oxide deposits due to the presence of dehydrated iron oxide particles and unequal the size of the particles. To eliminate these drawbacks, a method has been proposed for producing iron hydroxides. In addition, the known method eliminates all the distortions in the process of formation of iron oxide deposits inherent in all other research methods, and is much simpler in its implementation, since there is no need to calibrate particle sizes. Using the proposed method for obtaining fine suspensions of iron hydroxides, compared with the known possibility of obtaining products of fine suspension of iron hydroxides with particle sizes of 0.5-1 microns, the purity of the products obtained due to the operation of the device with distilled water, the possibility of continuous dosing of a certain concentration of fine suspension. for example, in experimental plants to study the formation of iron oxide deposits on heat transfer surfaces without This is an additional stage of filtration. In addition, the proposed method provides savings due to the elimination of the use of filters.

Claims (1)

METHOD FOR PRODUCING IRON HYDROXIDE by passing electric current through iron electrodes placed in an electrolyte, characterized in that, in order to increase the degree of purity of the product and to obtain particles with a size of 0.5-1.0 microns, distilled water is used as an electrolyte electrical conductivity 2 "10'-6'10 '* SMS *. and the process is conducted in galvanic-static mode with a current density of 0.010.1 mA / cm ² when changing the polarity of the electrodes. >