SU335920A1 - Method of purifying aluminate-alkali solutions - Google Patents

Description

BACKGROUND OF THE INVENTION The invention relates to technology for producing alumina by celiac methods.

There are known methods for producing alumina using aluminate-alkaline solutions, which are purified from iron impurities by controlling filtration of solutions through fabrics or pulp and paper pulp. There is also known a method in which potassium permanganate is added to the solution to further purify the solution from iron, and the solution is filtered through a layer of freshly precipitated hydroxy aluminum or tricalcium hydroaluminate. According to known methods, solutions of the required purity are not always obtained, and the use of potassium permanganate increases the cost of the process, since a lot of expensive product is consumed, which also contaminates the solutions with potassium and margaptic.

In order to increase the degree of purification and reduce the corrosion of equipment, it is recommended that oxygen compounds, such as oxygen, air, ozone, ozonized air, ozonized oxygen, be introduced into the solution.

Example I. A portion of crushed bauxite is treated with caustic alkali or circulating-alkaline solution; the obtained pulp is diluted, decanted, or filtered. The resulting aluminate-alkaline solution is treated in a contact apparatus with ozonized air or oxygen

(simple or ozonized) with a duration of several minutes to 6 hours. After treatment, the solution is filtered, for example, on sheet filters, through pulp and paper pulp or through another filtering material. The purified aluminate-alkaline solution is cooled to the required temperature provided for by the decomposition technology, and then the hydroxide is separated from it.

aluminum by known methods.

Example 2. Bauxite is crushed, leached with circulating aluminate-alkaline solution, the resulting suspension is diluted to a predetermined concentration and in a diluent or

contact apparatus is treated for 3-8 hours with oxygen. After treatment, the aluminate solution is separated from the red mud. Further processing of the solution is carried out according to the usual technological scheme.

The content of impurities in aluminal solutions (concentration of ABOz 139.6 g / l) obtained by various methods is given in Table. one.

Example 3. The experiment was carried out as in example 2.

The content of impurities in aluminate solutions (concentration 143 g / l), treated for 1-4 hours with technical acid Table 1

Example 4. The content of impurities in aluminate solutions (concentration 140.1 g / l), treated as in Example 1 with ozonized oxygen (ozonized air) from 20 minutes to 2 hours, is given in Table. 3

table 2

Table 3

When the mother liquor obtained after the decomposition of the ozonized aluminate solution is evaporated, deeper salts of MASCO3 and Na2SO4 (see Tables 4 and 5) are obtained; coarser soda crystals are obtained, which has a positive effect

on all technological operations of alumina production.

When leaching bauxite with a circulating solution obtained from ozonized aluminate-alkaline solutions, there is a decrease in the transition to sulphide solution, no sulphites are formed, which makes it possible to reduce the consumption of oxidizing agents several times when using a closed cycle. The leaching results are given in table. 6

The ozone content in ozonized oxygen is 11 g / nm. The determination of organic impurities is interfered with sodium thiosulfate present in the solution (the permanganate method with boiling solutions is used), therefore, the analysis of the solutions indicated the amount of oxygen KMnO4 (in% to Na2O2), which followed the oxidation of organic impurities and 52Oz (this also applies to Table. 1, 2, 6).

Table 4

Table 5

Table b