SU1682321A1 - Method for purifying from fluorine - Google Patents

Description

one

(21) 4711634/26

(22) 27 06.89

(46) 07 10.91. Bul №37

(71) All-Union Titanium Research and Design Institute

(72) VF Sokhan, OVOrlova. F.Kh.Enikeeva and V.Suslova (53) 663.631.8 (088.8)

(56) USSR Author's Certificate N-550346, cl. C 02 F 1/28, 1975.

(54) METHOD FOR CLEANING WASTE WATER FROM FLUORINE

(57) The invention relates to sorption methods for the treatment of wastewater from fluorine and allows the utilization of etching fluoro-titanium-containing solutions. The aim of the invention is to increase the degree of water purification from fluorine. The method includes the treatment of wastewater with lime milk to a pH of 8-11 and the tertiary treatment with water-soluble titanium fluorides in the amount of 20-100 mg / l in terms of titanium dioxide. As water-soluble titanium compounds, spent etching titanium-containing solutions are used. The method makes it possible to reduce the residual content of fluoride in purified water to 0.2-0.75 mg / l and to treat wastewater with a high initial content of fluorine (3-10 g / l) while reducing secondary pollution of wastewater. 1 hp ff. 1 tab.

The invention relates to methods of waste treatment, wastewater treatment from fluorine and can be used in the chemical, aluminum, glass and other industries.

The purpose of the invention is to increase the degree of purification of wastewater from fluorine.

To carry out the process, the treatment with a calcium-containing reagent and the purification with an adsorbent are carried out. Water-soluble titanium fluorides with a titanium fluoride content of 20-100 mg / l in terms of titanium dioxide are used as the adsorbent. As a water-soluble titanium fluoride, fluoro-titanium-containing etching solutions can be used.

The treatment of wastewater with a calcium-containing reagent makes it possible to purify the effluent to a fluorine content of 10–20 mg / l in them (support ° C / Y y by the solubility product CaF2)

With the introduction of the calcium-containing reagent into wastewater containing fluoride, the pH of the effluent rises and, when a pH of 2.0-1.5 is reached, hydrolysis of titanium fluorides begins with the formation of titanium hydroxide. Titanium hydroxide absorbs fluoride ion and goes to precipitate, since thermodynamically more stable is titanium hydroxyfluoride than titanium hydroxide. The solubility product of titanium hydroxyfluorides is lower than that of titanium hydroxide and the post-treatment of fluorine will go deeper.

The highly developed active surface of titanium hydroxide, a uniform distribution over the entire volume of effluent provides the process of sorption of fluorine with high technological indicators. The content of fluoride ion in the discharged wastewater is reduced to 0.2-0.3 mg / l with an MPC of 0.75 mg / l.

(L

WITH

about

00

u so yu

In addition, the proposed method allows to reduce the secondary contamination of the effluent compared to the known one, since the introduction of ions is eliminated and the amount of introduced Na ions is reduced by an order of magnitude.

The optimum content of water-soluble titanium fluorides in terms of titanium oxide is 20-100 mg / l. When the titanium fluoride content is lower than 20 mg / l in terms of TiO2, there is no degree of purification that allows discharge of sewage into water bodies. Increasing the content of the adsorbent to more than 100 mg / l is not economically feasible, since it leads to excessive consumption of the reagent and worsens the filtration process due to the formation of excessive fine precipitate of titanium hydroxyfluoride.

Example 1. A 10% - solution of potassium fluorotitanate in the amount of 280-1400 ml / m3 effluent and calcium-containing reagent, which is dispensed to pH 10-11, are mixed into an acidic initial stock with a fluorine content of 3-5 g / l and mixed for 10-20 minutes and filtered. In the effluent, the fluorine content is determined.

The filtrate is used in circulation, or is discharged into the sewage system. The precipitate is dried, it contains calcium and titanium fluoride compounds and can be disposed of in the glass industry as fluxing additives. Similarly, the treatment of wastewater from fluorine is carried out using a 10% aqueous solution of sodium and lithium fluorothitanates.

Example 2. Titanium-containing etching solutions of the following composition, g / l, are introduced into an acidic initial stock with a fluorine content of 3-5 g / l: TiO2 172; HOS 2-5; Zr02 2-5, in the amount of 70-350 ml / m and the calcium-containing reagent to pH 10-11, stirred, filtered. In the treated effluent, the fluorine content is determined. The results are shown in the table.

As can be seen from the obtained data, at the dosage of water-soluble titanium fluorides, for example, below the limit value of 20 mg / l in terms of titanium dioxide, the required degree of purification is not achieved. An excess of the adsorbent higher than 100 mg / l in terms of TUa, allows to obtain a deep degree of purification, but the process of filtering the sediment worsens, the secondary pollution of the effluent increases.

The use of the proposed method significantly reduces the secondary contamination of effluent: the introduction of the S04 2 anion is completely eliminated, and the introduction of, for example, the Na + cation is reduced to 11.5-57.5 mg / l versus 450 mg / l by a known method with MPC-120 mg / l Residual

fluorine spill waters by a known method of 0.8-1.3 mg / l and exceeds the MPC when discharged into water bodies of 0.75 mg / l.

Use as an adsorbent pickling solution improves the process.

sorption, since these solutions include components such as Zr, AI, which, hydrolyzing, form zirconium and aluminum hydroxides with high sorption properties. A joint

their presence in the solution contributes to a deeper purification as compared with the use of water-soluble titanium fluorides (pure reagents). In addition, it is possible to dispose of one of the

The most toxic wastewaters in the industry are non-contaminated wastewater secondary ions.

Thus, the proposed method, in comparison with the known, allows increasing the degree of purification of fluorine from high fluorine content (3-10 g / l) from fluorine, the content of fluoride ion in purified wastewater is reduced by 1.5-2 times. The method also makes it possible to reduce the secondary pollution of wastewater by the injected reagents and to dispose of the waste solutions used for etching titanium alloys.

Claims (2)

1. A method of purifying wastewater from fluorine, including treatment with lime milk to a pH of 8-11, additional purification with an adsorbent followed by separation of liquid and solid phases, characterized in that, in order to increase the degree of purification, 20 water-soluble titanium fluorides are used as an adsorbent. -100 mg / l in terms of titanium dioxide. 2. A method according to claim 1, characterized in that spent pickling fluoro-titanium-containing solutions are used as the adsorbent.