RU2214368C1 - Process of treatment of local sewage to get rid of toxic contamination - Google Patents

Abstract

FIELD: chemical industry, purification of local sewage from toxic contamination. SUBSTANCE: in compliance with invention local sewage is treated in electrolyser with use of soluble aluminum laminated electrodes with addition of up to 1.0 per cent by mass of ammonium chloride and up to 1.0 per cent by mass of sodium hydroxide. Process is conducted with density of alternating sinusoidal current 0.1-1.0 A/sq cm in temperature interval 40-95 C. Liquid effluent purified from toxic contamination is suitable for industrial utilization after separation of sediments. EFFECT: simplified implementation of process, improved degree of purification of sewage. 1 tbl

Description

 The invention relates to the chemical industry and is intended for the purification of local effluents from toxic pollution.

A known method of purification of industrial wastewater, in particular galvanic production from chromium, comprising contacting the wastewater with an inorganic sorbent, which is used as copper hydroxide (Cu (OH) ₂ ). The method consists in the fact that the chromium-containing wastewater is sent to neutralization and to sorption into a column containing solid granules of copper hydroxide. When sewage passes through solid granules, chromium is sorbed on the surface of copper hydroxide. Then the sorbent is discharged from the column and sent to the chromium flush with a solution of sulfuric acid, and after washing with water, the sorbent is again sent to the wastewater treatment. The disadvantage of this method is the complexity of preparing the sorbent, the use of a large amount of sulfuric acid and the complexity of restoring the sorbent (RF Application 94007334, 1996.01.10).

There is also known a method of treating wastewater from heavy non-ferrous metals, chromium and organic impurities. The method is carried out by electrocoagulation with alternating current using moving electrodes, the process being conducted at a current density of at least 3.0 A / dm ² .

 The disadvantages of this method include the use of a three-phase alternating current industrial frequency voltage of 380 V, the manufacture of a special housing for conducting the electrocoagulation process and moving electrodes associated with electrical safety of production (RF Patent 2071449, 1997.01.10).

 The task of the invention is to simplify the hardware design of the local wastewater treatment process, reduce costs and increase cleaning efficiency.

This is achieved by the fact that the purification of local effluents is carried out in an electrolyzer using aluminum plate electrodes and adding 0-1 wt. % ammonium chloride NH ₄ Cl, and 0-1 wt.% sodium hydroxide NaOH to maintain a pH in the range of 8-11 and supply an alternating single-phase sinusoidal voltage of industrial frequency (50 Hz) at a current density of 0.1-1.0 A / cm ² , in the temperature range 40-95 ^o C. This range of pH values is due to the fact that at pH values less than 8 and more than 11 the formation of aluminum hydroxide does not occur due to its amphotericity.

 A distinctive feature of the proposed method is that aluminum hydroxide, serving as an adsorbent, is formed during the electrochemical and chemical dissolution of aluminum electrodes in a cleaned local drain.

The range of current densities of 0.1-1 A / cm ^{2 is} determined by the fact that when the current density is below 0.1 A / cm ^{2 the} rate of formation of aluminum hydroxide is low, resulting in reduced cleaning efficiency; at a current density above 1 A / cm ² there is an intensive heating of the treated drain and its boiling off.

The temperature range of 40-95 ^o With is necessary for carrying out the process in optimal temperature conditions and to prevent boiling out of the treated local runoff.

 To achieve maximum cleaning efficiency, it is necessary to maintain the pH of the treated local runoff in the range of 8-11. This necessitates the addition of ammonium chloride and sodium hydroxide in an amount of 0-1 wt.%.

Example 1. In the electrolytic cell pour purified stream with an initial concentration of cyanide ions (CN ^- ) equal to 17000 mg / L. 0.1 wt.% Ammonium chloride and sodium hydroxide are added. Aluminum electrodes are placed in the electrolyzer to a depth corresponding to a current density of 0.1 A / cm ² . An alternating sinusoidal voltage (50 Hz, 7 V) is brought to them. After 1 h, the content of CN ^- in the solution was 13.9 mg / L, and after 2 h - 3.9 mg / L.

Example 2. In the electrolytic cell pour purified water with an initial concentration of formalin equal to 8137 mg / L. 0.1 wt.% Ammonium chloride and sodium hydroxide are added. Aluminum electrodes are placed in the electrolyzer to a depth corresponding to a current density of 0.1 A / cm ² . An alternating sinusoidal voltage (50 Hz, 7 V) is brought to them. After 1 h, the formalin content in the solution was 30.1 mg / l, and after 2 h - 12.1 mg / l.

Example 3. A cleaned effluent with an initial concentration of cadmium ions (Cd ²⁺ ) equal to 250 mg / L and copper ions (Cu ²⁺ ) equal to 160 mg / L is poured into the electrolyzer. 0.1 wt.% Ammonium chloride and sodium hydroxide are added. Aluminum electrodes are placed in the electrolyzer to a depth corresponding to a current density of 0.2 A / cm ² . An alternating sinusoidal voltage (50 Hz, 7 V) is brought to them. After 1 h, the content of Cd ²⁺ in the solution was 61.7 mg / L, and after 2 h, 2.0 mg / L. As for the copper content, it was not detected after 1 h of treatment.

 The effluent thus purified from toxic contaminants after separation of the sludge is suitable for industrial disposal. The cleaning effect is achieved both due to the electrochemical oxidation (reduction) of toxic components, and due to the adsorption of these components and the products of their electrochemical oxidation (reduction) on aluminum hydroxide, which is formed as a result of the electrochemical and chemical dissolution of aluminum electrodes in a cleaned local drain upon application of an alternating sinusoidal voltage industrial frequency.

 The research results are shown in the table.

Claims (1)

A method of purifying local effluents from toxic contaminants, including electrochemical oxidation or reduction and adsorption of toxic components and products of their electrochemical oxidation or reduction on aluminum hydroxide, characterized in that the effluent is purified in the electrolyzer using soluble aluminum plate electrodes, and the process is carried out with the addition of 0 -1 wt.% Ammonium chloride and 0-1 wt.% Sodium hydroxide with an alternating sinusoidal current density of 0.1-1 A / cm ² in the temperature range 40-95 ^o C.

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