A method for removing heavy metals by breaking cyanide in high-concentration cyanide wastewater

Abstract

A method for breaking cyanide and removing heavy metals from high-concentration cyanide wastewater, comprising the following steps: (1) injecting high-concentration cyanide wastewater into an electrolytic cell, and using a DC power supply for electrolysis under alkaline conditions; (2) during the electrolysis process, cyanide The content of cyanide gradually decreases, adding hydrogen peroxide to promote its reaction speed, and finally electrolysis to obtain low-concentration cyanide wastewater; (3) adjusting the pH value of the low-concentration cyanide wastewater obtained in step (2) to 10-11, adding EDTA and catalyst to react (4) adding hydrogen peroxide to the solution obtained in step (3) to carry out deep cyanide breaking treatment; (5) for the waste water obtained in step (4) after cyanide breaking completely, adopting the ferrite method to remove heavy metals in the solution. The invention is easy to operate, not only removes high-concentration cyanide, but also performs advanced treatment on the waste water after cyanide breaking, especially ferricyanide, and reaches the discharge standard.

Description

technical field [0001] The invention relates to the technical field of industrial wastewater treatment, in particular to a method for breaking cyanide and removing heavy metals from high-concentration cyanide wastewater. Background technique [0002] In industrial production, cyanide wastewater mainly comes from the two major industries of metallurgy and electroplating. Whether it is free cyanide, simple metal cyanide complexes or refractory metal cyanide, if these highly toxic wastewater is discharged without treatment, it will seriously Pollution of water resources will have a significant impact on human health. From the perspective of environmental protection, we must pay attention to the treatment of cyanide-containing wastewater. [0003] At present, there are many cyanide treatment methods at home and abroad, most of which are mainly aimed at the treatment of medium and low cyanide wastewater. The more mature methods are roughly divided into: 1. Alkaline chlorine meth...

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Problems solved by technology

The more mature methods are roughly divided into: 1. Alkaline chlorine method, adding some chlorine oxides, such as ClO, to the alkaline cyanide-containing wastewater 2 , chlorine gas, bleaching powder, sodium hypochlorite, liquid chlorine, etc. This method is simple to operate and has a wide range of reagent sources. The disadvantages are: first, if the equipment is not well sealed, CNCl will escape into the air and pollute the operating environment; Ferricyanide and cyanide in ferricyanide; third, when the chloride ion concentration is high, Ca and Mg dissolve in large quantities, and if the cyanide-breaking treatment is directly discharged, it will seriously affect water resources

[0004] 2. Acidification method, that is, under strong acidic conditions, use heating or some method to volatilize hydrogen cyanide, absorb it with lye, and make it recycle. Although this method is easy to operate, it can only be used for a single system , has no effect on metal cyanides that are difficult to decompose; and if the equipment is not sealed enough, there will be a major safety hazard of HCN overflow

[0005] 3. SO 2 ——Air method, mainly the SO 2 Mix with air and add to the waste liquid, control the appropriate pH value of 7-10, and oxidize the cyanide under the action of copper sulfate catalyst, which can remove most of the cyanide, including ferricyanide, free cyanide, etc., disadvantages The main reason is that the hydrolysis of sodium cyanate is slow, and there are many factors affecting the treatment. If the control is not good, not only the effect of breaking cyanide will be greatly reduced, but there will also be HCN and SO 2 spill hazards

[0006] 4. The biological treatment method mainly uses the activated sludge method to convert toxic cyanide into carbon dioxide, nitrogen or formic acid. The time requirement is strict, and the microbial load capacity is limited, and the cost is high

The electrolysis method is used to reduce the cyanide content. First, the original cyanide content is only 29.84ppm, and the removal rate of high concentration is not explained.

Second, although electrolysis can degrade part of the metal content Cu and Ag, ferricyanide cannot be removed by electrolysis. Patent CN201410325704.6 does not mention the removal process of ferricyanide

Third, activated carbon is used as the catalytic carrier. Since activated carbon itself has the property of adsorption, some metals and cyanides will be adsorbed during catalysis, resulting in secondary waste. It is difficult to reprocess activated carbon in the later stage.

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