A treatment method for chromium-containing sodium sulfate waste liquid and sulfuric acid pickling waste liquid in stainless steel production

Abstract

The present invention discloses a treatment method for a chromium-containing sodium sulfate waste solution and a sulfuric acid acid-washing waste solution in stainless steel production. The treatment method comprises that: a chromium-containing sodium sulfate waste solution and a sulfuric acid acid-washing waste solution are discharged into a first-stage reaction tank, the pH value is controlled to 2.5-3.5, part of Cr<6+> is reduced, Na2S is poured into the first-stage reaction tank to generate CuS precipite, NiS precipite and FeS precipitate, the precipitates are discharged into a first-stage precipitation tank, and the supernatant is discharged into a second-stage reaction tank; the sulfuric acid acid-washing waste solution is added to the first-stage precipitation tank, sludge only contains CuS and NiS after a reaction is performed, solid-liquid separation is performed, and the supernatant is discharged into the second-stage reaction tank; sulfuric acid and sodium bisulfite are added to the second-stage reaction tank to reduce the remaining Cr<6+>, sodium hydroxide is added to carry out a reaction to obtain ferrochromium hydroxide precipitate, solid-liquid separation is performed, and the supernatant is discharged into a third-stage reaction tank; and a heating stirring reaction is performed on the third-stage reaction tank to obtain the electrolyte only containing sodium sulfate, wherein CuS, NiS, ferrochromium hydroxide and sodium sulfate are easily subjected to subsequent recycling. The treatment method has characteristics of simple process, easy operation and low cost. With the treatment method, the waste solution and waste residue pollution problem in the stainless steel production can be effectively solved, the waste can be treated through the waste, pollution can be reduced, and the environment can be protected.

Description

technical field [0001] The invention belongs to the technical field of environmental protection, and relates to waste liquid and waste slag resource treatment technology, in particular to a treatment method for chromium-containing sodium sulfate waste liquid and sulfuric acid pickling waste liquid in stainless steel production. Background technique [0002] In recent years, with the continuous development of my country's economy and the continuous expansion of demand, the production of industrial stainless steel has continued to increase, and the industrial pollution caused by stainless steel production has become increasingly serious. The waste water produced in the production process is various and complex. , The water quality fluctuates greatly, which leads to the difficulty of pollution control in this industry. [0003] Aiming at one of the main waste liquids produced in the production of stainless steel - chromium-containing sodium sulfate waste liquid, the treatment me...

AI Technical Summary

Problems solved by technology

Although the effluent of this treatment method is basically up to the standard, it consumes a large amount of medicine, resulting in a huge amount of waste residue. The heavy metal ions in it are not only of low grade but also of various types. Heavy metals such as copper, iron, chromium, and nickel exist at the same time and are difficult to separate.

If you invest in advanced treatment and smelting, the cost will be too high and the economic benefits will be poor

Therefore, many small and medium-sized factories simply do not develop or reuse these waste residues, consume a lot of transportation vehicles, accumulate more and more, occupy a large amount of farmland, and pollute the environment; million

In addition, the higher concentration of sodium sulfate in the waste liquid is usually not recycled but wasted in vain

[0004] At present, for the treatment of sulfuric acid pickling waste, except for domestic large-scale or strong technical capital support factories that can recycle it, most small and medium-sized factories usually use it with hydrochloric acid, nitric acid, hydrofluoric acid and other mixed acid pickling waste After mixing together, add lime milk for neutralization and sedimentation treatment. Although the drainage meets the standard, the consumption of lime milk and the amount of waste residue are greatly increased, and the types of heavy metal ions are also particularly complicated, which is extremely unfavorable for subsequent extraction and recovery.

In addition, a large amount of free acid and ferrous ions in the pickling waste liquid are also wasted

[0005] In recent years, many scholars have studied the recycling of heavy metal-containing waste slag after ordinary water treatment of stainless steel waste liquid. Treatment after environmental pollution, or passive treatment of pollutants individually, is not a good way to solve pollution. These practices will lead to high investment and low returns, and even the speed of treatment cannot keep up with the speed of pollution increase

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