A comprehensive treatment and utilization method of chromium-containing waste acid

Abstract

The invention discloses a method for comprehensive treatment and utilization of chromium-containing waste acid. The waste acid treated by this method contains sulfate radicals and iron ions, including the following steps: adjusting the pH value of chromium-containing waste acid to 1~3, adding acid and iron ions for precipitation reaction, separating and obtaining ferrous precipitate and filtrate, adding acid During the process, the pH value of the system is maintained at 1-3; the separated filtrate is cooled, precipitated and crystallized, and filtered to obtain crystalline sodium sulfate and the secondary filtrate; the secondary filtrate is evaporated and concentrated to obtain chromium sulfate. The treatment method of the present invention realizes the graded recovery and recycling of acid, iron and chromium through step-by-step graded treatment, avoiding the generation of secondary hazardous waste caused by incineration after the precipitation of primary chromium in the existing treatment method and the low recovery value of resources The comprehensive high-value recycling of chromium-containing waste acid has been realized. Among them, the recovery rate of iron can reach 95.0%, the recovery rate of acid can reach 80.0%, and the recovery rate of chromium can reach 90.5%. It can be widely used in Recycling of waste chromium acid.

Description

technical field [0001] The invention relates to the technical field of cold rolling or electroplating, and more specifically relates to a method for comprehensive treatment and utilization of chromium-containing waste acid. Background technique [0002] In the cold rolling industry and other pickling industries, a large amount of stainless steel needs to be pickled. The steel contains different amounts of chromium and enters the pickling waste liquid after pickling. If these waste acids are to be comprehensively utilized, the chromium in them must be Chromium is separated, otherwise it will seriously affect the subsequent use. The existing method for removing chromium from waste acid is mainly to neutralize with alkali (caustic soda or lime), press filter after precipitation of iron and chromium, and incinerate hazardous waste filter cake. The disadvantage of this method is that a large amount of lime is required for neutralization And caustic soda, more precipitates are fo...

AI Technical Summary

Problems solved by technology

The existing method for removing chromium from waste acid is mainly to neutralize with alkali (caustic soda or lime), press filter after precipitation of iron and chromium, and incinerate hazardous waste filter cake. The disadvantage of this method is that a large amount of lime is required for neutralization And caustic soda, more precipitates are formed, the cost of filter cake reprocessing is higher, and effective components are not well utilized

Another way to remove chromium in waste acid is to directly incinerate and dispose of it. Direct incineration will cause a lot of waste of resources and energy. The treatment cost is too high, which is not conducive to the actual hazardous waste treatment, and it is easy to cause secondary secondary hazardous waste

In the prior art, there is also a method for disclosing related precipitation. The prior art CN106865729A discloses a method for treating chromium-containing heavy metal wastewater by using molten iron to pretreat desulfurization slag. , use magnetic substances to reduce hexavalent chromium to trivalent chromium, and then use iron tailings to remove the reduced trivalent chromium by chemical precipitation. The operation of this method is cumbersome and not suitable for actual production and treatment

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