Method for producing high-purity ferrous sulfate water and ferrous sulfate heptahydrate by using waste acid

A technology of ferrous sulfate and ferrous sulfate, applied in the direction of ferric sulfate, nitric acid, nitrogen oxides/oxyacids, etc., can solve the problems of high cost, high risk and high equipment requirements

Pending Publication Date: 2021-07-23
3R ENVIRONMENTAL TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0011] The above two methods can completely separate the solute and solvent in the solution, but this also determines that the two processes have high cost, high risk, and extremely high equipment requirements.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0038] A method utilizing waste acid to produce high-purity ferrous sulfate water and ferrous sulfate heptahydrate, comprising the following steps:

[0039] Add 4t of waste nitric acid and 0.5t of concentrated sulfuric acid to the stirring tank, wherein the raw material of waste nitric acid contains 5% nitrate, 7.98% total iron, 1.3% acidity (calculated as hydrochloric acid), 0.5% fluoride ion, and 98% concentrated sulfuric acid ; After fully stirring, slowly add 0.475t reducing iron powder, and then fully react for 1 hour. Now the pH has reached 3.67, add 2t of tap water to control the solution ferrous ion concentration in the stirring tank to be about 8.21%, to prevent the precipitation of ferrous sulfate solid. Then add 50kg of slaked lime powder (content about 80%) to the mixing tank, adjust the pH to 4.51, add 20kg of sodium sulfide solid, stir well for 2 hours and press filter. Obtain 6t of high-purity ferrous sulfate water (containing 7.67% of ferrous ions, 0.11% of ni...

Embodiment 2

[0041] A method utilizing waste acid to produce high-purity ferrous sulfate water and ferrous sulfate heptahydrate, comprising the following steps:

[0042] Add 2t of waste nitric acid and 3t of waste sulfuric acid to the stirring tank, wherein the raw material of waste nitric acid contains 5% nitrate, 7.98% total iron, 1.3% acidity (calculated as hydrochloric acid), 0.5% fluoride ion, and the acidity of waste sulfuric acid (calculated as hydrochloric acid ) was 10.78%, and ferrous iron was 1.56%; after fully stirring, slowly add 0.50t reducing iron powder, and then fully react for 1 hour. Now the pH has reached 3.76, add 2t of tap water to control the solution ferrous ion concentration in the stirring tank to about 8.02%, to prevent the precipitation of ferrous sulfate solid. Then add 25kg of slaked lime powder (about 80%) to the mixing tank, and adjust the pH to 4.67, then add 25kg of sodium sulfide solid, stir well for 2 hours and press filter. 6.3t of high-purity ferrous ...

Embodiment 3

[0044] A method utilizing waste acid to produce high-purity ferrous sulfate water and ferrous sulfate heptahydrate, comprising the following steps:

[0045] Add 8t of waste nitric acid and 12t of waste sulfuric acid to the stirring tank, wherein the raw material of waste nitric acid contains 5% nitrate, 7.98% total iron, 1.3% acidity (calculated as hydrochloric acid), 0.5% fluorine ion, and the acidity of waste sulfuric acid (calculated as hydrochloric acid ) is 10.78%, and ferrous iron is 1.56%; after fully stirring, slowly add 2.25t reducing iron powder, and then fully react for 1 hour. Now the pH has reached 3.91, add 8t tap water to control the solution ferrous ion concentration in the stirring tank to be about 7.98%, to prevent the precipitation of ferrous sulfate solid. Then add 100kg of slaked lime powder (content about 80%) to the mixing tank, and adjust the pH to 4.45, then add 125kg of sodium sulfide solid, stir well for 2 hours and press filter. 26t of high-purity ...

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PUM

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Abstract

The invention belongs to the technical field of environment-friendly wastewater and hazardous waste treatment, and provides a method for producing high-purity ferrous sulfate water and ferrous sulfate heptahydrate by using waste acid. The method comprises the following steps: mixing waste nitric acid or waste acid mixed liquor with a sulfuric acid reagent in proportion; adding iron powder, and performing stirring for 0.5-2 hours; adding a precipitator, then adding liquid caustic soda to adjust the pH value to 4.5-4.8, and adding sodium sulfide; carrying out filter pressing on the mixed solution to obtain high-purity ferrous sulfate water; adding a small amount of concentrated sulfuric acid into the high-purity ferrous sulfate water, pumping the mixture into a negative pressure evaporator for evaporation, discharging the mixture into a crystallization kettle for cooling crystallization, and discharging the mixture into a centrifugal machine for centrifugation to obtain the high-purity ferrous sulfate solid. According to the invention, through reasonable design of process steps and actual reaction, recycling of the waste nitric acid and the mixed acid is realized, waste of ferric salt resources is avoided, the problems of difficult treatment and high-cost emission of the waste nitric acid and the mixed acid are solved, resource comprehensive treatment and utilization of the waste nitric acid and the mixed acid are realized, and the method is simple in process, lower in cost and green and environment-friendly.

Description

technical field [0001] The invention relates to a method for resource utilization of waste nitric acid and mixed acid, which belongs to the technical field of environmental protection waste water and hazardous waste treatment, and specifically relates to a method for producing high-purity ferrous sulfate water and ferrous sulfate heptahydrate by using waste acid. Background technique [0002] In the stainless steel pickling and etching industry and the printed circuit board industry, nitric acid and the mixed acid formed by nitric acid, hydrofluoric acid, sulfuric acid, hydrochloric acid, etc. are widely used. For different industries, the required ratio is different, but it will be scrapped at last. The waste acid liquid generally contains a large amount of nitrate, fluoride, sulfate, ferric ions and heavy metal ions. At present, major hazardous waste disposal manufacturers capable of recycling and processing this kind of waste acid mainly rely on two methods for processing...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01G49/14C01B21/40
CPCC01G49/14C01B21/40C01P2006/80
Inventor 樊文星林国良梁茂杰罗莉娟
Owner 3R ENVIRONMENTAL TECH CO LTD
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