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Method for recovering hydrazine sulfate and chromium hydroxide from chromium-containing waste acid

A technology of chromium hydroxide and hydrazine sulfate, applied in chemical instruments and methods, chromium compounds, nitrogen and non-metallic compounds, etc., can solve the problems of low value of barium sulfate, no industrial implementation significance, etc., and achieves simple operation and obvious economic benefits. Effect

Inactive Publication Date: 2011-06-22
NANJING UNIV
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Problems solved by technology

But the value of barium sulfate is low, so this method has no industrial implementation significance

Method used

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Embodiment

[0016] Take 49.5mL of 40% hydrazine hydrate and dilute it into a 20% solution, take 40mL of chromium-containing waste acid (acidity 65%) to filter, and slowly add it dropwise to the 20% hydrazine hydrate solution under stirring for 2 hours , control the pH of the feed solution at the end of acid addition to 0.8, and generate a white crystalline hydrazine sulfate precipitate. The reaction formula is as follows:

[0017] NH 2 -NH 2 ·H 2 O+H 2 SO 4 = NH 2 -NH 2 ·H 2 SO 4

[0018] 2Cr 2 o 7 2- +4H + +3N 2 h 4 ·H 2 O→4Cr(OH) 3 +N 2 +5H 2 o

[0019] 2Cr(OH) 3 +3H 2 SO 4 →Cr 2 (SO4) 3 +6H 2 o

[0020] Let it stand for 0.5h, and then put it into a refrigerator at 5°C for 2h.

[0021] Filter, wash the hydrazine sulfate filter cake with a small amount of cold water (5°C), and combine the filtrate into the synthesis mother liquor. Take 155mL of clear water and heat it to 60°C (27.65g / 100g, 60°C), add the washed hydrazine sulfate filter cake and stir to dissolv...

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Abstract

The invention discloses a method for recovering hydrazine sulfate and chromium hydroxide from chromium-containing waste acid, which comprises the following steps of: diluting hydrazine hydrate, slowly adding waste acid into the hydrazine hydrate with stirring, ensuring an acid adding end point when the pH of feed liquid is 0.8-1.2, and reacting hexavalent chromium in the waste acid with the hydrazine hydrate to reduce the hexavalent chromium into trivalent chromium and generate indissoluble hydrazine sulfate crystals; performing solid-liquid separation to obtain crude hydrazine sulfate and acidic chromium sulfate solution; adding alkali into acidic chromium sulfate solution for neutralization to obtain a chromium hydroxide precipitate, performing solid-liquid separation, washing with water, and drying to obtain an industrial product chromium hydroxide meeting quality requirement; and treating wastewater subjected to solid-liquid separation and washing in a wastewater treatment device for up-to-standard emission. The method is easy to operate, and the chromium-containing waste acid is treated for up-to-standard emission; meanwhile, the hydrazine sulfate and chromium hydroxide are recovered, so that the resources are reasonably utilized and the economic benefit is obvious.

Description

technical field [0001] The invention relates to the treatment and resource recycling of chromium-containing waste acid. Background technique [0002] Vat red 31 is an important dye, but in its production, only by oxidation with hexavalent chromium in a strong acidic medium can the accurate color and light be guaranteed. Therefore, a large amount of waste acid is produced, about 10 tons / ton, and the acidity is about 55- 68%, containing about 0.5% of organic matter, containing about 3% of total chromium, including about 0.6% of hexavalent chromium. [0003] Because the waste acid contains chromium, it becomes a hazardous waste. At present, the enterprise adopts the method of first adding sodium sulfite to reduce hexavalent chromium to trivalent, and then adding alkali to neutralize it to generate chromium hydroxide and recover it. This method consumes a lot of alkali and produces a lot of salt. Wastewater, the cost of treatment is unbearable. [0004] The chromium-containing...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C02F9/04C01G37/00C01B21/16
Inventor 赵玉明毕琴周婷婷
Owner NANJING UNIV
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