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Neutralization aluminum removing method for sodium chromate alkali solution

A technology of alkaline liquid and sodium chromate, which is applied in the field of inorganic salt production and resources and environment, can solve the problems of large influence, difficulty in processing and utilization of aluminum sludge, difficulty in liquid-solid separation of dissolution slurry, etc., and achieve high recovery rate of chromium and easy recovery Utilize and compose simple effects

Inactive Publication Date: 2012-07-11
CENT SOUTH UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This method can fully recover the chromium and aluminum in the chromium-containing aluminum sludge, but it is found during the implementation of the patented technology that if the aluminum sludge contains trivalent chromium precipitates, it will have a great impact on the production of aluminum hydroxide by the Bayer process. Big
When this patented technology is used to treat the aluminum sludge produced by neutralization with chromium-containing sodium bisulfate, since the aluminum sludge contains trivalent chromium compound precipitation, the dissolution rate of aluminum oxide in the Bayer process is only about 60%, and The liquid-solid separation of the dissolution slurry is also very difficult, making it difficult for this technology to deal with the aluminum sludge produced by neutralization with chromium-containing sodium bisulfate

Method used

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  • Neutralization aluminum removing method for sodium chromate alkali solution

Examples

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Effect test

Embodiment 1

[0016] Using sodium chromate alkaline liquid from a chromium salt factory in my country as raw material, the main chemical composition is: Na 2 CrO 4 320g / L (as Na 2 Cr 2 o 7 2H 2 O meter, the same below), Al 2 o 3 15.7g / L, free base 23.7g / L (as Na 2 O meter, the same below), pH value 13.2. Carbon dioxide adopts industrial pure CO 2 Mixed with air to control CO in the mixed gas 2The concentration is 5-8%. Preheat the sodium chromate alkaline solution and keep it warm to 80°C. Under the condition of stirring, pass a mixed gas to neutralize and remove aluminum. Take out a small part of the solution at intervals and cool it down to measure the pH value. The first stage was aerated for 1.5 hours, and the final pH value of the slurry was 10.5. After the aeration and stirring were stopped, the aluminum hydroxide precipitate in the slurry settled rapidly. After the underflow filtration and washing, the filter cake contained 32% moisture, and the chromium band loss of the dr...

Embodiment 2

[0018] Using sodium chromate alkaline liquid from a chromium salt factory in my country as raw material, the main chemical composition is: Na 2 CrO 4 320g / L, Al 2 o 3 15.7g / L, free base 23.7g / L, pH 13.2. Carbon dioxide adopts industrial pure CO 2 Mixed with air to control CO in the mixed gas 2 The concentration is 15-20%. Preheat the sodium chromate alkaline solution and keep it warm to 50°C. Under the condition of stirring, pass a mixed gas to neutralize and remove aluminum. Take out a small part of the solution at intervals and cool it down to measure the pH value. The first stage is aerated for 2 hours, the pH value of the slurry is 10.1, stop the aeration and stirring, the aluminum hydroxide precipitate in the slurry settles rapidly, the upper layer solution is clear, after the supernatant is poured out, the bottom solid is filtered and washed, the water content of the filter cake is 38%, the filter cake Chromium strip loss after drying is 0.09%. In the second stage...

Embodiment 3

[0020] Take the same volume of alkaline solution as in Example 2, add the unwashed filter cake of the second stage in Example 2 to the alkaline solution, control the temperature of the solution to 100°C, and feed carbon dioxide to neutralize and remove aluminum. 30-35%. The first stage is ventilated for 0.5h, the final pH value of the slurry is 9.8, the slurry is filtered to separate solids, the water content of the filter cake is 30%, and the chromium band loss of the dry filter cake is 0.08%. In the second stage, carbon dioxide was continuously fed into the above-mentioned filtrate. After aeration for 1 hour, the pH of the slurry was 8.9, and the slurry was filtered without washing the filter cake.

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Abstract

The invention relates to a neutralization aluminum removing method for a sodium chromate alkali solution. The carbon dioxide is used as a neutralizer for the neutralization aluminum removal of the sodium chromate alkali solution, and a two-section neutralization method is adopted; in the first section, a neutralization pH value is controlled so that most of aluminum in the alkali solution forms and separate aluminium hydroxide sediment with thick and big particles; in the second section, the residual aluminum in the solution is completely neutralized and precipitated by continuously using thecarbon dioxide, and the aluminum sediment precipitated in the second section is returned to the first section; the solution after the neutralization aluminum removal by the carbon dioxide is neutralized and acidized by a by-product chromium-contained sodium hydrogen sulfate in the production process of chromium salt, the chromium-contained sodium hydrogen sulfate is comprehensively utilized, and the trivalent chromium is recycled. The invention has the advantages of easy separation and washing of aluminum mud, low water content, low chromium band loss, easy comprehensive utilization, and the like.

Description

technical field [0001] The invention relates to a method for removing aluminum by using carbon dioxide to neutralize sodium chromate alkaline solution in the production process of chromium salt, and belongs to the field of inorganic salt production and resource environment. Background technique [0002] At present, the main method of chromite production is the chromite ore oxidation roasting method, which is to oxidize and roast the mixed powder of chromite, soda ash, filler or return slag at 1100-1200 °C to convert the chromium in chromite It is water-soluble sodium chromate. The roasted clinker is leached and the leaching solution is purified to produce chromium salt. Chromite oxidation roasting method is divided into calcium roasting method and calcium-free roasting method. [0003] During the oxidation and roasting of chromite ore, part of the aluminum compounds in chromite ore will inevitably react with sodium carbonate to form water-soluble sodium aluminate, and durin...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01G37/14
Inventor 李小斌齐天贵彭志宏刘桂华周秋生
Owner CENT SOUTH UNIV
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