Method for recovering sodium dichromate form chromium-containing electroplating sludge

A sodium dichromate and sodium chromate-containing technology, applied in chromate/dichromate, sludge treatment, chemical instruments and methods, etc., can solve the problems of secondary pollution of ammonia nitrogen and strong acidity of wastewater

Inactive Publication Date: 2008-12-31
ZHEJIANG GONGSHANG UNIVERSITY
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Problems solved by technology

The above method uses a large amount of sulfuric acid and ammonium sulfate, and the waste water produced is highly acidic and contains a large amount of ammonia, resulting in secondary pollution of ammonia nitrogen

Method used

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  • Method for recovering sodium dichromate form chromium-containing electroplating sludge

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Embodiment Construction

[0034] (1) Sodium oxidation of electroplating sludge

[0035] Take chromium-containing electroplating sludge, and the measured chromium content is 8.9%, with Na 2 CO 3 After being fully mixed with it at a weight ratio of 1:1, it is roasted on a muffle furnace at a roasting temperature of 600-650°C for 2 hours; after taking it out, soak it in water 10 times its weight to dissolve sodium chromate (Na 2 CrO 4 ), soaking time in water for 1 hour; filter and separate the sludge, and filter out the sodium chromate solution.

[0036] (2), impurity removal

[0037]Adjust the pH of the filtered sodium chromate solution to 7.5, hydrolyze at a temperature of 90-95°C to form flocculent Zn and Al hydroxides, and filter to remove zinc hydroxide and aluminum hydroxide;

[0038] Then add sulfuric acid to the filtrate to adjust the pH to 4 ± 0.1, convert sodium chromate into sodium dichromate, and heat and concentrate the solution to 20% of the original volume, precipitate sodium sulfate a...

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Abstract

The invention discloses a method for recovering sodium acid chromate from chrome-containing electroplating sludge. The electroplating sludge is blended with Na2CO3 according to a certain proportion and is baked at a certain temperature to obtain Na2CrO4, Cr<3+> is oxidized into Cr<6+> chrome and aluminum and zinc are taken as corresponding oxides; Cr, Al and Zn are dissolved in liquid by water soaking to generate respective salt, and the solid containing the metals such as Ni, Cu, Fe, Ca, Mg, and the like, is filtered and separated; the Na2CrO4 solution is transformed by hydrolysis acidification and Al2(OH)3 and Zn(OH)2 are removed to realize the separation of Zn, Al and Cr; the chrome-containing solution is acidated into sodium acid chromate (Na2Cr2O7), cooled after being concentrated to a certain volume, and filtered to remove sodium sulfate; the sodium acid chromate solution is processed by condensation, crystallization, centrifugation and drying to obtain sodium acid chromate finished product. By adopting sodium treatment and oxidation process, the rate of recovering chrome from chrome-containing electroplating sludge can exceed 90 %, and the resource utilization of electroplating sludge can be realized.

Description

technical field [0001] The invention belongs to the technical field of chemical industry or environmental protection, and relates to solid waste treatment and resource recovery and utilization technology, especially the resource recovery and utilization technology of heavy metals in electroplating sludge, specifically a method for recovering sodium dichromate from chromium-containing electroplating sludge . Background technique [0002] Electroplating sludge is a product of electroplating wastewater treatment. Due to the high content of heavy metals in electroplating wastewater, after the electroplating wastewater is treated by various physical and chemical methods, the heavy metals in the wastewater form precipitates and enter the electroplating sludge, making the electroplating sludge a dangerous solid waste containing a certain amount of toxic and harmful heavy metals. Improper disposal may become secondary pollutants that cause surface water, soil, and groundwater pollu...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01G37/14C02F11/00
Inventor 郭茂新孙培德
Owner ZHEJIANG GONGSHANG UNIVERSITY
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