Method for producing chromium hydroxide by using electroplating sludge

Abstract

The invention provides a method for producing chromium hydroxide by using electroplating sludge. The invention relates to a method for producing chromium hydroxide by using electroplating sludge, which comprises the following steps: (1) slurrying: adding chromium-containing electroplating sludge into a slurrying kettle, adding a certain amount of water, and starting stirring for slurrying; according to the method, the chromium-containing waste liquid and the concentrated sulfuric acid are added into the pulpified electroplating sludge solution for leaching, a proper amount of sodium hypochlorite is added after more than half of the chromium sludge is dissolved, and alkali is added for neutralization after leaching is completed, so that impurity metals such as iron, aluminum, calcium and magnesium in the solution can be removed through a chemical precipitation method; and the follow-up chromium hydroxide preparation process is not interfered by the ions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electroplating sludge, and particularly relates to a method for producing chromium hydroxide from electroplating sludge. BACKGROUND

[0002] The electroplating sludge is a precipitate mainly composed of heavy metal hydroxides such as copper and chromium, which is generated in the electroplating wastewater treatment process. The electroplating sludge has the characteristics of complex composition, high water content, high thermal stability and easy migration of heavy metal components. The electroplating sludge is mainly generated from the wastewater produced in the pretreatment, electroplating process and post-treatment process of the electroplating process. After the wastewater is treated by acid-base neutralization, flocculation and sedimentation and other methods, the electroplating sludge is formed. Since the electroplating sludge contains various heavy metal compounds and soluble salts, if it is discharged without treatment, it will cause serious environmental pollution. Therefore, how to effectively treat the electroplating sludge to make it stable, harmless and resourceful has become an important issue in the current electroplating industry and environmental governance field. At present, the extraction of chromium ions contained in the electroplating sludge is not mature in China. Direct discharge of the electroplating sludge solution will cause waste of resources. Therefore, it is necessary to provide a method for producing chromium hydroxide from electroplating sludge to solve the above problems. SUMMARY

[0003] The technical content of the present application is to provide a method for producing chromium hydroxide from electroplating sludge.

[0004] To solve the above problems, the present application provides a method for producing chromium hydroxide from electroplating sludge, which comprises the following steps: (1) slurry: adding chromium-containing electroplating sludge into a slurry kettle, adding a certain amount of water, and starting stirring for slurry; (2) leaching and impurity removal: pumping the slurry obtained in step (1) into a leaching kettle, adding chromium-containing waste liquid and concentrated sulfuric acid in the leaching kettle for leaching, adding appropriate amount of sodium hypochlorite when more than half of the chromium sludge is dissolved, and adding alkali after leaching to neutralize, removing iron, aluminum, calcium, magnesium and other impurity metals in the solution by chemical precipitation method, and then filtering by a filter press, rinsing the filter residue with water, temporarily storing the produced iron, chromium, calcium and magnesium mixed residue, and filtering the filtrate into a hydrogen hydroxide precipitation process; (3) precipitating chromium hydroxide: pumping the slurry obtained in step (2) into a reaction kettle with a pump, adding a reducing agent, adding sodium hydroxide when the hexavalent chromium is completely reduced to trivalent chromium, combining the chromium ions in the solution with hydroxyl ions to generate chromium hydroxide precipitate, and then filtering by a filter press after the chromium precipitation is completed, and the filter residue is the chromium hydroxide product.

[0005] As a further solution of the present application, the reaction temperature required in step (1) is 40-70 DEG C, and the reaction time is 5-10 h.

[0006] As a further solution of the present application, the reaction temperature required by the leaching process of step (2) is 50-90 DEG C, the reaction PH is 1-4, and the reaction time is 3-6h.

[0007] As a further solution of the present application, the reaction temperature required by the impurity removal process of step (2) is 50-90 DEG C, the reaction PH is 1-4, and the reaction time is 1-3h.

[0008] As a further solution of the present application, the reaction temperature required by the water rinsing process of step (2) is 50-70 DEG C, and the reaction time is 1-3h, and the mixed slag of iron, chromium, calcium and magnesium produced in step (2) is generally sent to a qualified unit for disposal to prevent environmental pollution.

[0009] As a further solution of the present application, the reaction temperature required by step (3) is 50-90 DEG C, the reaction time is 5-7h, and the reaction PH is 3-8, and the filter press wastewater produced by the filter press of step (3) is generally sent to a wastewater treatment station for treatment.

[0010] Compared with the related art, the method for producing chromium hydroxide from electroplating sludge provided by the present application has the following beneficial effects:

[0011] 1. In the present application, chromium-containing waste liquid and concentrated sulfuric acid are added to the slurry electroplating sludge solution for leaching, and then an appropriate amount of sodium hypochlorite is added when the chromium sludge is dissolved by more than half, and after the leaching is completed, alkali is added for neutralization, so that the iron, aluminum, calcium, magnesium and other impurity metals in the solution can be removed by chemical precipitation method, so that the subsequent process of preparing chromium hydroxide will not be disturbed by these ions.

[0012] 2. In the present application, a reducing agent is added to the electroplating sludge solution after the impurity removal is completed, so that the hexavalent chromium can be completely reduced to trivalent chromium, and then sodium hydroxide can be added to the solution, so that the chromium ions in the solution combine with hydroxyl ions to generate chromium hydroxide precipitate, and after the chromium precipitation is completed, the filter press is pressed, and the filter residue is the chromium hydroxide product, and this step is very simple and efficient, and is suitable for large-scale production and use. DETAILED DESCRIPTION

[0013] A method for producing chromium hydroxide from electroplating sludge, the method comprising the following steps: (1) Slurrying: chromium-containing electroplating sludge is added to a slurrying kettle, a certain amount of water is added, and stirring is started for slurrying; (2) Leaching and impurity removal: the slurry obtained in step (1) is pumped into a leaching kettle, chromium-containing waste liquid and concentrated sulfuric acid are added to the leaching kettle for leaching, and after more than half of the chromium sludge is dissolved, an appropriate amount of sodium hypochlorite is added. After leaching, alkali is added for neutralization, and impurities such as iron, aluminum, calcium, and magnesium in the solution are removed by chemical precipitation. After impurity removal, the solution is filtered by a filter press, the filter residue is rinsed with water, and the resulting iron, chromium, calcium, and magnesium mixed residue is temporarily stored. The filtrate enters the chromium hydroxide precipitation process; (3) Precipitating chromium hydroxide: the slurry obtained in step (2) is pumped into a reaction kettle, a reducing agent is added, and when hexavalent chromium is completely reduced to trivalent chromium, sodium hydroxide is added so that chromium ions in the solution combine with hydroxide ions to generate chromium hydroxide precipitate. After chromium precipitation, the solution is filtered by a filter press, and the filter residue is the chromium hydroxide product.

[0014] Preferably, the reaction temperature required in step (1) is 40℃-70℃ and the reaction time is 5-10h;

[0015] Preferably, the reaction temperature required for the leaching process in step (2) is 50℃-90℃, the reaction pH is 1-4, and the reaction time is 3-6h;

[0016] Preferably, the reaction temperature required for the impurity removal process in step (2) is 50℃-90℃, the reaction pH is 1-4, and the reaction time is 1-3h;

[0017] Preferably, the reaction temperature required for rinsing with water in step (2) is 50℃-70℃ and the reaction time is 1-3h. The iron, chromium, calcium and magnesium mixed slag produced in step (2) is generally sent to a qualified unit for disposal to prevent environmental pollution.

[0018] Preferably, the reaction temperature required in step (3) is 50℃-90℃, the reaction time is 5-7h, the reaction pH is 3-8, and the filter wastewater generated by the filter press in step (3) is generally sent to the wastewater treatment plant for treatment.

[0019] The standard parts used in this embodiment can be purchased directly from the market, and can also be customized according to the instruction manual. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art, and the structure and principle of the components known to those skilled in the art can be known by those skilled in the art through technical manuals or conventional experimental methods.

[0020] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments, or they can be used directly or indirectly, without departing from the principles and spirit of the invention. In other related technical fields, the scope of the invention is defined by the appended claims and their equivalents, and they are similarly included within the scope of patent protection of the invention.

Claims

1. A method for producing chromium hydroxide from electroplating sludge, characterized in that, The method includes the following steps: (1) Pulping: Add chromium-containing electroplating sludge to the slurrying kettle, add a certain amount of water, and start stirring to slurry; (2) Leaching and impurity removal: The slurry obtained in step (1) is pumped into the leaching kettle. Chromium-containing waste liquid and concentrated sulfuric acid are added to the leaching kettle for leaching. After more than half of the chromium mud is dissolved, an appropriate amount of sodium hypochlorite is added. After leaching, alkali is added for neutralization. Iron, aluminum, calcium, magnesium and other impurity metals in the solution are removed by chemical precipitation. After impurity removal, the solution is filtered by a filter press. The filter residue is rinsed with water. The iron, chromium, calcium and magnesium mixed residue produced is temporarily stored. The filtrate enters the chromium hydroxide precipitation process. (3) Precipitation of chromium hydroxide: The slurry obtained in step (2) is pumped into the reactor, a reducing agent is added, and when the hexavalent chromium is completely reduced to trivalent chromium, sodium hydroxide is added so that the chromium ions in the solution combine with hydroxide ions to form chromium hydroxide precipitate. After the chromium precipitation is completed, the solution is filtered by a filter press, and the filter residue is chromium hydroxide product.

2. The method for producing chromium hydroxide from electroplating sludge according to claim 1, characterized in that: The required reaction temperature for step (1) is 40℃-70℃, and the reaction time is 5-10h.

3. The method for producing chromium hydroxide from electroplating sludge according to claim 1, characterized in that: The required reaction temperature for step (2) leaching is 50℃-90℃, the reaction pH is 1-4, and the reaction time is 3-6h.

4. The method for producing chromium hydroxide from electroplating sludge according to claim 1, characterized in that: The reaction temperature required for step (2) of the impurity removal process is 50℃-90℃, the reaction pH is 1-4, and the reaction time is 1-3h.

5. The method for producing chromium hydroxide from electroplating sludge according to claim 1, characterized in that: The required reaction temperature for rinsing with water in step (2) is 50℃-70℃, and the reaction time is 1-3h. The mixed slag containing iron, chromium, calcium and magnesium produced in step (2) is generally sent to a qualified unit for disposal to prevent environmental pollution.

6. The method for producing chromium hydroxide from electroplating sludge according to claim 1, characterized in that: The required reaction temperature for step (3) is 50℃-90℃, the reaction time is 5-7h, and the reaction pH is 3-8. The filter wastewater generated by the filter press in step (3) is generally sent to the wastewater treatment plant for treatment.