Disposal technology of waste chrome plating bath

A chrome plating tank and process technology, applied in the direction of chromium alum, chromium sulfate, etc., can solve the problems of low recovery rate, low product purity, inorganic acid, alkali and salt discharge, etc., and achieve the effect of high added value and high purity

Active Publication Date: 2022-08-05
SHANGHAI JIAOTONG UNIV +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The existing disposal method of electroplating aging solution is to reduce hexavalent chromium to trivalent chromium by reducing agent, then flocculate and precipitate, and convert heavy metal chromium, copper and nickel into electroplating sludge for disposal, which will generate a large amount of sludge hazardous waste, not only It wastes resources and also leads to the discharge of a large amount of inorganic acid-base salts to the environment; in addition, the prior art also has concentrated Cr by adding alkali to the aging solution. 6+ It is converted into sodium dichromate or sodium chromate with low solubility and recovered, but the product purity is low, the recovery rate is low, and Cr cannot be recovered 3+ 、Cu 2+ 、Ni 2+ and sulfate etc.

Method used

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  • Disposal technology of waste chrome plating bath

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0019] This embodiment specifically includes the following steps:

[0020] 1) Metal ion Cr 3+ Separation: slowly add KOH solution to the waste chrome plating bath, pH rises from 2.0 to final 4.0, stirring speed is 10 rev / min, KOH is added slowly and evenly; KOH addition amount and speed are based on the pH rising rate per hour (ΔpH / h) 0.30 is controlled, KOH is added for about 7h to form chromium hydroxide precipitate; filtrate A and chromium hydroxide precipitate are obtained by filtration; chromium hydroxide precipitate is reacted with 50% sulfuric acid in a stoichiometric ratio to obtain chromium sulfate solution B.

[0021] 2) Separation of iron impurities: in the filtrate A obtained in step 1), KOH solution was slowly and uniformly added to pH 4.50, and air was introduced, and the reaction was slowly stirred for 5 hours. The iron ions were converted into precipitation, and filtered to obtain chromic anhydride and Filtrate C of copper and nickel ions;

[0022] 3)Cu 2+ ,...

Embodiment 2

[0060] This embodiment specifically includes the following steps:

[0061] 1) Metal ion Cr 3+ Recycling: slowly add KOH solution to the discarded chrome plating bath, pH rises from 2.0 to final 4.0, stirring speed is 10 rev / min, KOH is added slowly and evenly; KOH addition amount and speed are based on the pH rising rate per hour (ΔpH / h) 0.25 was controlled, KOH was added for 8h to form chromium hydroxide precipitate; filtrate A and chromium hydroxide precipitate were obtained by filtration; chromium hydroxide precipitate was reacted with 50% sulfuric acid in a stoichiometric ratio to obtain chromium sulfate solution B.

[0062] 2) Removal of iron impurities: in the filtrate A obtained in step 1), KOH solution was slowly and uniformly added to pH 4.50, and air was introduced, and the reaction was slowly stirred for 5 hours. The iron ions were converted into precipitation, and filtered to obtain chromic anhydride and Filtrate C of copper and nickel ions;

[0063] 3)Cu 2+ , N...

Embodiment 3

[0071] This embodiment specifically includes the following steps:

[0072] 1) Metal ion Cr 3+ Recycling: slowly add KOH solution to the discarded chrome plating bath, pH rises from 2.0 to final 4.0, stirring speed is 10 rev / min, KOH is added slowly and evenly; KOH addition amount and speed are based on the pH rising rate per hour (ΔpH / h) 0.40 was controlled, KOH was added for 5h to form chromium hydroxide precipitate; filtrate A and chromium hydroxide precipitate were obtained by filtration; chromium hydroxide precipitate was reacted with 50% sulfuric acid in a stoichiometric ratio to obtain chromium sulfate solution B.

[0073] 2) Removal of iron impurities: in the filtrate A obtained in step 1), KOH solution was slowly and uniformly added to pH 4.50, and air was introduced, and the reaction was slowly stirred for 5 hours. The iron ions were converted into precipitation, and filtered to obtain chromic anhydride and Filtrate C of copper and nickel ions;

[0074] 3)Cu 2+ , N...

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Abstract

A process for disposing of a discarded chrome-plating bath. The KOH solution is slowly added to the discarded chrome-plating bath to react to obtain a chromium hydroxide precipitate and a filtrate, the chromium hydroxide precipitate is reacted with sulfuric acid to obtain a chromium sulfate solution, and the filtrate is subjected to impurity separation treatment and After the ion separation treatment, a solution containing chromium sulfate is reduced, and finally the chromium sulfate solution is combined and concentrated by heating to a supersaturated solution of potassium chromium sulfate, and crystallization is carried out on the basis of the supersaturated solution of potassium chromium sulfate to obtain potassium chromium sulfate. The invention has the characteristics of high recovery rate, high product purity, various recovery types, almost no acid and alkali salts discharged to the environment and the like.

Description

technical field [0001] The invention relates to a technology in the field of heavy metal recovery, in particular to a process for treating waste chrome plating baths. Background technique [0002] In the existing electroplating chromium, the main component of the chromium plating solution is CrO. 3 (Cr 6+ ) and H 2 SO 4 and a small amount of organic additives, Cr in the bath 3+ high concentration (CrO 3 , 200-300g / L) and acidic, but with the progress of electroplating, a large amount of metal ion impurities including Cr will accumulate in the plating tank 3+ , Fe 2+ / Fe 3+ , Cu 2+ , Ni 2+ Wait. The accumulation of metal impurity ions in the chrome plating tank is very harmful, resulting in a decrease in the quality of the coating. When the metal ion impurities are too high, the plating solution ages to form an electroplating aging solution, which is handed over to the hazardous waste qualified unit for disposal. The disposal method of the existing electroplating a...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01G37/10
CPCC01G37/10C01P2006/80
Inventor 周保学徐友良李金花
Owner SHANGHAI JIAOTONG UNIV
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