RU1778082C - Method for contracting nickel from used solutions of chemical nickel-plating - Google Patents

Abstract

Usage: in electroplating for the purification of spent electrolytes from nickel ions, utilization of the latter and its return to production. SUMMARY OF THE INVENTION: treating the spent solution with a dry alkaline agent and recovering a nickel-containing precipitate, which is used as an alkali metal carbonate or hydroxide or a mixture thereof. The best results were obtained with a molar ratio of hypophosphite and nickel in the treated solution 2. The optimum temperature is a solution temperature of 70-90 °; C and processing time 30-60 minutes Compared with the known one, it is possible to ensure a nickel content in the precipitate of up to 93% due to its separation from concentrated spent solutions mainly in the form of a metal powder, to ensure a degree of nickel recovery to 98-99.8%, to simplify the utilization and return of nickel to production, and to reduce the degree of contamination knowledge of wastewater. 1 s.p., crystals, 1 tab. sl c

Description

The invention relates to methods for purifying spent technological solutions from nickel ions and can be used to extract and utilize nickel from spent hypophosphite chemical nickel plating solutions.

A known method for the extraction and regeneration of nickel from waste solutions (nickel bath) containing nickel and hypophosphite by treatment with an alkali solution at 90-100 ° C, pH 9-10 for 30 minutes stirring in the presence of a catalyst. To improve the degree of purification, the treatment is carried out in the presence of additional hypophosphite. As a result of processing, a precipitate containing metallic nickel is released, and the residual content in the solution

nickel is 20 mg / l and is reduced to 1 mg / l after treatment. The precipitate is used again to prepare a nickel plating bath.

However, the known method is characterized by increased complexity of execution, since it requires constant monitoring and adjustment of the pH of the reaction mixture throughout the entire processing time, maintaining a high temperature of the solution, the use of scarce catalysts (palladium chloride). The known method is not technologically advanced when cleaning large volumes of industrial effluents from nickel, since maintaining a given pH of 9-11 requires the introduction of large volumes of alkali solution, which, firstly, leads to dilution of the initial solution and

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maximizing nickel recovery is difficult, and secondly, problems arise in neutralizing excess alkali in the final solution.

The aim of the invention is to simplify the process while maintaining the degree of recovery of nickel from the solution.

This object is achieved in that when nickel is recovered from spent hypophosphite solutions of chemical nickel plating in a known manner, including treatment with an alkaline agent solution and isolation of a nickel-containing precipitate, in accordance with the invention, the treatment is carried out with a dry alkaline agent, in which use a carbonate and / or / alkali metal hydroxide, and the butchering is carried out at a sodium hyphosphite content in the treated solution in an amount providing the total sodium hypophosphite: NI 2 ratio. In addition, the spent solution was treated at 70-90 ° C for 30-60 minutes using the heat of the spent electrolyte.

The essence of the claimed method is as follows.

It has been found that when the spent hypophosphite chemical nickel solution is treated with an effective amount of a dry alkaline agent, which uses an alkali metal carbonate or hydroxide or a mixture of them, a dark crystalline precipitate forms, the analysis of which revealed the presence of a large amount of metallic nickel in the form of a dispersed powder. The content of metallic nickel in the precipitate depends on the residual sodium hypophosphite content in the treated solution and at a molar ratio of hypophosphite: nickel 2 reaches more than 90%. The resulting precipitate is characterized by low humidity, compactness and a higher deposition rate. The residual nickel ion content in the solution after precipitation is 5-100 mg / L. When the solution is treated with a dry alkaline agent, but when calcium or magnesium hydroxides are used as the latter, a precipitate forms, which is a complex mixture of insoluble compounds of nickel, calcium / magnesium / with a nickel content of 20-30%.

The positive effect compared with the known method is explained by the fact that when the dry hypophosphite chemical nickel plating solution is treated with a dry alkaline agent, a sharp local increase in alkalinity occurs at the interface, which leads to a violation of the solution stability and activation of the nickel reduction reaction (the main chemical nickel plating reaction). With sufficient final alkalinity of the treated solution / pH

0 6.5 / and in the presence of an effective amount of hypophosphite in the solution, it is possible to almost completely isolate nickel mainly in the form of a metal powder.

5 With an insufficient amount of hypophosphite in the treated solution, the formation of sediment takes place in two stages. At the initial moment after the introduction of the dry alkaline agent, the nickel reduction reaction predominates, which slows down as the reduction concentration decreases, and the remaining nickel ions bind as hydroxide or basic carbonate. In this case, the precipitate contains

5 less than 90% nickel, since in addition to hydroxide and carbonate, nickel will contain a certain amount of metallic nickel,

Example 1. Into a 1 liter glass

200 ml of the spent chemical nickel-plating solution with a content of nickel ions of 0.038 mol / L and sodium hypophosphite / GF / 0.087 mol / L are poured, the pH of the solution is 3.56, and the temperature is 90 ° С.

5, 9.0 g of crystalline soda was added and stirred at the indicated temperature for 30 minutes. The resulting black precipitate was collected on a filter. The precipitate and filtrate are analyzed; the results of the analysis are presented in the table.

PRI me R 2. 200 ml of the spent chemical nickel plating solution / pH 3.56 / with a content of nickel ions of 0.043 mol / l and GF of 0.087 mol / l are treated with 3.0

5 g of crystalline sodium hydroxide. The solution at a temperature of 80 ° C is stirred for 45 minutes and filtered. The results of the analysis are presented in the table. Example 3. A mixture of 5 tons of soda and 1 g of dry potassium hydroxide was added to a container with 200 ml of an industrial chemical nickel-plating solution (pH 3.56) containing 0.056 mol / L nickel and 0.087 mol / g HF at 70 ° C. The solution was stirred at the indicated temperature for 30 minutes and filtered. The resulting precipitate and the filtrate are analyzed. The results of the analysis are presented in the table.

PRI me R 4. Spent chemical nickel plating solution according to example 1

process 4.6 g of dry potash. The solution at a temperature of 85 ° C is stirred for 60 minutes, and filtered. The results are presented in the table.

Example 5 100 l of a spent chemical nickel plating solution at pH 3.0 and a temperature of 75 ° C with a content of 0.092 mol / l nickel ions and 0.156 mol / l hypophosphite are mixed with 4 kg of dry soda. After 60 minutes, the solution is filtered, the precipitate and the filtrate analyzed. The results of the analysis are presented in the table.

Limerb / for comparison. 200 ml of an acidified solution of nickel sulfate / pH 3.0 / with a content of nickel ions of 0.05 mol / l are mixed with 9 g of dry soda. The solution was stirred at 85 ° C for 45 minutes and filtered. The results of the analysis of sediment and filtrate are presented in the table.

Analysis of the data presented in the table shows that the proposed method, in comparison with the known one, allows maintaining a high nickel content in the precipitate due to its precipitation mainly in the form of a metal powder. At the same time, the degree of nickel recovery from concentrated solutions containing a significant amount of ligands and stabilizers is preserved while simplifying the implementation of the method. The best results on the nickel content in the precipitate were obtained with a molar ratio in the initial solution of hypophosphite and nickel of at least 2, i.e. with a reducing agent content equal to greater than stoichiometric with respect to nickel. Under this condition, the nickel content in the precipitate is 92-93%, and its recovery is 98-99%. Under similar conditions, but in the absence of a reducing agent in the initial solution, treatment with a dry alkaline agent is not effective (Example 6), the nickel content in the precipitate does not exceed 50%. When treating solutions that do not contain or contain insufficient amounts of hypophosphite, it is recommended that an additional amount of hypophosphite be added to the solution before being treated with a dry alkaline agent.

From the point of view of technological process, the most optimal is the temperature range of 70-90 ° C / the main process of chemical nickel plating occurs at a temperature of 80-35 ° C /. In this case, a high degree of nickel release is achieved within 30-60 minutes, the precipitate is crystalline with a high deposition rate and

low humidity. As the temperature rises, the precipitation time decreases, however, raising the temperature above 90 ° C is not advisable, since it requires additional energy for heating. At temperatures below 70 ° C, the precipitate is more humid, finely dispersed, the time of its deposition increases, and the degree of nickel recovery decreases.

Consumption a (the Christmas-tree agent does not significantly affect the kinetics of the process. Its amount should be sufficient to neutralize the residual acid, to compensate for alkali costs by

the redox reaction of nickel release by nickels creating the necessary medium for this. The pH of the stock solution does not affect the process. The proposed method is effective at a final pH of the treated solution of 6.5-9.5.

This embodiment of the method allows you to remove constant control of the pH of the medium, significantly reduce the final alkalinity

the treated solution / up to a neutral reaction, see examples 4 and 5 of the description /, to avoid the need for additional dilution and to dispense with the use of catalysts, and processing

carry out at a lower temperature. In addition, the proposed method does not require a significant excess of hypophosphite in solution and is effective when the amount of hypophosphite is less than stoichiometric

/cm. Examples 3 and 5 of the description. The proposed method is technologically advanced under industrial conditions; it does not require special control and dosing equipment and additional energy costs. The nickel content in the resulting precipitate is not lower than the known method, which allows it to be used for the preparation of nickel-containing baths in galvanic production.

Claims (2)

1. A method for recovering nickel from spent chemical nickel-plating solutions by treating the initial solution with an alkaline agent in the presence of sodium hypophosphite at an elevated temperature, characterized in that, in order to simplify the process while maintaining the degree of nickel recovery, the treatment is carried out with dry carbonate and / or hydroxide alkali metal. 2. The method according to claim 1, with the exception of the fact that the treatment is carried out at 70-90 ° C.