JPS6148588A - Method for regenerating waste water after nickel plating as replenisher for electrolytic refining of nickle - Google Patents

Abstract

PURPOSE:To regenerate waste water produced by washing Ni plated articles as an Ni plating soln. having a low org. carbon content when the waste water is concd. and used as a plating soln., by blowing the concd. waste water into an aqueous alkali soln. together with an alkali compound, subjecting repeatedly a formed precipitate to repulping, washing and dehydration, and dissolving the resulting product in sulfuric acid. CONSTITUTION:Waste water produced by washing Ni plated articles contains Ni and has a high org. carbon content. When the waste water is concd. and used as an Ni plating soln., the concd. waste water contg. Ni and an alkali carbonate or alkali hydroxide soln. are simultaneously blown into an aqueous alkali soln. of 8-9pH from the bottom. At this time, the aqueous alkali soln. is heated to >=40 deg.C and stirred, and the pH and concn. of the soln. is kept constant. A formed precipitate is repeatedly subjected to repulping and washing with warm water and dehydration, and the resulting product having <=35% water content is dissolved in dil. sulfuric acid to prepare a soln. having 65-75g/l concn. of Ni and <=40ppm org. carbon content. This soln. is returned to an Ni plating tank and used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention purifies nickel plating wastewater, particularly reduces total organic carbon (hereinafter abbreviated as T00), and uses it as a replenishment liquid for nickel electrolytic refining. Regarding how to play.

[Conventional technology]

This plating wastewater is the concentrated plating washing water etc. generated in small and medium-sized plating factories.

Although the nickel concentration of the wastewater is accepted as relatively high, it contains a large amount of impurities such as Too.

Therefore, if this plating wastewater is supplied as is to the nickel electrolytic system, various problems will occur that are thought to be caused by the TOO concentration in the electrolyte.

For example, the nickel electrodeposited on the Ni seed plate may peel off due to electrolysis, or the hardness of the nickel may increase.

In order to avoid the above phenomenon, nickel plating waste water can only be replenished into the electrolyte in small amounts, which is not practical.

Another method is to add alkali to this nickel plating wastewater to separate the nickel as hydroxide, then roast it and melt it in an electric furnace to form an anode, followed by immersion electrolysis, but this method is complicated. Moreover, there was a drawback that the cost was high.

[Problem that the invention seeks to solve]

An object of the present invention is to solve the above-mentioned problems and provide a simple method for obtaining an aqueous nickel sulfate solution from the plating wastewater that can be used by adding it in a relatively large amount to the electrolytic solution for nickel electrorefining. .

[Means for solving problems]

The inventors of the present application conducted an experiment on the influence of the TOO concentration in the electrolytic solution for obtaining electrolytic nickel on the properties of the obtained nickel electrodeposit, and found that the Ni concentration in a normal nickel electrolytic solution was 65 to 75g7'1 It has been found that the TOO concentration needs to be 4 ppm or less in this case.

If the TOO concentration is higher than this, the above-mentioned phenomenon will occur to a greater or lesser extent. Therefore, an aqueous solution of nickel sulfate with an N1 concentration of 65 to 75 (y'l) obtained by regenerating nickel plating waste water can be added by volume to the electrolyte taken out from the electrolytic tank for nickel electrolytic refining. In order to achieve this, the TOO concentration in the nickel sulfate aqueous solution obtained by regenerating nickel plating wastewater must be 4.Opp.
What is necessary is to make it less than or equal to m.

That is, the present invention aims to obtain such an aqueous nickel sulfate solution from nickel plating wastewater by: 1. P
Add nickel plating waste water and alkali carbonate aqueous solution or alkali hydroxide aqueous solution simultaneously to the aqueous aqueous solution of H8.0 to 9.0 which is maintained above +oC and stirred. Maintain PR and temperature of the aqueous solution. At the same time, it was added by blowing into the bottom of the aqueous solution, and the resulting precipitate was washed with warm water and dehydrated several times to separate the washing water, so that the adhering moisture was at least 35% by weight in the final dehydration operation. It was then dissolved in dilute sulfuric acid to adjust the nickel concentration to a concentration suitable for electrolytic refining of nickel.

[Effect]

The reason why the reaction is carried out in the pH range of 8 to 9.0 in the method of the present invention is that if the pH is lower than this, some double salt with basic sulfate will be formed, and if the pH is higher than this, the removal of Too will be insufficient. Because it will be.

The reaction temperature is set to 40C or higher, preferably 60C or higher, because below this temperature, the filtration rate of the product is slow.

Next, first prepare a small amount of alkaline aqueous solution in the reaction tank, and add nickel plating wastewater and aqueous solution of alkali carbonate or alkali hydroxide to it by simultaneously blowing it while maintaining the pH value and temperature. Too et al. 0 The nickel precipitate as carbonate or hydroxide is separated from the mother liquor by strong suction filtration or centrifugation, and the resulting cake is kept at the temperature of the first step. Add a large amount of hot water at a similar temperature to the water, lube it, and then perform the dehydration operation two or more times to separate the washing water. Apply a strong suction filtration method. In the final dehydration operation at this time, the adhering moisture should be 35% by weight or less. If this washing and dehydration operation is performed more than once,
If 2 times or more is insufficient, the final dehydration operation will remove 30% of the adhering moisture.
By setting the TOC to 5% by weight or less, TOC can be removed later. When this precipitate is dissolved in dilute sulfuric acid and the nickel concentration is adjusted to a concentration suitable for electrolytic refining of nickel, the TOC concentration will be about 4.Oppm or less. This is because it becomes possible.

〔Example〕

Examples will be described below.

Example 1 A 50 C aqueous solution with a predetermined pn prepared by adding an aqueous sodium carbonate solution to water was placed in a beaker with a volume of fA 10 i.
0me, and while stirring this with a three-one motor, 84 g/l of nickel and 6.6 g/l of TOO.
of nickel plating waste water and 150 g/l aqueous sodium carbonate solution at room temperature using a roller pump, the plating waste water was mixed with 4 (00 to 500 equivalents) per minute, and each alkali was 1.05 to 1.1 equivalents per minute. At the same time, add the sodium carbonate aqueous solution by blowing it into the bottom of the beaker.During this time, the inside of the container was maintained at 50C with a water bath, and the pn was adjusted to 0N-O by using a PH controller manufactured by Teirika.
Each of the 51 nickel plating wastewaters was treated while maintaining a predetermined pH value while FF was applied, and the residence time of the reaction solution was varied, and the resulting slurry was filtered with a suction filter (Nutsche).

Next, the cake obtained was 600 m/100 g (!,
Perform Repulve cleaning with warm water at 50C for 30 minutes each,
Each time, the cake was filtered using a suction filter, and in the final filtration, the cake was dehydrated by suction until the moisture content of the cake became about 30% by weight. The cake thus obtained was dissolved in 1.1 equivalents of dilute sulfuric acid, water was further added to make an aqueous solution containing 175 gjl of N, and the TOC thereof was determined based on the J Engineering S standard. The results are shown in Table 1.

Table 1 As is clear from Table 1, the initial T content was 6.6 gel.
oo is expected value 3o ppm or less O, and 1 deviation is also certainG
I cleared this.

Example 2 The same procedure as Example 1 was carried out except that nickel plating wastewater containing 85 g/l of N1.12 g//1 TOO was used as an alkali, an aqueous solution of 200 g/l of sodium hydroxide, and the reaction temperature was 60C. TOC removal treatment was performed in the same manner. The results are shown in Table 2. However, the experimental dust 9 was subjected to normal light suction filtration both times.

Table 2 As can be seen from Table 2, the Toa concentration in the raw material was the same as in Example 1.
Even when the concentration is about twice as high as that of To
By separating and removing o, a low-concentration 'roa of about 20 to 3 o ppm was obtained. In Examples 1 and 2, the repulp washing and dehydration operation was performed twice, and by increasing the number of repulp washing and dehydration operations, it is possible to obtain a nickel regenerated liquid with a lower 'roa. Experiment 9, which applied the normal filtration method, was T even though the washing and dehydration method and recovery were the same.

Removal of C was poor.

By the way, in the case of Sample Flat 2 in Table 1 and Sample Flat 5 in Table 2, the cake after one washing and dehydration operation was dissolved in sulfuric acid and N175g7't.
The TOO concentration when made into an aqueous solution of each is 220 ppm 1
It was 160 ppm.

〔Effect of the invention〕

As described above, removal of TOO from nickel plating wastewater is extremely difficult compared to removal of general impurities, but when the method of the present invention is applied, more than 99.5% by weight of TOO is removed from the resulting recycled electrolyte. The concentration can be lowered to 65 to 75 g7'l l (TO010 to 80 ppm in the case of i) of the electrolytic solution when performing matte electrolysis.

Although not specifically shown as an example, application of the method of the present invention also provides the advantage that other impurities (those that do not precipitate due to the addition of alkali) are also removed at the same time. The yield of nickel recovered from the plating wastewater is 99.5% by weight or more.

The recycled nickel aqueous solution obtained by the method of the present invention can be used as it is without any problems by being extracted from the nickel matte electrolytic cell, purified as an electrolytic waste liquid, and then combined with the electrolytic waste liquid supplied to the electrolytic cell. can.

Claims (1)

[Claims] (1) An alkaline aqueous solution with a pH of 8.0 to 9.0 is maintained at 40°C or higher, and nickel plating wastewater and an alkali carbonate aqueous solution or an alkali hydroxide aqueous solution are simultaneously added to the aqueous solution while it is being stirred. While maintaining the pH and temperature of the aqueous solution, the resulting precipitate is repulped with hot water and dehydrated several times, and the final dehydration process reduces the adhering moisture to 35% by weight. A method for regenerating nickel-plated wastewater as a replenishment solution for electrolytic refining of nickel, which comprises: dissolving it in dilute sulfuric acid to adjust the nickel concentration to a concentration suitable for electrolytic refining of nickel.