JP2016056434A - Separation method of nickel from nickel sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily separate nickel from nickel sludge containing a plurality of kinds of impurities.SOLUTION: A nickel separation method that separates nickel from nickel sludge containing nickel and impurities includes a leaching step for adding sulfuric acid to the nickel sludge for pH 4-6 and then subjecting them to solid-liquid separation into a deposit and a leachate, a concentrating step for concentrating the leachate obtained in the leaching step to obtain a concentrated liquid, and a crystallization step for cooling the concentrated liquid obtained in the concentrating step to crystallize a nickel crystal and recovering the nickel crystal by solid-liquid separation. The nickel separation method may further include a cooling step for cooling the concentrated liquid obtained in the concentrating step and subjecting a deposited crystal of boric acid and the cooled liquid to solid-liquid separation. The cooled liquid obtained in the cooling step may be concentrated again to crystallize nickel.SELECTED DRAWING: None

Description

  The present invention efficiently separates impurities from sludge (precipitate mainly composed of nickel hydroxide) generated by neutralizing waste liquid generated in the electroplating or electroless plating industry, and has a high purity nickel compound The present invention relates to a method for separating nickel from nickel sludge that collects slag.

  As a method for separating impurities from the plating waste liquid, the electrolytic plating and the electroless plating have different separation methods. Specifically, the main coexisting substance in the electroplating waste liquid is boric acid, whereas the main coexisting substance in the electroless plating waste liquid is hypophosphorous acid and its oxidation products phosphorous acid and phosphorus. It is an acid.

  As a method for purifying the electroless plating solution, a precipitation method is mainly studied. For example, in Patent Document 1, a soluble alkaline earth compound is dissolved and coexisted in a plating solution of a hypophosphorous acid bath, and phosphorous acid and phosphate produced in the course of the plating reaction are sequentially separated as insoluble precipitates. How to do is described.

  Patent Document 2 describes a method in which an electroless plating waste solution is anodized in an electrolytic bath, completely converted into phosphoric acid, and then precipitated and separated as an insoluble phosphate.

  For boric acid separation from the electrolytic plating solution, a method using chelate resin fibers as described in Patent Document 3 is known.

JP 2000-503354 Gazette JP 2005-76103 A JP 2001-179253 A

However, in the method of separating the phosphate precipitate from the electroless plating waste solution described in Patent Documents 1 and 2, calcium phosphate (Ca ₃ (PO ₄ ) ₂ ) has a sufficiently low solubility and can be separated. The calcium phosphite, calcium hypophosphite, and calcium hydrogen phosphates such as calcium dihydrogen phosphate and calcium hydrogen phosphate are all highly soluble and difficult to remove completely.

  In addition, the method for separating boric acid from the electrolytic plating solution described in Patent Document 3 can be used with a simple bath composition, but when there are many coexisting elements such as anions other than boric acid, It is difficult to selectively and completely separate boric acid because it contains ions that are selectively and more strongly adsorbed to the chelate resin than the acid.

  Furthermore, the method described in Patent Document 3 requires a dedicated resin tower and adsorption, washing, and elution equipment, and uses a large amount of a separate chemical as the eluent, and the recovered boric acid-containing liquid is separately concentrated. Without purification, it is difficult to recycle and commercialize the product.

  As described above, it is difficult to effectively recover and utilize nickel as a resource from nickel sludge generated from a nickel plating waste liquid regardless of electroless plating or electrolytic plating, and as a result, many of them are disposed of in landfills.

  Therefore, the present invention has been proposed in view of such circumstances, and provides a method for separating nickel from nickel sludge that can easily recover nickel from nickel sludge containing phosphorus and boric acid. For the purpose.

  A method for separating nickel from nickel sludge according to the present invention that achieves the above-described object is a method for separating nickel from nickel sludge containing nickel and impurities. In the nickel separating method, a sulfuric acid solution is added to nickel sludge to adjust the pH. Adjust to 4-6, then leaching step for solid-liquid separation into precipitate and leachate, concentration step for concentrating leachate obtained in leaching step to obtain concentrate, and cooling the concentrate obtained in concentration step And crystallizing nickel sulfate crystals, and recovering the nickel sulfate crystals by solid-liquid separation.

  In the present invention, nickel can be selectively recovered by a simple operation without using a special apparatus even if it contains an impurity element, particularly phosphorus or boron, which is difficult to separate.

It is a figure which shows the leaching change of the element by the difference in pH performed in the Example.

  Hereinafter, a method for separating nickel from nickel sludge to which the present invention is applied will be described in detail with reference to the drawings. Note that the present invention is not limited to the following detailed description unless otherwise specified.

  Nickel sludge is sludge containing nickel neutralized by adding a neutralizing agent such as slaked lime, caustic soda or sodium carbonate to a solution containing nickel, such as nickel plating waste liquid. Nickel sludge is characterized in that a plurality of sludges are often mixed in various ratios, and there are more kinds of target elements than natural minerals, which are difficult to process. Therefore, when an industrial and economical process is assumed, instead of providing a process for separating individual elements as in ordinary nickel smelting, elements having similar properties are collected and separated as much as possible. It is important to build a process.

  In the present invention, the bulk separation of low basic impurities by selective leaching of nickel sludge and the two-stage crystal crystallization with controlled concentration are combined to separate most of coexisting elements including boric acid and phosphorus having low solubility. Is a process.

  Specifically, a method for separating nickel from nickel sludge (hereinafter simply referred to as nickel separation method) adjusts the pH to 4-6 by adding a sulfuric acid solution to the nickel sludge, and then precipitates, leachate, A leaching step for solid-liquid separation, a concentration step for concentrating the leachate obtained in the leaching step to obtain a concentrate, and cooling the concentrate obtained in the concentration step to crystallize nickel sulfate crystals. A crystallization step of solid-liquid separation of the crystals and impurities. In the nickel separation method, when the nickel sludge contains boric acid, after the concentration step, the concentrated liquid obtained in the concentration step is cooled, and the precipitated boric acid crystals and the cooled liquid are solid-liquid separated. In the crystallization step, the nickel sulfate crystals may be crystallized by concentrating and cooling the cooled liquid obtained in the cooling step. Nickel sludge contains one or more impurities of boron, magnesium, aluminum, iron, phosphorus, calcium, manganese, zinc, and fluorine. Boron is contained in the form of boric acid or borate, and phosphorus is contained in the form of phosphate, phosphite, hypophosphite, or their hydrogen salts.

[Leaching process]
The leaching step separates nickel contained in the nickel sludge from impurities aluminum, iron (III), manganese (III to IV), phosphoric acid, and phosphorous acid. Nickel is an element that is highly basic, that is, precipitates as a hydroxide at high pH. Therefore, selective leaching is possible by acid leaching by controlling the pH of the nickel sludge to a high pH. On the other hand, among the coexisting elements, aluminum, iron (III), and manganese (III to IV) are low in basicity and difficult to dissolve in acids, and therefore can be selectively separated into precipitate residues. is there.

  The pH of the nickel sludge in the leaching step is 4 to 6, and it is preferable to set the pH appropriately according to the type of impurities contained in the nickel sludge, and the selectivity is particularly high around pH 5. In the leaching step, by setting the pH of the nickel sludge to 4-6, aluminum, iron, and manganese can be distributed to the residue in a coexisting state with nickel hydroxide, and nickel can be selectively leached.

  As the acid used for adjusting the pH, sulfuric acid or an aqueous sulfuric acid solution is particularly desirable in view of prevention of reduction and elution of manganese (III to IV) with sulfate crystal separation as the core.

  When phosphorus is contained as an impurity, the behavior differs greatly depending on whether it is phosphoric acid, phosphorous acid, or hypophosphorous acid. When present in the form of phosphoric acid or phosphorous acid, it forms a slightly soluble precipitate with many of the metal ions contained in the nickel sludge, and therefore can be distributed to the residue in the leaching step.

  On the other hand, when it is present in the form of hypophosphorous acid, it does not form a hardly soluble salt with the metal ions present in the sludge, so that it is all distributed to the mother liquor in the subsequent nickel sulfate crystallization step. Can be separated. Also, phosphate, phosphite, and hypophosphite hydrogen salts are distributed into the mother liquor. Therefore, in the nickel separation method, it can be finally separated from nickel regardless of the form of phosphorus. That is, it can be said that this nickel separation method can be applied to sludge of electrolytic plating waste liquid.

  Therefore, in the leaching step, a sulfuric acid solution is added to nickel sludge to adjust the pH to 4 to 6, thereby allowing a precipitate containing aluminum, iron (III), manganese (III to IV), phosphoric acid, and phosphorous acid. And a leachate containing nickel and hypophosphorous acid can be obtained. In the leaching step, aluminum, iron (III), manganese (III to IV), phosphoric acid, and phosphorous acid can be removed from the leachate containing nickel by solid-liquid separation of the precipitate and the leachate. As the solid-liquid separation method, a general solid-liquid separation method such as filtration or centrifugation can be applied.

  In addition, when the moisture content of sludge is particularly low and it is not necessary to separate boric acid in a highly pure form, the sludge is suspended in a minimum amount of water, and after leaching with sulfuric acid, a temperature range of 0 to 20 ° C. After cooling to a low temperature, solid-liquid separation can distribute impurities having high temperature dependence such as boric acid into the residue, so that nickel can be leached.

  In addition, when alkali sulfate is adhered to the nickel sludge due to poor cleaning, it is possible to avoid the alkali from being mixed into the nickel sludge in the leaching step by washing again before the leaching step.

[Concentration process]
In the concentration step, the leachate obtained in the leaching step is concentrated to obtain a concentrated solution. When concentrating, it is preferable to concentrate until the nickel concentration in the leachate reaches 80 to 100 g / l. In this concentration region, when a cooling step is provided next, nickel crystals such as nickel sulfate heptahydrate do not precipitate even if the temperature of the solution is cooled to 0 to 20 ° C. in the cooling step. Boric acid is highly temperature dependent, and can be selectively separated and separated as colorless high-purity crystals in this temperature range.

  When the nickel concentration is less than 80 g / l, the concentration rate is low, and therefore the boric acid separation and recovery rate is lowered. On the other hand, if the nickel concentration exceeds 100 g / l, nickel crystals such as nickel sulfate heptahydrate may be mixed in the boric acid crystals to be recovered.

  The concentration factor for setting the nickel concentration to 80 to 100 g / l can be obtained without analysis every time concentration is performed, if the nickel grade in the nickel sludge and the relationship between the slurry concentration and the leachate concentration are investigated in advance. it can.

[Cooling process]
In the cooling step, impurities such as boric acid having high temperature dependency can be precipitated by cooling the concentrate, and therefore boric acid can be separated when the nickel sludge contains boric acid. Accordingly, this cooling step is performed when nickel sludge of the electrolytic plating solution containing boric acid or other impurities having high temperature dependency is included.

  Specifically, in the cooling step, as described above, by appropriately cooling the concentrated solution within the range of 0 to 20 ° C., nickel is not precipitated, but crystals of impurities having high temperature dependency are precipitated. be able to.

  If the cooling temperature is less than 0 ° C., the concentrated solution may freeze, and if it exceeds 20 ° C., the yield of impurities having high temperature dependence such as boric acid is not preferable. In particular, the lower the temperature, the larger the separation factor between boric acid and nickel. Therefore, it is desirable that the cooling temperature be as close to 0 ° C. as possible in the cooling process.

  In the cooling step, the precipitated crystals such as boric acid and the cooled liquid containing nickel are subjected to solid-liquid separation to separate nickel and impurities. As the solid-liquid separation method, a general solid-liquid separation method such as filtration or centrifugation can be applied.

[Crystalling process]
In the crystallization step, the concentrate obtained in the concentration step is cooled to precipitate nickel sulfate crystals, or the cooled solution obtained by solid-liquid separation in the cooling step is concentrated again. Cool down to precipitate nickel sulfate crystals, with soluble phosphorus compounds such as hypophosphorous acid, phosphate, phosphite, hydrogen hypophosphite, impurities such as magnesium, calcium, zinc and fluorine Separate and collect nickel sulfate crystals. A small amount of impurities such as boric acid may remain in the post-cooling solution obtained in the cooling step. For this reason, in the crystallization process, the impurities such as residual boric acid do not precipitate, and only the nickel sulfate crystals, which are the main component, are precipitated. To recover.

  Specifically, in the crystallization step, first, the volume (liquid amount) of the cooled liquid is 1/2 to 1/4 of the volume (liquid amount) before crystallization, that is, 2 to 4 times. Then, the concentrate is cooled with vigorous stirring, and the concentrate is maintained at 40 to 70 ° C. to crystallize nickel sulfate crystals such as nickel sulfate hexahydrate. When the concentration ratio of the liquid after cooling is less than 2 times, the nickel recovery rate (yield) decreases. On the other hand, if the concentration is concentrated until it exceeds 4 times, a small amount of residual boric acid crystals may be mixed in the nickel sulfate crystals. Therefore, in this crystallization process, it is preferable to make the concentration ratio of the liquid after cooling 2 to 4 times.

  Here, in the case of crystallization of nickel sulfate, if the temperature of the concentrated solution is less than 40 ° C., heptahydrate nickel sulfate that easily forms a double salt with an impurity cationic element is easily crystallized. Since the yield of nickel is greatly reduced, neither is preferable. Therefore, in the crystallization step, after concentration, by maintaining the concentrated solution at 40 to 70 ° C., nickel sulfate hexahydrate containing no impurities can be crystallized, and the yield of nickel sulfate can be increased.

  In the crystallization step, after the nickel sulfate crystal is crystallized, the nickel crystal can be separated and recovered from the impurities by solid-liquid separation. Impurity hypophosphorous acid, phosphate, phosphite, hydrogen hypophosphite, magnesium, calcium, zinc, fluorine are distributed in the mother liquor. As the solid-liquid separation method, a general solid-liquid separation method such as filtration or centrifugation can be applied.

  Furthermore, the liquid (mother liquor) after separating the nickel crystals is mixed with the leachate in the leaching step, and again through the concentration step, cooling step, and crystallization step, the nickel recovery rate, boric acid, etc. Impurity removal rate can be increased.

  In the method for separating nickel from nickel sludge as described above, first, low basic impurities such as aluminum, iron (III), manganese (III to IV), and poor solubility of phosphoric acid and phosphorous acid in the leaching step. Impurities that form precipitates are precipitated and separated in a lump, and then the leachate is concentrated and cooled in a concentration step and a cooling step to separate boric acid having a large temperature dependence, and after cooling By crystallizing the crystal of nickel sulfate in the crystallization process and solid-liquid separation from other impurities, nickel can be separated from the impurities and recovered at a high recovery rate.

  With this nickel separation method from nickel sludge, even if phosphorus or boron contained in electroless plating waste liquid or electrolytic plating waste liquid is difficult to select, it can be selected by simple operation without using special equipment. Thus, nickel can be recovered.

  Specific examples to which the present invention is applied will be described below, but the present invention is not limited to these examples.

  Table 1 shows the composition of the nickel sludge used as a raw material. The composition shown in Table 1 shows the content of elements contained in the dried nickel sludge.

  Nickel sludge 40 wet-g (12.7 g in dry matter equivalent) shown in Table 1 was suspended in 200 ml of water, and 64% by weight sulfuric acid was added, and pH 8.8 to pH 0.5 as shown in Table 2 was added. The leaching process was performed by gradually reducing the pH. The results of analyzing the leaching rate of each element at each stage are shown in Table 2 and FIG.

  As shown in Table 2, in the vicinity of pH 4, only Fe can remain in the residue, but Ni can be leached by nearly 90%. On the other hand, in the vicinity of pH 6, not only Fe but also Al, P, Mn, and Zn can be separated into residues, but the Ni leaching rate decreases to 55%. Therefore, it was confirmed that the optimum pH should be selected and leached in the range of pH 4 to 6 in consideration of the raw material composition.

  Then, the liquid obtained by leaching in the leaching step at pH 5 is filtered, concentrated to a Ni concentration of 80 g / l (concentration step), and then cooled to 10 ° C. (cooling step) to obtain colorless boric acid Crystals were recovered. Furthermore, the liquid was boiled and concentrated again, the liquid volume was further concentrated to ½ volume, cooled to 50 ° C. with vigorous stirring, and the precipitated nickel sulfate hexahydrate crystals were filtered while hot (crystals). Analysis step). The crystals of nickel sulfate hexahydrate were washed with 10 ml of pure water and analyzed for impurity components. The results are shown in Table 3.

  As shown in Table 3, the nickel sulfate hexahydrate contains almost no impurities, is highly basic due to the main component Ni, and is difficult to selectively separate in the leaching process. Ca, Mg, Mn, Zn In addition, since it was separated into a mother liquor in the crystallization step, it was confirmed that almost no impurities were mixed in the nickel sulfate crystal.

  From a series of tests, the main impurity elements can be obtained without chemical purification of individual elements by combining selective leaching in the leaching process and selective crystallization in two stages of the cooling process and the crystallization process. It can be confirmed that each can be reduced to a grade of 0.01% or less.

Claims (6)

In the nickel separation method of separating nickel from nickel sludge containing nickel and impurities,
A leaching step of adding a sulfuric acid solution to the nickel sludge to adjust the pH to 4-6, and then solid-liquid separation into a precipitate and a leachate;
A concentration step of concentrating the leachate obtained in the leaching step to obtain a concentrate,
Cooling the concentrate obtained in the concentration step to crystallize nickel sulfate crystals, and recovering the nickel sulfate crystals by solid-liquid separation; and
A method for separating nickel from nickel sludge. When the nickel sludge contains boric acid, it further has a cooling step of cooling the concentrated liquid obtained in the concentration step and solid-liquid separating the precipitated boric acid crystals and the liquid after cooling,
The post-cooling solution obtained in the cooling step is concentrated again in the crystallization step, and the concentrated solution is cooled to crystallize nickel sulfate crystals. Nickel separation method.   The said impurity is one or more of boron, magnesium, aluminum, iron, phosphorus, calcium, manganese, zinc, and fluorine, The nickel content from the nickel sludge according to claim 1 or 2, Separation method.   The method for separating nickel from nickel sludge according to any one of claims 1 to 3, wherein in the concentration step, the concentrated solution is concentrated until the nickel concentration reaches 80 to 100 g / l. .   In the crystallization step, the liquid after cooling is concentrated until the liquid volume reaches 1/2 to 1/4 times, and then the crystal of nickel sulfate is crystallized while maintaining the liquid temperature at 40 to 70 ° C. The method for separating nickel from nickel sludge according to any one of claims 1 to 4, wherein:   The method for separating nickel from nickel sludge according to any one of claims 2 to 5, wherein in the cooling step, cooling is performed until the temperature of the concentrate is in a range of 0 to 20 ° C. .