JP4216626B2 - Method for recovering nickel sulfate from nickel-containing waste liquid sludge - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a nickel-containing waste liquid sludge inevitably generated in a nickel plating process for the purpose of improving the corrosion resistance, wear resistance and electrical conductivity of the surface of a steel plate or steel product member, and further improving the gloss design. The present invention relates to a method for recovering and recycling nickel sulfate.
For example, the present invention relates to a method for recovering nickel sulfate from nickel-containing waste liquid sludge that can be applied to nickel-containing waste liquids and processes that generate nickel-containing waste liquids, such as nickel plating processes and etching processes for nickel-containing materials.
[0002]
[Prior art]
Various methods have been proposed for recovering valuable metals from waste liquid sludge containing valuable metals.
For example, sludges that are inevitably generated in the plating process are generally in the form of hydroxide, and as a conventional technique for recycling plating waste liquid sludge including valuable metals in the waste liquid, for example, JP-A-2001-2001 As disclosed in JP-A-49362 and JP-A-2002-192168, a method for recovering valuable metals by adjusting the pH of a solution in accordance with the precipitation pH range of each hydroxide is known.
However, the nickel recovered in these conventional techniques is Ni (OH).₂In order to obtain nickel sulfate as a plating raw material from this, the solid content is roasted (Ni (OH)₂→ NiO + H₂O), reduction (NiO + C → Ni + CO), sulfurization treatment (Ni + H)₂SO₄→ NiSO₄+ H₂) There is a problem that a large amount of energy is required.
[0003]
Further, as a method for recovering nickel sulfate more easily and with a minimum energy consumption, for example, Japanese Patent Application Laid-Open No. 2001-253719 proposes a technique characterized by oxidation roasting, sulfuric acid dissolution, and pH adjustment. Yes.
However, this method also requires a large amount of external heat input, and today there is a demand for a process that is more oriented toward the minimum energy consumption, as it is sought to suppress carbon dioxide emissions.
[0004]
[Patent Document 1]
JP 2001-49362 A
[Patent Document 2]
JP 2002-192168 A
[Patent Document 3]
JP 2001-253719 A
[0005]
[Problems to be solved by the invention]
The present invention solves the problems of the prior art as described above, can recover nickel from nickel-containing waste liquid sludge at a high recovery rate of 90% or more, and does not require a great amount of external heat input. To recover nickel sulfate from nickel-containing waste liquid sludge that can be treated with high energy consumption and that achieves zero emissions, so that the amount of waste discharged to the environment such as landfill and water is zero Let it be an issue.
[0006]
[Means for Solving the Problems]
According to the present invention, nickel can be recovered from nickel-containing waste liquid sludge at a high recovery rate of 90% or more by a wet process in which nickel-containing waste liquid sludge is dissolved with sulfuric acid and cooling crystallization is performed. Recovery of nickel sulfate from waste sludge containing nickel that can be processed with little energy consumption without requiring heat, and achieves zero emissions, so that the amount of waste discharged to the environment such as landfill and water is zero The present invention provides a method, the gist of which is as follows, as described in the claims.
[0007]
(1) Add sulfuric acid to the nickel-containing waste liquid sludge to dissolve the solids, and cool and crystallize the filtrate obtained by filtering residual foreign matter from the dissolved liquid.Sulfuric acidNickel crystals are crystallized, the crystallized crystals are redissolved in water, and a small amount of Fe contained in the crystals.³⁺A first step of recovering the nickel sulfate solution by removing the precipitates;
CrystallizedSulfuric acidNickel powder is recovered by adding a cementation treatment to replace iron and nickel by adding iron powder to the filtrate obtained by filtering nickel crystals, and then re-dissolving the nickel iron powder with sulfuric acid to recover the nickel sulfate liquid. A method for recovering nickel sulfate from nickel-containing waste liquid sludge.
(2) The method for recovering nickel sulfate from nickel-containing waste liquid sludge according to (1), wherein the nickel sulfate solution recovered in the first step and the second step is reused as a nickel plating solution.
(3) Fe contained in a small amount in the crystallized crystal before the cooling crystallizing treatment³⁺The amount of Fe by re-dissolution treatment of the crystallized crystal³⁺The method for recovering nickel sulfate from nickel-containing waste liquid sludge according to (1) or (2), wherein the step of removing is omitted.
(4) Sulfuric acid is added to the nickel-containing waste liquid sludge to dissolve the solid content, calcium carbonate is added to the dissolved liquid, and the iron content (Fe³⁺, Fe²⁺) Fe²⁺Fe³⁺The iron-containing gypsum is removed by adjusting the pH and filtering after oxidation to make a nickel stock solution. After concentrating the nickel stock solution, a cooling crystallization treatment is performed.Sulfuric acidNickel crystals are crystallized and recovered.Sulfuric acidThe sulfuric acid from nickel-containing waste liquid sludge is characterized by adding nickel-containing gypsum from which chlorine content has been removed by adjusting the pH and filtering the residual liquid after crystallization of nickel crystals to the nickel-containing waste liquid sludge and circulating it. Nickel recovery method.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to FIGS.
The present invention is a first invention in which a first step comprising a cooling and crystallization step of a solution obtained by dissolving a solid content in nickel-containing waste liquid sludge with sulfuric acid and a second step for improving the nickel recovery rate by a cementation method are combined. And a second invention comprising only a cooling and crystallization step of a solution obtained by dissolving a solid content in a nickel-containing waste liquid sludge with sulfuric acid. Embodiments of each invention will be described below.
<First invention>
1 to 4 show a combination of a first step consisting of a cooling crystallization step of a solution obtained by dissolving a solid content in a nickel-containing waste liquid sludge with sulfuric acid and a second step for improving the nickel recovery rate by a cementation method. It is a flowchart which illustrates embodiment of 1st invention.
[0009]
FIG. 1 is a flowchart illustrating a first step including a cooling crystallization step of a solution obtained by dissolving solid content in nickel-containing waste liquid sludge with concentrated sulfuric acid.
In the first step, concentrated sulfuric acid is added to the nickel-containing waste liquid sludge to dissolve the solid content, and the cooling crystallization process is performed on the filtrate obtained by filtering the residual foreign matter.
<Nickel sludge melting process>
First, the specific gravity of the nickel waste liquid sludge is measured in the stirring storage tank (S-1), and when the specific gravity is large, the specific gravity is adjusted with dilution water (S-2).
Next, about 70% concentrated sulfuric acid is added to the nickel waste liquid sludge, for example, heated by steam and dissolved by the reaction formula (A) below at a temperature of 50 to 100 ° C. (S-3). The reason why the temperature is set to 50 to 100 ° C. is to dissolve the nickel sludge by adjusting the concentration so that the concentration is close to the saturation concentration at a high temperature where the nickel sulfate saturation concentration is large.
Ni (OH)₂ + H₂SO4 → Ni²⁺+ SO_Four ^2- + 2H₂O (A)
Similarly, iron sludge contained in nickel sludge is also dissolved by the following reaction formula (B).
2Fe (OH)_Three + 3H₂SO_Four→ 2Fe³⁺ + 3SO_Four ^2- + 6H₂O (B)
  <Foreign matter and insoluble matter removal step>
Foreign matter in the solution is removed by sieving with, for example, a vibrating sieve (S-4).
Moreover, the fine powder which cannot be removed by the above sieving is removed using, for example, a centrifugal filtration device (S-5).
In addition, the defecation described later³⁺In the case of performing the treatment, this foreign matter and insoluble matter removing step can be omitted.
[0010]
<Cooling crystallization process> (Nickel sulfate crystal recovery)
For example, by using a refrigerator, the nickel sulfate crystals are crystallized in a high yield according to the following reaction formula (C) by cooling to about 0 ° C. where the solubility of nickel sulfate becomes small (S-6). Nickel sulfate crystals are obtained by filtration (S-7).
Ni²⁺ + SO_Four ^2-+ 6H₂O (or 7H₂O) → NiSO_Four・ 6H₂O ↓ (or NiSO_Four・ 7H₂O ↓) (C)
Similarly, a small amount of ferric sulfate contained in the nickel sulfate solution is crystallized by the following reaction formula (D).
2Fe³⁺ + 3SO_Four ^2-+ nH₂O → Fe₂(SO_Four)_Three・ NH₂O ↓ (D)
<Trace Fe³⁺Removal process> (Recovery of nickel sulfate solution)
Water is added to the nickel sulfate crystal and redissolved by the following reaction formula (E) (S-8), and the precipitate is removed (S-9).
NiSO_Four・ 6H₂O (or NiSO_Four・ 7H₂O) → Ni²⁺ + SO_Four ^2- + 6H₂O (or 7H₂O) (E)
Similarly, a small amount of ferric iron in the nickel sulfate crystal is precipitated and removed as ferric hydroxide precipitate by the following reaction formula (F).
Fe₂(SO_Four)_Three・ NH₂O + 6H₂O → 2Fe (OH)_Three↓ + 3H₂SO_Four  + nH₂O ... (F)
  However, a small amount of Fe in the crystal³⁺This step is unnecessary if is not a problem
In the first step above, concentrated sulfuric acid is added to the nickel-containing plating waste sludge to dissolve the solids, and when the sulfuric acid is increased to the sulfate radical saturation region, residual foreign matter that cannot be dissolved is filtered, and the filtrate is Nickel sulfate crystals can be obtained by cooling crystallization treatment.
However, at this stage, the nickel recovery rate is only 70%, and the crystal also contains a small amount of iron. Therefore, the nickel recovery rate can be increased to 90% or more by the next second step.
[0011]
FIG. 2 is a flowchart illustrating the second step of improving the nickel recovery rate by the cementation method.
In the second step, crystallization occurred in the first step.Sulfuric acidThis is a step of performing cementation treatment in which iron powder is added to the filtrate obtained by filtering nickel crystals to replace iron and nickel.
<Nickel cementation process> (Nickel iron powder recovery)
First, diluting water and concentrated sulfuric acid are added to the filtrate obtained in the first step to adjust pH, and iron powder (nickel iron powder is acceptable) is added (S-10), and the ionization tendency of nickel and iron By utilizing the difference, nickel is precipitated as metal in iron powder by the following reaction formula (G), and nickel iron powder is obtained, for example, by vacuum filtration (S-11). On the other hand, iron in the iron powder is replaced with nickel by the following reaction formula (G) and dissolved in the solution. At this time, Fe³⁺Is Fe and the following reaction formula (H)²⁺It becomes.
  Ni²⁺ + Fe → Ni ↓ + Fe²⁺... (G)
  2Fe³⁺  + Fe → 3Fe²⁺ ... (H)
  <Nickel sulfate recovery process>
By adjusting pH and liquid concentration, the amount of iron dissolved is kept to a minimum, nickel in nickel iron powder is dissolved and extracted with sulfuric acid (S-12), and filtered to form a nickel sulfate solution according to the following reaction formula (I) It can be recovered (S-13) and reused as a plating solution raw material in a plating factory.
  Ni + H₂SO_Four → NiSO_Four+ H₂↑ ・ ・ ・ (I)
Note that this step is not necessary when the recovered nickel iron powder is made into a nickel sulfate solution and not recycled to the plating line and supplied as a nickel metal raw material for stainless steel production.
[0012]
<De-nickel solution neutralization process>
The nickel-free solution filtered under vacuum is neutralized with slaked lime slurry by the following reaction formula (J), and iron in the solution becomes ferrous hydroxide starch, sulfate radical becomes gypsum, and becomes neutralized starch ( S-14), for example, it can be treated in a water treatment facility such as a filter press.
  Fe²⁺ + SO_Four ^2-+ Ca (OH)₂  + 2H₂O → Fe (OH)₂↓ + CaSO_Four・ 2H₂O ↓ ・ ・ ・ (J)
In addition, ferrous hydroxide having poor cohesiveness and dehydrating property can be converted into ferric hydroxide starch by air oxidation according to the following reaction formula (K), and a good dehydrated cake can be obtained.
  4Fe (OH)₂ + O₂ + 2H₂O → 4Fe (OH)_Three↓ ... (K)
  FIG. 3 shows a defecation which is a preferred embodiment of the present invention.³⁺It is a flowchart which illustrates a process.
<Fe³⁺Selective neutralization>
By maintaining the pH at around 3.5 using calcium carbonate powder so that the nickel in the solution does not become nickel hydroxide by neutralizing the solution dissolved in concentrated sulfuric acid in the first step (S -21), Fe according to the following reaction formula (L)³⁺Only as a ferric hydroxide precipitate (S-22). At the same time, the mixed precipitate with gypsum produced by the following reaction formula (M) is filtered and removed.³⁺Processing is performed (S-23). As a result, the nickel sulfate crystal obtained from the cooling crystallization process, which is a subsequent process, contains Fe.³⁺Therefore, nickel sulfate can be recovered as crystals. This defecation³⁺When the treatment is not carried out, the nickel sulfate crystals after crystallization are redissolved in water, and Fe³⁺Is removed as a ferric hydroxide precipitate, and nickel is recovered as a nickel sulfate solution. In addition, this Fe removal³⁺When the treatment is performed, the reaction in the cementation process can be promoted, and the amount of the nickel removal solution after the cementation treatment can be reduced. For this purpose only, Fe-free³⁺The treatment may be performed on the residual liquid after crystallization generated in the cooling crystallization process.
  Fe₂(SO_Four)_Three+ 3CaCO_Three+ 9H₂O → 2Fe (OH)_Three+ 3CaSO_Four2H₂O + 3CO₂... (L)
  H₂SO_Four+ CaCO_Three+ H₂O → CaSO_Four2H₂O + CO₂... (M)
[0013]
FIG. 4 is a detailed flowchart of the cementation process in the second step of the present invention.
80 to 90% of nickel in the residual liquid after crystallization is removed by No1 cementation step (S-31), and further, by providing No2 cementation step (S-32), the nickel removal rate is 90% or more. It can be raised to a level close to 100%. When the nickel content in the nickel iron powder is low, the nickel concentration in the nickel refining solution purified in the nickel extraction process does not increase, and the iron content also increases. It is necessary to increase the nickel content in the nickel iron powder to 70 to 80%. In order to increase the nickel content of the nickel iron powder to 70 to 80% while at the same time achieving the nickel removal rate of nickel in the crystallization residual liquid close to 100%, two stages of cementation are provided, and iron The powder is supplied from the No2 cementation process side, the nickel powder in the No2 cementation process containing a small amount of nickel is extracted in whole or in part, and supplied to the No1 cementation process. It is made to react with the crystallization residual liquid of a density | concentration, and it is set as the refined nickel iron powder of high nickel content. Moreover, the pH, oxidation-reduction potential (ORP), temperature, etc. in each cementation reaction tank need to be appropriately controlled.
[0014]
When the nickel is dissolved and extracted from the purified nickel iron powder with sulfuric acid and recovered as a nickel sulfate solution, the surface of the iron powder must be coated to prevent the iron from being dissolved in the nickel iron powder. Before the nickel is dissolved, the surface area of the iron under the coating layer increases, and the amount of dissolved iron increases, the nickel nickel dissolved and extracted refined nickel iron powder (insoluble iron) can be withdrawn from the reaction vessel. is important. The extracted insoluble iron can be effectively used by feeding it back to the No. 2 cementation process as iron powder for cementation. Also, adjust the pH, solution concentration, temperature, etc. of the reaction solution for nickel dissolution extraction to a suitable level so that the dissolution reaction of the purified nickel iron powder proceeds excessively and does not dissolve even a large amount of iron. is important.
Thus, nickel is recovered at a high recovery rate of 90% or more by the two-stage cementation process, and the recovered nickel sulfate can be recycled as a plating raw material. It can be processed with little energy consumption without requiring a great amount of external heat input, and the apparatus is also small. Furthermore, Fe removal³⁺When processing steps are added, Fe, which is an impurity of nickel sulfate recovered³⁺Can be removed, and the load of the cementation process can be extremely reduced.
[0015]
As mentioned above, in this invention, iron powder is added with respect to the filtrate which filtered the crystallized crystal, and nickel is collect | recovered as nickel iron powder by cementation.
As the second step, the nickel filtrate is removed from the filtrate, and iron powder is reacted. From the difference in the ionization tendency between iron and nickel, the remaining nickel is precipitated and recovered to obtain a total nickel recovery rate of 90% or more. it can. Furthermore, the nickel sulfate crystal recovered in the first step is dissolved in water, and the iron content contained in a trace amount is settled and removed as a floc. The nickel iron powder recovered in the second step is dissolved in sulfuric acid. Collect as a solution. The nickel sulfate solution can be reused in the plating step as it is as a nickel-containing plating solution.
In addition, before the cooling crystallization treatment by the above method, Fe contained in a small amount in the crystallized crystal.³⁺Is removed in advance, and a small amount of Fe by re-dissolution treatment of the crystallized crystal³⁺The fraction removal step can be omitted, and the nickel sulfate obtained from the first step can be recovered as crystals.
In the present invention, since the cooling crystallization method and the cementation method are well combined, nickel can be recovered with a high recovery rate of 90% or more, and the energy consumption is also large such as the evaporation drying process and the oxidation culture baking process. Since a process that requires extraneous heat input is not used, it can be processed with very little energy. Moreover, since the processing apparatus can be made small, the equipment cost and the processing facility site can be reduced.
[0016]
In addition, since the recovered nickel can be recovered not as nickel hydroxide but as nickel sulfate, which is a plating raw material, it can be recycled as it is to the plating line. Further, it is also excellent in that the defect that iron is contained at a high concentration as an impurity is greatly improved. When nickel sludge is contained in the nickel waste liquidSulfuric acidIf it does not contain nickel sludgeSulfuric acidWithout going through the dissolution step, cooling and crystallizing the waste liquid,Sulfuric acidAs nickel crystals orSulfuric acidAfter re-dissolving nickel crystals and going through a purification processSulfuric acidIt is recovered as an aqueous nickel solution and recycled to the plating process or supplied as a nickel raw material for other processes. Also, in the nickel waste liquid, ferric iron (Fe) in the form of ions or compounds.³⁺) In the case of Fe³⁺Is present as ions in the waste liquid,³⁺The nickel waste liquid is Fe³⁺When sludge is contained, it is dissolved with acid and then removed from Fe.³⁺The treatment may be performed, and then cooling crystallization may be performed. Thus, the crystal after cooling crystallization is Fe³⁺High-grade without containingSulfuric acidNickel. Note that Fe removal³⁺The treatment is Fe in the crystallization residual liquid.³⁺Since the concentration can be almost zero, the reaction can be promoted in the cementation step, and the amount of nickel removal solution after cementation can be greatly reduced. Furthermore, in order to recover the nickel in the crystallization residual liquid, the cementation method is used as nickel iron powder or from nickel iron powder.Sulfuric acidExtract nickel usingSulfuric acidIt is recovered as an aqueous nickel solution and recycled to the nickel waste solution generation process or supplied as a nickel raw material for other processes. Also, the nickel content in the nickel waste liquid is low, and after cooling crystallization, a sufficient amountSulfuric acidIf nickel crystals cannot be obtained or if the amount of nickel waste liquid generated is small, supply the nickel waste liquid directly to the cementation process without going through the cooling crystallization process, and use nickel iron powder or nickel iron powder.Sulfuric acidExtract nickel withSulfuric acidIt collects as nickel aqueous solution.
[0017]
Also recoveredSulfuric acidThe nickel aqueous solution is further concentrated and dried.Sulfuric acidIt may be recovered as nickel crystals. In the process according to the present invention, when the nickel waste liquid is treated by the cooling crystallization method alone, it is difficult to obtain a nickel recovery rate close to 100%, but the amount of nickel-containing waste can be reduced from the conventional amount. Needless to say. In addition, when nickel waste liquid is treated by the cementation method alone, it is technically possible to obtain a nickel recovery rate of nearly 100%, but in general, removal of nickel in the waste liquid by the cementation method is Compared with copper removal, it is much more difficult, so if you want to process a large amount of nickel waste liquid or high-concentration nickel waste liquid, the equipment will become larger and the operation technology will become more sophisticated. As much as possible in the cooling crystallization processSulfuric acidSince the amount of treatment in the cementation process can be suppressed by collecting nickel, it is desirable in terms of cost.
<Example>
FIG. 5 and FIG.³⁺It is a figure which shows the Example of 1st invention when not processing, FIG. 5 shows the Example of a 1st process, FIG. 6 shows a 2nd process.
In FIG. 5, 100.05 g of diluted water is added to 299.98 g of sludge (S-2), 84.1 g of 70% concentrated sulfuric acid is added and stirred (S-3), and centrifuged (S -5) Cooling crystallization was performed (S-6), and centrifugation was performed again (S-7).Sulfuric acid75% nickel was present in the nickel crystals, and the remaining 25% remained in the liquid after crystallization.
Therefore, by carrying out the No1 cementation step (S-31) and the No2 cementation step (S-32) of FIG. 6, the nickel in the nickel removal liquid could be reduced to 0.21 g / l.
[0018]
<Second invention>
FIG. 7 is a flow diagram illustrating an embodiment of the second invention consisting only of a cooling and crystallization step of a solution obtained by dissolving a solid content in nickel-containing waste liquid sludge with sulfuric acid.
In the second aspect of the invention, sulfuric acid is added to the nickel-containing waste liquid sludge to dissolve the solid content, calcium carbonate is added to the dissolved liquid, and the iron content (Fe³⁺, Fe²⁺) Fe²⁺Fe³⁺The iron-containing gypsum is removed by adjusting the pH and filtering after oxidation to make a nickel stock solution. After concentrating the nickel stock solution, a cooling crystallization treatment is performed.Sulfuric acidNickel crystals are crystallized and recovered.Sulfuric acidThe residual liquid after crystallization of nickel crystals is pH-adjusted and filtered to add nickel-containing gypsum from which chlorine content has been removed to the nickel-containing waste liquid sludge for circulation treatment.
[0019]
Sulfuric acid is added to the nickel-containing waste liquid sludge to dissolve the solids, and a large amount of iron (Fe) inevitably contained in the sludge.³⁺, Fe²⁺) Fe²⁺Is Fe³⁺Since it is oxidized and then removed by pH adjustment and solid-liquid separation operation, the solution used for cooling crystallization can be a nickel solution containing no iron. For this reason, a high-purity crystal can be obtained from the nickel sulfate crystal generated during the cooling crystallization treatment. In addition, the chlorine content derived from nickel chloride mixed and used with nickel sulfate in the plating bath is also removed by adjusting the pH and solid-liquid separation of the crystallization residual liquid. However, since iron and chlorine are not concentrated, the crystallization residual liquid does not need to be discharged out of the system and can be circulated in this process. Therefore, high-purity nickel sulfate can be recovered with a nickel recovery rate close to 100%.
In addition, this method does not use high-temperature dry processing such as calcination, which requires a large amount of energy, but produces nickel sulfate crystals directly only by wet processing, thus achieving an energy-saving process that uses very little energy. .
[0020]
Hereinafter, the flow of the second invention will be described in detail with reference to FIG.
<Nickel sludge melting process>
The nickel hydroxide in the sludge is dissolved by the following reaction formula (N) by dissolving the nickel sludge in, for example, about 70% concentrated sulfuric acid under the condition of pH <1. A condition of about pH 0.7 is preferable. The higher the liquid temperature, the higher the solubility of nickel sulfate and the easier the dissolution reaction to proceed, so a liquid temperature of 60-100 ° C. is preferred. At the same time, ferric hydroxide in the sludge is also dissolved by the following reaction formula (O) (S-41).
Ni (OH)₂ + H₂SO_Four→ Ni²⁺ + SO_Four ^2- + 2H₂O 2Fe (OH)_Three+ 3H₂SO_Four → 2Fe³⁺ + 3SO_Four ^2-+ 6H₂O (N)
2Fe (OH)_Three+ 3H₂SO_Four → 2Fe³⁺ + 3SO_Four ^2-+ 6H₂O ... (O)
  <Fe³⁺Neutralization removal process>
Next, when the pH is about 3.5 with calcium carbonate, ferric ions (Fe³⁺) Is OH⁻Since the solubility product with the anion is extremely small, ferric hydroxide is precipitated according to the following reaction formula (P), and is precipitated together with the gypsum generated simultaneously (S-42).
2Fe³⁺ + 3SO_Four ^2-+ 3CaCO_Three  + 9H₂O → 2Fe (OH)_Three↓ + 3CaSO_Four・ 2H₂O ↓ + 3CO₂↑
                                                    ... (P)
[0021]
<Fe²⁺Oxidation removal process>
Under conditions of about pH 3.5, ferrous ions (Fe²⁺) Does not precipitate as ferrous hydroxide, so hydrogen peroxide (H₂O₂) By Fe²⁺Ion to Fe³⁺By oxidation to ions, ferric hydroxide is precipitated according to the following reaction formula (Q) and precipitated together with gypsum (S-43).
2FeSO_Four + H₂O₂  + 2CaCO_Three  + 6H₂O → 2Fe (OH)_Three↓ + 2CaSO_Four・ 2H₂O ↓ + 2CO₂↑
                                                      ... (Q)
This Fe³⁺, Fe²⁺In the removal step, the phosphate present in the solution is precipitated together with the iron-containing gypsum, which is a mixture of ferric hydroxide and gypsum, so that the phosphate can be removed at the same time.
<Iron-containing gypsum cleaning and removal process>
After the solid-liquid separation, the nickel sulfate solution adhering to the iron-containing gypsum is washed with water or the like to prevent nickel from accompanying the iron-containing gypsum.
<Nickel sulfate solution concentration step>
Since the concentration of nickel sulfate in the iron-containing gypsum cleaning solution becomes dilute, the solution is concentrated to a concentration at which cooling crystallization is possible using a heating device such as an underwater burner (S-45).
[0022]
<Cooling crystallization process>
Since the solubility of the nickel sulfate solution decreases with decreasing temperature, nickel sulfate hydrate crystals are obtained by the following reaction formula (R) by cooling the solution to about 0 ° C. (S-46). This high-purity nickel sulfate crystal can be recycled to a plating factory and used for plating.
Ni²⁺ + SO_Four ^2-+ 6H₂O → NiSO_Four・ 6H₂O ↓ ・ ・ ・ (R)
  Since the residual liquid after cooling crystallization is a nickel sulfate solution close to saturation at room temperature, it contains a large amount of nickel and must be recovered without being discharged out of the system. A part of the solution may be recycled to the nickel stock solution for crystallization, or the whole amount may be sent to the nickel neutralization step of the next step for processing.
<Nickel neutralization process>
The residual liquid after cooling crystallization is diluted with clean water (S-48), and then the pH is adjusted to about 10.5 with calcium hydroxide.²⁺) Is OH⁻Since the solubility product with the anion becomes extremely small, nickel hydroxide is precipitated according to the following reaction formula (S), and is precipitated together with the gypsum generated at the same time (S-49).
In addition, chloride ions of nickel chloride (Cl⁻) Is salified according to the following reaction formula (T)calciumIn the liquid, and after filtration, it is discharged out of the system as a harmless calcium chloride dilute solution (S-50). The nickel-containing gypsum (mixture of nickel hydroxide and gypsum) after solid-liquid separation is washed with water and then circulated in the nickel sludge dissolving step. The nickel hydroxide in the nickel-containing gypsum is mixed with the nickel hydroxide in the sludge. Similarly, it is extracted from nickel-containing gypsum as nickel sulfate, returned to the present process, and finally recovered as nickel sulfate crystals (S-51).
Ni²⁺ + SO_Four ^2-+ Ca (OH)₂ + 2H₂O → Ni (OH)₂↓ + CaSO_Four・ 2H₂O ↓ (S)
Ni²⁺+ 2Cl^-+ Ca (OH)₂ → Ni (OH)₂↓ + CaCl₂... (T)
[0023]
The present invention removes iron and chlorine contained in nickel-containing waste liquid sludge by skillfully utilizing the phenomenon that the chemical equilibrium such as the solubility of iron hydroxide and the solubility of chloride greatly changes with the pH of the solution. In addition, residual liquid generated by cooling crystallization can be circulated.
For this reason, a nickel recovery rate of 90% or more and nearly 100% can be achieved, and at the same time, high-purity nickel sulfate crystals can be obtained. Further, since nickel sulfate crystals are directly generated only by the wet crystallization method, it is possible to provide an excellent process that can be recycled with extremely low energy consumption without requiring high temperature dry processing such as culturing.
Furthermore, with the aim of minimizing external heat input, a process that does not require a large amount of external heat input and can directly produce high-purity nickel sulfate crystals was sought.
In order to achieve a nickel recovery rate of 90% or more in a process that does not require a large amount of external heat input, a wet-processed cooling crystallization method is adopted, and it is recycled to a plating factory so that it can be used in a plating bath. In order to obtain pure nickel sulfate crystals, the iron component inevitably contained in the sludge and the chlorine component mixed in the plating bath are excellently removed in a very simple and effective manner. Regarding the removal of iron, Fe³⁺Is Fe (OH)₃Precipitates and nickel is Ni (OH)₂As the iron-containing gypsum is removed and recovered together with the gypsum generated at the same time by adjusting the pH to a pH range (about 3.5) that does not precipitate as²⁺Is H₂O₂In Fe³⁺After being oxidized, it is removed and recovered as iron-containing gypsum. In addition, regarding the removal of the chlorine content, once the crystallization residual liquid is Ni (OH)₂As a result, the chlorine content is removed by separating and distributing the chlorine content to the liquid side and the nickel content to the solid content side.
By skillfully utilizing the phenomenon that the chemical equilibrium such as the solubility of iron hydroxide and the solubility of chloride changes greatly with the pH of the solution, the iron and chlorine content contained in the waste sludge containing nickel is removed, and the cooling crystal The residual liquid generated in the analysis can also be circulated. For this reason, a nickel recovery rate of 90% or more can be achieved, and at the same time, high-purity nickel sulfate crystals can be obtained. In addition, since nickel sulfate crystals are generated directly only by the cooling crystallization method, it is possible to provide an excellent process that can be recycled with extremely low energy consumption without requiring high-temperature dry processing such as culturing.
<Example>
FIG. 8 is a diagram showing an embodiment of the second invention.
In FIG. 8, after adding 99.64 g of diluted water to the amount of 49.63 g of sludge, adding 120.73 g of 70% concentrated sulfuric acid and stirring, 57.3 g of calcium carbonate and 1.06 g of hydrogen peroxide water were added. Fe³⁺Neutralization, Fe²⁺After iron was removed by an oxidation reaction, iron-containing gypsum was separated by vacuum filtration (S-44).
The filtrate was concentrated by heating (S-45), and after freezing and crystallization (S-46), centrifugal filtration (S-47), it was possible to recover 133.02 g of nickel sulfate crystals, Nickel in the filtrate was 94.3 g / l.
Therefore, nickel was not contained in the filtrate after adding 25.47 g of calcium hydroxide to the filtrate and neutralizing it to separate the nickel-containing gypsum.
[0024]
【The invention's effect】
According to the present invention, nickel can be recovered from the nickel-containing waste liquid sludge at a high recovery rate of 90% or more by a wet treatment in which the nickel-containing waste liquid sludge is dissolved with sulfuric acid and cooling crystallization is performed. Nickel sulfate from nickel-containing waste liquid sludge that can be processed with little energy consumption without requiring external heat input, and achieves zero emissions, which can achieve zero emissions of waste to the environment such as landfills and water areas This method can provide an industrially useful and remarkable effect.
[Brief description of the drawings]
FIG. 1 is a flow diagram illustrating a first step comprising a cooling and crystallization step of a solution obtained by dissolving a solid content in a nickel-containing waste liquid sludge with concentrated sulfuric acid in the first invention.
FIG. 2 is a flowchart illustrating a second step of improving the nickel recovery rate by the cementation method in the first invention.
FIG. 3 shows a defecation which is a preferred embodiment of the first invention.³⁺It is a flowchart which illustrates a process.
FIG. 4 is a detailed flowchart of cementation processing in the second step of the first invention.
FIG. 5 shows the de-Fe removal in the first invention.³⁺It is a figure which shows the Example of the 1st process when not processing.
FIG. 6 shows de-Fe removal in the first invention.³⁺It is a figure which shows the Example of the 2nd process when not processing.
FIG. 7 is a flow diagram illustrating an embodiment of the second invention comprising only a cooling crystallization step of a solution obtained by dissolving solid content in nickel-containing waste liquid sludge with concentrated sulfuric acid.
FIG. 8 is a diagram showing an embodiment of the second invention.

Claims (4)

Sulfuric acid is added to the nickel-containing waste liquid sludge to dissolve the solids, and the filtrate obtained by filtering residual foreign matter from the dissolved liquid is subjected to cooling crystallization treatment to crystallize the nickel sulfate crystal. A first step of recovering a nickel sulfate solution by re-dissolving and precipitating and removing a trace amount of Fe ³⁺ contained in the crystal;
The filtrate obtained by filtering the crystallized nickel sulfate crystal is subjected to a cementation treatment in which iron powder is added to replace iron and nickel to recover nickel iron powder, and the nickel iron powder is redissolved in sulfuric acid to obtain sulfuric acid. And a second step of recovering the nickel liquid. A method for recovering nickel sulfate from the nickel-containing waste liquid sludge. The method for recovering nickel sulfate from nickel-containing waste liquid sludge according to claim 1, wherein the nickel sulfate solution recovered in the first step and the second step is reused as a nickel plating solution. Before the cooling crystallization process, by removing Fe ³⁺ to be trace amounts contained in the crystallization crystal claims, characterized in that to omit the step of removing trace amounts of Fe ³⁺ by remelting process of the crystallization crystals A method for recovering nickel sulfate from nickel-containing waste liquid sludge according to claim 1. By adding sulfuric acid to the nickel-containing waste sludge to dissolve the solids, with the addition of calcium carbonate dissolution liquid, iron contained in the lysis solution ^(Fe 3+, ^{Fe 2+)} to ^{Fe 2+} of the ^{Fe 3+} the iron-containing plaster was removed and the nickel concentrate by pH adjustment and filtration in terms of the oxide is subjected to a cooling crystallization process after concentrating the nickel stock solution was recovered by crystallization of nickel sulfate crystals, the nickel sulfate Nickel sulfate from nickel-containing waste liquid sludge is characterized by adding nickel-containing gypsum from which chlorine content has been removed by adjusting the pH and filtering the crystallized residual liquid to the nickel-containing waste liquid sludge and circulating it. Recovery method.

Images