A wastewater treatment process in the preparation of nickel cobalt hydroxide

Abstract

The invention discloses a wastewater treatment process in a nickel and cobalt hydroxide preparation process, comprising the following steps: S1. sequentially subjecting a laterite nickel ore acid leaching solution to iron and aluminum removal and nickel and cobalt precipitation treatments to obtain wastewater; S2. sequentially subjecting the wastewater to chromium ion, manganese ion, and silicon ion removal treatments to obtain a suspension; S3. reusing part of the suspension and continuing to subject it to iron and aluminum removal; sequentially subjecting the remaining suspension to homogenization, alkali adjustment, standing, and CCD countercurrent washing, followed by solid-liquid separation to obtain a supernatant and a slag phase, collecting the slag phase, and neutralizing and discharging the supernatant. The laterite nickel ore wastewater treated by the method can contain pollutants that meet emission standards, and the method has high safety.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgical wastewater treatment, and in particular to a wastewater treatment process in the preparation of nickel cobalt hydroxide. Background Art

[0002] Laterite nickel mine wastewater primarily contains pollutants such as nickel, cobalt, iron, zinc, manganese, and sulfate. The commonly used treatment method for laterite nickel mine wastewater is to add lime milk to the neutralized liquid from the laterite nickel ore tailings to remove manganese through precipitation. After filtration, the wastewater is discharged into the sea. To ensure that the wastewater meets discharge standards and achieves resource utilization during the treatment process, the primary focus is on removing nickel ions while ensuring effluent clarity and safety. Therefore, improvements to the commonly used laterite nickel mine wastewater treatment method are necessary.

[0003] In the related art, patent publication number CN217026042U discloses a nickel and cobalt removal system for the neutralized liquid of laterite nickel ore tailings. In this scheme, a filtration unit first filters the neutralized liquid of laterite nickel ore tailings, which can effectively reduce the solid content (such as leaching residue, neutralization residue or sand and gravel) in the neutralized liquid. Then, an adsorption unit is used to perform adsorption treatment on the filtered liquid. Through at least three sets of adsorption devices arranged in parallel, nickel and cobalt in the neutralized liquid of laterite nickel ore tailings are removed. Finally, a desorbent is introduced into the adsorption device through a desorbent supply unit, and the adsorption device is circulated and desorbed through the above-mentioned circulation pipeline.

[0004] Although the above method recycles nickel and cobalt, it does not completely treat high concentrations of other pollutants such as iron, aluminum, manganese, silicon, chromium, etc., and cannot achieve the recycling of wastewater. Summary of the Invention

[0005] In view of this, the present application provides a wastewater treatment process in the preparation process of nickel cobalt hydroxide, which can clean wastewater to meet emission standards and has high safety.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions:

[0007] The present application provides a wastewater treatment process in the preparation process of nickel cobalt hydroxide, comprising the following steps:

[0008] S1. The laterite nickel ore acid leaching solution was sequentially subjected to iron and aluminum removal, nickel and cobalt precipitation treatment to obtain wastewater;

[0009] S2. The wastewater is sequentially treated to remove chromium ions, manganese ions, and silicon ions to obtain a suspension;

[0010] S3. Reuse part of the suspension and continue to remove iron and aluminum; the remaining suspension is homogenized, adjusted with alkali and allowed to stand, and washed in CCD countercurrent, followed by solid-liquid separation to obtain a supernatant and a slag phase. The slag phase is collected, and the supernatant is discharged after neutralization.

[0011] Preferably, the number of stages of CCD countercurrent washing is 9, and the washing ratio is 2.0-2.5.

[0012] Preferably, the step of removing chromium ions is as follows: the step of removing chromium ions from wastewater is as follows: adding a reducing agent to the wastewater, performing a reduction reaction, and then precipitating and separating to obtain a primary liquid phase; the reducing agent is a hydrolyzate of biomass straw; the preparation method of the biomass straw hydrolyzate is as follows: ball-grinding the biomass straw into powder, and then adding concentrated sulfuric acid to hydrolyze the powder.

[0013] Preferably, the step of removing manganese ions is as follows: introducing a mixed gas of SO2 and air into the primary liquid phase, adjusting the pH of the primary liquid phase to 3-4 and the temperature to 30-80°C, and performing precipitation separation to obtain a secondary liquid phase.

[0014] Preferably, the step of removing silicon ions is as follows: at a pressure of 4.5-5.5 MPa, adjusting the pH of the secondary liquid phase to 1-2, controlling the temperature to 150-200° C., and performing precipitation separation to obtain a suspension.

[0015] Preferably, in step S3, the recycled suspension accounts for 20-30% of the mass of the entire suspension.

[0016] Preferably, the iron and aluminum removal step includes a first stage of iron and aluminum removal and a second stage of iron and aluminum removal.

[0017] Preferably, the process conditions for the one-stage iron and aluminum removal are: controlling the temperature to 80-85° C. and the pH to 3.6-4.0.

[0018] Preferably, the process conditions for the second-stage iron and aluminum removal are: controlling the temperature to 75-80°C and adjusting the pH to 4.6-5.0 using NaOH.

[0019] Preferably, the process conditions for nickel-cobalt precipitation are: adjusting the pH value to 7.8-8.3 using NaOH, adjusting the reaction temperature to 70° C., and the reaction time to 3-4 minutes.

[0020] The beneficial effects of this application are as follows:

[0021] The wastewater treatment process of the present application can realize the resource utilization of laterite nickel mine wastewater, and the purified liquid has high clarity, high safety and meets the discharge standards;

[0022] The wastewater treatment process of the present application recycles sodium salt and sulfate through a circulation process, reduces the amount of auxiliary material sodium sulfate, and has a good liquid-slag separation effect;

[0023] The process sequence of removing iron and aluminum, precipitating nickel and cobalt, and removing chromium ions, manganese ions, and silicon ions in the present application is beneficial to saving raw materials. The pH value in the liquid phase first rises and then falls, which reduces mutual interference and allows for more thorough treatment of each impurity ion.

[0024] The present application introduces multi-stage CCD countercurrent washing in the wastewater treatment process, which overcomes the disadvantage that the suspension cannot be directly subjected to filter press for solid-liquid separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the process flow chart of this scheme. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] like Figure 1 As shown, a wastewater treatment process in the preparation process of nickel cobalt hydroxide includes the following steps:

[0028] S1. The laterite nickel ore acid leaching solution was sequentially subjected to iron and aluminum removal, nickel and cobalt precipitation treatment to obtain wastewater;

[0029] S2. The wastewater is sequentially treated to remove chromium ions, manganese ions, and silicon ions to obtain a suspension;

[0030] S3. Reuse part of the suspension and continue to remove iron and aluminum; the remaining suspension is homogenized, adjusted with alkali and allowed to stand, and washed in CCD countercurrent, followed by solid-liquid separation to obtain a supernatant and a slag phase. The slag phase is collected, and the supernatant is discharged after neutralization.

[0031] The present application relates to the reuse of the suspension. As known to those skilled in the art, after laterite nickel ore undergoes acid leaching, iron and aluminum removal, and nickel and cobalt precipitation, a large amount of sodium ions and sulfate ions are present. Therefore, both the wastewater and the subsequent suspension contain a large amount of sodium salts and sulfates. This solution partially reuses the suspension to the iron and aluminum removal step and continues the subsequent process to reduce the use of auxiliary materials and further remove residual iron ions in the wastewater. Sodium sulfate reacts with the iron ions in the wastewater to form a precipitate of sodium ferroaluminate as follows:

[0032] 3Fe 3+ +2SO4 2- +Na + +6H2O→Na Fe3(SO4)2(OH)6+6H + ;

[0033] In this scheme, the number of CCD countercurrent washing stages is 9, and the washing ratio is 2.0-2.5; since the suspension contains a large amount of solid particles and is in a flocculent state, it is not easy to be directly separated into solid and liquid by the filter and the filter press, so this application designs a multi-stage CCD countercurrent washing process; the CCD countercurrent washing of this application utilizes 9 thickeners to perform solid-liquid separation on the treated suspension, and then the slag obtained from the 8 thickeners is passed to the 9th thickener, and the 9th thickener further filters, precipitates and washes the slag obtained by precipitation from No. 1 to No. 8, and the slag from No. 9 enters the filter press for filtration, and finally achieves solid-liquid separation.

[0034] The steps for removing chromium ions are as follows: the steps for removing chromium ions are as follows: adding a reducing agent to the wastewater, carrying out a reduction reaction, and then precipitating and separating to obtain a primary liquid phase; the reducing agent is a hydrolyzate of biomass straw; the preparation method of the biomass straw hydrolyzate is as follows: ball-grinding the biomass straw into powder, and then adding concentrated sulfuric acid to hydrolyze the powder, wherein the hydrolysis temperature is 30-80°C, the solid-liquid ratio of the hydrolysis is 10-100g / L, and the hydrolysis time is 1-20h; the original biomass straw does not have reducing properties, but the biomass straw is acid-hydrolyzed to obtain aldehyde substances that can be used as a reducing agent, and after adding the reducing agent, the hexavalent chromium ions in the wastewater are converted into trivalent chromium and precipitated in the form of Cr(OH)3, thereby removing the chromium in the wastewater, and obtaining a primary liquid phase through precipitation and separation.

[0035] The steps for removing manganese ions are as follows: a mixture of SO2 and air is introduced into the primary liquid phase, and the pH of the primary liquid phase is adjusted to 3-4, the temperature is 30-80°C, and precipitation and separation are performed to obtain a secondary liquid phase, in which MnO2 or Mn3O4 is precipitated. The reaction formula for removing manganese ions is:

[0036] MnSO4+SO2+O2+2H2O=MnO2+2H2SO4

[0037] 2MnSO4+SO2+O2+3H2O=Mn3O4+3H2SO4

[0038] The steps for removing silicon ions are as follows: at a pressure of 4.5-5.5 MPa, the pH of the secondary liquid phase is adjusted to 1-2, the temperature is controlled at 150-200°C, and precipitation and separation are performed to obtain a suspension. During this process, silicate radicals combine with hydrogen ions to convert into water-insoluble silicic acid precipitates. Under high temperature and high pressure conditions, the silicic acid reacts to form silicon dioxide and is removed. After precipitation and separation, a suspension is obtained. The advantage of converting silicic acid into silicon dioxide is that it overcomes the problem that silicic acid is extremely difficult to filter because it mostly exists in the form of hydrogel in the solution.

[0039] During the treatment process of removing chromium ions, manganese ions and silicon ions, since the liquid phase after precipitation contains a large amount of flocs, the precipitation separation is carried out by using a pipeline to extract the liquid phase from above the reaction tank, and the obtained liquid phase enters the next treatment process.

[0040] In step S3, the recycled suspension accounts for 20-30% of the mass of the total suspension. The recycled suspension carries a large amount of sodium ions and sulfate ions, which can reduce the use of sodium salts and sulfates. However, if too much suspension is recycled, the difficulty of removing iron and aluminum and precipitating nickel and chromium will increase due to the obstruction of particulate matter in the liquid.

[0041] The iron and aluminum removal steps include a first-stage iron and aluminum removal and a second-stage iron and aluminum removal.

[0042] The process conditions for the first-stage iron and aluminum removal are: controlling the temperature at 80-85°C and the pH at 3.6-4.0; after precipitation, a slag phase is obtained to remove the iron and aluminum; in the first-stage iron and aluminum removal process, impurity metal elements such as copper, zinc, and scandium are also removed simultaneously.

[0043] The process conditions for the second-stage iron and aluminum removal are: controlling the temperature at 75-80°C, adjusting the pH to 4.6-5.0 using NaOH; after precipitation, a slag phase is obtained to further remove iron and aluminum.

[0044] The process conditions for nickel-cobalt precipitation are: using NaOH to adjust the pH value to 7.8-8.3, adjusting the reaction temperature to 70°C, and the reaction time to 3-4 minutes; after precipitation, the slag phase is nickel-cobalt hydroxide, which is used for subsequent production, and the resulting liquid phase is wastewater, which enters the next stage of treatment.

[0045] The CCD 9-stage countercurrent washing of the present application is achieved by the following device: the CCD thickening device is provided with 9 thickeners arranged in sequence and a filter press connected to the last thickener; specifically, the CCD thickening device is provided with 8 thickening tanks, of which the first eight thickeners are arranged in sequence to perform solid-liquid separation on the wastewater, the slag from the first eight thickeners is directed to the ninth thickener, and the No. 9 thickener further filters, precipitates and washes the slag obtained by precipitation of No. 1 to No. 8, and the slag from No. 9 enters the filter press for filtration.

[0046] The present invention is further described below through specific examples.

[0047] Example 1

[0048] A wastewater treatment process in the preparation of nickel cobalt hydroxide comprises the following steps:

[0049] S1. The laterite nickel ore acid leaching solution is sequentially subjected to iron and aluminum removal and nickel and cobalt precipitation treatment to obtain wastewater; the iron and aluminum removal step includes a first iron and aluminum removal step and a second iron and aluminum removal step; the process conditions for the first iron and aluminum removal step are: controlling the temperature at 80°C and the pH at 3.6; the process conditions for the second iron and aluminum removal step are: controlling the temperature at 75°C and adjusting the pH to 4.6 using NaOH; the process conditions for nickel and cobalt precipitation are: adjusting the pH to 7.8 using NaOH, adjusting the reaction temperature to 70°C, and the reaction time to 3 min;

[0050] S2. The wastewater is sequentially treated to remove chromium ions, manganese ions, and silicon ions to obtain a suspension; the chromium ion removal step is as follows: adding a reducing agent to the wastewater to carry out a reduction reaction, followed by precipitation separation to obtain a primary liquid phase; the reducing agent is a hydrolyzate of biomass straw; the preparation method of the biomass straw hydrolyzate is as follows: the biomass straw is ball-milled into powder, and then concentrated sulfuric acid is added to hydrolyze the obtained product, the hydrolysis temperature is 80°C, the solid-liquid ratio of the hydrolysis is 10g / L, and the hydrolysis time is 20h; the manganese ion removal step is as follows: introducing a mixed gas of SO2 and air into the primary liquid phase, and adjusting the pH of the primary liquid phase to 3, the temperature to 30°C, and precipitation separation to obtain a secondary liquid phase; the silicon ion removal step is as follows: adjusting the pH of the secondary liquid phase to 1 at a pressure of 4.5MPa, controlling the temperature to 150°C, and precipitation separation to obtain a suspension;

[0051] S3. 30% of the suspension is reused and iron and aluminum removal is continued; the remaining suspension is homogenized, alkali-adjusted and allowed to stand, and CCD countercurrent washing is performed in sequence, followed by solid-liquid separation to obtain a supernatant and a slag phase. The slag phase is collected, and the supernatant is discharged after neutralization; the number of CCD countercurrent washing stages is 9, and the washing ratio is 2.0.

[0052] Example 2

[0053] A wastewater treatment process in the preparation of nickel cobalt hydroxide comprises the following steps:

[0054] S1. The laterite nickel ore acid leaching solution is sequentially subjected to iron and aluminum removal and nickel and cobalt precipitation treatment to obtain wastewater; the iron and aluminum removal step includes a first iron and aluminum removal step and a second iron and aluminum removal step; the process conditions for the first iron and aluminum removal step are: controlling the temperature at 85°C and the pH at 4.0; the process conditions for the second iron and aluminum removal step are: controlling the temperature at 80°C and adjusting the pH to 5.0 using NaOH; the process conditions for nickel and cobalt precipitation are: adjusting the pH to 8.3 using NaOH, adjusting the reaction temperature to 70°C, and the reaction time to 4 min;

[0055] S2. The wastewater is sequentially treated to remove chromium ions, manganese ions, and silicon ions to obtain a suspension; the chromium ion removal step is as follows: adding a reducing agent to the wastewater to carry out a reduction reaction, followed by precipitation separation to obtain a primary liquid phase; the reducing agent is a hydrolyzate of biomass straw; the preparation method of the biomass straw hydrolyzate is as follows: the biomass straw is ball-milled into powder, and then concentrated sulfuric acid is added to hydrolyze the obtained product, the hydrolysis temperature is 30°C, the solid-liquid ratio of the hydrolysis is 100g / L, and the hydrolysis time is 1h; the manganese ion removal step is as follows: introducing a mixed gas of SO2 and air into the primary liquid phase, and adjusting the pH of the primary liquid phase to 4, the temperature to 80°C, and precipitation separation to obtain a secondary liquid phase; the silicon ion removal step is as follows: adjusting the pH of the secondary liquid phase to 2 at a pressure of 5.5MPa, controlling the temperature to 200°C, and precipitation separation to obtain a suspension;

[0056] S3. 20% of the suspension is recycled and further iron and aluminum removal is performed; the remaining suspension is homogenized, alkali adjusted and allowed to stand, and CCD countercurrent washing is performed in sequence, followed by solid-liquid separation to obtain a supernatant and a slag phase. The slag phase is collected, and the supernatant is discharged after neutralization; the number of CCD countercurrent washing stages is 9, and the washing ratio is 2.5.

[0057] Test Evaluation

[0058] The concentrations of pollutants in the laterite nickel ore wastewater and the test results of the concentrations of the pollutants after treatment in Example 1 are shown in Table 1.

[0059] Table 1 Comparison of pollutant concentrations before and after treatment

[0060]

[0061] From the above results, it can be seen that the resource utilization of laterite nickel mine wastewater can be realized, and the purified liquid has high clarity, high safety and meets the emission standards.

[0062] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A wastewater treatment process in the preparation of nickel cobalt hydroxide, characterized in that: The following steps are involved: S1. The laterite nickel ore acid leaching solution was sequentially subjected to iron and aluminum removal, nickel and cobalt precipitation treatment to obtain wastewater; S2. The wastewater is sequentially treated to remove chromium ions, manganese ions, and silicon ions to obtain a suspension; S3. Reuse part of the suspension and continue the iron and aluminum removal step; homogenize the remaining suspension, adjust the alkali and let it stand, and perform CCD countercurrent washing, and then perform solid-liquid separation to obtain a supernatant and a slag phase, collect the slag phase, and discharge the supernatant after neutralization.

2. The wastewater treatment process in the preparation process of nickel cobalt hydroxide according to claim 1, characterized in that: The number of stages of the CCD countercurrent washing is 9, and the washing ratio is 2.0-2.

5.

3. The wastewater treatment process in the preparation process of nickel cobalt hydroxide according to claim 1, characterized in that: The steps of removing chromium ions are as follows: adding a reducing agent to the wastewater to carry out a reduction reaction, and then precipitating and separating to obtain a primary liquid phase; the reducing agent is a hydrolyzate of biomass straw; and the preparation method of the biomass straw hydrolyzate is as follows: ball-grinding the biomass straw into powder, and then adding concentrated sulfuric acid to hydrolyze the powder.

4. The wastewater treatment process in the preparation process of nickel cobalt hydroxide according to claim 3, characterized in that: The steps of removing manganese ions are as follows: introducing a mixed gas of SO2 and air into the primary liquid phase, adjusting the pH of the primary liquid phase to 3-4 and the temperature to 30-80°C, and performing precipitation separation to obtain a secondary liquid phase.

5. The wastewater treatment process in the preparation process of nickel cobalt hydroxide according to claim 4, characterized in that: The steps of removing silicon ions are as follows: adjusting the pH of the secondary liquid phase to 1-2 under a pressure of 4.5-5.5 MPa, controlling the temperature to 150-200° C., and performing precipitation separation to obtain a suspension.

6. The wastewater treatment process in the preparation process of nickel cobalt hydroxide according to claim 1, characterized in that: In step S3, the recycled suspension accounts for 20-30% of the mass of the entire suspension.

7. The wastewater treatment process in the preparation process of nickel cobalt hydroxide according to claim 1, characterized in that: The iron removal step includes a first stage of iron removal and a second stage of iron removal.

8. The wastewater treatment process in the preparation process of nickel cobalt hydroxide according to claim 7, characterized in that: The process conditions for the one-stage iron and aluminum removal are: controlling the temperature to 80-85° C. and the pH to 3.6-4.

0.

9. The wastewater treatment process in the preparation process of nickel cobalt hydroxide according to claim 7, characterized in that: The process conditions for the two-stage iron and aluminum removal are: controlling the temperature to 75-80° C. and adjusting the pH to 4.6-5.0 using NaOH.

10. The wastewater treatment process in the preparation process of nickel cobalt hydroxide according to claim 1, characterized in that: The process conditions for nickel and cobalt precipitation are: adjusting the pH value to 7.8-8.3 using NaOH, adjusting the reaction temperature to 70° C., and the reaction time to 3-4 minutes.

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