Process for deep nickel removal from wastewater containing nickel from a nickel carbonate production process

Abstract

The application discloses a kind of deep nickel removal process of nickel-containing wastewater produced in the preparation process of nickel carbonate, specifically: taking the nickel-containing wastewater produced in the preparation process of nickel carbonate, heating to 60-80 DEG C, adding persulfate, under the state of stirring, heat activation reaction 110-130 min, obtain after liquid and nickel-containing precipitate of deep nickel removal, nickel-containing precipitate returns preparation system of nickel carbonate and is reused, nickel removal liquid can be directly discharged as nickel content reaches standard wastewater.The process of the application realizes the heat activation of persulfate by heating, thereby producing high-valence nickel precipitate with lower solubility to achieve the purpose of deep nickel removal, and the deep nickel removal process has high nickel removal depth and efficiency, and strong practicability.

Description

A deep nickel removal process for nickel-containing wastewater in nickel carbonate preparation Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, specifically to a process for deep nickel removal from nickel-containing wastewater during nickel carbonate preparation. Background Technology

[0002] To maintain the sodium ion concentration within a certain range and ensure volume and sulfur balance in the nickel electrowinning production system, a certain amount of electrowinning anolyte is reacted with sodium carbonate solution to prepare nickel carbonate, thereby removing sodium salts and maintaining volume balance. With increasingly stringent environmental regulations, the high-salinity wastewater generated during nickel carbonate production cannot meet the 10 mg / L industrial wastewater nickel discharge standard, necessitating deep heavy metal removal to ensure the wastewater's nickel content complies with discharge standards. Furthermore, traditional soluble anode electrolysis processes also involve nickel carbonate production, typically using a nickel-containing solution with the addition of sodium carbonate solution. This process generates nickel-containing wastewater, primarily composed of sodium sulfate. To ensure nickel carbonate purity, this wastewater also suffers from excessive nickel levels, failing to meet industrial wastewater discharge standards and requiring deep nickel removal to achieve compliance with heavy metal discharge requirements.

[0003] Currently, methods for deep removal of heavy metals include chemical precipitation, adsorption, displacement / reduction, and ion exchange. Chemical precipitation includes inorganic sulfide precipitation and chelation precipitation. This method often requires the addition of large amounts of reagents, resulting in high treatment costs and the presence of sulfur dioxide (S). 2- The dosage is difficult to control, which can easily lead to problems such as foul odor and secondary pollution.

[0004] For example, patent CN111186932B discloses a method for treating nickel-containing wastewater, comprising: adding nickel-containing wastewater to a complex-breaking tank, adjusting its pH value to 2-3, adding ferrous sulfate and hydrogen peroxide to carry out a Fenton oxidation reaction, adjusting the pH value to 5.5-6.5, adding sodium hypochlorite and stirring to carry out the reaction, adding sodium metabisulfite to carry out the reaction, then adding alkali to adjust the pH value to 10.5-11.5, allowing it to settle, adding the obtained waste liquid to a coagulation tank, adding polyaluminum chloride and stirring to carry out the reaction, then adding it to a flocculation tank, adding polyacrylamide and stirring to carry out the reaction, then adding it to a sedimentation tank for sedimentation, and separating the solid and liquid to obtain pretreated wastewater; adjusting the pH value of the pretreated wastewater to 6-7, then adding an adsorbent for adsorption, allowing it to settle and separating the solid and liquid, detecting the total nickel content in the obtained liquid, and discharging it after it meets the standards; the adsorbent is a mixture composed of modified activated carbon, silica aerogel and montmorillonite in a weight ratio of 5-17:1-4:2-8.

[0005] Patent CN114751551A provides a method for treating nickel-containing wastewater in the production of aluminum alloy profiles, in order to solve the defects of low efficiency and poor removal effect of complexed nickel in the existing treatment methods. The method includes the following treatment steps: (1) Wastewater is enriched into a first waste liquid collection tank and the wastewater in the waste liquid collection tank is passed into a porous membrane treatment system for pre-filtration treatment; (2) Preliminary removal of free nickel ions; (3) Flocculant is added to the second waste liquid collection tank to further settle the precipitate; (4) The supernatant of step (2) is passed into a closed complex-breaking adsorption device and stirred for 40-60 minutes; (5) The liquid obtained after step (4) is sent to a third waste liquid collection tank, calcium hydroxide is added to the third waste liquid collection tank to adjust the pH of the wastewater to 10-11, and stirring is continued for 60-90 minutes to cause precipitation. The precipitate is separated to obtain a filtrate that meets the discharge standards.

[0006] All of the above patented technologies employ lengthy heavy metal removal processes. Due to the addition of various reagents, solid waste containing heavy metals is produced after wastewater treatment, requiring secondary treatment. They also suffer from drawbacks such as high equipment investment, leading to increased total investment in the wastewater treatment system and high operating and maintenance costs.

[0007] Patent CN104445731B provides a comprehensive recycling and purification system and process for the supernatant wastewater from nickel carbonate preparation in a nickel electrolysis purification system. The system includes a dechlorination reaction tank, a cooler, a pH adjustment tank, a transfer pump, a security filter, a high-pressure pump, a circulation pump, and a nanofiltration unit connected in sequence. The brine outlet of the nanofiltration unit is connected to a brine storage tank, and the concentrated phase water outlet is connected to a nanofiltration concentrated phase water storage tank. This patented technology achieves effective separation of sodium chloride, sodium sulfate, and heavy metal ions from the supernatant wastewater after nickel carbonate preparation in a nickel electrolysis purification system. It also comprehensively recycles and utilizes the separated sodium chloride solution and the concentrated phase water containing sodium sulfate and heavy metal ions, solving the problem of environmental pollution from wastewater discharge. However, the embodiment only analyzes the salt and does not analyze or detect the heavy metal nickel. Summary of the Invention

[0008] Based on the above, the purpose of this invention is to provide a deep nickel removal process for nickel-containing wastewater in the nickel carbonate preparation process that is short, fast, efficient, and low in cost, so as to achieve the standard discharge of nickel-containing wastewater.

[0009] To achieve its purpose, the present invention adopts the following technical solution:

[0010] A deep nickel removal process for nickel-containing wastewater generated during nickel carbonate preparation involves the following steps: taking nickel-containing wastewater generated during the nickel carbonate preparation process, heating it to 60-80℃, adding persulfate, and activating the reaction under stirring for 110-130 min, preferably 110-120 min, to obtain a deeply nickel-removed liquid and a nickel-containing precipitate. The nickel-containing precipitate is returned to the nickel carbonate preparation system for reuse, while the nickel-removed liquid is discharged as nickel-content wastewater that meets the standards.

[0011] The working principle of this invention is advanced oxidation for nickel removal using persulfate. Advanced oxidation processes (AOPs) refer to a series of chemical oxidation technologies that utilize hydroxyl radicals (•OH) to remove organic pollutants (and some inorganic pollutants) from wastewater. Due to their ability to generate highly reactive free radicals, lack of selectivity in pollutant degradation, rapid degradation rate, and low cost, they are widely used in water treatment.

[0012] Sulfate radicals also possess high redox potentials; the standard potential of sodium persulfate can reach 2.01V, which is higher than that of hydrogen peroxide (1.80V) and permanganate (1.4V). Upon activation, the O0 bonds in the molecule break to generate more potent sulfate radicals (•SO₄). 4- The standard potential can reach 2.6V, greatly improving the oxidation effect. Sulfate free radicals (•SO₄²⁻) 4- •OH is a highly reactive free radical, commonly found in aqueous solutions and the atmosphere. In aqueous solutions, compared to hydroxyl radicals (•OH), it is more reactive. - Sulfate radicals have a longer lifetime, meaning they have a longer contact time with contaminants in aqueous solutions, which is more conducive to the degradation of contaminants. This allows the nickel removal process of the present invention to achieve excellent deep nickel removal efficiency and depth, thereby achieving the purpose of deep nickel removal.

[0013] Furthermore, the present invention also includes the following steps: before heating and activation, the nickel-containing wastewater is sampled and its nickel content is analyzed. The purpose of this step is to understand the nickel content in the nickel-containing wastewater, facilitating the determination of the quality of persulfate to be added, in order to achieve a better deep nickel removal effect. Furthermore, when sampling the nickel-containing wastewater, it is essential to stir it thoroughly to ensure the accuracy of the nickel content detection data.

[0014] Furthermore, the nickel content in the nickel-containing wastewater is 50-80 mg / L.

[0015] Furthermore, the amount of persulfate added to the nickel-containing wastewater is 2.0-2.5 g / L. Within this range, the efficiency and depth of deep nickel removal can be greatly improved. Preferably, it is 2.0 g / L.

[0016] Furthermore, the persulfate is sodium persulfate. Compared with potassium and ammonium salts, sodium persulfate has advantages such as lower price, better solubility, greater stability, easier storage and transportation, and fewer side reactions.

[0017] Furthermore, the heating method of the present invention is water bath heating, which can make the persulfate advanced oxidation deep nickel removal system heat evenly and keep it within the activation temperature range, which is beneficial to the activation of persulfate.

[0018] Furthermore, the present invention employs a mechanical stirring method, with a rotation speed of 150-180 r / min, preferably 160 r / min.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. This invention uses persulfate advanced oxidation technology for deep nickel removal, which is a short process, simple to operate and requires little investment.

[0021] 2. This invention is the first to apply persulfate-based advanced oxidation technology to the deep removal of nickel from sulfate systems. Compared with traditional advanced oxidation technologies, persulfate advanced oxidation technology generates sulfate free radicals (•SO4). - It is a novel advanced oxidation technology with sulfate as the main active oxide, which has the advantages of higher redox potential, better selectivity, longer half-life, greater stability, less affected by solution acidity and alkalinity, more activation modes, and minimal impact of the final product sulfate on the system.

[0022] 3. The activation of persulfate in this invention is carried out by thermal activation. Compared with photoactivation, alkali activation, transition metal and oxide activation, activated carbon activation, and composite activation, thermal activation is simple and safe.

[0023] 4. The persulfate advanced oxidation deep nickel removal process involved in this invention can achieve the purpose of nickel precipitation and wastewater discharge meeting standards by automatically adding persulfate.

[0024] In summary, the process of this invention achieves thermal activation of persulfate through heating, thereby producing high-valence nickel precipitates with lower solubility and thus achieving the purpose of deep nickel removal. The deep nickel removal process has high nickel removal depth and efficiency, and is highly practical. Attached Figure Description

[0025] Figure 1 is a process flow diagram of the present invention. Detailed Implementation

[0026] The process flow of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] As shown in Figure 1, the present invention provides a deep nickel removal process for nickel-containing wastewater in the nickel carbonate preparation process, which specifically includes the following steps:

[0028] Step (1): The nickel carbonate supernatant produced by the thickener during the preparation of nickel carbonate is used as nickel-containing wastewater. The nickel content in the supernatant is sampled and analyzed.

[0029] Step (2): Add 2L of nickel-containing wastewater from step (1) into a 5L beaker and heat it to 60-80℃ using a water bath.

[0030] Step (3): Weigh a certain amount of sodium persulfate using an electronic balance and add it to the beaker heated in step (2). React under stirring for 110-120 minutes to obtain a liquid after deep nickel removal and a nickel-containing precipitate. The nickel-containing precipitate is returned to the nickel carbonate preparation system for reuse.

[0031] Step (4): After filtering the deep nickel removal solution obtained in step (3), take a sample and analyze its nickel content.

[0032] Example 1

[0033] The nickel content in the nickel-containing wastewater was 69 mg / L, the amount of sodium persulfate added was 2 g / L, the reaction temperature was 60-80℃, and the reaction time was 110 min.

[0034] Table 1. Analysis results of advanced oxidation method for deep nickel removal in Example 1

[0035]

[0036] Example 2

[0037] The nickel content in the nickel-containing wastewater is 65 mg / L, the sodium persulfate dosage is 2 g / L, the reaction temperature is 60-80℃, and the reaction time is 120 min.

[0038] Example 2: Analytical Results of Advanced Oxidation Method for Deep Nickel Removal

[0039]

[0040] The applicant found that within the activation temperature range of 60-80℃, temperature changes had no significant impact on the deep nickel removal effect. Furthermore, since water bath heating was used, the temperature fluctuated. Therefore, the reaction temperatures of Examples 1-2 were maintained between 60-80℃, rather than at a specific point value.

[0041] As can be seen from the two embodiments above, the present invention uses sodium persulfate for deep nickel removal, and the nickel removal rate can reach more than 93%, which can achieve rapid and efficient nickel removal effect. Moreover, the nickel content in the deep nickel-removed liquid produced is less than 10 mg / L, which meets the discharge standard for nickel-containing wastewater.

Claims

1. A process for deep nickel removal from nickel-containing wastewater during nickel carbonate preparation, characterized in that, The nickel-containing wastewater, mainly composed of sodium sulfate, generated during the nickel carbonate preparation process is heated to 60-80℃, and persulfate is added. The reaction is activated for 110-130 minutes under stirring to obtain a deeply nickel-removed liquid and a high-valence nickel precipitate. The high-valence nickel precipitate is returned to the nickel carbonate preparation system for reuse, while the nickel-removed liquid is discharged as nickel-content wastewater that meets the standards.

2. The deep nickel removal process for nickel-containing wastewater in the nickel carbonate preparation process according to claim 1, characterized in that, It also includes the following steps: Before heating and activation, the nickel-containing wastewater is sampled and the nickel content is analyzed.

3. The deep nickel removal process for nickel-containing wastewater in the nickel carbonate preparation process according to claim 2, characterized in that, The nickel content in the nickel-containing wastewater is 50-80 mg / L.

4. A deep nickel removal process for nickel-containing wastewater in nickel carbonate preparation according to any one of claims 1-3, characterized in that, The amount of persulfate added to the nickel-containing wastewater is 2.0-2.5 g / L.

5. The deep nickel removal process for nickel-containing wastewater in the nickel carbonate preparation process according to claim 4, characterized in that, The amount of persulfate added to the nickel-containing wastewater is 2.0 g / L.

6. A deep nickel removal process for nickel-containing wastewater in nickel carbonate preparation according to any one of claims 1-3 and 5, characterized in that, The persulfate is sodium persulfate.

7. The deep nickel removal process for nickel-containing wastewater in the nickel carbonate preparation process according to claim 6, characterized in that, The heating method is water bath heating.

8. The deep nickel removal process for nickel-containing wastewater in the nickel carbonate preparation process according to claim 6, characterized in that, Mechanical stirring is used, with a rotation speed of 150-180 r / min.

9. The deep nickel removal process for nickel-containing wastewater in the nickel carbonate preparation process according to claim 8, characterized in that, The rotational speed is 160 r / min.

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