Process for deeply removing nickel from nickel-containing wastewater in nickel carbonate preparation process

Abstract

The invention discloses a process for deeply removing nickel from nickel-containing wastewater produced in a nickel carbonate preparation process, which specifically comprises the following steps: heating the nickel-containing wastewater produced in the nickel carbonate preparation process to 60-80 DEG C, adding persulfate, carrying out thermal activation reaction for 110-130 minutes in a stirring state to obtain deeply nickel-removed liquid and nickel-containing precipitate, and returning the nickel-containing precipitate to a nickel carbonate preparation system for reuse, and the nickel-removed liquid can be directly discharged as wastewater with the nickel content reaching the standard. According to the process, persulfate thermal activation is achieved through heating, so that high-valence nickel precipitates with lower solubility are produced, the purpose of deep nickel removal is achieved, and the deep nickel removal process is high in nickel removal depth and nickel removal efficiency and high in practicability.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, and in particular to a process for deep nickel removal from nickel-containing wastewater in a nickel carbonate preparation process. Background Art

[0002] In order to keep the sodium ion concentration in the electrolytic nickel production system within a certain range and maintain the volume balance and sulfur balance of the production system, a certain amount of electrolytic anode liquid is required to react with sodium carbonate solution to prepare nickel carbonate to remove sodium salt and maintain volume balance. With the improvement of environmental protection requirements, the high-salt wastewater produced in the nickel carbonate preparation process cannot meet the 10mg / l industrial wastewater nickel discharge standard, and heavy metals must be deeply removed to ensure that the nickel content in the wastewater meets the discharge standard. At the same time, there is also a nickel carbonate preparation process in the traditional soluble anode electrolysis process. Nickel carbonate is usually produced by adding sodium carbonate solution to a nickel-containing solution. In the process of producing nickel carbonate, nickel-containing wastewater mainly composed of sodium sulfate is produced. In order to ensure the purity of nickel carbonate, the wastewater produced also has the problem of excessive nickel and cannot achieve the standard discharge of industrial wastewater. It is necessary to deeply remove nickel before the standard discharge of heavy metals can be achieved.

[0003] At present, the methods for deep removal of heavy metals include chemical precipitation, adsorption, replacement / reduction, ion exchange, etc. Chemical precipitation includes inorganic sulfide precipitation and chelation precipitation. This method often requires the addition of a large amount of reagents, with high treatment costs and the possibility of S 2- The dosage is difficult to control, which can easily cause odor and secondary pollution.

[0004] For example, patent CN111186932B discloses a method for treating nickel-containing wastewater, comprising: adding the nickel-containing wastewater to a decomposition tank, adjusting its pH value to 2-3, adding ferrous sulfate and hydrogen peroxide to perform Fenton oxidation reaction, adjusting the pH value to 5.5-6.5, adding sodium hypochlorite and stirring for reaction, adding sodium pyrosulfite for reaction, and then adding alkali to adjust the pH value to 10.5-11.5, standing and settling, adding the obtained waste liquid to a coagulation tank, adding polyaluminum chloride and stirring for reaction, then adding to a flocculation tank, adding polyacrylamide and stirring for reaction, and then adding to a sedimentation tank for precipitation, and solid-liquid separation to obtain primary treated wastewater; adjusting the pH value of the primary treated wastewater to 6-7, and then adding an adsorbent for adsorption, standing and performing solid-liquid separation, detecting the total nickel content in the obtained liquid, and discharging after meeting the standards; the adsorbent is a mixture 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 to solve the defects of low efficiency and poor removal effect of complexed nickel in the treatment method of the prior art, comprising the following treatment steps: (1) enriching the wastewater in a first waste liquid collection tank, and passing the wastewater in the waste liquid collection tank into a porous membrane treatment system for pre-filtration treatment; (2) preliminary removal of free nickel ions; (3) adding a flocculant to the second waste liquid collection tank to further settle the precipitate; (4) passing the supernatant of step (2) into a closed complex breaking adsorption device and stirring for 40-60 minutes; (5) sending the liquid obtained after the treatment in step (4) into a third waste liquid collection tank, adding calcium hydroxide to the third waste liquid collection tank to adjust the pH of the wastewater to 10-11, and continuously stirring for 60-90 minutes to cause precipitation, separating the precipitate, and obtaining a filtrate that meets the emission standards.

[0006] The above patented technologies all adopt a long process of weight removal. Due to the addition of multiple reagents, solid waste containing heavy metals is produced after the wastewater is treated, which requires secondary treatment. At the same time, there are also defects such as large equipment investment, which leads to an increase in the total investment of the wastewater treatment system and high operation and maintenance costs.

[0007] Patent CN104445731B provides a comprehensive recovery and purification system and process for supernatant wastewater after nickel carbonate is prepared by a nickel electrolytic liquid purification system. The system includes a dechlorination reaction tank, a cooler, a pH adjustment tank, a delivery 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 realizes the effective separation of sodium chloride from sodium sulfate and heavy metal ions in the supernatant wastewater after nickel carbonate is prepared by a nickel electrolytic liquid purification system, and comprehensively recycles the separated sodium chloride solution and the concentrated phase water containing sodium sulfate and heavy metal ions, solving the problem of waste liquid discharge polluting the environment. However, the example only analyzes salt, and does not analyze and detect heavy metal nickel. Summary of the invention

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

[0009] To achieve its purpose, the present invention adopts the following technical solution: A deep nickel removal process for nickel-containing wastewater in a nickel carbonate preparation process, specifically comprising the following steps: taking nickel-containing wastewater generated in the nickel carbonate preparation process, heating it to 60-80°C, adding persulfate, and performing an activation reaction under stirring for 110-130 minutes, preferably 110-120 minutes, to obtain a deep nickel-removed liquid and a nickel-containing precipitate, the nickel-containing precipitate is returned to a nickel carbonate preparation system for reuse, and the nickel-removed liquid is discharged as nickel-content wastewater meeting the standards.

[0010] The working principle of the present invention is deep nickel removal by persulfate advanced oxidation. Advanced oxidation processes (AOPs) refer to a series of chemical oxidation technologies that use hydroxyl radicals (•OH) to remove organic pollutants (and some inorganic pollutants) in sewage. They are widely used in water treatment processes because they can produce highly active free radicals, have no selectivity for pollutant degradation, have a fast degradation rate, and are low in price.

[0011] Sulfate radicals also have a high redox potential. The standard potential of sodium persulfate can reach 2.01V, which is higher than the 1.80V of hydrogen peroxide and the 1.4V of permanganate. After activation, the OO bond in the molecule breaks to generate sulfate radicals with stronger oxidizing properties (•SO 4- ), the standard potential can reach 2.6V, which greatly improves the oxidation effect. Sulfate radical (•SO 4- ) is a highly reactive free radical that is commonly found in aqueous solution and the atmosphere. In aqueous solution, compared to the hydroxyl radical (•OH - ), sulfate radical has a longer life span, which means that its contact time with pollutants in the aqueous solution is prolonged, which is more conducive to the degradation of pollutants. The nickel removal process of the present invention can achieve excellent deep nickel removal efficiency and nickel removal depth, thereby achieving the purpose of deep nickel removal.

[0012] Furthermore, the present invention further comprises the following steps: before heating and activation, the nickel-containing wastewater is sampled and the nickel content is analyzed. The purpose of this step is to understand the nickel content in the nickel-containing wastewater, so as to facilitate the determination of the mass of the persulfate to be added, so as to achieve a better deep nickel removal effect. Furthermore, when sampling the nickel-containing wastewater, it is necessary to fully stir it to ensure the accuracy of the nickel content detection data.

[0013] Furthermore, the nickel content in the nickel-containing wastewater is 50-80 mg / L.

[0014] Furthermore, the amount of persulfate added to the nickel-containing wastewater is 2.0-2.5 g / L. Within this ratio range, the efficiency and depth of deep nickel removal can be greatly improved. Preferably, it is 2.0 g / L.

[0015] Furthermore, the persulfate is sodium persulfate. Compared with potassium salt and ammonium salt, sodium persulfate has the advantages of lower price, better solubility, greater stability, easier storage and transportation, and fewer side reactions.

[0016] Furthermore, the heating method of the present invention is water bath heating, which can make the persulfate advanced oxidation deep nickel removal system heated evenly and can always be kept within the activation temperature range, which is beneficial to the activation of persulfate.

[0017] Furthermore, the present invention adopts a mechanical stirring method, and the rotation speed is 150-180r / min, preferably 160r / min.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adopts persulfate advanced oxidation technology to deeply remove nickel, which belongs to a short process with simple operation and small investment.

[0019] 2. This invention is the first to use persulfate-based advanced oxidation technology for deep nickel removal in sulfate systems. Compared with traditional advanced oxidation technology, persulfate-based advanced oxidation technology is based on the production of sulfate free radicals (•SO4 - ) is a new type of advanced oxidation technology with 2-nitrogen sulfide as the main active oxide, which has the advantages of higher redox potential, better selectivity, longer half-life, more stability, less affected by the acidity and alkalinity of the solution, more activation methods and the final product sulfate has the least impact on the system; 3. The activation of persulfate in the present invention adopts a thermal activation method. Compared with light activation, alkali activation, transition metal and oxide activation, activated carbon activation, composite activation and the like, the thermal activation method is simple and safe; 4. The persulfate advanced oxidation deep nickel removal process involved in the present invention can achieve the purpose of nickel precipitation and wastewater discharge meeting the standards by automatically adding persulfate.

[0020] In summary, the process of the present invention achieves thermal activation of persulfate by heating, thereby producing a high-valent nickel precipitate with lower solubility, thereby achieving the purpose of deep nickel removal. The deep nickel removal process has high nickel removal depth and nickel removal efficiency and is highly practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0022] The process flow of the present invention is described in detail below in conjunction with the accompanying drawings.

[0023] like Figure 1 As shown, the present invention provides a process for deep nickel removal from nickel-containing wastewater in a nickel carbonate preparation process, which specifically comprises the following steps: Step (1): sampling the nickel carbonate supernatant produced by the thickener in the nickel carbonate preparation process as nickel-containing wastewater, and performing chemical analysis on the nickel content therein; Step (2): add 2 L of nickel-containing wastewater from step (1) into a 5 L beaker and heat it in a water bath to 60-80° C.; Step (3): weigh a certain amount of sodium persulfate using an electronic balance, add it to the beaker heated in step (2), and react for 110-120 minutes under stirring to obtain a deep nickel-removed liquid and a nickel-containing precipitate, which is returned to the nickel carbonate preparation system for reuse.

[0024] Step (4): filtering the deep nickel-removal liquid obtained in step (3), taking samples, and analyzing the nickel content therein.

[0025] Example 1 The nickel content in the nickel-containing wastewater is 69 mg / L, the amount of sodium persulfate added is 2 g / L, the reaction temperature is 60-80°C, and the reaction time is 110 min.

[0026] Table 1 Analysis results of deep nickel removal by advanced oxidation method in Example 1 Example 2 The nickel content in the nickel-containing wastewater is 65 mg / L, the amount of sodium persulfate added is 2 g / L, the reaction temperature is 60-80°C, and the reaction time is 120 min.

[0027] Example 2 Analysis results of deep nickel removal by advanced oxidation method Among them, the applicant found that within the activation temperature range of 60-80°C, temperature changes had no obvious effect on the deep nickel removal effect, and because it was heated in a water bath, the temperature fluctuated, so the reaction temperature of Examples 1-2 was always maintained between 60-80°C, rather than a specific point value.

[0028] It can be seen from the above two embodiments that the present invention adopts sodium persulfate for deep nickel removal, and the nickel removal rate can reach more than 93%, which can achieve a fast and efficient nickel removal effect, and the nickel content in the output liquid after deep nickel removal is less than 10 mg / L, meeting the discharge standard for nickel-containing wastewater.

Claims

1. A process for deep nickel removal from nickel-containing wastewater in a nickel carbonate preparation process, characterized in that: Take the nickel-containing wastewater generated in the nickel carbonate preparation process, heat it to 60-80°C, add persulfate, and activate the reaction for 110-130 minutes under stirring to obtain a deep nickel-removed liquid and a nickel-containing precipitate. The nickel-containing precipitate is returned to the nickel carbonate preparation system for reuse, and the nickel-removed liquid is discharged as nickel-content wastewater that meets the standards.

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

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

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

5. A process for deep nickel removal from nickel-containing wastewater in a 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 process for deep nickel removal from nickel-containing wastewater in a nickel carbonate preparation process according to claims 1-3 and 5, characterized in that: The persulfate is sodium persulfate.

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

8. A process for deep nickel removal from nickel-containing wastewater in a nickel carbonate preparation process according to claim 6, characterized in that: Mechanical stirring is adopted, and the speed is 150-180r / min.

9. A process for deep nickel removal from nickel-containing wastewater in a nickel carbonate preparation process according to claim 8, characterized in that: The rotating speed is 160 r / min.

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