A method for preparing high-purity cobalt

Abstract

The application discloses a preparation method of high-purity cobalt and relates to the technical field of high-purity metal purification, which comprises the following steps: pretreatment reagent purification: filtering analytical pure hydrogen peroxide through a filter containing organic carbon at a rate of 8-10 L / h, then performing normal pressure rectification reflux for 5h at 54 DEG C to obtain electronic grade hydrogen peroxide; crushing analytical pure sodium phosphate, adding pure water, heating to 70-80 DEG C to dissolve, filtering, adding 5L of high-purity acetic acid, washing with pure water to obtain sodium phosphate precipitate, and adding 50L of pure water to redissolve for standby; through the synergistic optimization of front-end chemical deep impurity removal and rear-end ion exchange and electrodeposition process, the strict requirement of high-end fields on impurity content is accurately met; through the balance control of the best dosage window of 0.3-0.5L / 100kg of hydrogen peroxide / sodium phosphate and 4-5V electrolysis voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-purity metal purification, in particular to a preparation method of high-purity cobalt. BACKGROUND

[0002] At present, the production of high-purity cobalt generally needs ion exchange resins with outstanding characteristics and conditions for controlling electrodeposition, and the purification is carried out by using the resins to adsorb specific impurity ions and adjusting the size of current and voltage to control the deposition rate of metal ions; the impurity content of the electrolyte prepared by this method is still high, and the control of the electrodeposition rate inevitably sacrifices the yield, so this method has high production cost, low efficiency and poor stability. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides a preparation method of high-purity cobalt, which purifies cobalt salt at the front end to ensure the fault tolerance at the rear end and improve the electrolysis yield.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a preparation method of high-purity cobalt, comprising the following steps:

[0005] Step (1) purification of pretreatment reagent:

[0006] The analytical pure hydrogen peroxide is filtered through a filter containing organic carbon at a rate of 8-10 L / h, and then distilled under normal pressure at 54℃ for 5h to obtain electronic grade hydrogen peroxide;

[0007] The analytical pure sodium phosphate is crushed, then pure water is added and heated to 70-80℃ to dissolve, and after filtration, 5L of high-purity acetic acid is added, and the sodium phosphate precipitate is washed with pure water to obtain a sodium phosphate precipitate, and 50L of pure water is added to dissolve again for standby use;

[0008] Step (2) chemical deep impurity removal:

[0009] The cobalt chloride crystals are dissolved in 50-60℃ pure water, and after filtration, 0.3-0.5L / 100kg of electronic grade hydrogen peroxide obtained in step (1) is added, and stirred for 10min;

[0010] 0.3-0.5L / 100kg of sodium phosphate solution obtained in step (1) is added, stirred for 10min, and after standing and cooling for 1h, filtration is carried out;

[0011] Step (3) ion exchange copper removal:

[0012] The filtrate of step (2) is passed through an ion exchange column filled with copper removal chelating resin at a flow rate of 3-5L / h;

[0013] Step (4) preparation of high-purity cobalt by electrodeposition:

[0014] The solution obtained in step (3) is supplemented with 50 ml of hydrogen peroxide and 50 ml of sodium phosphate, and after dilution, it is transferred to an electrolytic cell;

[0015] High-purity cobalt is obtained by electrolytic deposition with a titanium plate as cathode and a ruthenium mesh as anode at a cell voltage of 4-5 V.

[0016] Preferably, the sodium phosphate in step (1) is at least one of trisodium phosphate, sodium metaphosphate, sodium tripolyphosphate or sodium pyrophosphate.

[0017] Preferably, in step (2), hydrogen peroxide oxidizes Fe²⁺ to Fe³⁺ (wherein hydrogen peroxide has adsorbed organic impurities and oxidizing property, and can oxidize Fe²⁺ to Fe³⁺, the reaction formula is as follows: Fe²⁺+H2O2→Fe³⁺+H2O+O2, Fe³⁺ is more easily precipitated and removed), and sodium phosphate reacts with at least one of Fe³⁺, Mg²⁺, Cu²⁺, Ag⁺, Pb²⁺, Cd²⁺, Hg²⁺ and Cr³⁺ to form a precipitate or a complex, which has excellent effect on the removal of Fe which is difficult to remove in the preparation of high-purity cobalt, and the relevant reactions are as follows:

[0018] 3(PO4)³⁻+Fe³⁺→

Fe(PO4)3

[0019] Na3PO4+3Ag⁺→Ag3PO4+3Na⁺

[0020] Pb²⁺+2Na3PO4→Pb3(PO4)2+2Na⁺

[0021] 2Mg²⁺+Na3PO4+H⁺=Mg2HPO4+2Na⁺

[0022] Cd²⁺+PO4³⁻→Cd3(PO4)2

[0023] Hg²⁺+2PO4³⁻→Hg3(PO4)2

[0024] 2Cr³⁺+3PO4³⁻→Cr2(PO4)3。

[0025] Preferably, the dilution ratio of the solution before electrolysis in step (4) is 300 L of electrolytic cell volume corresponding to 100 kg of raw cobalt chloride.

[0026] A high-purity cobalt with purity ≥99.9995%, Fe ≤0.2 ppm, Pb, Zn, Ag, Al, Mg, Mn ≤0.1 ppm, and Ni ≤0.5 ppm.

[0027] Compared with the prior art, the present application provides a preparation method of high-purity cobalt, which has the following beneficial effects: the present application precisely meets the stringent requirements of high-end fields on impurity content through the synergistic optimization of front-end chemical deep impurity removal and rear-end ion exchange and electrodeposition process; and the balance control of the optimal dosage window of 0.3-0.5 L / 100 kg of hydrogen peroxide / sodium phosphate and the electrolysis voltage of 4-5 V not only avoids the problems of insufficient impurity removal and sodium pollution, but also realizes the shortening of the production cycle and the improvement of the yield. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A column chart of the production cycle of the examples and the comparative examples of the present application is generated. DETAILED DESCRIPTION

[0029] The technical solutions in the examples of the present application will be clearly and completely described below, obviously, the described examples are only a part of the examples of the present application, rather than all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0030] Purity and impurity content analysis

[0031] Glow discharge mass spectrometry (GD-MS): reference to “GB / T25934-2010 High-purity gold chemical analysis method-glow discharge mass spectrometry for determination of impurity element content”, suitable for full element analysis of high-purity metals above 99.999%.

[0032] Inductively coupled plasma mass spectrometry (ICP-MS): reference to “GB / T23364-2009 High-purity indium hydroxide chemical analysis method-inductively coupled plasma mass spectrometry for determination of magnesium, aluminum, silicon, chromium, manganese, iron, nickel, copper, zinc, arsenic, cadmium, tin, antimony, tungsten, lead and bismuth content”, auxiliary verification of ppm level impurity content.

[0033] Atomic absorption spectrophotometry (AAS): reference to “GB / T15072.6-2008 Noble metal alloy chemical analysis method-determination of copper, manganese, nickel, aluminum, iron, zinc, tin, lead and silicon content in silver alloy by atomic absorption spectrophotometry”, used for precise calibration of specific elements (such as Cu, Fe).

[0034] Production capacity parameter determination

[0035] Production cycle timing: reference to the principle of “test duration record” in “GB / T3354-2014 Tensile properties test method for directional fiber reinforced plastics”, accurately record the continuous time from the beginning to the end of electrolysis.

[0036] Yield weighing: Refer to the sample weighing specification in GB / T 223.1-2008 Determination of carbon content in steel and alloy - Gravimetric method, use an electronic balance with a precision of 0.1 g to determine the mass of the cobalt product after electrolysis.

[0037] High purity cobalt purity and impurity content test (GD-MS method)

[0038] Sample pretreatment: Cut a 10 mm x 10 mm x 2 mm sample block from the high purity cobalt product obtained by electrolysis, ultrasonically clean it with anhydrous ethanol for 15 minutes to remove surface oil and attachments. Rinse with deionized water 3 times, place in a vacuum drying oven (60°C, -0.1 MPa) for 2 hours, cool to room temperature and reserve.

[0039] Instrument preparation: Start the glow discharge mass spectrometer and preheat for 1 hour to ensure that the instrument vacuum reaches more than 5 x 10^-7 Pa.

[0040] Calibrate the instrument using a standard sample (cobalt standard with a purity of 99.9999%) that covers the target elements Fe, Pb, Zn, Ag, Al, Mg, Mn, Ni, Cu, Na, etc. involved in this application.

[0041] Test condition setting: Discharge voltage: 700 V, discharge current: 30 mA, argon carrier gas flow: 450 mL / min.

[0042] Mass spectrometer resolution: 5000 (10% peak-to-valley ratio), scan range: 1-250 amu (atomic mass unit).

[0043] Scan each sample 3 times, each scan time: 60 seconds, take the average as the test result.

[0044] Data acquisition and calculation

[0045] Record the ion intensity of each impurity element, and convert it to mass fraction (unit: %) through the calibration curve.

[0046] Purity calculation formula: Purity of high purity cobalt (%) = 100% minus the sum of the mass fractions of all impurity elements (%).

[0047] Impurity content (ppm) calculation: Impurity content of an element (ppm) = mass fraction of the element (%) multiplied by 10^6.

[0048] Impurity content auxiliary verification (ICP-MS method)

[0049] Sample dissolution: 0.5 g (accurate to 0.0001 g) of high-purity cobalt sample was weighed into a polytetrafluoroethylene beaker, 10 mL of nitric acid (superior grade) was added, and low-temperature heating was performed until complete dissolution. After cooling, it was transferred to a 100 mL volumetric flask, diluted to the mark with deionized water, shaken well, and the test solution (concentration about 5 mg / mL) was obtained.

[0050] Instrument parameters: radio frequency power: 1550 W, plasma gas flow rate: 18 L / min, auxiliary gas flow rate: 1.2 L / min. Atomizer flow rate: 0.9 L / min, sampling depth: 8 mm, integration time: 0.1 seconds / element.

[0051] Calibration and testing: prepare multi-element standard solutions with concentrations of 0.1 ppb, 1 ppb, 10 ppb, and 100 ppb, and draw a calibration curve (correlation coefficient ≥ 0.999). The test solution was diluted 100 times and injected into the instrument, and the signal intensity of each element was measured. The concentration was calculated according to the calibration curve.

[0052] Results conversion: the content of a certain element impurity (ppm) = (element concentration in the test solution (μg / L) x constant volume (L)) ÷ sample mass (g).

[0053] Production capacity parameter test

[0054] Production cycle determination: timing starts from the beginning of power supply to the electrolytic cell, and stops when the electrolysis ends (the thickness of cobalt deposition reaches the preset value). The time recorded is the production cycle (unit: hours). The timing tool uses an electronic stopwatch with an accuracy of 0.1 seconds, and the average value is taken from three parallel tests.

[0055] Yield determination: after the electrolysis is completed, the cobalt product on the cathode titanium plate is taken out, washed with deionized water to neutral, and vacuum dried at 60°C for 2 hours. The mass of the dried cobalt product is weighed using an electronic balance with an accuracy of 0.1 g, which is the single yield (unit: kg).

[0056] Calculate the yield corresponding to 100 kg of cobalt chloride raw material: yield (kg / 100 kg of raw material) = (actual yield ÷ cobalt chloride raw material consumption) x 100.

[0057] Example 1: A method for preparing high-purity cobalt, specifically comprising the following steps:

[0058] Pretreatment reagent purification: Analytical grade hydrogen peroxide is filtered through an organic carbon-containing filter at a rate of 8 L / h, then distilled at 54°C under normal pressure with reflux for 5 h to obtain electronic grade hydrogen peroxide; analytical grade sodium phosphate (selecting trisodium phosphate) is crushed, then dissolved by adding pure water at 70°C, filtered, then 5 L of superior grade acetic acid is added, and the sodium phosphate precipitate is obtained by washing with pure water, and then dissolved in 50 L of pure water for use.

[0059] Chemical deep purification: 100 kg of cobalt chloride crystals were dissolved in 50 °C pure water, after filtration, 0.3 L of electronic grade hydrogen peroxide obtained in step 1 was added, stirred for 10 min; 0.3 L of sodium phosphate solution obtained in step 1 was added, stirred for 10 min, after standing and cooling for 1 h, a filter membrane with a pore size of 1 μm was used to filter at a rate of 10 L / h.

[0060] Ion exchange copper removal: the filtrate of step 2 was passed through an ion exchange column filled with copper removal chelating resin at a flow rate of 3 L / h.

[0061] Electrodeposition of high purity cobalt: the solution obtained in step 3 was supplemented with 50 ml of hydrogen peroxide and sodium phosphate each, diluted according to 300 L electrolytic tank volume corresponding to every 100 kg of raw material, and then transferred to the electrolytic tank; titanium plate as cathode, ruthenium mesh as anode, electrolysis deposition at 4 V tank voltage, high purity cobalt was obtained.

[0062] Example two, purification of pretreatment reagents: analytical pure hydrogen peroxide was filtered through a filter containing organic carbon at a rate of 9 L / h, then distilled under normal pressure at 54 °C for 5 h with reflux, to obtain electronic grade hydrogen peroxide; analytical pure sodium phosphate (a mixture of sodium metaphosphate and sodium tripolyphosphate was selected) was crushed, dissolved in pure water by heating to 75 °C, filtered, 5 L of extra pure acetic acid was added, the sodium phosphate precipitate was washed with pure water, and 50 L of pure water was added to redissolve it for use.

[0063] Chemical deep purification: 100 kg of cobalt chloride crystals were dissolved in 55 °C pure water, after filtration, 0.4 L of electronic grade hydrogen peroxide obtained in step 1 was added, stirred for 10 min; 0.4 L of sodium phosphate solution obtained in step 1 was added, stirred for 10 min, after standing and cooling for 1 h, a filter membrane with a pore size of 0.8 μm was used to filter at a rate of 15 L / h.

[0064] Ion exchange copper removal: the filtrate of step 2 was passed through an ion exchange column filled with copper removal chelating resin at a flow rate of 4 L / h.

[0065] Electrodeposition of high purity cobalt: the solution obtained in step 3 was supplemented with 50 ml of hydrogen peroxide and sodium phosphate each, diluted according to 300 L electrolytic tank volume corresponding to every 100 kg of raw material, and then transferred to the electrolytic tank; titanium plate as cathode, ruthenium mesh as anode, electrolysis deposition at 4.5 V tank voltage, high purity cobalt was obtained.

[0066] Example three, purification of pretreatment reagents: analytical pure hydrogen peroxide was filtered through a filter containing organic carbon at a rate of 10 L / h, then distilled under normal pressure at 54 °C for 5 h with reflux, to obtain electronic grade hydrogen peroxide; analytical pure sodium phosphate (sodium pyrophosphate was selected) was crushed, dissolved in pure water by heating to 80 °C, filtered, 5 L of extra pure acetic acid was added, the sodium phosphate precipitate was washed with pure water, and 50 L of pure water was added to redissolve it for use.

[0067] Chemical deep purification: Weigh 100 kg of cobalt chloride crystals and dissolve them in pure water at 60 °C. After filtration, add 0.5 L of the electronic-grade hydrogen peroxide obtained in step 1 and stir for 10 min. Add 0.5 L of the sodium phosphate solution obtained in step 1 and stir for 10 min. After standing and cooling for 1 h, filter at a rate of 20 L / h using a filter membrane with a pore size of 0.5 μm.

[0068] Ion exchange for copper removal: The filtrate from step 2 is passed through an ion exchange column packed with copper removal chelating resin at a flow rate of 5 L / h.

[0069] Electrodeposition preparation of high-purity cobalt: Add 50 ml each of hydrogen peroxide and sodium phosphate to the solution obtained in step 3, dilute it according to the 300 L electrolytic cell volume corresponding to 100 kg of raw material, and transfer it to the electrolytic cell; use a titanium plate as the cathode and a ruthenium mesh as the anode, and electrolyze at a cell voltage of 5 V to obtain high-purity cobalt.

[0070] Comparative Example 1 was the same as Example 2 except that it used unpurified analytical grade hydrogen peroxide and sodium phosphate.

[0071] Comparative Example 2: Except for the absence of hydrogen peroxide, the other steps are the same as in Example 2.

[0072] Comparative Example 3 was performed in the same manner as Example 2, except that sodium phosphate was not added.

[0073] Comparative Example 4 is the same as Example 2 except that the ion exchange step is omitted.

[0074] Comparative Example 5: The reagent dosage was 0.2 L / 100 kg, and the rest was the same as in Example 2.

[0075] Comparative Example 6: The reagent dosage was 0.6 L / 100 kg, and the rest was the same as in Example 2.

[0076] Comparative Example 7: Voltage 3V, otherwise the same as Example 2.

[0077] Comparative Example 8: Voltage 6V, otherwise the same as Example 2.

[0078] The high-purity cobalt obtained in Examples 1, 2, 3 and Comparative Examples 1, 2, 3, 4, 5, 6, 7, and 8 were grouped as GCG-01, GCG-02, GCG-03, GCG-04, GCG-05, GCG-06, GCG-07, GCG-08, GCG-09, GCG-10, and GCG-11, respectively. Production cycle and yield tests were conducted on the examples and comparative examples, and impurity tests (unit: ppm) were performed on the high-purity cobalt obtained in the examples and comparative examples. Detailed test results are shown in Tables 1 and 2.

[0079] Table 1

[0080]

[0081] Table 2

[0082]

[0083] The present application stably prepares high-purity cobalt with purity ≥99.9995% by the "three-stage impurity removal + optimized electrodeposition" process, wherein Fe≤0.2ppm, Pb, Zn, Ag, Al, Mg, Mn≤0.1ppm, and Ni≤0.5ppm; the present application removes impurities in advance through front-end chemical impurity removal, and the pressure of the rear-end ion exchange and electrodeposition is greatly reduced, the purity is improved from 99.99% to above 99.9995%, and the impurity control precision is improved by 2 orders of magnitude; the electrolysis cycle is only 6-8h under 4-5V voltage, the yield reaches 85-95kg / 100kg of raw material, which is more than 150% higher than the traditional method, and the synergy of high purity and high productivity is realized; hydrogen peroxide / sodium phosphate 0.3-0.5L / 100kg is the best window: less than 0.3L, impurity removal is not complete, and more than 0.5L introduces sodium pollution, which can stably guarantee that the impurity index meets the standard; 4-5V voltage realizes balance: less than 4V, the rate is halved, and more than 5V, impurities are precipitated, which takes into account productivity and purity in this interval.

[0084] The use of cheap reagents after purification reduces only the cost, and the purity fluctuation is smaller in continuous production, and the stability is excellent.

[0085] The above are only specific embodiments of the present application, but the technical features of the present application are not limited thereto. Any simple change, equivalent replacement or modification made on the basis of the present application to solve the basically same technical problem and realize the basically same technical effect is covered in the protection scope of the present application.

Claims

1. A method for producing high purity cobalt, characterized by, The method comprises the following steps: Step (1) purification of pretreatment reagent: Analyzed pure hydrogen peroxide is filtered through a filter containing organic carbon at a rate of 8-10 L / h, then distilled at 54℃ under normal pressure with reflux for 5h to obtain electronic grade hydrogen peroxide; Analyzed pure sodium phosphate is crushed, then added with pure water and heated to 70-80℃ to dissolve, filtered, then added with 5L pure acetic acid, washed with pure water to obtain sodium phosphate precipitate, then added with 50L pure water to redissolve for standby use; Step (2) chemical deep impurity removal: Cobalt chloride crystals are dissolved in 50-60℃ pure water, then filtered, then added with 0.3-0.5L / 100kg electronic grade hydrogen peroxide obtained in step (1) and stirred for 10min; 0.3-0.5L / 100kg sodium phosphate solution obtained in step (1) is added, stirred for 10min, then cooled for 1h and filtered; Step (3) ion exchange removal of copper: The filtrate obtained in step (2) is passed through an ion exchange column filled with copper removal chelating resin at a flow rate of 3-5L / h; Step (4) preparation of high-purity cobalt by electrodeposition: The solution obtained in step (3) is supplemented with 50ml of hydrogen peroxide and sodium phosphate respectively, then diluted and transferred to an electrolytic cell; Titanium plate is used as cathode and ruthenium mesh is used as anode to electrolyze and deposit under a cell voltage of 4-5V to obtain high-purity cobalt; The sodium phosphate in step (1) is at least one of trisodium phosphate, sodium metaphosphate, sodium tripolyphosphate or sodium pyrophosphate; In step (2), hydrogen peroxide oxidizes Fe²⁺ to Fe³⁺, and sodium phosphate reacts with at least one of Fe³⁺, Mg²⁺, Cu²⁺, Ag⁺, Pb²⁺, Cd²⁺, Hg²⁺ and Cr³⁺ to form precipitate or complex.

2. The method of claim 1, wherein: In step (2), filtration is performed using a filter membrane with a pore size of ≤1μm at a filtration rate of 10-20L / h.

3. The method of claim 1, wherein the high purity cobalt is prepared by the steps of: In step (4), the solution is diluted to a ratio of 300L electrolytic cell volume per 100kg of raw cobalt chloride before electrolysis. ​

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