CN113445063A - Preparation method of electrolytic manganese dioxide - Google Patents
Preparation method of electrolytic manganese dioxide Download PDFInfo
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Abstract
The invention relates to a preparation method of electrolytic manganese dioxide, which comprises the steps of using aqueous solution of manganese sulfate and sulfuric acid as electrolyte, adding a flocculating agent into the electrolyte to carry out electrolysis to obtain the electrolytic manganese dioxide at a high temperature, continuously adding the flocculating agent into the sulfuric acid-manganese sulfate electrolytic solution to ensure that the concentration of the flocculating agent in the sulfuric acid-manganese sulfate mixed solution is 10-50 mg/L, the concentration of the sulfuric acid in the sulfuric acid-manganese sulfate mixed solution is 30-80 g/L, the concentration of the manganese sulfate is controlled to be 30-100 g/L, and the electrolytic current density is 0.4-0.8A/dm < 2 >. The electrolytic manganese dioxide produced by the method obtains high discharge capacity during the multiplying power discharge and the low multiplying power discharge, and simultaneously considers the discharge capacity of the high multiplying power discharge; meanwhile, the hardness of the product is reduced, the die abrasion in battery manufacturing is reduced, and the forming performance and the production efficiency are improved in battery production. Meanwhile, the invention has the advantages of stable voltage during production operation, easy control of production and uniform product.
Description
Technical Field
The invention relates to the field of electrochemical metallurgy, in particular to a preparation method of electrolytic manganese dioxide.
Background
Electrolytic manganese dioxide is used as a positive electrode active material for primary zinc-manganese batteries, particularly alkaline-manganese dry batteries. Conventionally, a dry battery suitable for applications requiring high-rate discharge (large discharge current), i.e., a dry battery having excellent high-rate discharge characteristics, has been demanded. However, due to the recent demands for power saving and energy saving and environmental protection of portable electronic devices, dry batteries requiring medium-rate discharge (medium discharge current) and low-rate discharge (small discharge current) are required as compared with high-rate discharge. Accordingly, electrolytic manganese dioxide excellent in medium-rate discharge and low-rate discharge characteristics is required.
In the existing industrial production of electrolytic manganese dioxide, under a high temperature state, an aqueous solution of manganese sulfate and sulfuric acid is used as an electrolyte, pure titanium or a titanium-manganese alloy is used as an anode, copper, graphite or a lead alloy is used as a cathode, and electrolytic manganese dioxide is precipitated on the anode through direct current electrolysis.
The electrolysis mechanism is generally considered to be:
Mn 2+ ＝Mn 3+ +e
Mn 3+ ＝Mn 4+ +e
Mn 4+ +2H 2 O＝MnO 2 +4H +
as a method for producing electrolytic manganese dioxide, "clear electrolysis method" is known in which electrolysis is carried out without adding other materials to an electrolyte, and substantially a trace amount of MnO is suspended in the electrolyte 2 Particles of this MnO 2 The particles are generated by the disproportionation reaction of the electrolytic process, which is one of the commonly used methods, and is currently used by almost all electrolytic manganese dioxide manufacturers.
Another commonly used method is an electrolysis method in which manganese oxide particles (patent nos. CN95118783 and CN 104136662B) or other particles (CN 94116718.6) are added to an electrolytic solution and suspended, which is contrary to the above method, and this method is called a suspension electrolysis method, which has been used in JMC in japan but has been stopped, and is used in large scale by electrolytic manganese dioxide manufacturers in china, but is totally abandoned.
CN1125784A provides a manganese dioxide suitable for alkaline batteries and manganese batteries and capable of improving initial properties and storability thereof, and a production method of the manganese dioxide. The electrolytic manganese dioxide of the invention has a thickness of less than 30m 2 BET specific surface area in g (less than 27 m) 2 More preferably,/g) and a degree of suspension of less than 50mg/L. The method of producing electrolytic manganese dioxide according to the present invention may be a suspension method, a clarification method, and alternately a suspension method and a clarification method. Whether in suspension or clarification, the anodic current density can be periodically switched between two or more values within a defined range.
Kerr-McGee patent (U.S. Pat. No. 6,527,941) proposes a method for improving the production of electrolytic manganese dioxide having a high discharge capacity at high discharge rates by maintaining an aqueous electrolyte solution of sulfuric acid and manganese sulfate at a high temperature in an electrolytic cell. The main characteristics of the method are high acidity, low manganese sulfate concentration and low current density, and the defects are that the yield is low, and the cell voltage is high and difficult to control.
Davis (Gillette patent U.S. Pat. No. 6,585,881B) proposes a process for producing electrolytic manganese dioxide at high temperatures having a high discharge capacity at high discharge rates, characterized by a high electrolysis temperature (. Gtoreq.1100C) and the disadvantages of too harsh conditions and difficult industrialization.
Although the prior art has been studied on the electrolytic manganese dioxide clarification method, the following problems exist: 1. the clarification method in the prior art is not strictly clear in nature, and trace MnO is naturally suspended in the electrolyte 2 Particles of this MnO 2 The particles are generated due to disproportionation reaction in the electrolytic process, the electrolytic product is uneven and is a mixture, the discharge performance of medium-rate (medium current) and low-rate (small current) is good, the discharge capacity of high-rate (large current) is lower, the hardness of the product is larger, and the abrasion of a mold is larger during the manufacturing of the battery; 2. the suspension method artificially adds manganese oxide particles or other particles in the electrolytic solution, can improve the high-rate (large current) and medium-rate (medium current) discharge capacity, but low-rate (small current)The discharge capacity is low, the hardness is larger, the die abrasion is large during the battery manufacturing, and the battery production efficiency is reduced; 3. other electrolytic manganese dioxide manufacturing methods have good laboratory effects, but are difficult to industrialize.
Electrolytic manganese dioxide is used as a positive electrode active material for primary batteries, particularly alkaline manganese dry batteries. Conventionally, a dry battery suitable for applications requiring high-rate discharge (large discharge current), i.e., a dry battery having excellent high-rate discharge characteristics, has been demanded.
However, due to the recent demands for power saving and energy saving and environmental protection of portable electronic devices, dry batteries requiring medium-rate discharge (medium discharge current) and low-rate discharge (small discharge current) are required as compared with high-rate discharge. Accordingly, electrolytic manganese dioxide excellent in medium-rate discharge and low-rate discharge characteristics has been demanded.
Therefore, there is a need for a method for producing electrolytic manganese dioxide that can obtain high discharge capacity at the time of medium-rate discharge and low-rate discharge and can achieve high discharge capacity at the same time.
Disclosure of Invention
The invention aims to provide a method for manufacturing electrolytic manganese dioxide, which can obtain high discharge capacity during medium-rate discharge and low-rate discharge and simultaneously give consideration to the high-rate discharge capacity; meanwhile, the hardness of the product is reduced, the die abrasion during battery manufacturing is reduced, and the forming performance and the production efficiency are improved during battery production. The invention aims to provide electrolytic manganese dioxide which has high medium-rate discharge capacity and low-rate discharge capacity, excellent battery formability and low-rate discharge capacity, and the micro Vickers hardness of the electrolytic manganese dioxide is lower than 500HV.
In order to achieve the above object and solve the above problems, the present application provides a method for producing electrolytic manganese dioxide by adding an organic flocculant to an electrolytic solution to completely clarify the electrolytic solution. The flocculant in the production of electrolytic manganese dioxide of the present invention has a function of capturing a trace amount of MnO in the electrolyte by the flocculant 2 The particles are settled at the bottom of the electrolytic tank, and the electrolytic reaction is carried out in the completely clarified electrolyte; at the same time, the flocculating agent canThe surface state of the electrolytic manganese dioxide deposited on the anode plate is improved, so that the electrolytic manganese dioxide is uniform and flat.
The method is characterized in that a flocculating agent is continuously added into a sulfuric acid-manganese sulfate electrolytic solution, so that the concentration of the flocculating agent in the sulfuric acid-manganese sulfate mixed solution is 10-50 mg/L, the concentration of sulfuric acid in the sulfuric acid-manganese sulfate mixed solution is 30-80 g/L, the concentration of manganese sulfate is controlled to be 30-100 g/L, and the electrolytic current density is 0.4-0.8A/dm 2 Electrolyzing, and adding 85-105g/L manganese sulfate to the electrolyte to supplement 1 solution according to needs.
In some embodiments, the additive species added to the electrolyte is a non-ionic organic flocculant PMA (polyacrylamide).
In some embodiments, the flocculant (PMA) added to the electrolyte has a molecular weight of 1200 to 1800 ten thousand.
In some embodiments, the additive is added to the electrolyte in an amount of 10 to 50mg/L.
In some embodiments, the high temperature state is controlled above 95 ℃ and below 99 ℃.
In some embodiments, after the electrolyzing, further comprising: in the crushing and grinding process, the rinsing process and the neutralization process.
In some embodiments, in the crushing and grinding process, the electrolytic manganese dioxide is crushed and ball-milled to a desired particle size as required.
In some embodiments, in the rinsing step, the electrolytic manganese dioxide obtained by electrolysis is washed to remove the adhered electrolyte. Wherein the electrolytic manganese dioxide is immersed in a water bath or a warm water bath.
In some embodiments, in the neutralization step, the electrolytic manganese dioxide is immersed in an aqueous alkali metal solution to adjust the pH of the electrolytic manganese dioxide. The aqueous alkali metal solution is limited to only aqueous sodium hydroxide solution, aqueous sodium carbonate solution and aqueous sodium bicarbonate solution.
In some embodiments, the electrolytic manganese dioxide produced by the present invention can be used as a positive electrode active material for primary batteries such as alkaline zinc-manganese batteries.
Advantageous effects
Compared with the prior art, the invention has the following technical effects:
the method for electrolyzing the manganese dioxide, disclosed by the invention, has the advantages that high discharge capacity is obtained during multiplying power discharge (medium discharge current) and low multiplying power discharge (small discharge current), and high multiplying power discharge (large discharge current) capacity is considered; meanwhile, the hardness of the product is reduced, the die abrasion in battery manufacturing is reduced, and the forming performance and the production efficiency are improved in battery production. Meanwhile, the invention has the advantages of stable voltage of the slot during production and operation, easy control of production and uniform product.
Drawings
Figure 1 shows the BET of manganese dioxide deposited in different regions of the anodes of example 4 and comparative example 4.
Detailed Description
The present invention is described in more detail below to facilitate an understanding of the present invention.
Those skilled in the art will recognize that: the chemical reactions described herein may be used to suitably prepare a number of other compounds of the invention, and other methods for preparing the compounds of the invention are considered to be within the scope of the invention. For example, the synthesis of those non-exemplified compounds according to the present invention can be successfully accomplished by those skilled in the art by modification, such as appropriate protection of interfering groups, by the use of other known reagents other than those described herein, or by some routine modification of the reaction conditions. In addition, the reactions disclosed herein or known reaction conditions are also recognized as being applicable to the preparation of other compounds of the present invention.
Hereinafter, a method for producing electrolytic manganese dioxide of the present invention will be described.
In the method for manufacturing electrolytic manganese dioxide by adding a flocculant into a sulfuric acid-manganese sulfate mixed solution, the flocculant is continuously added into the sulfuric acid-manganese sulfate mixed solution, so that the concentration of the flocculant in the sulfuric acid-manganese sulfate mixed solution is 10-50 mg/L, the concentration of sulfuric acid in the sulfuric acid-manganese sulfate mixed solution is 30-80 g/L, and the electrolytic current density is 0.4-0.8A/dm 2 The electrolytic manganese dioxide of the present invention can be produced by electrolysis.
The method of the present invention is a method of manufacturing electrolytic manganese dioxide by adding a flocculant to an electrolytic solution. Therefore, a method for producing electrolytic manganese dioxide or a so-called clarification electrolysis method, in which an electrolytic solution containing substantially no flocculant is electrolyzed, is different from a method for electrolyzing a sulfuric acid-manganese sulfate mixed solution containing no flocculant. Electrolytic manganese dioxide excellent in the property of being controlled in the porous structure, the crystal structure and the BET specific surface area can be produced by carrying out an electrolytic method in which a flocculant is added. On the basis of the method, the surface structure and the electrolytic current efficiency of the product are improved compared with a clarification electrolytic method without adding a flocculating agent. Further, in the clarification electrolysis, there is a tendency that the physical properties of electrolytic manganese dioxide deposited during the electrolysis are not uniform, and for example, BET surface areas of the respective portions of the electrode are different.
The manufacturing method of the invention continuously adds the flocculating agent into the mixed solution of sulfuric acid and manganese sulfate. Thus, the concentration of the flocculant added to the sulfuric acid-manganese sulfate mixed solution during electrolysis can be stabilized, and the electrolytic manganese dioxide manufacturing method can be used for electrolyzing an electrolyte solution containing a flocculant with a certain concentration during electrolysis. This makes the physical properties, particularly the state of pores, of the electrolytic manganese dioxide obtained throughout the electrolysis uniform.
As a method of continuously adding a flocculant to a sulfuric acid-manganese sulfate mixed solution, the following method may be used: adding a flocculating agent to dissolve the mixture to prepare a concentrated solution with a certain proportion, and then adding the concentrated solution into the electrolyte replenishing solution according to a set proportion.
Adding a flocculating agent into the sulfuric acid-manganese sulfate mixed solution, wherein the flocculating agent is nonionic.
Adding flocculant into the sulfuric acid-manganese sulfate mixed solution, wherein the molecular weight of the flocculant is 1200-1800 ten thousand.
The concentration of the flocculant added into the sulfuric acid-manganese sulfate mixed solution is 10-50 mg/L.
In the range of the electrolytic current density of the production method of the present invention, if the concentration of the flocculant is higher than 50mg/L, the effect is the same as that of the flocculant at 10 to 50mg/L, and the quality of the electrolytic manganese dioxide obtained is not changed.
On the other hand, if the concentration of the flocculant is less than 10mg/L, the effect of adding the flocculant to the sulfuric acid-manganese sulfate mixed solution cannot be obtained.
The sulfuric acid-manganese sulfate mixed solution used in the production method of the present invention has a sulfuric acid concentration of 30 to 80g/L. By setting the sulfuric acid concentration of the sulfuric acid-manganese sulfate mixed solution within this range, the electrolytic manganese dioxide obtained is excellent in performance.
The electrolytic current density of the production method of the present invention is 0.4 to 0.8A/dm 2 . At the flocculant concentration in the sulfuric acid-manganese sulfate mixed solution of the invention, if the electrolytic current density is less than 0.4A/dm 2 When the BET surface area of electrolytic manganese dioxide is too low, the volume of mesopores effective for the discharge reaction becomes too small, or the alkaline potential of electrolytic manganese dioxide tends to be lowered.
On the other hand, when the electrolytic current density becomes too high at the flocculant concentration in the sulfuric acid-manganese sulfate mixed solution of the present invention, the BET specific surface area of the electrolytic manganese dioxide becomes large, the volume of the mesopores contributing to the discharge reaction becomes too large, or the alkaline potential becomes liable to decrease. Therefore, the electrolytic current density of the production method of the present invention is preferably 0.80A/dm 2 The following. In the present invention, the electrolytic current density refers to the electrolytic current density of the anode plate.
The concentration of manganese sulfate in the electrolyte-replenishing solution of the present invention is not limited, and may be, for example, 85g/L or more and 105g/L or less.
As the electrolysis temperature is higher, the quality of electrolytic manganese dioxide is higher and the production efficiency tends to be higher. As an example of a suitable electrolysis temperature, electrolytic manganese dioxide having the most excellent properties at 95 ℃ to 99 ℃ is given.
The production method of the present invention may further include the following steps: and 1 of any one of a crushing and grinding process, a rinsing process and a neutralizing process.
In the crushing and grinding step, any method of changing the electrolytic manganese dioxide to any particle size can be used, but impurities other than a small amount of iron must not be introduced.
In the rinsing step, electrolytic manganese dioxide obtained by electrolysis is washed to remove the adhering electrolyte solution and the like. The washing method includes immersing electrolytic manganese dioxide in a water bath or a warm water bath.
In the neutralization step, electrolytic manganese dioxide is immersed in an aqueous alkali metal solution or the like, and the pH of electrolytic manganese dioxide can be adjusted.
The electrolytic manganese dioxide produced by the invention can be used as the positive electrode active material of primary batteries such as alkaline zinc-manganese batteries and the like.
The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.
[ determination of electrolytic manganese dioxide content in electrolytic bath electrolyte ]
The content of electrolytic manganese dioxide in electrolyte of the electrolytic cell is determined by an iodometry method, namely 100ml of electrolyte is sucked and put into an iodometry bottle, 0.32g of solid potassium iodide is added, a bottle plug is immediately covered and shaken evenly and sealed by a water seal, the mixture is placed in a dark room for 10min and taken out to be titrated by a sodium thiosulfate standard solution, and the content of electrolytic manganese dioxide is calculated according to the consumed volume.
[ BET specific surface area measurement of electrolytic manganese dioxide ]
The BET specific surface area of electrolytic manganese dioxide is determined by a nitrogen adsorption 6-point method (NOVA 4200e, antopaca instruments Co., ltd.), a sample is placed in a 105-110 ℃ forced air drying oven to be dried for 2 hours, and after taking out and cooling, 0.2000g of the sample is weighed, degassed at 120 + -1 ℃ for 2 hours, and placed in an instrument analysis station to be analyzed.
[ determination of alkaline potential of electrolytic manganese dioxide ]
The alkaline potential value of electrolytic manganese dioxide in a 45% KOH aqueous solution was measured as follows.
Weighing 0.3500g of electrolytic manganese dioxide (quasi-0.0001 g) in a steel shell (four parallel samples are weighed for each sample), transferring 0.1ml of 45 KOH solution in the steel shell by using an injector, lightly and forcefully knocking the steel shell to ensure that the electrolytic manganese dioxide is completely soaked and uniformly distributed in the steel shell, putting diaphragm paper, compacting the diaphragm paper by using a press bar and sucking the residual solution on the outer wall of the steel shell by using filter paper, taking down the steel shell and putting the steel shell on a copper plate, placing the steel shell at room temperature for 40 minutes, connecting a copper plate wiring part by using a red wire end of a multimeter, connecting a black wire end with a reference electrode, adjusting the gear of the multimeter to 2V gear, inserting the reference electrode into the center of the steel shell, recording the potential value after reading is stable, and calculating the alkaline potential of the sample according to a standard measurement value.
[ determination of microscopic Vickers hardness of electrolytic manganese dioxide ]
The microvicker hardness of the electrolytic manganese dioxide is measured by a microvicker hardness tester (BUEHLER ltd, manufactured by BUEHLER 5104, usa).
Putting an electrolytic manganese dioxide sample into a test chamber (23 +/-5 ℃) for 4 hours, putting the sample on a clean test table, contacting a pressure head with the surface of the sample, applying a test force perpendicular to a test surface until the test force is applied to a nominal value of 0.2452N, wherein the force application process cannot exceed 10S, the descending speed of the pressure head is controlled to be 40um/S until the sample does not generate plastic deformation, and the retention time of the test force is about 12S. Throughout the test period, the micro vickers should be protected from shock and vibration, and the measurement should be repeated if shock and vibration occur.
And (3) searching a proper indentation measuring surface by using a 10X eyepiece, observing the indentation of the measuring head by using a 40X objective lens and measuring the diagonal length of the indentation.
The distance from the center of any indentation to the edge of the sample is 2.5 times of the length of the diagonal line of the indentation, if the sizes of the adjacent indentations are different, the interval of the indentation is determined by the larger indentation, and the Vickers hardness value is calculated by measuring the lengths of the two diagonal lines and using an arithmetic mean value pressing formula.
HV×0.025＝[2×F×sin(136°/2)]/d 2 ≈0.1891×F/d 2
Where F is the test force in N and d is the arithmetic mean of the two diagonals in mm.
[ measurement of discharge characteristics of electrolytic manganese dioxide ]
Testing high, medium and low rate discharge characteristics: putting 0.5g of a sample uniformly mixed by 93.2% of electrolytic manganese dioxide and 6.8% of graphite powder into a steel shell by using 1.5 tons of pressure, maintaining the pressure for 15 seconds by using 1.5 tons of pressure, then loosening, adding a nickel net and diaphragm paper into the steel shell, repressing by using 1.0 ton of pressure, loosening after maintaining the pressure for 10 seconds, taking out the steel shell, putting the steel shell into a discharge die, adding 9mol/LKOH solution and 99.99% zinc wire (phi 1.5 mm) into the die, and connecting a DM3000 three-in-one battery automatic discharge instrument to perform continuous discharge detection in a form of 1000mA/g, 250mA/g and 10mA/g of discharge current.
In the measurement of the high-rate discharge characteristic, the discharge was continued as a discharge current of 1000mA/g, and the discharge time was measured as a terminal voltage @ 0.9V.
In the measurement of the medium-rate discharge characteristic, the discharge was continued as a discharge current of 250mA/g, and the discharge time was measured as a terminal voltage @ 0.9V.
In the measurement of the low-rate discharge characteristic, the discharge was continued as a discharge current of 10mA/g, and the discharge time was measured as a termination voltage @ 0.9V.
The discharge time of the high, medium and low rate discharge in each example is represented by a relative value corresponding to 100% of the discharge time of the comparative example in the electrolytic process.
In each embodiment, the molecular weight of the nonionic flocculant is 800 ten thousand, 1000 ten thousand, 1200 ten thousand, 1500 ten thousand, 1800 ten thousand, 2000 ten thousand, 2500 ten thousand; the preparation concentration of the non-ionic flocculant is 2mg/L, 5mg/L, 10mg/L, 20mg/L, 30mg/L, 50mg/L and 80mg/L;
the concentration of sulfuric acid in the mixed solution of sulfuric acid and manganese sulfate is 50g/L, and the electrolytic current density is 0.6A/dm 2 Taking the solution in the electrolytic bath, stirring for 5 minutes (coded as A), taking the upper solution to measure the content (unit: mg/L) of the electrolytic manganese dioxide; adding the solution in the same electrolytic tank into the above-mentioned electrolytic tank respectivelyAfter the flocculant was stirred for 5 minutes, the upper layer solution was taken to measure the content (unit: mg/L) of electrolytic manganese dioxide.
The results are shown in Table 1.
TABLE 1 (Unit: mg/L)
When large and small floccules are generated after the flocculating agent is added, the electrolytic manganese dioxide content in the electrolyte is ND, but the existence of the floccules is not beneficial to electrolysis. The anionic and cationic ionic flocculants are taken, and the test is repeated, so that no effect is obtained.
According to the results of the above test table 1, the present invention is intended to select a non-ionic flocculant having a molecular weight of 1200 to 1800 ten thousand and a concentration of 10 to 50mg/L in the electrolyte.
The invention is implemented on a production line, and the specific conditions are as follows:
common hardware facilities of the examples and comparative examples
Cell size (hollow): 5.4 meters long, 1.4 meters deep, 1.2 meters wide; inner liner polyvinyl chloride (PVC);
anode: the material is pure titanium (TA 2), the plate with the length of 1200 mm, the width of 100 mm and the thickness of 4 mm is combined, the effective area is 2.76 square meters, and the support adopts a cast aluminum cross arm; cathode: the material is carbon, and is formed by combining carbon rods with the diameter of 30 millimeters and the length of 1400 millimeters, the effective area is 2.64 square meters, and cast aluminum cross arms are adopted for supporting.
The electrolysis temperature of the electrolytic cell is controlled at 95-99 ℃, sodium lauryl sulfate (K12 powder) is used as a cell sealing agent, 1-5 Mpa boiler steam is used for heating and heat preservation, and the material of a heating pipe is pure titanium.
The following examples and comparative examples all employ the hardware facilities described above.
Example 1
Additive: polyacrylamide (PMA), molecular weight 1200 ten thousand.
The electrolyte comprises the following components: the sulfuric acid concentration is 33 +/-3 g/L, the manganese sulfate concentration is 57 +/-10 g/L, and the Polyacrylamide (PMA) concentration is 10mg/L.
Composition of the electrolyte replenishing solution: the concentration of manganese sulfate is 95 +/-10 g/L.
The electrolysis conditions are as follows: the current density is 0.4A/dm 2 The temperature is controlled to be 97 +/-2 ℃, and the electrolysis period is 15 days.
Continuously adding the additive into the electrolyte according to the required additive of 10mg/L in the electrolyte, and adding a supplementary manganese sulfate solution into the electrolyte according to the condition that the sulfuric acid concentration in the electrolyte is maintained at 33 +/-3 g/L.
And (3) processing a finished product: the electrolytic manganese dioxide block obtained by the process conditions of the embodiment adopts powdery electrolytic manganese dioxide with the average particle size (D50) of 34-39 um obtained by crushing 5-15 mm particles and grinding, and then washing, neutralizing (drying) are carried out.
The production conditions of this example are shown in Table 2, and the test evaluation results of the obtained electrolytic oxidation product are shown in Table 3.
Example 2
Additive: polyacrylamide (PMA), molecular weight 1200 ten thousand.
The electrolyte comprises the following components: the concentration of sulfuric acid is 45 +/-3 g/L, the concentration of manganese sulfate is 45 +/-10 g/L, and the concentration of Polyacrylamide (PMA) is 20mg/L.
Composition of the electrolyte replenishing solution: the concentration of manganese sulfate is 95 +/-10 g/L.
The electrolysis conditions are as follows: the current density is 0.54A/dm 2 Controlling the temperature to 97 +/-2 ℃ and the electrolysis period to 15 days.
Controlling additives in the electrolytic process: continuously adding the additive into the electrolyte according to the required additive of 20mg/L in the electrolyte, and adding a supplementary manganese sulfate solution into the electrolyte according to the condition that the sulfuric acid concentration in the electrolyte is maintained at 45 +/-3 g/L.
And (3) processing a finished product: electrolytic manganese dioxide powder was obtained in the same manner as in example 1.
The production conditions of this example are shown in Table 2, and the test evaluation results of the obtained electrolytic oxidation product are shown in Table 3.
Example 3
Additive: polyacrylamide (PMA), molecular weight 1500 ten thousand.
The electrolyte comprises the following components: the concentration of sulfuric acid is 57 +/-3 g/L, the concentration of manganese sulfate is 35 +/-10 g/L, and the concentration of Polyacrylamide (PMA) is 30mg/L.
Composition of the electrolyte replenishing solution: the concentration of manganese sulfate is 95 +/-10 g/L.
The electrolysis conditions are as follows: the current density is 0.65A/dm 2 The temperature is controlled to be 97 +/-2 ℃, and the electrolysis cycle is 15 days.
Controlling additives in the electrolytic process: continuously adding the additive into the electrolyte according to the required additive of 30mg/L in the electrolyte, and adding a supplementary manganese sulfate solution into the electrolyte according to the aim of maintaining the sulfuric acid concentration of the electrolyte at 57 +/-3 g/L.
And (3) processing a finished product: electrolytic manganese dioxide powder was obtained in the same manner as in example 1.
The production conditions of this example are shown in Table 2, and the test evaluation results of the obtained electrolytic dioxide product are shown in Table 3.
Example 4
Additive: polyacrylamide (PMA), molecular weight 1800 ten thousand.
The electrolyte comprises the following components: the concentration of sulfuric acid is 65 +/-3 g/L, the concentration of manganese sulfate is 30 +/-10 g/L, and the concentration of Polyacrylamide (PMA) is 40mg/L.
Composition of electrolyte replenisher: the concentration of manganese sulfate is 95 +/-10 g/L.
The electrolysis conditions are as follows: the current density is 0.70A/dm 2 Controlling the temperature to 97 +/-2 ℃ and the electrolysis period to 15 days.
Controlling additives in the electrolytic process: continuously adding the additive into the electrolyte according to 40mg/L of the required additive in the electrolyte, and adding a supplementary manganese sulfate solution into the electrolyte according to the aim of maintaining the sulfuric acid concentration of the electrolyte at 65 +/-3 g/L.
And (3) processing a finished product: electrolytic manganese dioxide powder was obtained in the same manner as in example 1.
The production conditions of this example are shown in Table 2, and the test evaluation results of the obtained electrolytic oxidation product are shown in Table 3.
Example 5
Additive: polyacrylamide (PMA), molecular weight 1800 ten thousand.
The electrolyte comprises the following components: the concentration of sulfuric acid is 77 +/-3 g/L, the concentration of manganese sulfate is 25 +/-10 g/L, and the concentration of Polyacrylamide (PMA) is 50mg/L.
Composition of electrolyte replenisher: the concentration of manganese sulfate is 95 +/-10 g/L.
The electrolysis conditions are as follows: the current density is 0.80A/dm 2 The temperature is controlled to be 97 +/-2 ℃, and the electrolysis cycle is 15 days.
Controlling additives in the electrolytic process: continuously adding the additive into the electrolyte according to the required additive 50mg/L in the electrolyte, and adding a supplementary manganese sulfate solution into the electrolyte according to the aim of maintaining the sulfuric acid concentration of the electrolyte at 77 +/-3 g/L.
And (3) processing a finished product: powdery electrolytic manganese dioxide was obtained in the same manner as in example 1.
The production conditions of this example are shown in Table 2, and the test evaluation results of the obtained electrolytic oxidation product are shown in Table 3.
Comparative example 1
The electrolyte comprises the following components: the concentration of sulfuric acid is 33 +/-3 g/L, and the concentration of manganese sulfate is 57 +/-10 g/L.
Composition of electrolyte replenisher: the concentration of manganese sulfate is 95 +/-10 g/L.
The electrolysis conditions are as follows: the current density is 0.4A/dm 2 Controlling the temperature to 97 +/-2 ℃ and the electrolysis period to 15 days.
The manganese sulfate solution was supplemented to the electrolyte so that the concentration of sulfuric acid in the electrolyte was maintained at 33. + -.3 g/L.
And (3) processing a finished product: powdery electrolytic manganese dioxide was obtained in the same manner as in example 1.
The production conditions of this comparative example are shown in Table 2, and the results of the test evaluation of the electrolytic di-oxide product obtained are shown in Table 3.
Comparative example 2
The electrolyte comprises the following components: the concentration of sulfuric acid is 45 +/-3 g/L, and the concentration of manganese sulfate is 45 +/-10 g/L.
Composition of the electrolyte replenishing solution: the concentration of manganese sulfate is 95 +/-10 g/L.
The electrolysis conditions are as follows: the current density is 0.54A/dm2, the temperature is controlled to be 97 +/-2 ℃, and the electrolysis period is 15 days.
The manganese sulfate solution was supplemented to the electrolyte so that the concentration of sulfuric acid in the electrolyte was maintained at 45. + -.3 g/L.
And (3) processing a finished product: electrolytic manganese dioxide powder was obtained in the same manner as in example 1.
The production conditions of this comparative example are shown in Table 2, and the results of the test evaluation of the electrolytic di-oxide product obtained are shown in Table 3.
Comparative example 3
The electrolyte comprises the following components: the concentration of sulfuric acid is 57 +/-3 g/L, and the concentration of manganese sulfate is 35 +/-10 g/L.
Composition of the electrolyte replenishing solution: the concentration of manganese sulfate is 95 +/-10 g/L.
The electrolysis conditions are as follows: the current density is 0.65A/dm 2 Controlling the temperature to 97 +/-2 ℃ and the electrolysis period to 15 days.
A supplementary manganese sulfate solution was added to the electrolyte so as to maintain the sulfuric acid concentration in the electrolyte at 57. + -.3 g/L.
And (3) processing a finished product: powdery electrolytic manganese dioxide was obtained in the same manner as in example 1.
The production conditions of this comparative example are shown in Table 2, and the results of the test evaluation of the electrolytic di-oxide product obtained are shown in Table 3.
Comparative example 4
The electrolyte comprises the following components: the concentration of the sulfuric acid is 65 +/-3 g/L, and the concentration of the manganese sulfate is 30 +/-10 g/L.
Composition of electrolyte replenisher: the concentration of manganese sulfate is 95 +/-10 g/L.
The electrolysis conditions are as follows: the current density is 0.70A/dm 2 The temperature is controlled to be 97 +/-2 ℃, and the electrolysis cycle is 15 days.
The manganese sulfate solution was supplemented to the electrolyte so as to maintain the sulfuric acid concentration in the electrolyte at 65. + -.3 g/L.
And (3) processing a finished product: powdery electrolytic manganese dioxide was obtained in the same manner as in example 1.
The production conditions of this comparative example are shown in Table 2, and the test evaluation results of the obtained electrolytic dioxide product are shown in Table 2.
Comparative example 5
The electrolyte comprises the following components: the concentration of sulfuric acid is 77 +/-3 g/L, and the concentration of manganese sulfate is 25 +/-10 g/L.
Composition of electrolyte replenisher: the concentration of manganese sulfate is 95 +/-10 g/L.
The electrolysis conditions are as follows: the current density is 0.80A/dm 2 The temperature is controlled to be 97 +/-2 ℃, and the electrolysis cycle is 15 days.
The manganese sulfate solution was supplemented to the electrolyte so that the sulfuric acid concentration in the electrolyte was maintained at 77. + -.3 g/L.
And (3) processing a finished product: electrolytic manganese dioxide powder was obtained in the same manner as in example 1.
The parameter conditions of the preparation methods of the inventive examples and comparative examples are shown in Table 2, and the test evaluation results of the obtained electrolytic oxidation products are shown in Table 3.
TABLE 2
TABLE 3
Note: ND represents the content of manganese dioxide not measured.
Referring to FIG. 1, the deposited electrolytic manganese dioxide BET (unit: m) at each part of the anode (example 4vs, comparative example 4) is shown 2 /g)), the manufacturing method of electrolytic manganese dioxide by adding a flocculant in an electrolyte in the example of the present invention is different from the method of electrolyzing a sulfuric acid-manganese sulfate mixed solution without using a flocculant, that is, the example of the present invention is different from the "clarified electrolysis method" of electrolytic manganese dioxide without adding a flocculant at the time of electrolysis. In this example, electrolytic manganese dioxide excellent in the ability to control the pore structure, crystal structure and BET specific surface area was produced by electrolytic method with flocculant. On the basis of the method, the surface structure and the electrolytic current efficiency of the product are improved compared with a clarification electrolytic method without adding a flocculating agent. In the general concept of "clarification electrolysis method", there is a tendency that physical properties of electrolytic manganese dioxide precipitated during electrolysis are not uniform, and for example, BET surface areas of respective portions of an electrode are different.
Specifically, in the examples of the present invention, the production method of the present invention continuously added a flocculant to a sulfuric acid-manganese sulfate mixed solution. Thus, the concentration of the flocculant added to the sulfuric acid-manganese sulfate mixed solution in the electrolytic process can be stabilized, and the electrolytic manganese dioxide manufacturing method can be used for electrolyzing the electrolyte containing the flocculant added at a certain concentration in the electrolytic process. This makes the physical properties, particularly the state of pores, of the electrolytic manganese dioxide obtained through the entire electrolysis uniform.
The above description is of the preferred embodiment of the present invention, but it is not intended to limit the present invention. Modifications and variations of the embodiments disclosed herein may be made by those skilled in the art without departing from the scope and spirit of the invention.
Claims (10)
1. A preparation method of electrolytic manganese dioxide, under the high temperature state, using aqueous solution of manganese sulfate and sulfuric acid as electrolyte, adding flocculant to the electrolyte to obtain manganese dioxide by electrolysis, characterized in that flocculant is continuously added to sulfuric acid-manganese sulfate electrolytic solution, so that the concentration of flocculant in sulfuric acid-manganese sulfate mixed solution is 10-50 mg/L, the concentration of sulfuric acid in sulfuric acid-manganese sulfate mixed solution is 30-80 g/L, the concentration of manganese sulfate is controlled to be 30-100 g/L, andthe electrolytic current density is 0.4-0.8A/dm 2 To carry out electrolysis.
2. The method of claim 1, wherein the additive is selected from the group consisting of PMA (polyacrylamide), which is a non-ionic organic flocculant.
3. The method of claim 1, wherein the flocculant (PMA) added to the electrolyte has a molecular weight of 1200 to 1800 ten thousand.
4. The method of claim 1, wherein the additive is added to the electrolyte in an amount of 10-50 mg/L.
5. The method of claim 1, wherein the temperature during electrolysis is controlled to be 95 ℃ to 99 ℃.
6. The method of claim 1, further comprising, after electrolysis: crushing and grinding, rinsing and neutralizing.
7. The method of claim 1, wherein the step of crushing and grinding comprises crushing and ball-milling the electrolytic manganese dioxide to a desired particle size.
8. The method of claim 1, wherein the electrolytic manganese dioxide obtained by electrolysis is washed to remove an electrolyte adhering thereto in the rinsing step. Wherein the electrolytic manganese dioxide is immersed in a water bath or a warm water bath.
9. The method of claim 1, wherein the neutralization step comprises adjusting the pH of the electrolytic manganese dioxide by immersing the electrolytic manganese dioxide in an aqueous alkali metal solution. The aqueous alkali metal solution is limited to only aqueous sodium hydroxide solution, aqueous sodium carbonate solution and aqueous sodium bicarbonate solution.
10. According to the method of claim 1, the electrolytic manganese dioxide produced by the present invention can be used as a positive electrode active material of a primary battery such as an alkaline zinc-manganese battery.
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