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Essential characteristics and preparation method of manganese dioxide

wallpapers Tech 2020-06-09
Manganese dioxide, also known as "manganese peroxide" or "black manganese oxide," appears as black orthogonal crystals or brownish-black powder with many variations. Insoluble in water, nitric acid, cold sulfuric acid, and acetic acid, soluble in crisp and concentrated hydrochloric acid, producing unstable light brownish green MnCl4, reacts with concentrated hydrochloric acid to give off chlorine gas. It reacts with concentrated sulfuric acid slowly to release oxygen. It can be dissolved in dilute sulfuric acid or nitric acid in the presence of H2O2 or H2C2O4. When heated to 600°C in the air, it emits oxygen, which turns into Mn2O3, and turns into Mn3O4 during white heat. It is a strong oxidant and must not be heated or rubbed together with organic substances or other oxidizable substances such as sulfur, sulfide, phosphide, etc. Found as pyrolusite in nature. Preparation method: It can be prepared by heating manganese nitrate crystal in the air at 150~190℃ for a long time.

Its uses are: in the laboratory for the production of chlorine or other halogens, a large number of users as a depolarizer in the manufacture of dry batteries, also used in the production of paints, varnishes, enamels, glass, glaze, manganese steel, and manganese compounds.

1. Method for preparing electrolytic manganese dioxide with high-pressure solid density

Since electrolytic manganese dioxide is an inexpensive and abundant material, and it has an excellent discharge and long-term storage performance, it is generally used as an active material for dry battery cells. For example, electrolytic manganese dioxide is used as the material of the positive electrode in alkaline primary batteries. Electrolytic manganese dioxide is usually prepared by passing a direct current through an electroplating bath containing an acid solution of manganese sulfate and sulfuric acid.

The positive electrode of the electroplating bath may include a titanium plate on which electrolytic manganese dioxide is deposited. The negative electrode may be made of graphite or copper or similar materials. When the stored electrolytic manganese dioxide reaches a thickness of about 1mm to about 75mm, it is removed from the titanium plate with external force, and it can be crushed to a maximum size of 25-100mm to obtain electrolytic dioxide for further processing Manganese fragments. Grinding or crushing processes are used further to reduce the size of electrolytic manganese dioxide fragments to meet the requirements of battery manufacturers. Since electrolytic manganese dioxide is prepared in an acid bath, the preparation of electrolytic manganese dioxide generally requires washing or acid treatment of electrolytic manganese dioxide to neutralize the acid bath's residual acidity.

This treatment can be performed before or after crushing electrolytic manganese dioxide. If the neutralization step is performed after the crushing stage, the electrolytic manganese dioxide particles are usually suspended in an aqueous solution to which sodium hydroxide is added. Once the acidity is neutralized, dehydration is performed to separate the aqueous solution from the solid electrolytic manganese dioxide particles. The material obtained after the neutralization step is called neutralized electrolytic manganese dioxide. In the final stage, the electrolytic manganese dioxide is dried to a specific size.

For example, for alkaline primary battery applications, the drying step is generally mild, leaving physically adsorbed water, which can account for about 1% to about 3% by weight of the product. The resulting material is an active material for alkaline primary batteries. Battery manufacturers use electrolytic manganese dioxide as the active material of the positive electrode in alkaline batteries to support the zinc anode. Combine electrolytic manganese dioxide with other elements that make up the cathode precursor, and compact it with a tool. The amount of electrolytic manganese dioxide encapsulated in a battery of a predetermined volume is an essential factor determining battery performance. The electrolytic manganese dioxide compacted density is a parameter used to predict the amount of electrolytic manganese dioxide that can be loaded into a battery. Battery manufacturers should use high-density densification because when electrolytic manganese dioxide is compacted more densely, a cell with a predetermined volume will have better performance.

2. Ultrasonic cleaning method of manganese dioxide

Electrolytic manganese dioxide is the best depolarizer material for zinc-manganese batteries. With the development of the battery industry, battery manufacturers are increasingly demanding electrolytic manganese dioxide materials, of which the discharge performance of electrolytic manganese dioxide is the top priority. Weight. To this end, electrolysis manufacturers and many scientific research departments have invested a lot of power, looking for a more reasonable process from the electrolysis process and the post-treatment process to produce electrolytic manganese dioxide of higher quality—especially the product washing process.

In the past, industrial production methods used hot water, long-time stirring, and soaking to wash and then filter repeatedly. The disadvantage of this method is that the water consumption is large, the immersion time is extended, the equipment takes a long time, the production efficiency is low, and the long-term stirring consumes too much electricity. Moreover, the impurity washing effect is not good. A high-pressure steam washing method can be used. This method involves high pressure, and it is difficult to realize a large amount of manganese dioxide processing equipment, and the process is complicated. The object of the present invention is to provide a method for ultrasonic cleaning of manganese dioxide with good effect of removing impurities, short production time, high efficiency, and significantly improving the discharge performance of manganese dioxide.

3. A controllable method for preparing nano-manganese dioxide

The current methods for preparing MnO2 mainly include liquid phase co-precipitation method, low-temperature solid-phase method, thermal decomposition method, hydrothermal synthesis method, and solvent-gel method. The liquid-phase precipitation method has the characteristics of a simple reaction, rapid, complete, and low cost. Still, the disadvantage is that during the response, the reaction product's morphology cannot be controlled, and the resulting particle size is large.

Step 1: Preparation of manganese dioxide active material: Add surfactant to 200mol concentration of 0.1mol/L KMn04, add dropwise 300mol concentration of 0.2mol/L Mn(CH3COO) 2 in 2h, stir for 8h, then The precipitated product is washed with deionized water and ethanol and filtered, and the screened material is dried and ground to obtain a brownish-black manganese dioxide active substance;

Step 2: Prepare manganese dioxide electrode pads: mix manganese dioxide active material, conductive carbon black and binder polytetrafluoroethylene (PTFE), mix with N-methyl pyrrolidone into plasticine, and press down on Ti The manganese dioxide electrode sheet is prepared on the sheet.

Trunnano is one of the world's largest producers of manganese dioxide. In addition to manganese dioxide, the company also has nano-oxide products such as manganese trioxide. If you are interested, you can consult Dr. Leo, email: brad@ihpa.net.

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