Application background and overview of ferrous carbonate
Ferous carbonate is also called “siderite” in nature. It is slightly soluble in water and dissolves in an aqueous solution of carbon dioxide to form Fe(HCO3)2. When its solution is exposed to the air, excess carbon dioxide escapes, and the precipitated FeCO3 is rapidly hydrolyzed and oxidized, and transformed into FeO(OH) precipitation. Strong thermal decomposition generates carbon dioxide and ferrous oxide. In the laboratory, it can be obtained by isolating the air and adding an alkali metal carbonate solution to the ferrous salt solution. The product quickly darkens when exposed to air and eventually turns into brown FeO(OH). Ferrous carbonate can be used as a flame retardant and as an iron additive for animal feed.
Applications of ferrous carbonate
Ferous carbonate can be used as a flame retardant and an iron additive for animal feed. Examples of its application are as follows:
1) Preparation of a ferrous carbonate/graphene composite material used as anode material for lithium ion batteries,
It includes, step 1: forming a suspension of graphene material, water-soluble ferrous salt, urea and water; wherein the mass ratio of the graphene material and the water-soluble ferrous salt is 0.02~0.2: 1; The ratio of the amount and concentration of the urea and the water-soluble ferrous salt is 20~100:1; Step 2: Place the suspension into a reaction kettle, and control the temperature to 100~180°C for water After thermal reaction for 4 to 12 hours, ferrous carbonate/graphene composite material is obtained. The invention also provides a lithium-ion battery prepared by using the ferrous carbonate/graphene composite material as a negative electrode material. The invention adopts low-temperature hydrothermal synthesis of ferrous carbonate/graphene negative electrode material, has high specific capacity and good cycleability, and has good development prospects when applied to lithium-ion battery negative electrode materials.
2) Prepare a submicron lithium iron phosphate cathode material, which belongs to the technical field of lithium-ion battery cathode materials.
Including preparation of ferrous carbonate slurry: adding antioxidants and carbonates to the ferrous sulfate solution to produce ferrous carbonate precipitation, filtering and washing to obtain ferrous carbonate filter cake, adding water and stirring to prepare ferrous carbonate slurry; Synthesis of lithium iron phosphate precursor: Pump lithium dihydrogen phosphate solution and ferrous carbonate slurry into a counter-flow mixing reactor to generate lithium iron phosphate precursor slurry. The slurry is aged, dehydrated and concentrated to obtain a thick slurry; phosphoric acid Preparation of lithium iron cathode material: Add soluble organic matter, carbon nanotubes and dispersant to the thick slurry, and obtain carbon-containing lithium iron phosphate cathode material after cyclic dispersion, spray drying, calcination, cooling and pulverization. The present invention uses a counter-flow mixing reactor to synthesize lithium iron phosphate precursor, and the product particle size reaches sub-micron level, effectively shortening the reaction time; the raw material utilization rate is high, the cost is low, and the product conductivity is good.
Application and preparation of ferrous carbonate
Method 1: A method for producing ferrous carbonate and sodium sulfate from waste acid obtained by producing titanium dioxide using the sulfuric acid method. The method includes the following specific steps:
Step A: Mix the waste acid obtained from the production of titanium dioxide by the sulfuric acid method with excess hydrogen cyanopyridine ferrous oxide solution to react sulfuric acid with ferrous hydroxide to generate ferrous sulfate; filter the reaction liquid to obtain mainly ferrous sulfate. Iron filtrate, filter residue containing a small amount of unreacted ferrous hydroxide and insoluble impurities, the filter residue is deeply buried or processed by other processes;
Step B: Add excess sodium carbonate to the filtrate mainly containing ferrous sulfate obtained in step A, react with stirring to generate ferrous carbonate and sodium sulfate, filter the reaction liquid, and separate the ferrous carbonate precipitate and sodium sulfate solution. ;In this step, a small amount of unreacted sodium carbonate is also in the sodium sulfate solution;
Step C: Wash, dry and pulverize the ferrous carbonate precipitate obtained in step B to obtain the ferrous carbonate product.
Method 2: A process for producing ferrous carbonate and sodium nitrate from waste liquid. This method includes the following specific steps:
Step A: Mix the waste acid obtained from the production of titanium dioxide by the nitric acid method with excess iron oxypicoline solution to react the nitric acid with the iron hydroxide to generate ferrous nitrate; filter the reaction solution to obtain mainly ferrous nitrate. The filtrate contains a small amount of unreacted ferric hydroxide and filter residue containing insoluble impurities. The filter residue is deeply buried or processed by other processes;
Step B: Add excess sodium carbonate to the filtrate mainly containing ferrous nitrate obtained in step A, react with stirring to generate ferrous carbonate and sodium nitrate, filter the reaction liquid, and separate the ferrous carbonate precipitate and sodium nitrate solution ;In this step, a small amount of unreacted sodium carbonate is also in the sodium nitrate solution;
Step C: Wash, dry and pulverize the ferrous carbonate precipitate obtained in step B to obtain the ferrous carbonate product.
