Method for comprehensive utilization of low-grade forsterite mineral

Abstract

The application discloses a method for comprehensive utilization of low-grade forsterite minerals, and belongs to the technical field of forsterite mineral processing. The method comprises the following steps: pretreating low-grade forsterite minerals to a target particle size, and then performing heat preservation and acid leaching treatment; collecting silicon-containing filter residue I and filter liquor I magnesium-iron leaching liquor; washing and dissolving the silicon-containing filter residue I in alkali liquor, and then collecting filter liquor II sodium silicate solution; performing acidification and filtration on the filter liquor II to obtain filter residue II, and then performing heat drying on the filter residue II to obtain white carbon black; taking the filter liquor I magnesium-iron leaching liquor as electrolyte to perform pre-electrolysis and remove iron, filtering slurry after electrolysis, collecting filter residue III and filter liquor III magnesium chloride solution; washing and heat drying the filter residue III, and then performing calcination treatment to obtain iron red; and taking the filter liquor III magnesium chloride solution as electrolyte to perform electrolysis and obtain pure magnesium hydroxide. The method takes low-grade forsterite as raw material, removes silicon, iron and other impurities in the ore, realizes enrichment of magnesium in the forsterite ore, and obtains high-value-added product magnesium hydroxide.

Description

Technical Field

[0001] This invention belongs to the field of magnesium olivine mineral processing technology, specifically relating to a method for the comprehensive utilization of low-grade magnesium olivine minerals. Background Technology

[0002] Forsterite is an ultramafic plutonic rock, a common rock-forming mineral, and one of the minerals formed during the early crystallization of magma in the Earth's crust. It is a major component of igneous rocks such as gabbro, basalt, and peridotite. Magnesium oxide and silicon dioxide are the main components of forsterite. The theoretical chemical formula of pure forsterite should be 2MgO·SiO2 or Mg2SiO4. Natural forsterite minerals, in addition to the main chemical components MgO and SiO2, also contain certain amounts of Fe2O3, Fe3O4, and small amounts of Al2O3 and CaO. Its theoretical chemical composition is 57.2% MgO and 42.8% SiO2, but due to the interference of impurities, the actual content of MgO and SiO2 is generally lower than the theoretical value. The unique crystal structure of forsterite allows magnesium ions to be replaced by iron ions from surrounding minerals. Therefore, forsterite and fir peridot often form a solid solution state in the mineral, with fir peridot generally accounting for 0%-10% of the co-dissolved minerals.

[0003] The comprehensive utilization of forsterite mainly focuses on the following aspects: On the one hand, in the preparation of refractory materials: forsterite-type refractory materials are weakly alkaline refractory materials, with high strength, high melting point, good chemical and mineral stability, low thermal conductivity, and good compatibility with most alkaline refractory materials, which can partially replace magnesia bricks; on the other hand, in the preparation of casting sand materials: at present, advanced countries in the world mostly use forsterite and sand in the production of manganese steel parts and other cast steel parts. Due to its good high temperature resistance, corrosion resistance and chemical stability, it is an excellent molding material in the casting sand process.

[0004] The Shangluo mountainous area, bordering Henan and Shaanxi provinces, has reserves of approximately 500 million tons of calcium magnesium olivine. However, its comprehensive utilization faces several challenges: firstly, the quality of the raw materials is problematic, as the MgO content of the magnesium olivine ore in this area is only about 47%, with low magnesium content and high levels of impurities such as iron; secondly, there are economic issues. Existing technologies cannot solve these problems. For example, Chinese patent CN103553560A discloses a method for preparing magnesium olivine from olivine ore, which involves calcining silicate olivine ore and sintering aids in a microwave kiln to obtain clinker magnesium olivine; Chinese patent CN112537788A discloses a process for producing magnesium sulfate and precipitated silica from magnesium olivine tailings, which involves leaching the tailings with sulfuric acid at high temperatures, followed by pH adjustment, filtration, and dehydration to produce magnesium sulfate and precipitated silica. Both of these processes are limited by the purity of the raw magnesium olivine, resulting in low product purity and complex impurity removal processes. Chinese patent CN106830991A discloses a magnesium olivine lightweight refractory material and its preparation method. The refractory material produced by this method has low added value, and the process is long, complex, and uneconomical, making it difficult to industrialize.

[0005] In summary, developing new production processes to achieve high-value-added utilization of magnesium olivine ore has become an urgent need. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention aims to provide a method for the comprehensive utilization of low-grade magnesium olivine minerals. This method uses magnesium olivine as a raw material to prepare magnesium hydroxide, while simultaneously producing byproducts such as silica, hydrogen, chlorine, and iron oxide. This achieves high-value-added utilization of low-grade magnesium olivine minerals and improves the current situation where it is difficult to achieve high-value-added utilization of low-grade magnesium olivine minerals.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for the comprehensive utilization of low-grade magnesium olivine minerals includes the following steps:

[0009] Raw material pretreatment: The forsterite mineral is crushed, ground and sieved to obtain forsterite mineral powder with the target particle size;

[0010] Acid leaching treatment: Mix magnesium olivine mineral powder of the target particle size with hydrochloric acid solution, heat and keep warm to carry out acid leaching reaction; after the acid leaching reaction is completed, filter the acid leaching product and collect silica-containing filter residue I and magnesium-iron leaching solution I.

[0011] Washing and alkaline dissolution of silica-containing filter residue: Wash silica-containing filter residue I with deionized water until the pH of the washing solution is neutral; add sodium hydroxide solution to the washed filter residue until the filter residue is fully dissolved, filter after dissolution, and collect filtrate II, sodium silicate solution.

[0012] Preparation of by-product silica: Hydrochloric acid solution is added to sodium silicate solution in filtrate II until the target pH value is reached, acidification is carried out to generate silicic acid, and filter residue II is collected after filtration; filter residue II is washed with deionized water until the pH value of the washing solution is neutral; the washed and filtered filter residue II is heated and dried by blowing air to obtain by-product silica.

[0013] Pre-electrolysis of iron: Add filtrate I (magnesium-iron leaching solution) to a self-made electrolytic cell, arranging it in the order of cathode-diaphragm-anode. Adjust the distance between the cathode and anode plates and the diaphragm, and connect the cathode and anode to the negative and positive terminals of the power supply, respectively, to form an electrolytic system. Turn on the power supply, set the current density and voltage upper limit, and perform constant current electrolysis. Stop electrolysis when the pH value of the electrolyte reaches the target value. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and iron hydroxide is generated at the cathode plate. After the pre-electrolysis reaction is completed, filter the product iron hydroxide slurry and collect filter residue III and filtrate III (magnesium chloride solution).

[0014] Preparation of by-product iron red: Wash filter residue III with deionized water until the pH of the washing solution is neutral. Heat and dry the washed and filtered filter residue III with forced air to obtain pure ferric hydroxide. Then, calcine the ferric hydroxide to obtain the by-product iron red.

[0015] Electrolytic preparation of magnesium hydroxide: Filtrate III (magnesium chloride solution) is added to a self-made electrolytic cell, arranged in a cathode-diaphragm-anode configuration. The distance between the cathode and anode plates and the diaphragm is adjusted. The cathode and anode are connected to the negative and positive terminals of the power supply, respectively, to form an electrolytic system. The power supply is turned on, and the current density and voltage upper limit are set for constant current electrolysis. During electrolysis, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and magnesium hydroxide is produced at the cathode plate. After the electrolysis reaction is completed, the product magnesium hydroxide slurry is filtered, and filter residue IV is collected. Filter residue IV is washed with deionized water until the pH of the washing solution is neutral. The washed and filtered filter residue IV is then heated and dried by forced air to obtain pure magnesium hydroxide.

[0016] Furthermore, in the raw material pretreatment, the target particle size of the magnesium olivine mineral powder is ≤150μm.

[0017] Furthermore, in the acid leaching treatment, the concentration of hydrochloric acid solution is 2.4 mol / L-6 mol / L, and the liquid-solid ratio of hydrochloric acid solution to mineral powder is 10 mL / g-16 mL / g; the acid leaching reaction temperature is 60℃-90℃, and the time is 2h-4h.

[0018] Furthermore, in the washing and alkaline dissolution of the silica-containing filter residue, the concentration of sodium hydroxide solution is 0.05 mol / L-0.2 mol / L.

[0019] Furthermore, in the preparation of the byproduct silica, the concentration of hydrochloric acid solution added is 2.4 mol / L-6 mol / L, with a target pH value of 5.5.

[0020] Furthermore, in the pre-electrolytic iron dissolution, the current density is 0.025 A / cm². 2 -0.05A / cm 2 The upper limit of the voltage is 3V-6V, and electrolysis is stopped when the pH value of the electrolyte reaches 3.7.

[0021] Furthermore, in the preparation of the byproduct iron red, the calcination temperature of ferric hydroxide is 500℃-700℃, and the time is 1h-3h.

[0022] Furthermore, in the electrolytic preparation of magnesium hydroxide, the current density is 0.025 A / cm². 2 -0.05A / cm 2 The upper limit of voltage is 3V-6V, and the electrolysis time is 2h-6h.

[0023] Furthermore, the temperature for heating and drying filter residues II, III, and IV with forced air is 60℃-90℃, and the time is 8h-24h.

[0024] Furthermore, in the pre-electrolysis of iron and the electrolytic preparation of magnesium hydroxide, the diaphragm is a polytetrafluoroethylene membrane, an ion-exchange membrane, etc.; the cathode and anode plates are both titanium-based metals coated with anti-corrosion coatings, and are flat or mesh-shaped; the distance between the cathode and anode plates and the diaphragm is 1cm-4cm.

[0025] Advantages and effects of the present invention:

[0026] This invention prepares magnesium hydroxide through acid leaching-pre-electrolysis to remove iron and then electrolysis. Using low-grade forsterite as raw material, it removes impurities such as silicon and iron from the ore, achieving an iron removal efficiency of over 91.83%. This process enriches magnesium in the forsterite ore, providing the necessary raw material for subsequent magnesium hydroxide production. Ultimately, it yields high-value-added magnesium hydroxide, providing a high-value-added utilization solution for low-grade forsterite and effectively solving the problem of low-grade calcium magnesium olivine ore and low product added value in the Shangluo mountain area. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the process flow for a method of comprehensive utilization of low-grade magnesium olivine mineral according to the present invention.

[0028] Figure 2 The X-ray diffraction (XRD) pattern of magnesium hydroxide obtained in Example 1;

[0029] Figure 3 This is a scanning electron microscope (SEM) image of magnesium hydroxide obtained in Example 1.

[0030] Figure 4 The image shows the X-ray diffraction (XRD) pattern of magnesium hydroxide obtained in Example 3. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0032] A method for the comprehensive utilization of low-grade magnesium olivine minerals, such as Figure 1 The process flow shown includes the following steps:

[0033] Raw material pretreatment: The forsterite mineral is crushed, ground and sieved to obtain forsterite mineral powder with a particle size ≤150μm.

[0034] Acid leaching treatment: The sieved magnesium olivine mineral powder is mixed with a 2.4 mol / L-6 mol / L hydrochloric acid solution, and the liquid-solid ratio of the hydrochloric acid solution to the mineral powder is controlled at 10 mL / g-16 mL / g. The acid leaching reaction is carried out at 60℃-90℃ for 2-4 hours. After the acid leaching reaction is completed, the acid leaching product is filtered, and the silica-containing filter residue I and the filtrate I magnesium-iron leaching solution are collected.

[0035] Washing and alkaline dissolution of silica-containing filter residue: Wash silica-containing filter residue I with deionized water until the pH of the washing solution is neutral; add 0.05mol / L-0.2mol / L sodium hydroxide solution to the washed filter residue until the filter residue is fully dissolved, filter after dissolution, and collect filtrate II sodium silicate solution.

[0036] Preparation of by-product silica: 2.4 mol / L-6 mol / L hydrochloric acid solution is added to sodium silicate solution in filtrate II until the pH reaches 5.5, acidifying to generate silicic acid. After filtration, filter residue II is collected. Filter residue II is washed with deionized water until the pH of the washing solution is neutral. The washed and filtered filter residue II is dried in a forced-air dryer at 60℃-90℃ for 8h-24h to obtain by-product silica.

[0037] Pre-electrolysis of iron: Add filtrate I (magnesium-iron leaching solution) to a self-made electrolytic cell, arranging it in a cathode-diaphragm-anode configuration. The diaphragm can be a polytetrafluoroethylene membrane, ion-exchange membrane, etc. Both the cathode and anode plates are made of titanium-based metal with an anti-corrosion coating, and are flat or mesh-shaped. Adjust the distance between the cathode and anode plates and the diaphragm to 1cm-4cm. Connect the cathode and anode to the negative and positive terminals of the power supply, respectively, to form an electrolytic system. Turn on the power supply and set the current density to 0.025A / cm². 2 -0.05A / cm 2 The voltage limit is 3V-6V, and constant current electrolysis is performed. Electrolysis is stopped when the pH value of the electrolyte reaches 3.7. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and iron hydroxide is generated at the cathode plate. After the pre-electrolysis reaction is completed, the product iron hydroxide slurry is filtered, and filter residue III and filtrate III magnesium chloride solution are collected.

[0038] Preparation of by-product iron red: Wash filter residue III with deionized water until the pH of the washing solution is neutral. Dry the washed and filtered filter residue III in a forced-air dryer at 60℃-90℃ for 8h-24h to obtain pure ferric hydroxide. Then calcine the ferric hydroxide at 500℃-700℃ for 1h-3h to obtain the by-product iron red.

[0039] Electrolytic preparation of magnesium hydroxide: Filtrate III (magnesium chloride solution) is added to a self-made electrolytic cell, arranged in a cathode-diaphragm-anode configuration. The diaphragm can be a polytetrafluoroethylene membrane, ion-exchange membrane, etc. The distance between the cathode and anode plates and the diaphragm is adjusted to 1cm-4cm. The cathode and anode are connected to the negative and positive terminals of the power supply, respectively, to form an electrolytic system. The power supply is turned on, and the current density is set to 0.025A / cm². 2 -0.05A / cm 2 The voltage limit is 3V-6V, and constant current electrolysis is carried out for 2h-6h. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and magnesium hydroxide is generated at the cathode plate. After the electrolysis reaction is completed, the product magnesium hydroxide slurry is filtered, and filter residue IV is collected. Filter residue IV is washed with deionized water until the pH value of the washing liquid is neutral. The washed and filtered filter residue IV is dried by forced air at 60℃-90℃ for 8h-24h to obtain pure magnesium hydroxide.

[0040] Example 1

[0041] A method for the comprehensive utilization of low-grade magnesium olivine minerals includes the following steps:

[0042] Raw material pretreatment: The forsterite mineral is broken into small blocks and placed in a universal crusher for 10 minutes; the forsterite mineral powder after crushing is placed in a corundum mortar and repeatedly ground with a corundum grinding rod; the forsterite mineral powder after crushing and grinding is placed on a 200-mesh sieve and sieved to obtain forsterite mineral powder with a particle size <74μm.

[0043] Acid leaching treatment: Take 10g of sieved magnesium olivine mineral powder and add it to an Erlenmeyer flask. Then add 120mL of 6mol / L hydrochloric acid solution and leach at 90℃ for 3h. After the acid leaching reaction is completed, filter the acid leaching product and collect the silica-containing filter residue I and the magnesium-iron leaching solution I.

[0044] Washing and alkaline dissolution of silica-containing filter residue: Wash silica-containing filter residue I with deionized water until the pH of the washing solution is neutral; add 0.1 mol / L sodium hydroxide solution to the washed filter residue until the filter residue is fully dissolved, filter after dissolution, and collect filtrate II sodium silicate solution.

[0045] Preparation of by-product silica: 3 mol / L hydrochloric acid solution was added to sodium silicate solution in filtrate II until the pH value reached 5.5, acidification to generate silicic acid, and filter residue II was collected after filtration; filter residue II was washed with deionized water until the pH value of the washing solution was neutral; the washed and filtered filter residue II was dried in a forced-air dryer at 70℃ for 24 h to obtain by-product silica.

[0046] Pre-electrolysis of iron: Add filtrate I (magnesium-iron leaching solution) to a self-made electrolytic cell, arranging it in a cathode-diaphragm-anode configuration. The diaphragm is a tetrafluoroethylene membrane, and both the cathode and anode plates are made of titanium-based metal with an anti-corrosion coating, in a mesh shape. Adjust the distance between the cathode and anode plates and the diaphragm to 2 cm. Connect the cathode and anode to the negative and positive terminals of the power supply, respectively, to form an electrolytic system. Turn on the power supply and set the current density to 0.025 A / cm². 2 The voltage limit is 5V, and constant current electrolysis is performed. Electrolysis is stopped when the pH value of the electrolyte reaches 3.7. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and iron hydroxide is generated at the cathode plate. After the pre-electrolysis reaction is completed, the product iron hydroxide slurry is filtered, and filter residue III and filtrate III magnesium chloride solution are collected.

[0047] Preparation of by-product iron red: Wash filter residue III with deionized water until the pH of the washing solution is neutral. Dry the washed and filtered filter residue III in a forced-air dryer at 70°C for 24 hours to obtain pure ferric hydroxide. Then calcine the ferric hydroxide at 600°C for 2 hours to obtain the by-product iron red.

[0048] Electrolytic preparation of magnesium hydroxide: Filtrate III (magnesium chloride solution) was added to a self-made electrolytic cell, arranged in a cathode-diaphragm-anode configuration. The diaphragm was a tetrafluoroethylene membrane, and both the cathode and anode plates were made of titanium-based metal with an anti-corrosion coating, in a mesh shape. The distance between the cathode and anode plates and the diaphragm was adjusted to 2 cm. The cathode and anode were then connected to the negative and positive terminals of the power supply, respectively, to form the electrolytic system. The power supply was turned on, and the current density was set to 0.025 A / cm². 2 The voltage limit is 4V, and constant current electrolysis is carried out for 4 hours. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and magnesium hydroxide is generated at the cathode plate. After the electrolysis reaction is completed, the product magnesium hydroxide slurry is filtered, and filter residue IV is collected. Filter residue IV is washed with deionized water until the pH value of the washing solution is neutral. The washed and filtered filter residue IV is dried in a forced air at 70℃ for 24 hours to obtain pure magnesium hydroxide.

[0049] like Figure 2 The XRD pattern shown indicates that the magnesium hydroxide prepared in Example 1 exhibits the standard peaks of magnesium hydroxide, without any additional impurity peaks not belonging to magnesium hydroxide, indicating that the prepared magnesium hydroxide is pure. Figure 3 The SEM image shown shows that the prepared magnesium hydroxide has a regular and uniform flake structure with few pores and no curling at the edges, exhibiting excellent morphological characteristics.

[0050] In Example 1, the magnesium ion leaching rate during the acid leaching process was 79.29%; the iron removal efficiency was 91.83%; the current efficiency of electrolytic magnesium hydroxide was 77.17%; and the median particle size of the magnesium hydroxide product was 15.42 μm.

[0051] Example 2

[0052] A method for the comprehensive utilization of low-grade magnesium olivine minerals includes the following steps:

[0053] Raw material pretreatment: The forsterite mineral is broken into small blocks and placed in a universal crusher for 10 minutes; the forsterite mineral powder after crushing is placed in a corundum mortar and repeatedly ground with a corundum grinding rod; the forsterite mineral powder after crushing and grinding is placed on a 150-mesh sieve and screened to obtain forsterite mineral powder with a particle size <106μm.

[0054] Acid leaching treatment: Take 10g of sieved magnesium olivine mineral powder and add it to an Erlenmeyer flask. Then add 160mL of 6mol / L hydrochloric acid solution and leach at 80℃ for 3h. After the acid leaching reaction is completed, filter the acid leaching product and collect the silica-containing filter residue I and the magnesium-iron leaching solution I.

[0055] Washing and alkaline dissolution of silica-containing filter residue: Wash silica-containing filter residue I with deionized water until the pH of the washing solution is neutral; add 0.1 mol / L sodium hydroxide solution to the washed filter residue until the filter residue is fully dissolved, filter after dissolution, and collect filtrate II sodium silicate solution.

[0056] Preparation of by-product silica: 3 mol / L hydrochloric acid solution was added to sodium silicate solution in filtrate II until the pH value reached 5.5, acidification to generate silicic acid, and filter residue II was collected after filtration; filter residue II was washed with deionized water until the pH value of the washing solution was neutral; the washed and filtered filter residue II was dried in a forced-air dryer at 70℃ for 24 h to obtain by-product silica.

[0057] Pre-electrolysis of iron: Add filtrate I (magnesium-iron leaching solution) to a self-made electrolytic cell, arranging it in a cathode-diaphragm-anode configuration. The diaphragm is an ion-exchange membrane, and both the cathode and anode plates are flat titanium-based metals coated with an anti-corrosion coating. Adjust the distance between the cathode and anode plates and the diaphragm to 2 cm. Connect the cathode and anode to the negative and positive terminals of the power supply, respectively, to form an electrolytic system. Turn on the power supply and set the current density to 0.025 A / cm². 2 The voltage limit is 5V, and constant current electrolysis is performed. Electrolysis is stopped when the pH value of the electrolyte reaches 3.7. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and iron hydroxide is generated at the cathode plate. After the pre-electrolysis reaction is completed, the product iron hydroxide slurry is filtered, and filter residue III and filtrate III magnesium chloride solution are collected.

[0058] Preparation of by-product iron red: Wash filter residue III with deionized water until the pH of the washing solution is neutral. Dry the washed and filtered filter residue III in a forced-air dryer at 70°C for 24 hours to obtain pure ferric hydroxide. Then calcine the ferric hydroxide at 600°C for 2 hours to obtain the by-product iron red.

[0059] Electrolytic preparation of magnesium hydroxide: Filtrate III (magnesium chloride solution) was added to a self-made electrolytic cell, arranged in a cathode-diaphragm-anode configuration. The diaphragm was an ion-exchange membrane, and both the cathode and anode plates were flat titanium-based metals coated with an anti-corrosion coating. The distance between the cathode and anode plates and the diaphragm was adjusted to 3 cm. The cathode and anode were then connected to the negative and positive terminals of the power supply, respectively, to form the electrolytic system. The power supply was turned on, and the current density was set to 0.025 A / cm². 2 The voltage limit is 4V, and constant current electrolysis is carried out for 4 hours. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and magnesium hydroxide is generated at the cathode plate. After the electrolysis reaction is completed, the product magnesium hydroxide slurry is filtered, and filter residue IV is collected. Filter residue IV is washed with deionized water until the pH value of the washing solution is neutral. The washed and filtered filter residue IV is dried in a forced air at 70℃ for 24 hours to obtain pure magnesium hydroxide.

[0060] In Example 2, the magnesium ion leaching rate during the acid leaching process was 71.67%; the iron removal efficiency was 91.83%; the current efficiency of electrolytic magnesium hydroxide was 69.35%; and the median particle size of the magnesium hydroxide product was 13.18 μm.

[0061] Example 3

[0062] A method for the comprehensive utilization of low-grade magnesium olivine minerals includes the following steps:

[0063] Raw material pretreatment: The forsterite mineral is broken into small blocks and placed in a universal crusher for 10 minutes; the forsterite mineral powder after crushing is placed in a corundum mortar and repeatedly ground with a corundum grinding rod; the forsterite mineral powder after crushing and grinding is placed on a 200-mesh sieve and sieved to obtain forsterite mineral powder with a particle size <74μm.

[0064] Acid leaching treatment: Take 10g of sieved magnesium olivine mineral powder and add it to an Erlenmeyer flask. Then add 160mL of 3.6mol / L hydrochloric acid solution and leach at 90℃ for 3h. After the acid leaching reaction is completed, filter the acid leaching product and collect the silica-containing filter residue I and the magnesium-iron leaching solution I.

[0065] Washing and alkaline dissolution of silica-containing filter residue: Wash silica-containing filter residue I with deionized water until the pH of the washing solution is neutral; add 0.1 mol / L sodium hydroxide solution to the washed filter residue until the filter residue is fully dissolved, filter after dissolution, and collect filtrate II sodium silicate solution.

[0066] Preparation of by-product silica: 3 mol / L hydrochloric acid solution was added to sodium silicate solution in filtrate II until the pH value reached 5.5, acidification to generate silicic acid, and filter residue II was collected after filtration; filter residue II was washed with deionized water until the pH value of the washing solution was neutral; the washed and filtered filter residue II was dried in a forced-air dryer at 70℃ for 24 h to obtain by-product silica.

[0067] Pre-electrolysis of iron: Add filtrate I (magnesium-iron leaching solution) to a self-made electrolytic cell, arranging it in a cathode-diaphragm-anode configuration. The diaphragm is a tetrafluoroethylene membrane, and both the cathode and anode plates are flat titanium-based metals coated with an anti-corrosion coating. Adjust the distance between the cathode and anode plates and the diaphragm to 2 cm. Connect the cathode and anode to the negative and positive terminals of the power supply, respectively, to form an electrolytic system. Turn on the power supply and set the current density to 0.025 A / cm². 2 The voltage limit is 5V, and constant current electrolysis is performed. Electrolysis is stopped when the pH value of the electrolyte reaches 3.7. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and iron hydroxide is generated at the cathode plate. After the pre-electrolysis reaction is completed, the product iron hydroxide slurry is filtered, and filter residue III and filtrate III magnesium chloride solution are collected.

[0068] Preparation of by-product iron red: Wash filter residue III with deionized water until the pH of the washing solution is neutral. Dry the washed and filtered filter residue III in a forced-air dryer at 70°C for 24 hours to obtain pure ferric hydroxide. Then calcine the ferric hydroxide at 600°C for 2 hours to obtain the by-product iron red.

[0069] Electrolytic preparation of magnesium hydroxide: Filtrate III (magnesium chloride solution) was added to a self-made electrolytic cell, arranged in a cathode-diaphragm-anode configuration. The diaphragm was a tetrafluoroethylene membrane, and both the cathode and anode plates were flat titanium-based metals coated with an anti-corrosion layer. The distance between the cathode and anode plates and the diaphragm was adjusted to 2 cm. The cathode and anode were then connected to the negative and positive terminals of the power supply, respectively, to form the electrolytic system. The power supply was turned on, and the current density was set to 0.05 A / cm². 2 The voltage limit is 6V, and constant current electrolysis is carried out for 4 hours. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and magnesium hydroxide is generated at the cathode plate. After the electrolysis reaction is completed, the product magnesium hydroxide slurry is filtered, and filter residue IV is collected. Filter residue IV is washed with deionized water until the pH value of the washing liquid is neutral. The washed and filtered filter residue IV is dried in a forced air at 70℃ for 24 hours to obtain pure magnesium hydroxide.

[0070] like Figure 4 The XRD pattern shown indicates that the magnesium hydroxide prepared in Example 3 exhibits the standard peaks of magnesium hydroxide, without any additional impurity peaks not belonging to magnesium hydroxide, indicating that the prepared magnesium hydroxide is pure. In Example 3, the magnesium ion leaching rate during the acid leaching process was 92.06%; the iron removal efficiency was 91.83%; the electrolytic current efficiency of magnesium hydroxide was 58.72%; and the median particle size of the product magnesium hydroxide was 32.71 μm.

[0071] Example 4

[0072] A method for the comprehensive utilization of low-grade magnesium olivine minerals includes the following steps:

[0073] Raw material pretreatment: The forsterite mineral is broken into small blocks and placed in a universal crusher for 10 minutes; the forsterite mineral powder after crushing is placed in a corundum mortar and repeatedly ground with a corundum grinding rod; the forsterite mineral powder after crushing and grinding is placed on a 150-mesh sieve and screened to obtain forsterite mineral powder with a particle size <106μm.

[0074] Acid leaching treatment: Take 10g of sieved magnesium olivine mineral powder and add it to an Erlenmeyer flask. Then add 160mL of 6mol / L hydrochloric acid solution and leach at 90℃ for 4h. After the acid leaching reaction is completed, filter the acid leaching product and collect the silica-containing filter residue I and the magnesium-iron leaching solution I.

[0075] Washing and alkaline dissolution of silica-containing filter residue: Wash silica-containing filter residue I with deionized water until the pH of the washing solution is neutral; add 0.1 mol / L sodium hydroxide solution to the washed filter residue until the filter residue is fully dissolved, filter after dissolution, and collect filtrate II sodium silicate solution.

[0076] Preparation of by-product silica: 3 mol / L hydrochloric acid solution was added to sodium silicate solution in filtrate II until the pH value reached 5.5, acidification to generate silicic acid, and filter residue II was collected after filtration; filter residue II was washed with deionized water until the pH value of the washing solution was neutral; the washed and filtered filter residue II was dried in a forced-air dryer at 70℃ for 24 h to obtain by-product silica.

[0077] Pre-electrolysis of iron: Add filtrate I (magnesium-iron leaching solution) to a self-made electrolytic cell, arranging it in a cathode-diaphragm-anode configuration. The diaphragm is a tetrafluoroethylene membrane, and both the cathode and anode plates are flat titanium-based metals coated with an anti-corrosion coating. Adjust the distance between the cathode and anode plates and the diaphragm to 2 cm. Connect the cathode and anode to the negative and positive terminals of the power supply, respectively, to form an electrolytic system. Turn on the power supply and set the current density to 0.05 A / cm². 2 The voltage limit is 5V, and constant current electrolysis is performed. Electrolysis is stopped when the pH value of the electrolyte reaches 3.7. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and iron hydroxide is generated at the cathode plate. After the pre-electrolysis reaction is completed, the product iron hydroxide slurry is filtered, and filter residue III and filtrate III magnesium chloride solution are collected.

[0078] Preparation of by-product iron red: Wash filter residue III with deionized water until the pH of the washing solution is neutral. Dry the washed and filtered filter residue III in a forced-air dryer at 70°C for 24 hours to obtain pure ferric hydroxide. Then calcine the ferric hydroxide at 600°C for 2 hours to obtain the by-product iron red.

[0079] Electrolytic preparation of magnesium hydroxide: Filtrate III (magnesium chloride solution) was added to a self-made electrolytic cell, arranged in a cathode-diaphragm-anode configuration. The diaphragm was a tetrafluoroethylene membrane, and both the cathode and anode plates were flat titanium-based metals coated with an anti-corrosion coating. The distance between the cathode and anode plates and the diaphragm was adjusted to 2 cm. The cathode and anode were then connected to the negative and positive terminals of the power supply, respectively, to form the electrolytic system. The power supply was turned on, and the current density was set to 0.035 A / cm². 2 The voltage limit is 5V, and constant current electrolysis is carried out for 4 hours. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and magnesium hydroxide is generated at the cathode plate. After the electrolysis reaction is completed, the product magnesium hydroxide slurry is filtered, and filter residue IV is collected. Filter residue IV is washed with deionized water until the pH value of the washing liquid is neutral. The washed and filtered filter residue IV is dried in a forced air at 70℃ for 24 hours to obtain pure magnesium hydroxide.

[0080] In Example 4, the magnesium ion leaching rate during the acid leaching process was 76.47%; the iron removal efficiency was 91.83%; the current efficiency of electrolytic magnesium hydroxide was 73.29%; and the median particle size of the magnesium hydroxide product was 25.68 μm.

Claims

1. A method for the comprehensive utilization of low-grade magnesium olivine minerals, characterized in that, Includes the following steps: Raw material pretreatment: The forsterite mineral is crushed, ground and sieved to obtain forsterite mineral powder with the target particle size; Acid leaching treatment: Mix magnesium olivine mineral powder of the target particle size with hydrochloric acid solution, heat and keep warm to carry out acid leaching reaction; after the acid leaching reaction is completed, filter the acid leaching product and collect silica-containing filter residue I and magnesium-iron leaching solution I. Washing and alkaline dissolution of silica-containing filter residue: Wash silica-containing filter residue I with deionized water until the pH of the washing solution is neutral; Add sodium hydroxide solution to the washed filter residue until the residue is fully dissolved. After dissolution, filter the residue and collect the filtrate, which is sodium silicate solution. Preparation of by-product silica: Continue to add hydrochloric acid solution to sodium silicate solution in filtrate II until the target pH value is reached, acidification to generate silicic acid, and collect filter residue II after filtration; Wash filter residue II with deionized water until the pH of the washing solution is neutral. The washed and filtered filter residue II was heated and dried by blowing air to obtain the byproduct silica. Pre-electrolysis of iron: Add the filtrate I magnesium iron leaching solution to the self-made electrolytic cell, arrange it in the order of cathode-diaphragm-anode, adjust the distance between the cathode and anode plates and the diaphragm, and connect the cathode and anode to the negative and positive terminals of the power supply respectively to form an electrolytic system; Turn on the power, set the current density and voltage limit, and perform constant current electrolysis. Stop electrolysis when the pH value of the electrolyte reaches the target value. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and iron hydroxide is generated on the cathode plate. After the pre-electrolysis reaction is completed, the product ferric hydroxide slurry is filtered, and filter residue III and filtrate III magnesium chloride solution are collected. Preparation of by-product iron red: Wash filter residue III with deionized water until the pH of the washing solution is neutral. Heat and dry the washed and filtered filter residue III with forced air to obtain pure ferric hydroxide. Then, calcine the ferric hydroxide to obtain the by-product iron red. Electrolytic preparation of magnesium hydroxide: Filtrate III magnesium chloride solution is added to a self-made electrolytic cell and arranged in the order of cathode-diaphragm-anode. The distance between the cathode and anode plates and the diaphragm is adjusted, and the cathode and anode are connected to the negative and positive terminals of the power supply, respectively, to form an electrolytic system. Turn on the power, set the current density and voltage limit, and perform constant current electrolysis. During the electrolysis process, chlorine gas is generated at the anode, hydrogen gas is generated at the cathode, and magnesium hydroxide is generated at the cathode plate. After the electrolysis reaction is completed, the product magnesium hydroxide slurry is filtered, and filter residue IV is collected. Filter residue IV is washed with deionized water until the pH value of the washing solution is neutral. The washed and filtered filter residue IV was heated and dried by forced air to obtain pure magnesium hydroxide.

2. The method for comprehensive utilization of low-grade magnesium olivine minerals as described in claim 1, characterized in that, In the raw material pretreatment, the target particle size of the magnesium olivine mineral powder is ≤150μm.

3. The method for comprehensive utilization of low-grade magnesium olivine minerals as described in claim 1, characterized in that, In the acid leaching treatment, the concentration of hydrochloric acid solution is 2.4 mol / L-6 mol / L, and the liquid-solid ratio of hydrochloric acid solution to mineral powder is 10 mL / g-16 mL / g; the acid leaching reaction temperature is 60℃-90℃, and the time is 2h-4h.

4. The method for comprehensive utilization of low-grade magnesium olivine minerals as described in claim 1, characterized in that, In the washing and alkaline dissolution of silica-containing filter residue, the concentration of sodium hydroxide solution is 0.05 mol / L-0.2 mol / L.

5. The method for comprehensive utilization of low-grade magnesium olivine minerals as described in claim 1, characterized in that, In the preparation of the byproduct silica, the concentration of hydrochloric acid solution added is 2.4 mol / L-6 mol / L, with a target pH value of 5.

5.

6. The method for comprehensive utilization of low-grade magnesium olivine minerals as described in claim 1, characterized in that, In the pre-electrolytic iron dissolution, the current density is 0.025 A / cm². 2 -0.05A / cm 2 The upper limit of the voltage is 3V-6V, and electrolysis is stopped when the pH value of the electrolyte reaches 3.

7.

7. The method for comprehensive utilization of low-grade magnesium olivine minerals as described in claim 1, characterized in that, In the preparation of the byproduct iron red, the calcination temperature of ferric hydroxide is 500℃-700℃, and the time is 1h-3h.

8. The method for comprehensive utilization of low-grade magnesium olivine minerals as described in claim 1, characterized in that, In the electrolytic preparation of magnesium hydroxide, the current density is 0.025 A / cm². 2 -0.05A / cm 2 The upper limit of voltage is 3V-6V, and the electrolysis time is 2h-6h.

9. A method for comprehensive utilization of low-grade magnesium olivine minerals as described in claim 1, characterized in that, The temperature for heating and drying filter residues II, III, and IV with forced air is 60℃-90℃, and the time is 8h-24h.

10. A method for comprehensive utilization of low-grade magnesium olivine minerals as described in claim 1, characterized in that, In the pre-electrolysis of iron and the electrolytic preparation of magnesium hydroxide, the diaphragm is a polytetrafluoroethylene membrane, an ion-exchange membrane, etc.; the cathode and anode plates are both titanium-based metals coated with anti-corrosion coatings, and are flat or mesh-shaped; the distance between the cathode and anode plates and the diaphragm is 1cm-4cm.

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